Central Herniated Disc

Clinical Vignette

A 68-year-old, part-time musician suddenly fell as he was reaching for his morning newspaper while standing on an icy, hilly driveway. He was paralyzed from his neck down, and he noted numbness in all extremities. He recalled a brief involuntary ballistic movement of his right arm. A diagnosis of a brainstem stroke was made at the local hospital as it was presumed that the stroke led to his fall. Brain computed tomography (CT) was normal. Within a few days, he recovered some right-sided motor function.

The family sought a second opinion at Lahey Clinic. Here he had a left > right quadriparesis, bilaterally brisk muscle stretch reflexes, left Babinski sign, and a midcervical right-sided sensory level for pain and temperature with preserved position sense, an exaggerated Brown–Sequard syndrome. MRI demonstrated a centrally herniated nucleus pulposus at C3–C4 with spinal cord compression, contusion, and a severe stenotic spondylotic lesion at that level. Emergency surgical decompression was performed. He had a gradual increase in function; within 1 year he could perform most activities of daily living independently, although his finger dexterity for clarinet playing was not back to his preinjury level.

In retrospect, he had sustained a syncopal event secondary to a cardiac arrhythmia. The fall per se led to the spinal column injury, the extruded central disc and cord injury. A careful neurologic examination sorted out the site of pathology and led to the diagnostic and therapeutic triumph!

Comment: Initially, this patient was thought to have a basically untreatable brainstem stroke, that is, a lesion in an entirely different part of the neuraxis. A more careful subsequent clinical examination, lying the patient on his side and examining for a specific sensory level, was the key to diagnosis, as patients with brainstem stroke rarely have total loss of sensory function in a spinal cord–level distribution (see Figs. 44-11 and 44-12).

Acute spinal cord injuries, with subsequent paraplegia or quadriplegia, are among the most dreaded sequelae to a serious bodily injury (Box 45-1). There is a tragic propensity for traumatic myelopathies to occur among vigorous and healthy young persons. Automobile and motorcycle accidents as well as sports injuries are the most common etiologies. Gunshot wounds, whether resulting from war, accident, or assault, are another source of traumatic spinal cord injury.

Box 45-1 Acute Extradural Extramedullary Myelopathies

• Trauma

• Metastatic bone tumors with secondary invasion of the epidural space:

• Breast

• Lung

• Prostate

• Kidney

• Colon

• Thyroid

• Myeloma

• Plasmacytoma

• Lymphoma

• Epidural abscess with disc space infection

• Disc herniation affecting central cord

• Arteriovenous malformation

• Hematoma epidural,

• Subdural hematoma as acute intradural extramedullary

Cervical spinal fracture dislocation with resultant ligamentous tear, allowing bony fragments to directly tear or transect the spinal cord, is the common denominator in this setting (Fig. 45-2). Sometimes, there is concomitant compromise of the spinal arteries causing an associated spinal cord infarction, hematomyelia, or both. Typically, in the acute setting, spinal shock results with complete paralysis, loss of sensation, areflexia distal to the trauma site, and loss of bladder and bowel function.

Figure 45-2 Trauma.

Occasionally, these traumatic spinal lesions are amenable to immediate surgical correction or external traction (Chapter 60). Prognosis is always guarded. Once emergent management is completed, these patients are cared for at specialized spinal rehabilitation centers. Treatment of autonomic and sphincter dysfunction has greatly improved the long-term survival for many patients. Spinal cord repair, leading to functional recovery, is one of the greatest challenges for 21st-century neuroscientists.

Among senior citizens, unexpected falls at home, as in the above vignette, may lead to an acute central disc protrusion. Their inherent gait instability secondary to chronic neurologic or orthopedic handicaps make them susceptible to tripping on stairs, rugs, or door jams. Cardiac bradyarrhythmias leading to syncope, or epileptic seizure, with sudden loss of consciousness have a similar risk of serious spinal cord injury.

As these lesions are eminently treatable with neurosurgical intervention, consideration of these less common lesions is vital in patients who have sudden unexplained falls leading to immediate paralysis. Anatomically, the extruded disc compressed the anterior spinal cord between two vertebral bodies. Occasionally, these lesions present subacutely or chronically. Because associated bony pain or tenderness may be present, these lesions often mimic metastatic or primary tumors. However, if the patient does not have a history of malignancy, a benign mechanism, such as a central disc, must be sought (Figs. 45-3 and 45-4). Rarely, a dural arteriovenous malformation (AVM) or spinal epidural hematoma (SEH) mimics this clinical picture.

Figure 45-3 Cervical Disc Herniation.

Figure 45-4 Idiopathic Spinal Stenosis.

Surgery is the treatment of choice. Prognosis depends on the degree of cord compromise before surgery, the acuity of the event, the patient’s general health status, and the disc location. Cervical lesions are treated by a neurosurgeon, although a combined approach with an orthopedic surgeon is sometimes indicated. When the central disc is in the thoracic cord area, a combined neurologic and thoracic surgical approach is required.

