Thoracic Pain Syndromes

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CHAPTER 74 Thoracic Pain Syndromes

Thoracic pain accounts for approximately 5% of all referrals to the authors’ pain clinic in a University Hospital in the Netherlands,¹ which is consistent with that of other clinics.² Thoracic pain has a varied spectrum of possible etiologies including visceral pain from cardiac and lung pathology to pain from intra-abdominal organs (upper abdominal organs such as gall bladder and pancreas may be referred to the chest). In the lower thoracic regions pain must be differentiated from renal pathology.³ Pain from C5 may be referred over the anterior chest, while pain from C6, C7, and C8 may be referred to the scapular region.

Thoracic pain may have an underlying pathology such as disc herniations, aneurysms, tumors,⁵ postoperative sternal wound infection,⁶ trauma,⁷ old fractures, or herpetic infections,⁸ and stress fractures in athletes.^9,¹⁰ Chronic postsurgical pain has been described following many different operations, most notably thoracotomy, mastectomy, and coronary artery bypass grafting (CABG) postsurgical pain syndromes.¹¹^–¹⁵

However, in most cases of thoracic pain there is no specific pathology identified as the cause of the pain and by default the pain is judged to be of spinal origin, emanating from nociceptive nerve endings in the periosteum, ligaments, discs, or joints.¹⁶

Diagnostically and clinically, thoracic pain can be divided into thoracic mechanical joint pain and thoracic segmental pain. An appreciation of the intricate anatomy of the thoracic spine is required to understand the various pain syndromes of the thoracic spine. It is somewhat surprising that there is any mechanical pain in the thoracic spines since it is a relatively immobile section of the spine. The range of motion for both flexion and extension is of the order of 10°, and lateral flexion is minimal. Rotation of the thoracic spine provides the only meaningful movement of the thoracic spine. Pain in the thoracic region may come from the articulations with ribs, costovertebral joints between the rib and the vertebral body, and the costotransverse joints between the transverse process and tubercle of the rib. The costotransverse joints are absent at T1, T11, and T12.

THORACIC MECHANICAL PAIN FEATURES

Clinical syndrome

Thoracic mechanical pain includes pain from both thoracic facet joints and thoracic discs.

Pain emanating from thoracic facet joints is usually related to degenerative processes, vertebral collapse, and continuous mechanical straining.¹⁶^–¹⁸ The initial problem can be in the facet joint but may be elsewhere in the spine.¹⁹ As with lumbar and cervical facet syndromes there are no specific criteria which have been established whereby facet joint pain could be diagnosed based on patient’s history and/or physical examination. A diagnosis of thoracic facet joint syndrome can be made based on similarity of symptoms to lumbar and cervical facet syndromes.

Extensive examination should be performed to exclude any other pathology as a primary cause for the patient’s signs and symptoms.

In 1993, Stolker et al. defined ‘major’ and ‘minor’ criteria for the diagnosis of thoracic facet joint pain.¹⁸

Major criteria include:

1 Continuous or nearly continuous unilateral or bilateral paravertebral pain in a distinct thoracic area of the back, in the absence of objective neurological signs.

2 Tenderness over paravertebral muscles in the same region by palpating the facet joints.

Minor additional diagnostic criteria include:

1 Exacerbation of all complaints following back movements, most notably hyperextension and rotation.

2 Pain aggravated more in sitting position than in other positions.

3 Localization of radiation (if present) in more than one segment but not extending through a complete segment.

4 Decreased or absent mobility in the painful region of the back

5 Radiological signs (although uncommon) may illustrate slight rotation and curvature of the vertebral column.

When thoracic spinal pain becomes chronic and resistant to conservative modalities of treatment such as physical therapy, pharmacological therapy, and transcutaneous electric nerve stimulation (TENS), more aggressive treatment of thoracic pain including radiofrequency ablation of the facet joints can be considered.

Indications for radiofrequency procedures

These criteria were the basis for a study by Stolker et al. when they evaluated 40 patients who had a diagnosis of thoracic facet syndrome based on the above-mentioned criteria. These patients underwent percutaneous facet joint denervation (PFD). Included were 24 left sided, 21 right sided and 6 bilateral cases. Seven study patients underwent two sessions and two patients had three PFD sessions. Eighty-two percent of patients had 50–75% pain relief at 2 months. Four patients were lost to long-term follow-up (18–54 months; mean 31 months). Forty-four percent of study patients were pain free while 39% had a 50% or greater reduction in their pain.¹⁸ Interestingly, considering that these criteria were non-specific for thoracic facet syndrome, all patients in this study had positive diagnostic blocks performed prior to radiofrequency ablation. Stolker et al. attributed the results to the consistent course that the medial branch of the dorsal rami of the thoracic spinal nerves travel as they leave the intertransverse space; however, the anatomical target point (junction between the superior articular process and the transverse process) utilized in their study is at variance with the anatomical course of thoracic medial branch described by Chua and Bogduk.²⁰

