Naming the finding
She describes an electric-shock feeling that runs down her back and into her legs when she bends her head forward. This is Lhermitte sign: an electric-shock sensation running down the spine, often into the limbs, when the neck flexes; it reflects demyelination in the cervical cord. The nurse records the finding as Lhermitte sign.
The mechanism
In multiple sclerosis (MS), immune-mediated inflammation strips myelin from nerve fibers in the brain and spinal cord. Demyelinated fibers in the posterior columns of the cervical cord become abnormally sensitive to mechanical stretch. Flexing the neck stretches the cord slightly, and these damaged fibers fire spontaneously, producing a brief, shock-like sensation that travels down the spine and limbs. Lhermitte sign is a sensory symptom elicited by the client's own movement, not a test of meningeal irritation. It is common in MS but can also occur with other cervical cord lesions.
| Sign or phenomenon | What happens | Meaning |
|---|
| Uhthoff phenomenon | Symptoms temporarily worsen with heat | Heat slows conduction in demyelinated nerves |
| Lhermitte sign | Electric shock down spine on neck flexion | Cervical cord demyelination |
| Brudzinski sign | Hips and knees flex when neck is flexed passively | Meningeal irritation |
| Kernig sign | Pain and resistance on knee extension with hip flexed to 90 degrees | Meningeal irritation |
Why the other names are wrong
Uhthoff phenomenon is a temporary worsening of existing MS symptoms when body temperature rises, as with exercise, hot weather, or fever; it is relevant to this client who lives in a hot, humid area, but it does not describe a shock on neck flexion. Brudzinski sign is involuntary flexion of the hips and knees when the examiner flexes the neck passively, and Kernig sign is pain and resistance when the knee is extended with the hip flexed; both are meningeal signs seen in meningitis or subarachnoid hemorrhage, not features of MS.
Nursing application
The nurse documents the finding accurately, reassures the client that it is a recognized MS symptom, and teaches her to avoid sudden neck flexion if the sensation is distressing. New or worsening Lhermitte sign may accompany a relapse and is reported along with other new neurologic symptoms.
Exam takeaway
Key point Neck flexion with an electric shock down the spine is Lhermitte sign, a feature of MS. Kernig and Brudzinski signs are meningeal; Uhthoff is heat sensitivity.