This medical term is named after a French neurologist who lived in the late 1800s and early 1900s. It refers to an electric, shock-like sensation down the arms. It happens when the neck is bent forward, bringing the chin to chest. The underlying cause may signify multiple sclerosis or pressure on the spinal cord in the neck.

Pressure on the spinal cord can develop when the opening for the spinal cord, called the spinal canal, is too small. This may be due to the shape of the bone or spinal canal at birth. Pressure can also come from changes in the bone from arthritis or trauma, or from disc protrusion. Whatever the cause, the presence of Lhermitte's sign requires a doctor's attention.