Lhermitte s sign (also known as Lhermitte s phenomenon also referred to as the barber chair phenomenon is the name which describes an electric shock-like sensation that occurs on flexion of the neck. This sensation radiates down the spine, often into the legs, arms, and sometimes to the trunk. Causes of Lhermitte s sign : Lhermitte s sign is caused by miscommunication between the nerves that have become demyelinated. The pathophysiology of Lhermitte s sign was described as the stretching of the hyper excitable demyelinated dorsal column of the spinal cord, particularly at the cervical level, thus triggering an electric shock-like sensation. Till date, hyper excitability is considered as the main pathophysiological mechanism for the occurrence of Lhermitte s sign. Also, from an etiological point of view, in the original paper by Lhermitte, the shock-like sensations were supposed to be caused by medullary lesions due to demyelination or trauma of the dorsal column. Neck movements are said to exacerbate Lhermitte s sign where Lhermitte s phenomenon is said to be induced by neck flexion while the reverse Lhermitte s phenomena is defined when symptoms are induced by neck extension. Reverse Lhermitte s phenomenon is said to be induced by extrinsic compression of the cervical cord and neck collar immobilization. A relatively rare form called inverse Lhermitte phenomenon can be described by upward moving paresthesia with neck flexion which can be a sign of myelopathy. It is common in multiple sclerosis, if symptoms aggravating consult your doctor immediately.