Antibodies to the presynaptic membrane reduce release of ACh from the nerve terminal. Heroin and Ecstacy may cause rhabdomyolysis . Demyelination Primary segmental demyelination is the loss of one or more segments of myelin from the axon in the absence of axonal pathology, sometimes restricted to the paranodal region. Secondary demyelination is the loss of myelin due to an alteration in axon caliber, usually from atrophy. After removal of myelin debris, Schwann cells divide and move along the denuded axon.
New internodes are of various lengths and the myelin sheath is thinner than normal.
Repeated episodes will result in the production of excess Schwann cells, forming onion bulbs . When a myelinated axon disintegrates, the myelin sheath also collapses to form ovoids of myelin around the axonal debris. The fibers then break at the nodes of Ranvier and the Schmidt-Lanterman clefts . Bands of Bungner are longitudinally continuous columns of Schmwann cells which proliferate within the basal lamina after the loss of myelinated fibers. Reich granules are in myelinate fibers only.