Clinical Vignette

A 60-year-old man with diabetes and a recent history of dental extractions developed lumbar and soon thereafter thoracic spine pain. During the next 2 days, his pain worsened even while lying in bed. Neither meperidine, a narcotic agent, nor a muscle relaxant relieved his pain and paraspinal muscle spasm. His difficulties rapidly worsened as he began to have trouble walking, lost sensation in his legs, and became unable to urinate.

Neurologic examination demonstrated an acutely ill febrile individual with a flaccid paraplegia, brisk muscle stretch reflexes at the knees, bilateral Babinski signs, loss of position sense in the feet and a cord level to both pin and temperature sensation at T6. There was percussion tenderness over his upper thoracic spinous processes. MRI demonstrated an extensive epidural collection extending from C6 to T10. Emergency laminectomy was performed, which demonstrated a purulent epidural abscess. Despite the emergent surgery, the patient was still significantly limited a few months later.

Epidural spinal abscess is a rare clinical process occurring in 2–20 cases per 100,000 hospital admissions. Its incidence appears to be increasing; these are usually seen in middle-aged adults, more often men. Despite its rarity, the potential for an epidural abscess to cause permanent paraplegia makes it one of the most urgent spinal cord emergencies (Fig. 45-6). Even though back pain is such a ubiquitous and usually benign process, it is very important for any physician to consider the potential diagnosis of an epidural abscess in every patient presenting with acute and increasing back pain, especially when febrile. The epidural space in the posterior thoracic cord is the primary site for an epidural spinal abscess to develop. These may extend to the cervical cord and rarely into the lumbar spine. Experimental studies suggest that the mass effect of the abscess, leading to cord compression, is the important clinicopathologic mechanism.

Figure 45-6 Epidural Abscess and Epidural Hematoma.

Staphylococcus aureus is the predominant etiologic microorganism leading to epidural spinal abscesses. Usually a distant septic focus provides bacterial seeding via the bloodstream, for example, skin furuncles, dental abscesses, simple pharyngitis, or a recently infected traumatic site (see Fig. 45-6). Often there is a concomitant history of diabetes mellitus, alcoholism, drug abuse, or recent spinal or extraspinal trauma. Less commonly, epidural spinal abscesses develop subsequent to vertebral osteomyelitis, pulmonary or urinary infection, sepsis, or extremely rarely bacterial endocarditis. Invasive procedures, including epidural anesthesia, spinal surgery, vascular access lines, and paravertebral injections, also provide potential mechanisms for bacterial seeding. Corticosteroid therapy may contribute to immune suppression and the possibility of secondary nosocomial infections.

Percussion tenderness over the posterior spinal processes, as well as fever, are important diagnostic clues compatible with an epidural spinal abscess Some of these individuals also develop signs of meningeal irritation such as Kernig’s sign. A rapidly developing combination of motor, sensory, and sphincter dysfunction then occurs. Often the patient becomes paraplegic and demonstrates a spinal cord sensory level. The differential diagnosis includes acute central disc, epidural metastasis often with acute pathologic fracture, and spontaneous or anticoagulation-induced hematoma.

An urgent MRI easily identifies the epidural abscess. Concomitantly, there may be a highly elevated C-reactive protein and erythrocyte sedimentation rate, often >70 mm/hour, with a modestly elevated WBC count. Emergency surgical decompression is the treatment of choice. Occasionally when no significant neurologic compromise exists, antibiotics are the primary treatment. However, careful follow-up is indicated as the patient’s clinical picture may rapidly evolve with motor and sensory loss leading to need for another MRI and surgical intervention.

Prognosis depends entirely on the patient’s expeditious presentation to a medical facility and the clinician’s level of suspicion leading to relatively early diagnosis of the epidural spinal abscess. If treatment is not initiated until after the patient becomes paraplegic, prognosis is extremely guarded.

Clinical Vignette

Right arm weakness acutely developed in a 30-year-old woman. In retrospect, she had noted some numbness in that arm for the past 3 months, and 16 months earlier she experienced blurred vision in her right eye, with intermittent dizziness. She also had experienced episodic momentary electric shock, lightning-like sensation radiating to her buttocks often precipitated by bending her neck. Hot weather was more uncomfortable for her as she reported worsening of these symptoms and nonspecific fatigue. She had a slightly spastic left-sided gait, increased muscle stretch reflexes with a left Babinski sign, poor left-side position sense, and reduced pin and temperature sensation over her right arm and thigh.

Cervical spine MRI demonstrated an area of increased signal with ill-defined enhancement located posteriorly and on the left side of the cord (Fig. 45-7A). Brain MRI with and without gadolinium demonstrated a few periventricular lesions and other abnormalities oriented perpendicularly along vessels (Dawson fingers) within the corpus callosum. Visual evoked responses (VERs) were prolonged for her right eye. Her cerebrospinal fluid (CSF) was significant for 10 white blood cells (99% lymphocytes, 1% monocytes), and the presence of oligoclonal bands that was not identified in her serum.

