Inadvertent puncture of the thecal sac while injecting local anesthetic for an epidural can result in prolonged paresthesia, pains in the legs, and even transient paralysis.³ Bupivacaine can cause degeneration of muscle fibers after a single injection into a skeletal muscle.⁴ There have been reports of anesthetic injections outside of the neurofascicle which can lead to alterations in the blood–nerve barrier and consequent edema and swelling of the nerve.⁵ This can lead to a progressive decrease in nerve blood flow as the concentration increases.⁶ If a local anesthetic is injected intrafascicularly there can be devastating consequences from cytotoxicity and edema.^7,⁸ These possible complications can be avoided using appropriate techniques, and utilizing contrast media prior to introduction of anesthetic near a nerve.

Attention must be given to the amount of anesthetic administered in order to avoid the possibility of central nervous system toxicity. The total dosage of lidocaine should remain below 400–500 mg or 40 mL of 1% lidocaine. Bupivacaine is about 4 times more toxic than 1% lidocaine with a toxic bolus of 175 mg (or 17.5 cc) in a 70 kg patient.⁹ The signs of central nervous toxicity are disorientation, light-headedness, nystagmus, tinnitus, and muscle twitching in the face or distal extremities. Peak plasma concentrations occur 10–20 minutes after injection. Therefore, ongoing monitoring of the patient for the postoperative period for over 30 minutes is suggested strongly to avoid any possible potential nervous system toxicity from anesthetics.

Other complications which can arise from local anesthetics for epidural analgesia include motor block, hypotension, urinary retention, and pressure necrosis.¹⁰ Higher doses of local anesthetics appear to increase the risk of motor block and hypotension.^11,¹²

Cardiovascular complications

If high systemic levels of local anesthetics are injected intravascularly and/or intrathecally during a spinal interventional procedure cardiovascular complications can arise. Usually, such reactions are preceded by central nervous system toxicity prior to cardiovascular complications arising. The cardiovascular toxicity is a direct result of anesthetics acting upon the myocardium and peripheral vasculature. In vitro studies using isolated myocardial tissue have shown anesthetics to have a dose-dependent negative inotropic action.^13,¹⁴ The effects of local anesthetics on the cardiovascular system when at low levels can slightly increase blood pressure due to an increase in cardiac output and heart rate, which can enhance sympathetic activity and cause direct vasoconstrictor action. At higher concentrations, which produce CNS toxicity, they can cause a marked increase in heart rate, cardiac output, peripheral resistance, and blood pressure. With further increase in dosage there can be severe hypotension and cardiovascular collapse due to decreased cardiac output and peripheral vascular dilation. Prevention of such complications certainly depends on avoiding intravascular injection. Thus, appropriate needle localization with fluoroscopy and contrast media is essential.

Once CNS toxicity symptoms are present, the interventionist needs to prepare for possible cardiovascular complications. Institution of appropriate cardiopulmonary resuscitation is imperative for the management of such complications. Management of the patient using advanced cardiac life support (ACLS) would be implemented any time there is such a need. Appropriate management through emergency cardiac care algorithms is recommended and the reader is referred to more detailed sources for further information with regard to these algorithms and management.¹⁵^–¹⁷

Corticosteroids

Several injectable corticosteroid preparations have been utilized in interventional spinal procedures. These include, most commonly, triamcinolone, methylprednisolone, and betamethasone. Each of these corticosteroids has a different chemical composition. There have been several reports in the literature that have stated arachnoiditis may be related to the use of intrathecal steroids.¹⁸^–²² A study by Latham²³ has been done to assess intrathecally injected betamethasone in sheep, which did not reveal any evidence of arachnoiditis until high doses were utilized, and thus the study concluded intrathecal injection of betamethasone in low doses, such as those given in humans, is unlikely to cause arachnoiditis.²³ Several studies have examined the effects of epidural and subarachnoid-deposited injections into the meninges and spinal cord.

Cicala et al.²⁴ looked for evidence of acute neurotoxicity (within 30 days) after injection of epidural corticosteroids. They examined the effects of a mixture of 1% lidocaine and methylprednisolone on the meningeal membranes and nerve roots 4 or 10 days after epidural injection. Microscopic examination revealed a complete lack of inflammatory changes in neural tissue and meningeal thickening.

Abram et al.²⁵ examined histological sections of spinal cords of rats that received 4 subarachnoid injections of triamcinolone at 5-day intervals and compared them with sections from animals that received subarachnoid saline solution during the same time periods. They found a few large, common dark-stained neurons in several preparations, but these were invariably in areas adjacent to spinal catheters, where mechanical compression of the cord was evident. There was no difference in the incidence of such occurrences between steroid-treated and saline-treated animals.

A study by Delaney and colleagues ²⁶ evaluated possible long-term histological effects of a mixture of 2% lidocaine and triamcinolone following epidural injection and catheterizations. They found that the nerve root and the root entry zone in the meninges when examined by light microscopy 30 and 100 days after injection showed only a minor inflammatory response at the 30 day period. The reaction was completely resolved at 100 days.

It has been proposed that polyethylene glycol (PEG), a preservative agent in methylprednisolone, has been implicated in cases of sterile meningitis and arachnoiditis when injected intrathecally.²⁰ A study performed on the toxicity of PEG was performed by Benzon et al.²⁷ They showed a concentration of 20% PEG or greater resulted in a swelling and a reduction in compound muscle potential in isolated nerve preparations. However, this concentration is clearly higher than that found in commercial corticosteroids preparations, which is 3–9%. These preparations are subsequently diluted with saline and local anesthetics, which would indicate an even lower predisposition for any neurotoxicity.

