Lhermitte's Sign in Multiple Sclerosis
Lhermitte's sign is the medical term for the electric shock-like sensation that radiates down the spine when the neck is flexed in multiple sclerosis patients, caused by demyelination in the posterior columns of the cervical spinal cord.
Definition and Pathophysiology
Lhermitte's sign is characterized by:
- Transient electric shock-like sensations that radiate down the spine into the extremities
- Typically triggered by neck flexion (bending the head forward)
- Results from demyelination and hyperexcitability of sensory pathways in the posterior columns of the cervical spinal cord 1
- Occurs in approximately 25% of MS patients at some point during their disease course 2
Mechanism in Multiple Sclerosis
The pathophysiological basis of Lhermitte's sign in MS involves:
- Demyelination of sensory axons in the posterior columns of the cervical spinal cord
- Mechanical distortion of these demyelinated fibers during neck movement
- Generation of ectopic excitation that spreads along demyelinated plaques 2
- Hyperexcitability of affected neurons leading to abnormal signal propagation
Clinical Significance
Lhermitte's sign has important diagnostic implications:
- Often indicates active disease or exacerbation in MS patients 2
- Can be an early presenting symptom of MS
- May correlate with cervical spinal cord lesions visible on MRI 3
- Usually not painful but can cause significant distress to patients 2
Differential Diagnosis
While Lhermitte's sign is commonly associated with MS, it can occur in other conditions:
- Cervical spondylosis with cord compression 4
- Transverse myelitis
- Behçet's disease
- Trauma to the cervical spine
- Radiation-induced myelopathy
- Cisplatin and other chemotherapy-induced neurotoxicity
- Vitamin B12 deficiency
- Primary spinal cord tumors (rare) 5
Reverse Lhermitte's Phenomenon
It's important to distinguish Lhermitte's sign from reverse Lhermitte's phenomenon:
- Reverse Lhermitte's is triggered by neck extension rather than flexion
- More commonly associated with extrinsic compression of the cervical cord (e.g., spondylosis)
- May require different management approaches, such as neck collar immobilization 4
Diagnostic Evaluation
When Lhermitte's sign is present, diagnostic workup should include:
- MRI of the cervical spine to identify demyelinating lesions in the posterior columns
- Brain MRI to look for other MS-characteristic lesions (periventricular, juxtacortical, infratentorial) 3
- Consider spinal cord MRI even when brain findings are minimal or equivocal 6
- CSF analysis for oligoclonal bands and IgG index if diagnosis remains uncertain 6
Management Approaches
Treatment options for Lhermitte's sign in MS include:
- Treatment of the underlying MS with appropriate disease-modifying therapies
- Symptomatic management with anticonvulsants:
- Carbamazepine and gabapentin are most commonly used 7
- Response to these medications is variable
- Non-pharmacological approaches may provide mild to moderate symptomatic improvement 7
- In severe cases that don't respond to conventional treatments, electromagnetic field therapy has shown some promise in case reports 2
Clinical Pearls
- Lhermitte's sign is often transient and may resolve spontaneously or with treatment of the underlying MS
- The presence of Lhermitte's sign along with other MS symptoms strengthens diagnostic certainty
- The sign may reappear during periods of disease exacerbation
- Patients should be educated about this phenomenon to reduce anxiety when it occurs
Lhermitte's sign represents an important clinical marker in MS that can aid in diagnosis and monitoring of disease activity. While it is not specific to MS, its presence in the appropriate clinical context should prompt evaluation for demyelinating disease.