The most common cause of impairment in MS is some form of disturbance of gait. This can be due to weakness, spasticity, incoordination, imbalance, tremor, or any combination of these signs. Similar involvement may occur in the arms at times with or without gait disturbance, but usually some form of gait disturbance is present. The degree to which the gait disturbance impairs function must be established. Other factors such as speech, fatigue, paresthesias, or dysesthesias may also be present in different areas of the body.

Certain mental changes in patients with MS are well-recognized, and most frequently noted is euphoria, but not infrequently there also is emotional depression. It is important to consider emotional depression when related to fatigue since when fatigue is based primarily on emotional depression, it can usually be treated with appropriate psychotherapeutic drugs. Depending on where the abnormal demyelinating plaque lesions might lie anatomically, there can be other types of behavorial aberrations associated with MS. These can be, in most cases, adequately treated either with psychotherapy and/or with some of the psychotherapeutic drugs which help to control these abnormalities. However, in certain cases of MS, there is evidence of mild to marked signs of organic dementia which cannot be adequately treated.

Fatigue can be a factor in individuals with MS. However, fatigue is difficult to assess because, like other symptoms (see DI 24501.021), there are no objective tests to measure it. The individual must demonstrate some objective ongoing neurological deficit; a claim cannot be allowed on the basis of fatigue alone. Clinical and laboratory data and a well-documented medical history must establish findings which may reasonably account for fatigue.

The best means of assessing fatigue is by inference in terms of documentation of the claimant's activities of daily living, the extent of physical activity before fatigue occurs, and the frequency at which the claimant requires periods of rest. Individuals either living with the claimant (e.g., spouse, son, daughter) or individuals in close contact with the claimant should be good sources of such information. After such information is obtained, an inference in terms of documentation of the claimant's activities of daily living to see what effect fatigue plays in the claimant's overall physical activities should be made. However, conclusions about the intensity and persistence of fatigue and the effect on the person's work capacity must be drawn from the clinical and laboratory data and other evidence. In effect, a judgment is required as to whether findings relative to fatigue are consistent with the clinical course of the disorder and substantiated by the medical and other evidence. A judgment must be made on an individual case-by-case basis.

Most cases of MS involve intermittent periods of symptoms and signs (exacerbation) followed by a period of improvement (remission). Exacerbations vary in frequency, duration, character and severity. Remissions similarly vary in duration and in the extent of improvement.

Often mental abnormalities fluctuate with the classical presentation of the disease during periods of remission and are more obvious during periods of exacerbations. In the less frequent chronic progressive form of the disease, the physical as well as the mental deficits do not improve and continue to progress with increasing impairment of the various functions affected. The current neurological listings adequately address both the organic and nonorganic factors and include descriptions that would incorporate an assessment of both mental and physical functioning in an overall evaluation of the claimant's allegations. If only a mental impairment exists due to MS, we would evaluate the mental impairment under the mental disorders body system.

Consideration should be given to the course of the disease process during the few years preceding adjudication. An attempt should be made to decide if the case under consideration has developed a specific course.