Epidural administration of corticosteroids has several known side effects. These include fluid retention, which can lead to congestive heart failure.²⁸^–³⁰ Case reports of steroid myopathy have been reported.¹³ There have also been reports of irregular menses.³¹ Epidural lipomatosis has been associated with prolonged corticosteroid therapy.³²^–³⁴ Minor digestive disturbances and occasional minor changes in serum glucose have been documented.³⁵ Less-common side effects are elevated temperature, euphoria, depression, mood swings, local fat atrophy, deep pigmentation of the skin, and pain flare. Other rare but reported side effects include weight gain,²⁸ deep vein thrombosis,³⁶ and hypertension,³⁷ and allergic reactions to triamcinolone.¹

An uncommon but serious complication is development of Cushing’s syndrome from excess glucocorticoid administration.³⁸ This syndrome usually occurs when exceptionally high dosages of corticosteroid are given over a short period of time. One such case occurred when a patient received two 80 mg injections of methylprednisolone 1 week apart.³⁹ Serum cortisol levels have been shown to be depressed for 1–2 weeks after epidural injections but may return to normal after 3 weeks.^40,⁴¹ The recommended dose to avoid systemic side effects from epidural steroids has been stated by Knight and Burrell⁴² to be no more than 3 mL/kg of methylprednisolone. Despite adhering to this, there have been reports of cumulative effects from long durations of steroid preparations. Kay⁴³ and coworkers have shown both acute and chronic suppression of the hypothalamic–pituitary–adrenal axis in a clinically relevant study of 14 patients who received a total of three epidural steroid injections once weekly with 80 mg of triamcinolone in 7 mL of 1% lidocaine. Within 15 minutes of injection, there was evidence of the suppression of endogenous corticosteroids, manifested by a significant decrease in both ACTH and cortisol. The median duration of such effect was 1 month, but 5 of 14 patients showed suppression for up to 3 months. Adrenal function returned to a normal status after 3 months.

In a study by Manchikanti ⁴⁴ it was concluded that low-dose administration of neuroaxial steroids are not deleterious and did not result in any significant deterioration in bone mineral density, causing neither osteopenia or osteoporosis.

Contrast media

Because fluoroscopic procedures are combined with introduction of radiographic contrast media, it is important to know the potential adverse effects of contrast media. The largest study to compare the effects of intrathecal nonionic (iopmanidol) to ionic (metrizamide) contrast found substantially fewer adverse reactions in the nonionic group.⁴⁵

The contrast currently used in myelography and fluoroscopic injections is nonionic, either iso-osmolar or of a low osmolality. The risk of anaphylactic reaction using iso-osmolar contrast is extremely low (0.04%)

In 337 647 cases in which iso-osmolar contrast was used, only 1 death occurred.⁴⁶ Patients with a known sensitivity to iodine, prior reaction to contrast media, food allergies, asthma, and hay fever have a higher incidence of anaphylactic or cardiovascular reactions. Premedication with histamine H₁ and histamine H₂ blockers and corticosteroids may reduce the incidence and severity of life-threatening reactions in patients with a known allergy. Controlled studies on nonionic contrast agents used intrathecally in myelography have shown adverse reactions including headache (18%), nausea (7.3%), muscular pain (3.7%), and hypotension (1.1%).⁴⁷ These studies were performed using 10–15 mL of contrast injectate, which is a larger dose than the 1–3 mL used during fluoroscopic injections.

The fluoroscopic technique in combination with extradural myelography can avoid intrathecal injections. Intravascular injection can occur in 9.2% of cases despite a negative aspiration for blood in lumbar epidural injections, without fluoroscopic guidance.⁴⁸ When utilizing fluoroscopy and contrast media, Sullivan et al.⁴⁹ found a similar overall incidence of 8.5% intravascular uptake in lumbar spinal injections. The caudal and transforaminal routes were intravascular 10.9% (Fig. 20.2) and 10.8% of the time, respectively, sacroiliac joint injections 6.3% (Fig. 20.3), zygapophyseal joint injections 6.1%, and interlaminar injections 1.9%. The intravascular pattern in lumbar transforaminal epidural injections was also described by Furman to be 11.2%⁵⁰ and in cervical transforaminal injections, and intravascular uptake is 19.4%.⁵¹ These studies unequivocally demonstrate the importance of introducing contrast media prior to the infusion of anesthetics or corticosteroids in spinal interventional injections. Prophylaxis may be utilized in patients with known allergy to contrast media (Fig. 20.4). An alternative in patients allergic to iodinated contrast is to utilize gadolinium contrast.⁵²

Fig. 20.2 AP/PA fluoroscopic image showing intravascular contrast during a caudal injection.

Fig. 20.3 Fluoroscopic image of sacroiliac joint showing intervascular contrast pattern.

Fig. 20.4 Pro-phylaxis for patients with known allergy to contrast media.

Infectious complications

Infectious complications can arise from spinal injections. These complications can include epidural abscess,⁵³^–⁵⁵ meningitis⁵⁶^–⁵⁸ and osteomyelits/discitis.⁵⁹

Epidural abscess

These have been reported after epidural injections in the cervical, thoracic, and lumbar spine. There have been cases of epidural abscess following thoracic epidural injections of steroids and bupivacaine to treat postherpetic neuralgia.^57,⁶⁰ A thoracic epidural abscess has also been reported after four epidural injections in a patient with metastatic disease.⁵³ Five other cases of abscesses were reported, three after lumbar, one after cervical, and one after caudal epidural injections.^54,^55,⁶¹^–⁶³ The bacteria identified in these cases was Staphylococcus aureus. Of these patients, three patients had diabetes mellitus, one had a surgical infection with S. aureus 2 weeks prior to the epidural injection, and one had carcinoma with spinal metastasis. All of these patients presented with fever, spinal pain, radicular pain, and/or progressive neurologic deficit 3 days to 3 weeks following their injections. It is presumed that the most common bacterial etiology for spinal infection from a spinal injection is S. aureus. The likely mechanism of infection is introduction by the needle, carrying an inoculum from the skin to deeper structures.

In order to diagnose an epidural abscess resulting from a spinal procedure, there must be careful and close clinical observation. There should be a high suspicion for this potential complication in any patient with a history of an immunocompromised condition or diabetes mellitus.

Clinically, the patient with epidural abscess presents with pain in the local area, neck or back stiffness, soreness, fever, and/or malaise. Prompt diagnosis of infection is necessary in order for a patient to recover with intact neurologic function.

Laboratory evaluation with erythrocyte sedimentation rate (ESR), C-reactive protein, and complete blood count (CBC) needs to be obtained. Magnetic resonance imaging (MRI) with contrast is the radiological procedure of choice for the diagnosis of epidural abscess.^55,⁶⁴ Once diagnosed, appropriate antibiotic therapy can be administered and surgical debridement performed if necessary.

