Immunoreactive myelin basic protein in cerebrospinal fluid of patients with peripheral neuropathies

The presence of myelin basic protein (MBP)–like material in cerebrospinal fluid (CSF) usually reflects breakdown of central nervous system myelin. Immunoreactive MBP levels were measured in 70 CSF specimens from 66 patients with a variety of peripheral neuropathies. Immunoreactive MBP was present in CSF in 70% (16 of 23) of patients with biopsy‐proved chronic demyelinating polyneuropathies, whereas in neuropathies producing primarily axonal damage it was present in only 22% (5 of 23). In Guillain‐Barré syndrome, 45% (9 of 20) of patients had immunoreactive MBP in the CSF. We conclude that MBP‐like material is present in the CSF of most patients with longstanding demyelinating polyradiculoneuropathies and probably reflects detection of peripheral nervous system P₁ protein.