Lhermitte sign

Specialty: Neurology.

• barber chair phenomenon
• sensation of cervical electric shock when flexing the neck

Why it occurs

• Multiple sclerosis (active demyelination plaque in the posterior cords of the cervical spinal cord)
• Cervical spondylotic myelopathy (mechanical compression of the posterior cords by osteophytes or herniated disc during cervical movement)
• Severe vitamin B12 deficiency (subacute combined degeneration of the spinal cord)
• Cervical syringomyelia (centromedullary cystic cavity)
• Previous cervical radiotherapy (benign or progressive late actinic myelopathy)
• Cervical trauma due to whiplash mechanism or mild spinal contusion

Initial workup

Provocation of the symptom through passive or active flexion of the patient's neck, documenting the downward irradiation of the electrical current through the back towards the limbs; high-resolution magnetic resonance imaging (MRI) of the cervical spine with sagittal and axial sequences in T2 and FLAIR, with and without contrast; dosage of serum vitamin B12, folic acid, and methylmalonic acid levels to rule out deficiency myelopathy.

Standard management

• Methylprednisolone — 1000 mg/day intravenously for 3 days if associated with an acute flare of multiple sclerosis or inflammatory myelitis
• Hydroxocobalamin or Cyanocobalamin — 1000 micrograms intramuscularly daily the first week, then weekly and monthly if B12 deficiency is confirmed
• Carbamazepine (100-400 mg/day, useful to suppress paroxysmal sensory discharges of Lhermitte's sign if they are very bothersome).