Meningitis

This is a rare phenomenon, which can occur following spinal injections. It can occur when the dura is accidentally punctured during epidural procedures or other spinal interventional procedures. There are two types of meningitis that have been reported following spinal injections: bacterial and aseptic. Several cases of bacterial meningitis have been reported following lumbar epidural injections.⁵⁷ Of the two cases reported by Dougherty, one patient had a documented dural puncture and the other patient had an inadvertent unrecognized dural puncture.

Cases of aseptic meningitis have been reported by Nelson et al.¹⁹ following subarachnoid injection with methylprednisolone. The manifestations included headache, fever, nausea, leg pain, and convulsions. Cerebrospinal fluid (CSF) analysis revealed elevated protein, leukocytes, and red blood cells, while CSF culture was negative. Spontaneous recovery ensued over a 3-week period. Several other cases of aseptic meningitis have been reported after a subarachnoid injection.^25,^64,⁶⁵ In each instance the symptoms resolved within several days. A case report by Morris⁶⁶ of aseptic meningitis began 48 hours after an epidural injection of methylprednisolone without any anesthetic. The symptoms included fever, headaches, lethargy, and meningismus. CSF evaluation in this case revealed pleocytosis, elevated protein values, and diminished glucose levels. CSF culture was negative.

Thus, in a patient with presumptive meningitis, appropriate evaluation of CSF fluid is needed in order to appropriately treat this potential complication. A history needs to be obtained from the patient regarding headache, lethargy, and photophobia, followed by evaluation for signs of meningeal irritation.

Prevention of meningitis can be enhanced by utilizing a strict sterile technique, but even the best precautions do not entirely mitigate this possible complication.

Osteomylitis/discitis

Cases of osteomyelitis and discitis have been reported following cervical, thoracic, and lumbar discography. This is a potential life-threatening complication if it develops in the cervical or thoracic spine. As previously mentioned, these infectious complications can be minimized by adhering to sterile technique along with the use of intravenous and intradiscal antibiotics. The use of antibiotics are further discussed in the section on discography. Patients who have undergone a discographic procedure should be observed clinically for symptoms of osteomyelitis or discitis. The typical signs of infection include fever, malaise, lethargy, pain, and/or neurological symptoms. These typically present 1–4 weeks after injection although neurological symptoms are uncommon. Laboratory studies can reveal leukocytosis, elevated sedimentation rate, and/or an increase in C-reactive protein. MRI with contrast has been shown to be superior to bone scan for the early diagnosis of discitis and osteomyelitis.⁶⁷

In summary, early detection of infectious complications from injection procedures is necessary in order to avoid morbidity and mortality. In patients who have a history of prior infection, consideration should be given to prophylactic antibiotic treatment in these patients, prior to their procedure. An algorithmic approach to managing these infectious complications is seen in Figure 20.5.

Fig. 20.5 Possible spinal abscess, meningitis, or osteomyelitis/discitis.

Hematologic complications

Many factors are involved in evaluating the bleeding risk in patients who are undergoing spinal interventional procedures. Patients who suffer from coagulation disorders are at increased risk of bleeding.⁶⁸ These include patients with hemophilia and von Willebrand’s disease. Spinal blocks have been performed in hemophiliacs utilizing recombinant factor VIIa.⁶⁹ Von Willebrand’s disease can lead to spontaneous bleeding following epidural procedures.⁷⁰ However, there are cases of epidural catheterization which have been performed in patients with von Willebrand’s disease without complications.⁷¹^–⁷³ Patients with thrombocytopenia and idiopathic thrombocytopenic purpura can be at risk for complications from spinal injections. Epidural catheterization is believed to be safe in patients with platelet counts of greater then 100 000.⁷⁴ There are, however, case reports of patients safely receiving epidural injections with platelet counts below 100, 000.^75,⁷⁶ Obtaining a baseline CBC prior to a spinal injection can identify a patient with thrombocytopenia.

Patients who have liver and renal disease may have altered coagulation, which could lead to a complication with hepatic dysfunction accompanied with portal hypertension, resulting in increased epidural venous congestion, which can lead to increased likelihood of bleeding.⁷⁷ Epidural hematomas following lumbar puncture⁷⁸ and epidural catheter placement^79,⁸⁰ have been reported in patients with known liver disease. They have also been reported in patients with renal disease.^81,⁸²

Epidural hematoma

Epidural hematomas can develop spontaneously and in patients with no evidence of any bleeding tendency, anticoagulation, or traumatic needle insertion.^83,⁸⁴ In a review of epidural steroid injections in 65 published series with a total of 69 047 patients receiving one or more epidural injections, there was only one case of an epidural hematoma.⁸⁵ Hematomas can be localized in the cervical, thoracic, or lumbosacral spine. Symptoms will vary depending on the location and size f the hematoma. The presentation can be immediate or delayed up to several days.^86,⁸⁷ In order to diagnose patients with such a complication, prompt spinal imaging is recommended. MRI is the most sensitive modality in order to diagnose a hematoma, define the extent of its spread, and distinguish it from other space-occupying lesions.⁸⁸^–⁹⁰ Once identified, treatment of the hematoma can involve high-dose corticosteroid therapy and/or emergency decompressive surgery in order to prevent further compromise of neurologic function. If an epidural catheter is present with a hematoma, infusion should be stopped and the catheter removed in order to avoid increasing compression.⁸⁴ In order to minimize the risks to the patient when performing spinal interventional procedures, the interventionist can do several things that can minimize the potential possibility of causing an epidural hematoma. These include minimizing the passes of the needle (needle trauma) utilizing fluoroscopic guidance, use of smaller-caliber needles,⁹¹ and aspiration can be performed in order to determine if the needle is intravascular. See Figure 20.6 for an algorithmic approach to the evaluation of a patient with a presumptive epidural hematoma.

Fig. 20.6 Evaluation of patient with suspected epidural hematoma.

