This classic multiple sclerosis (MS) sign is named for a French neurologist, Jean Lhermitte (1877-1959). It describes sudden transient electric-like shocks which extend from the neck down the spine when the head is flexed forward. It can be due to a disorder such as compression of the cervical spine (the portion of the spinal cord within the neck), and suggests a lesion of the dorsal columns of the cervical cord or of the caudal medulla.

Other possible causes include Behçet's disease, trauma, radiation myelopathy, vitamin B12 deficiency (subacute combined degeneration), and compression of the spinal cord in the neck (spondylosis, disc herniation, tumor, Arnold-Chiari malformation).