Lhermitte's sign

A transient, electric shock-like dysesthesia radiating down the spine, often into the limbs, typically precipitated by neck flexion and indicating involvement of the cervical spinal cord dorsal columns or lower brainstem. Possible causes are neurological disease (multiple sclerosis, neuromyelitis optica spectrum disorder), spinal degenration (cervical spondylosis, herniated discs, spinal stenosis), inflammation (transverse myelitis, SLE, Behçet's disease), vitamin B12 deficiency, neck injury/tumor, Chiari malformation, radiation myelopathy, and chemotherapy.