Management of anticoagulant medications in interventional spinal procedures

Clinically apparent epidural hematomas are rare, with an incidence between 1:40 000 and 1:150 000.^84,^85,^92,⁹³ Aspirin and nonsteroidal antiinflammatory drugs may effect platelet function and subsequently increase the risk of an epidural hematoma. These medications have been reported to increase the occurrence of epidural hematoma from both spinal anesthesia and epidural injection.⁹⁴^–⁹⁷ It should be noted, however, that there are other studies, which report no increased incidence of epidural hematomas in patients who are receiving aspirin and nonsteroidal antiinflammatory medications.⁹⁸^–¹⁰¹

Patients using thienopyridine derivatives and glycoprotein receptor antagonists have developed hematomas from interventional spinal injections.^86,¹⁰² Since the risk associated with these medications is unknown, the American Society of Regional Anesthesia recommends withholding ticlopidine 14 days, clopidogrel 7 days, and Gp antagonists for 4 weeks prior to procedure.⁸⁷ Oral anticoagulation with warfarin is a contraindication to spinal anesthesia.⁸⁷ The American Association of Regional Anesthesia suggests that warfarin should ideally be stopped 4–5 days prior to spinal injection. The prothrombin time (PT) and international normalized ratio (INR) should be checked prior to a spinal injection. There is no consensus regarding the delineation of a safe PT/INR prior to performing a spinal injection. There is some literature that supports an INR of 1.5 as safe for major surgical procedures including spinal injections while an INR greater than 1.5 is unsafe.^103,¹⁰⁴ It should be noted that identification of risk factors for bleeding disorders does not eliminate the risk of a spinal hematoma. This has been shown in the study by Vandermeulen⁹⁴ in which 87% of patients who had spinal hematomas had a hemostatic abnormality but, 13% had no identifiable risks. See Figure 20.7 for an algorithmic approach to the management of patients on warfarin, aspirin, or NSAIDs.

Fig. 20.7 Anticoagulated patterns,

Neurological complications

Neurological injuries are an uncommon complication which can occur when performing spinal injections.

Several studies have shown prospectively that the incidence of neurological injuries is approximately 0.002–0.7% and that they are usually self-limiting.¹⁰⁵^–¹⁰⁷ Placement of thoracic epidural catheters has been shown to have an incidence of neurological injury of 0.7%.¹⁰⁷ There have been case reports of upper limb weakness and nerve root injury and even intrinsic spinal cord damage from spinal injections.^54,¹⁰⁸^–¹¹⁰ Neurological compromise can also occur from spinal infection such as epidural abscess or epidural hematoma.

There have been case reports of transiently increased sciatic pain and paresthesia following spinal injections.¹¹¹^–¹¹⁹

Spinal injections carry a higher risk when performed in the cervical spine. In particular, this is due to the closer proximity of important structures to the target site, such as the vertebral or carotid artery. Inadvertent injection into these arteries could result in stroke, hematoma formation, or even an occlusion of the involved vessel. In order to avoid these potential complications, constant and careful fluoroscopic guidance with administration of contrast media prior to injection of anesthetics and corticosteroid medications is essential.

CNS toxicity can occur in patients who received local anesthetic as a component of a spinal injection. Signs of this toxicity can be light-headedness, tinnitus, perioral numbness, numbness of the tongue, and blurred vision. As the symptoms become more advanced, patients may show signs of nervous system excitation, which can present as shivering, muscle twitches, confusion, and tremors of the facial muscles followed by those of the extremities. As the central nervous system toxicity progresses, CNS activity is slowed and can become depressed and manifest as respiratory depression or arrest.

Seizures can also result from spinal injections. These seizures may be a result of anesthetic or cardiac-induced hypotension secondary to neural blockade. Prolonged seizures can result in brain injury if they last longer than 30 minutes.¹²⁰^–¹²² In order to possibly prevent such consequences the interventional physician should carry out a comprehensive neurologic and physical examination and immediately treat the seizure activity. See Figure 20.8 for an algorithmic approach in the management of a seizure.

Fig. 20.8 Management of seizures.

Dural puncture and post-dural puncture headache

The potential complication of entering the subarachnoid space due to penetration of the dura exists with any spinal injection. This can occur in any region of the spine (cervical, thoracic, or lumbosacral). The incidence of an inadvertent dural puncture in lumbar epidural injections has been reported to be as low as 0.5% and as high as 5%.^109,¹²³ Incidence of dural puncture in the cervical spine can be as high as 20%.¹⁰⁸ The incidence of headache following dural puncture in the lumbar spine has been reported to be 7.5–75% depending on technique, experience, and size of needle used.^124,¹²⁵ These headaches may emanate from an unrecognized dural puncture causing a leakage of cerebrospinal fluid (CSF) or they may result from inadvertent injection of air into the subarachnoid space.^126,¹²⁷

When small-gauge needles are used in spinal anesthesia there is a lower incidence of postdural puncture headache. The incidence is approximately 40% with a 22-gauge (ga) needle, 25% with a 25-ga needle,^128,¹²⁹ 2–12% with a 26-ga Quincke needle,¹³⁰ and less than 2% with a 29-ga needle.¹³¹

If a postdural puncture headache occurs, the headache will usually occur within 3 days of the procedure. Up to 66% start within the first 48 hours.^132,¹³³ The headache can also present immediately following a dural puncture.¹³⁴

The pain associated with the headache is described as being a shearing and severe spreading pain. Distribution of the pain appears to be in the frontal and occipital areas, which can radiate into the neck and shoulders. There tends to be stiffness in the neck and the pain is exacerbated with head movements and relieved by lying down.^134,¹³⁵ Symptoms that can also appear in dural puncture headaches include nausea, vomiting, hearing loss, tinnitus, vertigo, dizziness, paresthesias of the scalp, and upper/lower limb pains. There have also been reports of visual disturbances such as diplopia or cortical blindness.^3,^136,¹³⁷ There are also reports of intracranial subdural hematomas, cerebral herniation, and death.¹³⁸

A review of the literature has revealed that the spontaneous rate of recovery from postdural puncture headache is typical with 85% recovering within 6 weeks.^3,^139,¹⁴⁰ Even though this side effect can spontaneously resolve, there are frequent circumstances during which the severity of the headaches necessitates treatment. A variety of strategies can be undertaken including rehydration, acetaminophen, nonsteroidal antiinflammatory drugs, opioids, and antiemetics.¹⁴¹ Caffeine has been utilized in the treatment of postdural headache at a dose of 300–500 mg of oral or i.v. caffeine once or twice daily.^142,¹⁴³

