The classic presentation of myelopathy is numbness and clumsiness of the hands in association with a stiff, spastic unsteady gait. Patients with CSM generally report neck stiffness; unilateral or bilateral deep, aching neck, arm, and shoulder pain; and possibly stiffness or clumsiness while walking. Patients sometimes report greater difficulty walking at night, owing to reduced proprioceptive input.

CSM usually develops insidiously and with a stepwise “stuttering” progression. In the early stages of CSM, complaints of neck stiffness are common because of the presence of advanced cervical spondylosis. Other common complaints include crepitus in the neck with movement; brachialgia, which is characterized as a stabbing pain in the preaxial or postaxial border of the arm, elbow, wrist, or fingers; a dull, achy feeling in the arm; and numbness or tingling in the hands. Symptoms may be asymmetric, particularly in the legs. Loss of sphincter control or frank incontinence is rare; however, some patients may complain of slight hesitancy on urination.

The clumsiness experienced in the hands reflects the neuroanatomy of the efferent innervation of the hand musculature. The corticospinal tracts and extrapyramidal system travel down the posterolateral funiculus of the spinal cord to synapse with internuncial neurons two to three segments above the primary motor neuron. For example, intrinsic muscles of the hand are driven by motor fibers descending down the corticospinal tract to end and synapse with internuncial neurons as high as C5 and C6. Here, there is an internuncial neuronal pool with a variety of both inhibitory and facilitatory influences from the local afferent input. The internuncial neuronal pool then feeds down the cord to the anterior horn cells at the C8 cord level. Here, the anterior horn cell output is modulated and emerges as the final output from C8 and T1 and goes to the hand. If the internuncial neuronal pool is disrupted, normal coordination and smoothness of hand function is disrupted, and clumsiness appears. With disruption of the neuronal pool higher in the spinal cord, the hand can appear as if it has a lower motor neuron disease. Within the cervical enlargement with its corresponding large quantity of gray matter in the cervical cord, disruption of the internuncial neurons can lead to the classic symptoms of numbness and clumsiness, which are difficult to fit with a single radicular pattern. This is an important part of the myelopathy and is termed myelopathy hand. OPLL as high as C2 can present with this clinical finding. Loss of hand dexterity, with painful dysesthesias and difficulty in writing, is common. The syndrome of myelopathy hand may be the most important indicator of a good response to surgery.

In patients with myelopathy, the cord signs and symptoms generally outweigh the focal radicular disorder, and motor loss exceeds sensory loss. Lower motor involvement occurs at the level of the lesion, with atrophy of upper extremity muscles, especially hand intrinsics. Upper motor neuron findings are noted below the level of the lesion, with lower extremity spasticity and hyperreflexia. The sensory fibers are polysynaptic, and the posterior columns remain intact because the circulation is well collateralized, enters dorsally, and is therefore minimally affected. Focal sensory loss is less readily appreciated. Many patients have a subtle loss of sharpness to pinprick on the lower half of the body, with a sensory gradient across the trunk to normal sensation. Analgesia is more common than anesthesia, which is more common than proprioceptive loss. Reflex changes may be present, with relative hyperreflexia in the legs as compared with the arms. Bilateral Hoffman and Babinski signs are commonly present.

Lhermitte sign is the axial shock-like sensation elicited by neck flexion, extension, or axial compression. It is classically produced by pressing down on the top of the head. Lhermitte sign is present in as many as 25% of myelopathic patients. Babinski and Hoffman signs are nonspecific findings with upper motor neuron lesions and can be demonstrated in patients with myelopathy secondary to cervical disk disease. Determination of the range of motion of the cervical spine should be performed actively, passively, and against resistance.