Chua and Bogduk reported that the medial branch crosses the superolateral corner of the transverse processes and then passes medially and inferiorly along the posterior surfaces of the transverse processes, before entering the multifidus muscle which it supplies.²⁰ Chua and Bogduk have called for the need for a double-blind, controlled clinical trials of Stolker et al.’s approach to thoracic facet nerve denervation or modification of their procedure so as to be consistent with the surgical anatomy of the thoracic medial branches.²⁰

In another study by Tzaan and Tasker in 2000 which evaluated 17 patients with thoracic facet syndrome, 15 patients had satisfactory pain relief at follow-up with 2 patients having their procedure repeated.²¹

Pevsner et al. evaluated radio frequency ablation in 122 patients with mechanical spinal pain at cervical (20%) and thoracolumbar (80%) levels. At 1-year follow-up 63% had good results (at least 50% decrease in pain levels) and 37% had no effect (<30 % reduction in their pain levels).²²

Side effects and complications

Spinal thermocoagulation procedures are generally free from side effects other than local contusion and edema at the needle sites. The most common side effect was sensory loss and neuropathic pain in the distribution of the cutaneous branches of the posterior rami.²¹ Minor complications occurred in 27 patients (22%) who had transient discomfort and burning pain.²²

Serious complications of radiofrequency are fortunately rare when optimum target point needle positioning is utilized, i.e. in the lateral facet line on the anteroposterior (AP) projection and posteriorly in the foramen on the transverse projection.

Outcomes

While the evidence base is low in the management of thoracic facet pain there is evidence to support the use of percutaneous radiofrequency procedures as therapy.^18,^21,²²

THORACIC DISC LESIONS

Clinical syndrome

Thoracic disc lesions account for 0.5–2% of all disc lesions.^23,²⁴

Symptomatic disc disease is thought to be an uncommon problem with a prevalence of asymptomatic cases of 14.3%.²⁵ Degenerative disc disease is more commonly found in the lower thoracic spine with the upper third (T1–2 to T4–5) being the least affected area.^26,²⁷ However, T1–2 is the most common level affected when the upper thoracic spine is involved.²⁸

Recently, Arana et al., in a study of 156 patients with cervical disc pain, reported that 13.4% of these patients had degenerative changes in the upper thoracic spine, most notably at T2–3, with correlation between degenerative disc contour at the C7–T1 level and T1–2, T2–3, T3–4.²⁹

Girard, in another study, evaluated temporal changes in thoracic disc in 40 patients with pain.^29a Baseline presence of disc herniation was 10%, degenerative disease 14%, endplate marrow signal alteration 2.3%, Schmorl’s nodes 9.6%; follow-up was 4–149 weeks. Repeat scan revealed a new incidence of disc herniation of 1.5%, degenerative disc disease 2%, all findings predominated in the lower thoracic vertebrae T6–10. Herniations showed the most ability to modify over time with just over one-quarter (27%) showing change. Schmorl nodes showed the least change over time.²⁹

While the majority of prediction indicator studies have been done on lumbar spine, one can infer that a similar clinical picture holds for the thoracic spine. A tissue can only generate pain if it is innervated. In a normal human lumbar disc, nerve endings can only be found in the periphery of the outer anulus at a depth of a few millimeters.³⁰ In highly degenerated discs nerves may even penetrate into the nucleus pulposus.³¹ Most of these nerve fibers, which are identified by immunohistochemistry, accompany blood vessels relating probably to vasoregulation. Another set of neural fibers has been found in the nucleus of painful discs of those undergoing anterior fusion surgery for low back pain. These neural structures express substance P and have a morphology of nociceptive nerve terminals. These findings emphasize the role of nerve terminals of the degenerated disc in the pathology of back pain and make the distinction between painful disc disease and nonpainful disc disease degeneration more plausible.