The most definitive method of treatment, however, is an epidural blood patch.¹⁴⁴^–¹⁴⁶ The first report of epidural blood patch for treatment of postdural puncture headache was described by Gormley in 1960.¹⁴⁷ This technique has a success rate of 70–98%.¹⁴⁸ The exact mechanism by which the epidural blood patch eliminates the headache is unknown. However, it has been postulated that the headache is believed to be due to a reduction of CSF volume or pressure, which leads to traction and tension across the pain-sensitive dural sinuses that occurs in the upright position.¹⁴⁹ It should be noted that lumbar extradural blood patch has been shown to be effective even in the treatment of a cervical postdural puncture headache, supporting this theory.¹⁴⁹

Slipman et al.¹⁵⁰ have reported the successful use of a cervical transforaminal epidural blood patch in a patient with a postdural puncture headache from an interlaminar cervical epidural injection in which cervical interlaminar epidural blood patch failed to relieve symptoms.

Another theory for how the blood patch works is that the blood clot adheres to the dura matter which may perhaps seal the hole in the dura and prevent CSF leak.¹⁵¹ Another possible mechanism of action is that the mixing of blood with the CSF lends to rapid coagulation response, sealing the dural tear even if it is far from the blood patch site.¹⁵¹

Complications can arise as well from the epidural blood patch. These can include exacerbation of symptoms and radicular pain.¹⁵² Pneumocephalus has also been described following epidural blood patch.¹⁵³ An inadvertent subdural blood patch has been described, resulting in a nonpositional persistent headache with resulting lower extremity discomfort.¹³²

An algorithmic approach to avoiding dural puncture, and the treatment of dural puncture can be seen in Figure 20.9.

Fig. 20.9 Dural puncture prevention and management of postdural puncture headache.

Respiratory complications

Respiratory complications can arise following interventional spinal procedures. These complications are very rare and may be the result of sedation, central nervous system trauma due to needle puncture of the spinal cord (SC), or lung (pneumothorax).

Pneumothorax can occur in a lower cervical or any thoracic spinal interventional procedure. A pneumothorax tends to be self-limiting and the treatment of this potential complication would require supportive care, observation, and follow-up serial chest radiographs. If a pneumothorax becomes significant, with greater than 25% collapse of the lung, then a chest tube may need to be placed to maintain respiration.¹⁵⁴ Cervical spinal injections can injure the recurrent laryngeal nerve. A patient with such an injury may present with a reduction in the ability to protect the airway and may also have hoarseness. This condition is usually self-limiting and resolves. Vocal cord dysfunction has been reported transiently with a 12% incidence in patients receiving steroid injections in the axial skeleton.¹⁵⁵

Respiratory depression can arise from all neuraxial opioids. The incidence of clinical respiratory depression with a bolus of morphine is 0.2%.^156,¹⁵⁷

Urological complications

The incidence of urological complications are very few, if any, from interventional spinal procedures. The most common problem is urinary retention, which may follow injections of spinal local anesthetic.¹⁵⁸ The other possible cause of urological problems can be an infection such as an epidural abscess or epidural hematoma, which can compromise the spinal cord and/or cauda equina.

SPECIFIC COMPLICATIONS OF CERVICAL SPINAL INJECTIONS

Cervical spinal injections

Cervical epidural steroid injections

The complications of cervical epidural steroid injections include dural puncture headache, pneumothorax, pneumocephalus,¹⁵⁹ bloating, nausea,^108,¹⁶⁰ vomiting, fever, spinal nerve injury, epidural hematoma,⁹³ subdural hematoma,¹⁶¹ hypotension, transient paresis, and respiratory insuffiency.¹⁶² Facial flushing has a 9.3% incidence and a stiff neck has a 13.2% incidence.^108,¹⁶³ Cervical epidural abscess^61,^164,¹⁶⁵ and complex regional pain syndrome¹⁶⁶ have also been reported. Subdural or subarachnoid injections of large doses of anesthetic may cause loss of consciousness,¹⁶³ hypotension, spinal anesthesia, cardiovascular arrest, apnea, or death.

An infrequent although serious complication of cervical interlaminar epidural steroid injection is spinal cord injury from direct needle trauma.^53,^54,^110,¹⁶⁴ Spinal cord injuries from direct trauma have occurred when patients were sedated to such a degree that they did not report pain.¹¹⁰ Therefore, heavy sedation is contraindicated for cervical interlaminar epidurals. Botwin et al.¹⁶⁷ found an incidence of minor complications in fluoroscopically guided interlaminar cervical epidural injections of 16.8%. The most common complications were neck pain 6.7%, nonpositional headache 4.6%, insomnia 1.7%, vasovagal reactions 1.7%, facial flushing 1.5%, and dural puncture 0.3%.

Spinal cord infarction has been reported in cervical transforaminal epidurals, possibly through intravascular injection into a radicular artery.^166,^168,¹⁶⁹ Brouwers et al. described a cervical anterior spinal artery syndrome after a diagnostic block of the right C6 nerve.¹⁷⁰ Similarly, Ludwig¹⁶⁹ described spinal cord infarction following a left C6 transforaminal epidural steroid injection. A case of quadriparesis and brainstem herniation after a selective cervical transforaminal injection on the right at C5–6 has been reported by Tiso et al.¹⁷¹ Brady et al.¹⁶³ found two complications following 357 transforaminal epidural steroid injections. Both complications were transient loss of consciousness followed by nausea and vomiting. A study by Slipman et al.¹⁷² reported no complications in 20 patients with cervical spondylitic radicular pain who underwent cervical transforaminal injection. Slipman et al.,¹⁷³ in a prospective study of 89 cervical selective nerve root injections found immediately following the procedure, found that 22.7% of injections resulted in increased pain at the injection site, 18.2% had increased radicular pain, 13% had light-headedness, 9.1% had increased spine pain, 4.5% had non-specific headache, and 3.4% had nausea. Ninety-one percent experienced no complications or side effects during the procedure.

