A positive Lhermitte sign results from stretching of the Meninges caused by flexion of the Spine in the cervical region.
Testing
To test for the Lhermitte sign, the head is passively flexed forward. In the presence of a positive Lhermitte sign, paresthesias occur in the extremities or trunk. The abnormal sensation usually originates in the neck and radiates caudally along the back.
Pathophysiology
The pathophysiology of the Lhermitte sign is not fully understood. It is assumed that part of the spinal cord, particularly in the cervical region, becomes hyperexcitable in the presence of demyelinating processes or injuries to the dorsal column tracts[^1].
Causes
A positive Lhermitte sign may have various possible causes[^1]:
Multiple sclerosis
Cervical spondylitis
Transverse myelitis
Behçet disease
Radiation-induced myelopathy
High-dose chemotherapy
SSRI withdrawal syndrome
Trauma
Arachnoiditis
Vitamin B12 deficiency
Spinal cord compression
Cisplatin neurotoxicity
NO neurotoxicity
Systemic lupus erythematosus
Parasitic infection of the spinal cord
Postdural puncture headache
Herpes zoster infection