Discography has been regarded as the gold standard in the diagnosis of discogenic pain. Discographic studies have shown that only annular ruptures extending to the outer anulus reproduce exact or similar pain to that previously described by the patient.³² Discography has been widely used to study and compare to magnetic resonance imaging (MRI) findings of patients with discogenic pain. In addition to annular ruptures, potential discogenic signs on MRI include high intensity zones (HIZs) lesions and endplate degeneration known as modic changes.³³ HIZ lesions are not as useful in predicting which individuals will have discogenic pain³⁴ compared with modic changes which are a more reliable imaging predictor of discogenic pain.³⁵ Thoracic discography has been utilized by Schellhas et al. in a study of 100 patients with clinical pain and MRI imaging with morphologically abnormal thoracic disc(s). Abnormal thoracic discs on MRI and at least one control disc adjacent to the abnormal discs were injected with nonionic contrast or normal saline, X-rays were obtained, and pain was rated in intensity from 0 to 10. Discs with annular tears were found to be painful approximately 75% of the time (with a clinical concordance of 50%). Control discs were invariably painless. Schellhas et al. concluded that thoracic discography can be performed safely as a tertiary diagnostic procedure to determine if degenerated discs on MRI studies are related to clinical complaints.³⁶ In another study, the Wood et al. evaluated 10 healthy volunteers using MRI and four-level discography. Provocative responses were graded from 0 to 10. The mean pain response was 2.4/10; however, three discs were intensely painful, on MRI 27 discs of 40 were abnormal with endplate abnormalities, annular tears, and/or herniations. In parallel, they evaluated 10 adults, without pending litigation who had thoracic pain; the mean pain response was 6.3/10 on discography. Twenty-four discs were concordantly painful of the 48 discs studied, and MRI revealed that 21 discs were normal; however, on discography only 10 were judged as normal. Schellhas et al. concluded that thoracic discs with prominent Schmorl’s nodes may be intensely painful even in lifelong asymptomatic individuals but the pain is concordant.³⁷

Thoracic intradiscal pressure has been evaluated as an aid in to understanding the biomechanics of thoracic spine.³⁸ Although discography is the gold standard in the diagnosis of discogenic pain, it is an invasive procedure and not employed for routine diagnosis. Unfortunately, in the chronic low back pain patient population no clinical discriminator has been found that can differentiate discogenic from nondiscogenic back pain.³⁹ The bony vibration test, whereby a small hand-held vibrator is used to produce pain provocation, similar to that in discography, has been tried as a noninvasive pain provocation method to be used in combination with MRI in identifying symptomatic disc pathology.⁴⁰

Genetic variations in collagen IX and aggrecan have been held accountable for lumbar disc disease, it is highly probable that similar variations will be accountable for thoracic disc disease.⁴¹

Indications for therapies in discogenic pain

Treatment programs for discogenic pain include stabilization of the symptomatic motion segments in order to eliminate painful motion,⁴² but the external validity of spinal fixation is now being compared with conservative care. The results of randomized, controlled trials do not unequivocally support the use of spinal stabilization procedures.^43,⁴⁴ Video-assisted thorascopic (VAT) surgery has been reported to be successful in thoracic disc herniations. Anand and Regan evaluated 100 patients with a minimum of 2 years’ follow-up after VATs for thoracic disc herniation. They reported an overall 84% satisfaction rate with long-term clinical success rate of 70% in this study population.⁴⁵ The role of intradiscal electrothermal therapy (IDET) has an exciting prospect as future therapy for the management of discogenic pain as an alternative to spinal fusion in selected patients. To date, IDET has been only described in the management of lumbar disc pain. This may prove especially useful for the young patient with preserved disc height and patients with inoperable multilevel disease.⁴⁶ However, its effects have been described predominantly in lumbar disc pain to date.⁴⁷ The long-term benefits of IDET therapy still have to undergo the rigorous of clinical trials,⁴⁸ but for the present its role is as an antecedent rather than alternative to spinal fusion.

Side effects and complications

Spinal stabilization procedures are associated with the usual postoperative complications including blood loss and infection. Neurological complication secondary to vascular compromise is fortunately very rare.⁴⁹

Outcomes

For the present, surgical stabilization procedures and conservative management programs form the mainstay of therapy in treating thoracic discogenic pain. The role of IDET is for the present restricted to lumbar disc pain. However, IDET seems a promising therapy, but scientific data regarding the pathophysiology, biologic effects, and clinical results are relatively scarce. Early biomechanical and histological investigations into the effects of IDET are conflicting. However, in early prospective human trials, IDET seems to provide some benefit with low risk. IDET is a potentially beneficial treatment for internal disc disruption in carefully selected patients as an alternative to spinal fusion. More basic science and clinical research with long-term follow-up evaluation is necessary.⁴⁸ Emerging therapies with monoclonal antibodies are only at a conceptual stage and it will be many years before they are adopted as meaningful therapeutic options in the management of discogenic pain.

THORACIC SEGMENTAL PAIN SYNDROMES

Clinical syndrome

Thoracic segmental pain syndromes have many etiologies including disease and/or lesions of ribs, disorders of the thoracic skeletal spine (fractures, arthritis, metabolic disorders, and tumors), or neuropathies originating from spinal roots, spinal nerves, or intercostal nerves.¹⁶ Some thoracic segmental pain syndromes are iatrogenic postsurgery, such as post-thoracotomy and postmastectomy syndromes and scar tissue pain after upper gastrointestinal surgery.¹²^–¹⁵ Percutaneous thoracic sympathectomy is considered the most efficacious for sympathetic mediated pain, Raynaud’s syndrome, hyperhidrosis, and vasculopathy.⁵⁰ Percutaneous radiofrequency adjacent to the thoracic dorsal root ganglion (DRG) has been described for segmental nerve pain related to intercostal pain, rib tip syndrome, twelfth rib syndrome, vertebral collapse, and segmental peripheral neuralgia.

