[Determination of myelin basic protein in the cerebrospinal fluid in neurologic diseases]

Myelin basic protein (BP) is a specific constituent of the myelin sheath. This structural protein cannot be detected in the cerebrospinal fluid (CSF) unless myelin is acutely degraded. In order to detect active demyelinating diseases, BP was measured in CSF samples of radioimmunoassay. The assay is specific and sensitive to as little as 1.5 to 2.5 ng/ml BP. A moderate non-parallelism between the standard curve and various dilutions of CSF samples indicates that in CSF BP is present in an altered state. Over 1000 CSF samples have been measured in a double-blind study, in which 100 patients were selected and their clinical records evaluated. Twenty-eight patients without demyelinating disease had BP levels lower than 2.5 ng/ml. 72 patients had values higher than 2.5 ng/ml. Among them, the most frequent causes of demyelination were multiple sclerosis (19 cases), brain tumors (22 cases) and cerebral or spinal vascular accidents (12 cases). During a single acute demyelinating episode, BP levels revert to background levels within a few days. In contrast to immunological anomalies observed in the CSF, the presence of BP is concomitant with the breakdown of myelin. The size and location of the lesion influence the level of BP in the CSF. Thus, the assay is useful for the detection of active demyelination in the central nervous system and in following the course of the disease, although normal values do not rule out the presence of demyelinating lesions. For the time being, therefore, this assay should be restricted to specialized neurological centers and selected patients.