The incidence of dural puncture using the cervical interlaminar technique is 0.25–2.0%.^108,¹⁶⁴ Slipman¹⁷³ reported an incidence of dural puncture in cervical selective nerve root injections of 0.33%. Dural headaches may be from unrecognized dural punctures causing leakage of cerebral spinal fluid or they may result from inadvertent injection of air into the subarachnoid space.^126,¹²⁷ A study injecting 10 mL of intrathecal normal saline prophylactically showed a favorable response in reducing the severity of postdural puncture headaches.¹⁷³ Many headaches resolve with conservative management including bed rest and fluids. Persistent postural headache may require an epidural blood patch using 5–30 mL of autologous blood under aseptic conditions and using fluoroscopy.

The cervical epidural space is densely vascularized.¹⁷⁴ The incidence of intravascular penetration in cervical transforaminal injections is 19.4%.⁵⁰ The incidence of intravascular injection using interlaminar technique is considered to be much lower but has not been studied. Unrecognized inadvertent intravascular needle placement delivers the medication systemically instead of locally and the treatment effect may not be obtained. Misplacement of the anesthetic intravascularly may result in local anesthetic toxicity, requiring immediate supportive measures.¹⁷⁴

Neuropathic pain has been reported after cervical epidurals and may result from spinal nerve irritation caused by the injectate or by compression of neural elements.¹⁷⁵^–¹⁷⁷

Absolute contraindications to cervical epidural injections include anticoagulation and coagulopathy because of a risk of epidural hematoma. Batson’s plexus may potentiate the hematogenous spread of an existing infection; thus, epidural injections should be avoided in patients with local infection and sepsis. Laminectomy and significant central canal stenosis resulting from congenital shortening of the pedicles, central disc herniation, or bone spurring are absolute contraindications to an interlaminar epidural injection at the affected level. Pregnancy is a contraindication for cervical transforaminal injections because of the necessity for fluoroscopic guidance.

Relative contraindications to injection are a known anaphylactic reaction to the contrast, an immunocompromised state, hypertension, hypotension, and/or an inability to remain still for the procedure. Introduction of contrast under fluoroscopic guidance is required for all cervical epidurals. In the patient allergic to contrast one may consider gadolinium or use prophylactic treatment.

Cervical zygapophyseal intra-articular injections

While performing the cervical zygapophyseal joint injection (z-joint) there is a risk of entry into the intervertebral foramen, spinal canal, and vertebral artery, which can result in direct trauma to a vessel or motor and sensory blockade. Further, local pain, postinjection, and light-headedness are possible transient complications from local anesthetics.

Puncture of the vertebral artery may result in air embolus, stroke, hematoma, or occlusion of a vessel. Seizure and/or cardiac-induced hypotension may occur if local anesthetic is injected into a vessel. Spinal anesthesia may occur with cervical z-joint injection if the thecal sac is entered through abnormal communication with the z-joint capsule. Further leakage into the epidural space may occur with over distension of the z-joints.

Absolute contraindications include localized infection, bleeding diathesis, an unsigned consent form, a patient unable to remain still, and inability to assess patient response to procedure.

Cervical median branch block/radiofrequency ablation

Potential complications from cervical radiofrequency ablation (RFA) include needle entry into the vertebral artery, intervertebral foramen, and spinal canal. Another potential complication is lidocaine extravasation when anesthetizing the medial branch prior to neurotomy. Local pain at the procedure site may occur but is usually transient.

According to the literature, complications from third occipital nerve (TON) lesioning include ataxia, numbness, dysesthesias and hypersensitivity in the area of the treated nerves.^178,¹⁷⁹ Numbness is a predictable side effect which is usually well tolerated by patients.¹⁷⁸^–¹⁸⁰ In fact, absence of numbness indicates a technical failure.¹⁷⁸ The dysesthesia is temporary and not usually distressing to the patient.¹⁷⁸ Tricyclic antidepressants and anticonvulsants can be used to manage these symptoms. Ataxia can be expected due to the interruption of the tonic neck reflexes and proprioception when the semispinalis is denervated in TON neurotomy.¹⁸¹ The ataxia causes unsteadiness when looking down and, according to Govind, was not disabling to the patient.¹⁷⁸

Cervical discography

Discitis is the most widely recognized complication associated with discography and can be difficult to eradicate due to the limited blood supply of the disc. The most common infectious etiologic agent is S. aureus followed by other staphylococcus species and anaerobic organisms.^170,¹⁷⁷ Inadvertently piercing the esophagus during the procedure may seed the disc with Gram-negative and anaerobic organisms. The patient usually presents 1–4 weeks after the procedure with increased neck pain. Initially, there is usually no change at neurologic examination.

Epidural abscess may follow cervical discography and generally presents within 24–48 hours. The signs and symptoms are high fever, spine pain, and progressive neurologic deficit. White blood cell count (WBC), ESR, and C-reactive protein should be obtained if either discitis or epidural abscess is suspected. WBC is an unreliable marker. ESR and the C-reactive protein are the most sensitive laboratory markers.¹⁸¹ MRI with contrast is the radiographic imaging modality of choice in diagnosing postprocedural discitis and epidural abscess. MRI has a reported sensitivity of 93% and specificity of 97% in suspected cases of discitis.¹⁸² Blood cultures have a 55.6% positive rate in the setting of a culture-positive discitis.¹⁸³ When the organism is determined, antibiotics should be instituted. Surgical intervention is required with large lesions or lack of improvement with antibiotics and immobilization.

Another potential complication from cervical discography is injury to the recurrent laryngeal nerve, which can cause vocal cord paralysis, hoarseness, and decreased ability to protect the airway. The injury is usually self-limited and resolves without intervention. The patient’s respiratory status should be monitored during recovery from sedation. Patients with preexisting oropharyngeal dysfunction are at greater risk of aspiration.

Pneumothorax is another rare complication of cervical discography. It usually is self-limited and causes only minor lung collapses (10%).¹⁸⁴ Treatment includes supportive care in a hospital setting with serial chest X-rays and possibly placement of a chest tube.

Direct trauma to the spinal cord and the spinal nerves can occur if the needle is placed too far lateral or allowed to traverse the entire disc. Cervical cord trauma can result in syrinx formation and progressive neurologic deficits including tetraplegia. These complications should rarely occur if fluoroscopic guidance and appropriate technique are used.

