A special problem arises when imaging procedures reveal a regional swelling of the spinal cord suggestive of a tumor. In a patient with this finding and a subacute, saltatory myelopathy restricted to several adjacent levels (usually thoracic), a search for an arteriovenous malformation or dural fistula may be required. In several of our patients, this finding has led to an ill-advised attempt at spinal cord biopsy. Sarcoidosis affecting the cord presents similar problems; steroid-responsive granulomatous lesions of sarcoid that follow a venous pattern in the cerebrum may cause confusion with MS when viewed by MRI. A subpial pattern of enhancement with gadolinium is helpful in identifying sarcoid.
The problem of differentiating chronic spinal MS from TSP (human lymphotropic virus, myelitis of the HTLV-1 type) and progressive familial spastic paraplegia may also arise occasionally (Chap. 32). Amyotrophic lateral sclerosis (ALS) and SCD may be confused with MS, but ALS can be identified by the presence of muscle wasting, fasciculations, and the absence of sensory involvement, whereas SCD is characterized by symmetrical involvement of the posterior and then lateral columns of the spinal cord. Reports that vitamin B12 levels are marginally low in a proportion of MS patients have suggested an underlying disturbance of homocysteine metabolism but this has not been confirmed (Vrethem et al).
Platybasia and basilar impression of the skull should also be considered in the differential diagnosis of spinal MS, but patients with these conditions usually have a characteristic shortening of the neck; images of the base of the skull are diagnostic. Neurologic syndromes resulting from the Chiari malformation, syringomyelia, rheumatoid destruction of the upper cervical segments, and tumors of the foramen magnum, cerebellopontine angle, clivus, and other parts of the posterior fossa have been misdiagnosed clinically as MS but clarified by imaging. In each of these instances, a solitary, strategically placed lesion may give rise to a variety of neurologic symptoms and signs referable to the lower brainstem and cranial nerves, cerebellum, and upper cervical cord, giving the impression of dissemination of lesions. It is a dependable clinical dictum that a diagnosis of MS should be made with caution when all of the patient’s symptoms and signs can be explained by a single lesion in one region of the neuraxis.
Occasionally, the chronic progressive form of MS may be confused with the hereditary ataxias, particularly the spinocerebellar types. The latter are generally distinguished by their familial incidence and other associated genetic traits; by their insidious onset and slow, steady progression; and by their relative symmetry and stereotyped clinical pattern. Intactness of abdominal reflexes and sphincter function and the presence of pes cavus, kyphoscoliosis, and cardiac disease are other features that favor the diagnosis of a heredodegenerative disorder (see Chap. 38).
Treatment of Multiple Sclerosis