Acute myelopathy can occur spontaneously or after minor or major trauma. The common presentation is a central spinal cord syndrome with pain. The neurologic loss is that of lower motor abnormalities in arms and hands with hyperreflexia and with spasticity in the legs. Acute myelopathy after minor trauma can occur without fracture or dislocation. It is often associated with spondylosis or congenital stenosis. Static cord impingement often cannot be demonstrated radiographically. Acute myelopathy also occurs in young people with congenital spinal stenosis or multiple sports traumas. Such patients may develop diffuse cervical spinal stenosis as a result of multiple minor spinal injuries. Patients with congenital or acquired stenosis and an AP diameter of less than 10 mm are vulnerable to acute spinal cord injury when the spine is sufficiently hyperextended. Such patients typically are football players who present after some trivial trauma with what has been described as neurapraxia, stinger, or spinal cord concussion. Cervical spondylosis produces canal narrowing, and hyperextension precipitates acute compression and injury. Dynamic compression of the spinal cord results in neurologic injury, often a central cord syndrome.

The anterior spinal artery syndrome has a variety of causes. Acute quadriparesis and dissociation of sensory loss with preservation of posterior column functions are its hallmarks. Acute soft disk herniation with cord compression can present with myelopathy and requires urgent surgical intervention. This should be suspected in patients whose plain radiographs demonstrate congenital or spontaneous fusion and in patients with previous cervical injury.

Few studies of the natural history of spondylotic myelopathy have been performed, and those that have were small, with dissimilar disability grading systems and with outcomes that are not comparable. Despite these limitations, some information can be gleaned from the available literature. Myelopathy secondary to spondylosis typically has an insidious onset, developing over a prolonged period. The natural history is characterized by long intervals of clinical stability punctuated by short periods of worsening and ultimately intermittent progression. Myelopathy may initially appear as an isolated condition, in conjunction with a severe radiculopathy or as a significant component of myeloradiculopathy. Patients may have very minor degenerative changes and become symptomatic. Their neurologic deficits can be dramatic and anxiety producing, causing patients to present for evaluation. Once myelopathy occurs, complete reversal is rare. Patients with myelopathy often go for long periods of time without development of new or worsening signs and symptoms.

Spondylotic myelopathy may present as a stepwise deterioration (75%), as a relentless downhill slide without plateaus or remissions (20%), or as a downhill course with occasional remissions (5%). In few patients, the myelopathy will reverse with conservative care or no care. Significant reduction in neurologic deficits is unusual. After conservative treatment, most myelopathic patients experience periods of stable disability punctuated by episodes of progressive deterioration. Reported improvements may represent a plateau with lack of progression or with the patients growing accustomed to their disability. After onset of clinical myelopathy, rarely do patients regain neurologic normality, and spontaneous remission of symptoms is unlikely.

Nurick (3) postulated that the degree of disability in cervical myelopathy was established early in the disease process and rarely progressed. In a clinical review of 1,355 patients with CSM, Epstein reported that conservative therapy resulted in 36% improvement and 64% nonimprovement. In the group with nonimprovement, 26% of patients significantly deteriorated neurologically.

A subset of patients presents with relentless progression that proceeds to severe disability. Our clinical experience is most similar to that of Symon and Lavender, who reported that more than two-thirds of the patients with myelopathy whom they studied displayed relentless deterioration of neurologic function rather than a series of plateaus and downhill progression. Patients presenting with markedly myelopathic findings in association with drastically reduced spinal canal dimensions over several levels can expect progressive deterioration.

Real improvement in patients with myelopathy can be expected after operative cord decompression if symptoms have been present for less than 2 years. When the duration of symptoms exceeds 2 years, demonstrable significant improvement in patients is rare. Age at presentation and duration of disease before treatment are the most important factors affecting prognosis. Increased age is associated with poorer outcome. Age and clinical severity are less important factors than duration of disease and the operation performed. Myelopathy is a treatable condition, and prompt diagnosis improves the likelihood of favorable outcome.

Attempts at grading myelopathy have focused on the effects on patient performance. Patient grading is essential to evaluate the results of various available therapies. A standardized grading system for myelopathy would allow
more complete understanding of the natural history of this disorder as well as provide a valid means of comparing the results of the different treatment modalities. Identification of more serious neurologic problems, the rapidity of their progress, and their response to therapy would then dictate the urgency for treatment. Double-blinded, prospective, randomized trials of both ventral and dorsal procedures as well as conservative therapy are the best methods for determining the efficacy of the various therapies available today.