Absolute contraindications to cervical discography include the patient unable or unwilling to sign consent, localizing infection, known bleeding diathesis, inability to assess patient response to the procedure, and the patient being unable to remain still during procedure.

Thoracic spinal injections

Potential complications of thoracic spinal injections include dural puncture, infection, vascular and neurological injury.^107,¹⁸⁴ Thoracic spinal procedures have greater propensity for occurrence of complications secondary to unique inherent anatomical properties of the thoracic region. These include a narrow epidural space, which leads to a closer proximity to the spinal cord. The proximity of the lung poses a significant risk of developing a pneumothorax. Injection of local anesthetic in the mid-thoracic epidural space may cause inhibition of the cardiac accelerator leading to bradycardia and/or hypotension.¹⁸⁵ Thoracic motor blockade can impair ventilation with up to 50% reduction in tidal volume.¹⁸⁵ Slipman et al.¹⁸⁶ have reported persistent hiccups associated with thoracic epidural injection. Arterial supply by means of the artery of Adamkiewicz and its anatomical variations make it vulnerable to injury during lower thoracic or upper lumbar transforaminal epidural injections.¹⁸⁷^–¹⁸⁹

Lumbar spinal injections

Lumbar epidural steroid injections

Interlaminar lumbar epidural injections

Complications following interlaminar lumbar epidural injections can be broadly divided into septic, vascular, neurological, and idiopathic. Vascular complications include vascular damage and development of epidural hematoma. Vascular infiltration can lead to subsequent cardiorespiratory and/or neurologic complications (i.e. seizures), which have been discussed in depth in the beginning of this chapter. Since the lumbar epidural space is highly vascularized, inadvertent intravenous placement of the epidural needle can occur in 0.5–1% of patients undergoing lumbar epidural injection.¹²³ When fluoroscopy is used, the injection of contrast can rule out any significant intravascular injection. Development of an epidural hematoma is a potentially dangerous complication of vascular injury. Any rapidly progressive neurological deficit or cauda equina syndrome should elevate the suspicion of the development of an epidural hematoma and CT/MRI scan should be done to rule this out.^190,¹⁹¹ The presence of an epidural hematoma should be dealt with by prompt surgical decompression.

Neurologic complications include dural puncture and injury to the cauda equina or nerve roots. The former has been discussed in detail earlier in this chapter. Direct nerve injury usually elicits painful symptoms. Therefore, increased pain during insertion of the spinal needle should alarm the interventionist to reconfirm needle placement to avoid possible nerve injury.¹²³ McLain et al.¹⁹² reported transient, profound paralysis after an epidural steroid injection, which was carried out without fluoroscopic control and was complicated by a puncture of the thecal sac. Radiographic studies suggested three possible explanations for the paralysis: (1) inadvertent thecal penetration during injection may have produced an atypical anesthetic block; (2) location of the injected fluid may have caused a transient compressive lesion; or (3) intrathecal injection may have produced an iatrogenic arachnoid cyst. Conscious sedation or general anesthesia prior to epidural injection can reduce the patient’s ability to provide optimal feedback to painful stimuli; thus, greater caution should be exercised while using them.^193,¹⁹⁴

Idiopathic complications of lumbar epidural steroid injections include acute retinal necrosis and retinal hemorrhage. The retinal adverse effects are related to rapid increase in intracranial pressure. Browning ¹⁹⁵ reported acute retinal necrosis following epidural steroid injections. Young¹⁹⁶ published a case report and literature review of transient blindness after lumbar epidural steroid injection and suggested strategies for prevention of this complication. This included avoidance of rapid injection into the epidural space and limiting of the amount of fluid injected during the procedure. Although these complications were noted with volumes of injectate as high as 20 mL, the literature fails to advocate ideal volume of injectate to avoid such complications.

Caudal epidural injections

Specific complications of caudal epidural steroid injections include dural puncture, infection, and effects of local anesthesia. Failure of correct needle placement has been reported to be as high as 25–40%¹⁹⁷^–²⁰⁰ using a blind technique. This can lead to the injection of air or fluid into subcutaneous tissues, periosteum, sacrococcygeal ligament, sacral marrow cavity, and pelvic cavity with the likelihood of penetrating the rectum or vagina. Renfrew et al.⁴⁸ reported 9.2% of vascular infiltration with caudal epidural injections. Figure 20.2 shows a case of vascular infiltration during a caudal epidural injection. Fluoroscopy can help recognize these potential pitfalls. El Khoury et al.²⁰¹ supported this, as they found the incidence of incorrect placement of needle during caudal injections was reduced to 2.5% when fluoroscopy was utilized. Dural puncture following caudal epidural injection is very rare. Although the thecal sac usually ends at the S2 bony level, in rare variants it may end as low as S4. Hence, the needle should not be placed superior than absolutely necessary to assure epidural injection.¹⁸⁸

The use of anesthesia in caudal injections can anesthetize the sacral nerve roots. This can lead to an increased incidence of urinary retention. The use of smaller doses of local anesthetic can minimize this complication without adversely affecting the efficacy of caudal epidural steroid injections when treating painful conditions.¹⁸⁸

Earlier literature mentions use of higher volumes of injectate for caudal epidural injections.^202,²⁰³ Surprisingly, the adverse effects noted with higher volumes of injectate during the interlaminar epidural approach do not necessarily translate to the caudal epidural approach. Cyriax²⁰³ reported on the use of 50 mL of procaine following 50 000 caudal injections and had only five adverse effects; one case of hypersensitivity, two cases of transient paraplegia, and two cases of chemical meningitis. All these recovered without any residual damage. Bogduk²⁰⁴ suggested volumes of 10 mL and 15 mL of epidural injectate are adequate to reach L5 and L4 levels, respectively, during a caudal approach.

Bryan et al.²⁰⁵ found that contrast reaches the L4–5 intervertebral level in 85% of patients with a volume of <8 mL during caudal approach.

Botwin et al.²⁰⁶ reported a 15.6% incidence of minor complications in fluoroscopically guided caudal epidural injections. The most common minor complications observed was 4.7% insomnia the night of injection, 3.5% nonpositional headache, 3.1% increased back pain at injection site, and 0.4% increased leg pain.