Figure 45-7 Myelitis Secondary to Neuromyelitis Optica (Devic) and Multiple Sclerosis.

The brief sensation of an electric shock running out the arms or down the back when a patient bends their neck is known as the Lhermitte sign. It is a classic symptom of cervical spinal cord posterior column pathology. Although most commonly seen in MS, because of the high incidence of this disorder, it is a non-specific symptom that is also seen in other intramedullary lesions such as vitamin B₁₂ deficiency, or a number of extramedullary lesions causing cord compression.

Comment: This vignette presents a classic clinical picture of early multiple sclerosis (MS). The patient has an incomplete demyelinating myelitis consistent with classic hemicord syndrome, affecting ipsilateral motor and proprioceptive function and crossed sensory fibers. This is known as the Brown–Sequard syndrome. However, she also had involvement of her right arm, implying extension into the right anterior horn. The presence of the subclinical brain MRI abnormalities, as well as the prolonged VERs, point to multiplicity of demyelinating lesions in time and space consistent with the diagnosis of MS (Table 45-1).

Table 45-1 Acute Intradural Intramedullary Myelopathies

Clinical Vignette

An obese septuagenarian, with previously diagnosed diabetic polyneuropathy manifested by burning discomfort in his feet, presented with a 4- to 6-month history of increasing leg numbness. These new symptoms were totally different from the mild tingling and burning that had been chronically present for the past 10 years. He began to require a cane to maintain his equilibrium when walking. Although he initially tolerated the newer symptoms, he began to be concerned that he could not walk safely without relying on a walker. He sought further medical opinion. He previously had a myocardial infarction.

Neurologic examination demonstrated a broad-based, spastic gait, brisk muscle stretch reflexes, and bilateral Babinski signs. Pinprick and temperature sensation were reduced in a stocking-glove distribution in his legs. There was a question of a bilateral cord level to pin sensation at C-7. Position sense was absent at the toes, and vibratory sense lost at the ankles.

MRI revealed spinal stenosis and cord edema at C5–C6. He had severe spinal stenosis with multilevel spondylosis, disc protrusion, and end-plate osteophytes. After a 3-month period of observation, his gait difficulties increased. A cervical posterior laminectomy was performed. Subsequently, after a period of rehabilitation hospitalization, he gradually regained the ability to walk independently.

One needs to always carefully evaluate the patient with a chronic primary sensory polyneuropathy who begins to develop disproportionately increased gait difficulty. Cervical spinal stenosis is a common chronic disorder. As occurred in this instance, one may define a quite remediable condition.

Spondylosis, a normal aging process, is the most common cause of a cervical myelopathy (Figs. 45-9 and 45-10; Box 45-2). This results from disc degeneration followed by reactive osteophyte formation, fibrocartilaginous bars, spondylotic transverse bars, articular facet hypertrophy, and thickening of the ligamentum flavum causing spinal canal narrowing. Subsequently, gradual spinal cord compression may occur; it is particularly likely in patients having congenitally narrowed spinal canals. In its simplest form, a chronically herniated central nucleus pulposus in patients with congenital stenosis can produce a cervical myelopathy. Although many senior individuals have radiographic signs of cervical spondylosis, most are asymptomatic. When a myelopathy develops, clinical findings can present acutely, subacutely, or over many years. Sometimes both a cervical myelopathy and adjacent radiculopathy may occur in the same spondylotic patient.

Figure 45-9 Cervical Spondylosis.

Figure 45-10 Imaging of Ossification of Posterior Longitudinal Ligament (OPLL).

Pathophysiology and Etiology

Typically, the spinal canal is 17–18 mm in diameter between C3 and C7. A narrower cervical spinal canal may range from 9 to 15 mm; however, a compressive spondylitic myelopathy rarely occurs when the canal diameter is >13 mm. Cervical cord diameter ranges from 8.5 to 11.5 mm, averaging approximately 10 mm. Disc protrusion and other reactive and degenerative processes further reduce canal dimension. Direct cord compression, compromised blood supply to the cord or venous stasis, and other mechanical factors, such as rheumatoid arthritis, can in combination or independently cause irreversible damage.

Normally, the spinal cord moves cephalad and posteriorly within the canal during neck flexion and caudally and anteriorly during neck extension. If osteophytes, discs, and hypertrophied ligaments make contact with the cord, the cord sustains additive trauma, leading to development of a clinical myelopathy. The disc levels affected are C5–C6, C6–C7, and C3–C4, in order of their clinical frequency.

In this setting, the spinal cord may become pathologically, grossly flattened, distorted, or indented. Demyelination of the lateral columns occurs at the lesion site with consequent lateral column degeneration below the lesion. Concomitant dorsal column degeneration occurs at and above the damaged segment(s). There may also be damage and loss of nerve cells in gray matter. Ischemic changes, gliosis, demyelination, and even cavitation necrosis sometimes also result.

Clinical Presentation