Lhermitte's sign is elicited by which maneuver?

• A. Flex neck
• B. Extend neck
• C. Turn head to the side
• D. Raise shoulders upward

Answer: (A)

Lhermitte's sign occurs when the neck is flexed. In people with cervical spinal cord involvement, especially from demyelinating disease like multiple sclerosis, bending the neck forward stretches the dorsal columns where demyelination has occurred. This stretch can trigger abnormal electrical discharges, producing a sudden electric shock-like sensation that radiates down the spine and sometimes into the limbs. The sign is not produced by extending the neck, turning the head, or shrugging the shoulders, which do not place the same stretch on the posterior columns. It’s a helpful clue to cervical myelopathy, though not entirely specific to MS.