Lumbar transforaminal epidural steroid injections

Complications related to the lumbar transforaminal technique are relatively fewer as compared to the interlaminar technique. Lutz and Wisneski ²⁰⁷ as well as Kraemer et al.²⁰⁸ reported no dural punctures or any other major complications related to this technique. The placement of the needle in the safe triangle described by Derby et al.²⁰⁹ reduces the chances of dural puncture or nerve injury. Botwin et al.,²¹⁰ in their study of 322 lumbar transforaminal injections, reported a 9.6% incidence of minor complications, which were entirely transient and resolved without morbidity. Complications included postprocedural back pain at the injection site, increased leg pain, and transient leg weakness.

Slipman et al.,¹⁷³ in a prospective study of 217 lumbosacral nerve root injections, found no major complications but did report an immediate postprocedure incidence of 17.1% increased pain at injection site, 8.8% increased radicular pain, 6.5% light-headedness, 5.1% increased spine pain, 3.7% nausea, 1.4% non-specific headache, and 0.5% vomiting per injection.

The potential complications of lumbar transforaminal epidural injections include infection, dural puncture, nerve injury, and vascular infiltration. Furman et al.⁵⁰ reported an 11.2% incidence of intravascular injections in 761 transforaminal epidural injections with a significantly higher rate of intravascular injections (21.3%) at S1 level. They also concluded that contrast enhancement is mandatory to rule out vascular infiltration, as negative flash or aspiration was found to be unreliable. There have been reports of acute paraplegia following left-sided high lumbar transforaminal injections, possibly secondary to disruption of the artery of Adamkiewicz leading to anterior spinal artery ischemia and cord infarction.^189,²¹¹ The artery of Adamkiewicz is the principal blood supply to the lower spinal cord and like other radicular arteries typically enters the spinal canal along the anterior, superior aspect of the spinal nerve.²¹² The usual technique of placing a needle tip for a left transforaminal epidural injection at the mid-thoracic to upper lumbar region can place the artery of Adamkiewicz at risk. A modified technique has been suggested to keep the needle tip in the posterior, inferior location within the foramen in order to reduce disruption of the radicular artery.¹⁸⁵ More research is needed to reduce the risk of entering the artery of Adamkiewicz. Extreme caution should also be exercised in rare conditions such as far lateral/foraminal disc herniations where there can be likelihood of injecting the disc itself if the needle tip is too far medial in the intervertebral foramen.

Lumbar zygapophyseal joint injections

Potential complications include infections and inadvertent entry into intervertebral foramen or spinal canal causing dural puncture and/or nerve injury. Infectious complications range from delayed septic arthritis of facet joints to development of an epidural abscess.²¹³^–²¹⁵ The most often noted complication (2%) is transient exacerbation of pain.²¹⁶ Spinal anesthesia can occur if there is an abnormal communication between facet joint capsule and the thecal sac. Authors have reported chemical meningitis following facet joint blocks.^217,²¹⁸

Lumbar medial branch block/radiofrequency ablation

Potential complications of radiofrequency zygapophyseal denervation or medial branch block include infection, nerve root injury, and dural puncture. The reported complication rate for radiofrequency zygapophyseal denervation is quite low.²¹⁹^–²²³ Superficial infections and reactions to the local anesthetic are the most common complications incurred.²²⁴

In a recent study of 92 patients who received 616 radiofrequency lesions, six complications arose for a 1% complication rate per lesion site. Among these complications were three cases of localized pain at lesion site lasting more than 2 weeks and three cases of neuropathic pain lasting less than 2 weeks.²²⁵

Lumbar discography

Potential complications of discography include nerve root injury, dural puncture, intradural injection, meningitis, arachnoiditis, intrathecal hemorrhage, and discitis. Discitis is the single most significant complication of discography with the incidence ranging from 0% to 4.9%.^2,^224,²²⁶^–²²⁹ Osti et al.²²⁷ performed a prospective clinical study of 127 patients treated with intradiscal cefazolin 1 mg/mL mixed with diatrozoate contrast. None of these patients developed discitis. Klessig et al.²³⁰ indicated that intradiscal antibiotics mixed with iohexol provided adequate antibacterial prophylaxis against discitis. Use of intradiscal antibiotics has been recommended as an integral part of practice guidelines issued by the International Spinal Injection Society.²³¹ Other rare complications of discography include vascular injury, retroperitoneal hemorrhage,²³² disc herniation,²³³ and pulmonary embolism.²³⁴ DeSeze²³⁵ and Bernard²²⁸ have raised the possibility of discography causing degenerative changes; however, various other studies have disputed these claims.²³⁵^–²³⁸ There has been a case of seizure and death from an inadvertent injection of 12.5 mg/mL of cefazolin intrathecally during a discogram at L5/S1.²³⁹

Lumbar intradiscal electrothermal annuloplasty/nucleoplasty

Potential complications of intradiscal annuloplasty would include those incurred with discography. Reported complications of intradiscal electrothermal annulopasty (IDEA) include cauda equina syndrome ²⁴⁰ and disc herniation.²⁴¹ There have been no reports of infection, bleeding, or other equipment- or technique-related complications so far mentioned in the literature.^242,²⁴³ Cohen et al.,²⁴⁴ in their study of 78 patients treated with IDEA, reported a 10% incidence of transient complications ranging from paresthesia radicular pain to weakness.

No complications have been reported in two prospective outcome studies evaluating percutaneous disc decompression using nucleoplasty.^245,²⁴⁶

Lumbar sympathetic blocks

Potential complications of lumbar sympathetic blocks consist of accidental spread of anesthetic to the neuraxis causing a blockade of somatic nerves (lumbar plexus). Vascular injury/infiltration, lymphatic infiltration, or nerve root injury can occur as well.²⁴⁷^–²⁵² If the transverse process is mistakenly identified as the vertebral body, and a large volume of drug is injected into the intervertebral foramen, an ipsilateral lumbar plexus block and/or epidural spread of solution may occur. Therefore, authors advocate diluting the concentration of anesthetic so as not to produce motor blockade.²⁴⁸ Anterior advancement of needle has the potential danger of penetrating either the aorta or the inferior vena cava where injection of local anesthetic could produce systemic toxicity.²⁵² Fluoroscopic guidance can help minimize these potential complications.