Dull, aching, but otherwise nondescript pain in the low back is a common complaint, and its relation to the lesions of MS is uncertain. Infrequently, there is sharp, burning, poorly localized, or lancinating radicular pain, localized to a limb or discrete part of the trunk. Nevertheless, these types of pains, presumably caused by demyelinating foci involving the dorsal root entry zones, have a few times been the presenting feature of the disease or have appeared at a later time in established cases (see Ramirez-Lassepas et al for a discussion of pain in MS).
Symptoms and Signs in the Established Disease
In the later stages when the diagnosis of MS has become clinically definite, a number of syndromes are observed to occur with regularity. Approximately one-half of the patients will manifest a clinical picture of mixed or generalized type with signs pointing to involvement of the optic nerves, brainstem, cerebellum, and spinal cord—specifically signs relating to the posterior columns and corticospinal tracts. Another 30 to 40 percent will exhibit only varying degrees of spastic ataxia and deep sensory changes in the extremities, that is, essentially a spinal form of the disease. In either case, an asymmetrical spastic paraparesis with some degree of impaired joint position and vibration sense in the legs is probably the most common manifestation of progressive MS. A predominantly cerebellar or brainstem–cerebellar form occurs in approximately 5 percent of cases. Thus the mixed and spinal forms together have made up at least 80 percent of our clinical material.
It has become evident that some degree of cognitive impairment, and probably a progressive decline, is present in perhaps one-half of patients with long-standing MS. The process is characterized by reduced attention, diminished processing speed and executive skills, and memory decline, while language skills and other intellectual functions are preserved, features that have been subsumed under “subcortical dementia,” as discussed in Chap. 20. Other mental disturbances, such as a loss of retentive memory, global dementia, or a confusional–psychotic state, also occur in a limited number of cases in the advanced stages of the disease, but we have found this degree of deterioration to be exceptional. The decline in cognitive functions correlates with quantifiable MRI measurements, particularly loss of white matter volume, thinning of the corpus callosum, and brain atrophy (reviewed by Bobholz and Rao).
Some patients with MS manifest an abnormal euphoria, a pathologic cheerfulness or elation that seems inappropriate in the face of the obvious neurologic deficit. (Charcot spoke of this phenomenon as “stupid indifference” and Vulpian as “morbid optimism,” but the term “la belle indefference” was most popular in the last century.) In recent years, the association with MS has been largely dispelled.
Similar findings of inappropriate laughing (or crying) can manifest as a part of the syndrome of pseudobulbar palsy as a result of longstanding MS. A larger number of MS patients, however, are depressed, irritable, and short-tempered, sometimes as a reaction to the disabling features of the disease but also apparently as a primary effect of the brain disease; the incidence of depression has been estimated to be as high as 25 to 40 percent in some series. Dalos and coworkers, in comparing MS patients with a group of traumatic paraplegics, found a significantly higher incidence of emotional disturbance in the former group, especially during periods of relapse. As mentioned above, the cognitive impairment is in keeping with what has been ascribed to “subcortical dementia” (see Chap. 20) but demyelination in the cortical layers is now well recognized as an important basis for dementia in MS. Loss of the volume of gray matter, for example, appears to be predictive of dementia as much as loss of central white matter. Either can give rise to global cerebral atrophy.