Indications for percutaneous radiofrequency lesioning

Stolker et al.⁵¹ evaluated 45 patients with thoracic segmental pain who fulfilled the following criteria:

1 Patients had radiating pain in the thoracic region that followed a segmental pattern.

2 No response to conservative therapy including pharmacological, physical therapy, and transcutaneous electrical nerve stimulation.

3 Symptom duration longer than 6 months.

4 No causal therapy was available.

5 Temporary response to an intercostal blockade with lidocaine.

Exclusion criteria included patients with loss of sensation in the painful area, such as postherpetic neuralgia, those with major psychiatric illness, and those awaiting a compensation liability suit in progress.

Clinical diagnoses included intercostal neuralgia, post-thoracotomy pain syndrome, postmastectomy pain syndrome, twelfth rib syndrome, rib resection, osteoporosis, vertebral metastasis, and traumatic collapsed vertebra. The 45 patients participating in this study underwent 53 percutaneous radiofrequency procedures adjacent to the dorsal root ganglion, 37 at one level, one patient bilaterally at one level, and seven patients at two levels unilaterally. At first evaluation (using a five-grade evaluation scale) 2 months postprocedure, 66.7% were pain free, 24% obtained more than 50% pain relief, and 9% obtained no pain relief. Four patients were lost to long-term follow up (died from their malignant disease). After a follow-up of 13–46 months (median 24 months) 49% were pain free, 37% had good pain relief, and 14.6% had no pain relief.⁵¹

The authors of this study advocate prognostic lidocaine blockade as essential to (1) confirm the diagnosis of segmental pain, (2) determine appropriate level of treatment, and (3) assess potential benefit of percutaneous radiofrequency adjacent to the dorsal root ganglion.

In a similar study, van Kleef et al.¹ evaluated effects of a single-level radiofrequency lesioning adjacent to the dorsal root ganglion in thoracic segmental pain. In this study, 43 patients were evaluated with a minimum of 6 months’ history of unilateral thoracic segmental pain unresponsive to conservative therapies. Twenty-seven of the patients had pain in the distribution of one or two segments (group I) only, while 16 patients had pain in more than two segmental levels (group II). Short-term analysis at 8 weeks postprocedure showed patients in group I were pain free or had good pain relief in 52% of patients, while only 18% of patients in group II were pain free or had good pain relief. Long-term follow-up (36–168 weeks; mean 99 weeks) demonstrated freedom from pain or good pain relief in 37% of patients in group I while only 18% of patients in group II at long-term follow-up (40–160 weeks; mean 128 weeks) were pain free or had good pain relief.

Side effect and complications

In the study by Stolker et al., 13% of patients suffered a transient burning pain that subsided within 3 weeks. Four percent of patients suffered a slight sensory loss in the corresponding dermatome, the sensory loss resolved in 3 months. There was no motor loss and no incidence of pneumothorax.⁵¹ In the study by Van Kleef et al., a similar side effect profile was noted with 16% suffering a slight burning pain in the treated dermatome; in addition, 16% of patients had slight hypoesthesia in the treated dermatome at initial follow-up. These side effects had resolved by 12 weeks postprocedure. There was no dysthesias or pneumothorax.¹

It is interesting to note in both studies that dorsal root ganglion lesioning above T7 was performed via a hole drilled in the lamina. This was done because the angle of the ribs prevent accurate passage of a needle. A more lateral approach could have been employed in these studies to approach the foramen but, due to the proximity of the pleura, there was a substantial risk of pneumothorax and neither group of authors felt such a technique was justifiable. Complications can occur. Ischemic spinal cord lesions have been reported previously,⁵² which describe percutaneous radiofrequency lesioning provoking an ischemic lesion on the opposite side to where the lesion was made and one segment lower in two patients. The authors postulated that the lesion was secondary to a ‘steal’ of the local circulation due to the percutaneous radiofrequency spinal lesioning. However, both of these complications were in elderly patients with cardiorespiratory and general vascular disease. Even though radiofrequency is advocated in elderly patients, they are at a higher risk of complication than in the healthy population. When performing radiofrequency procedures, one must be mindful of the blood supply in the thoracic region of the spinal cord. The upper and lower areas are well supplied, but the midthoracic region (T5–8) has poor circulation; the arteries are smaller and less numerous, leaving this region more vulnerable to ischemic lesions.⁵³