[2] It can also be evoked when a practitioner pounds on the cervical spine while the neck is flexed; this is caused by involvement of the posterior columns.
[citation needed] Although often considered a classic finding in multiple sclerosis, it can be caused by a number of conditions, including transverse myelitis, Behçet disease,[4] osteogenesis imperfecta,[5] trauma, radiation myelopathy,[6] vitamin B12 deficiency (subacute combined degeneration), compression of the spinal cord in the neck from any cause such as cervical spondylosis, disc herniation, tumor, and Arnold–Chiari malformation.
Fluoxetine, given its very long half-life, can be given as a single small dose, and often avoid Lhermitte's sign and other withdrawal symptoms.
[11] In the dental field, three studies (Layzer 1978, Gutmann 1979, Blanco 1983) have identified Lhermitte sign among nitrous oxide abusers.
This is likely due to nitrous oxide depletion of vitamin B12 leading to a very severe, rapid deficiency in the absence of supplementation.