Revisiting Lhermitte sign: From adult eponym to pediatric breakthroughs

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Author: Joaquin A Pena MD

Lhermitte sign, often called the “barber chair phenomenon,” is an important part of the neurologic exam. It is usually described as a brief, electric-shock-like sensation that radiates down the spine or into the limbs when the neck is flexed, serving as a clear clinical sign of cervical spinal cord issues. Although mainly documented in adults, particularly in multiple sclerosis, recent research is significantly changing how we understand Lhermitte sign in pediatric-onset multiple sclerosis and other childhood demyelinating disorders, such as myelin oligodendrocyte glycoprotein antibody-associated disorder (MOGAD).

A brief history: from trauma to demyelination

Although named after Jean Lhermitte, who described the phenomenon in patients with multiple sclerosis in 1924, the earliest account actually dates to 1917 when Marie and Chatelin observed it in a soldier with a head injury. Over time, Lhermitte sign has become closely associated with multiple sclerosis, but its occurrence covers a wide range of diagnoses, including neuromyelitis optica, vitamin B12 deficiency, radiation myelopathy, and cervical trauma.

The pathophysiology of the “zap”

The underlying mechanism is the mechanosensitivity of demyelinated axons in the cervical posterior columns. When myelin is damaged, these fragile fibers become hyperexcitable; the physical act of neck flexion stretches the spinal cord, triggering ectopic discharges that the brain perceives as an electric shock.

Recent molecular insights suggest that this process involves activated microglia, proinflammatory cytokine signaling, and increased Wnt signaling, all of which lower the threshold for neuronal firing and pain.

Breakthroughs in pediatric neurology: the 2025 AI milestone

Until recently, research on Lhermitte sign in children was surprisingly limited. However, a 2025 breakthrough study by Uysal and colleagues has offered the first large-scale systematic assessment of Lhermitte sign in pediatric-onset multiple sclerosis using artificial intelligence.

Key findings from the pediatric-onset multiple sclerosis frontier:

• AI-enhanced localization. Using AI-based radiologic segmentation, researchers confirmed that Lhermitte sign in children is significantly associated with upper cervical lesions (C1–C4).
• Prevalence. Lhermitte sign was found in approximately one third (31.5%) of a pediatric-onset cohort, a rate comparable to adult estimates but higher than previously assumed for children.
• A predictor, not a disability marker. Much like in adults, the presence of Lhermitte sign in children does not correlate with gender, disease pattern (eg, relapsing-remitting vs. secondary progressive multiple sclerosis), or the level of physical disability (EDSS). It is a localizing tool, not a marker of disease severity.

Lhermitte sign in MOGAD: A diagnostic rescue

Another recent breakthrough involves MOGAD. A 2024 case study highlighted how Lhermitte sign can be the deciding factor in diagnosing pediatric myelitis when initial imaging is deceptive.

In an 8-year-old girl with cortical encephalitis (FLAMES), initial contrast-enhanced spinal MRIs appeared normal. However, the report of Lhermitte sign—reproduced during physical examination—prompted clinicians to suspect “MRI-negative” myelitis. This suspicion was later confirmed by a follow-up MRI, which revealed a lesion that had been invisible during the acute phase. This highlights that Lhermitte sign can provide objective clinical evidence of cord involvement even when initial imaging fails.

Unresolved debates and field controversies

Despite its longevity in clinical practice, Lhermitte sign remains a subject of active debate:

1. The “symptom versus sign” paradox. Technically, Lhermitte sign is a symptom because it is a subjective sensation. However, many experts argue it should be classified as a sign because it is reproducible and can be elicited by the examiner through passive neck flexion. Some refer to it as an “elicited symptom,” placing it in the same category as Tinel’s or Lasègue’s.

2. The enhancement mystery. A major unresolved debate is whether Lhermitte sign reflects active inflammation. Although some studies show Lhermitte sign correlates with lesions, multiple researchers (including the 2025 Uysal study) found no consistent correlation between Lhermitte sign and gadolinium enhancement on MRI. This suggests that Lhermitte sign might be triggered by chronic, stable demyelinated plaques rather than by acute relapses alone.

3. Underreporting in pediatrics. There is increasing concern that Lhermitte sign is significantly underreported in children. Younger children or those with communication difficulties might describe the sensation as “buzzing,” “funny feelings,” or “ants crawling” rather than an “electric shock.” Clinicians are often advised to avoid leading questions and instead ask straightforward ones: “When you bend your head forward, do you feel a quick tingling sensation down your back?”

Clinical highlights for the modern neurologist

• Suspected pediatric-onset multiple sclerosis versus acute disseminated encephalomyelitis. In the challenging task of distinguishing pediatric-onset multiple sclerosis from acute disseminated encephalomyelitis, a positive Lhermitte sign indicates focal cervical involvement, which is more typical of multiple sclerosis or neuromyelitis optica spectrum disorders.
• The power of the bedside. Lhermitte sign is quick, free, and noninvasive. Its presence can justify prioritizing spinal imaging—especially in children, where an MRI may require sedation—even if a brain MRI isn’t enough for diagnosis.
• Neuropathic pain screening. Recent advancements suggest using modified adult tools, such as PainDETECT, to quantitatively assess Lhermitte sign-related pain in children as young as 8 years.

Conclusion

Lhermitte sign is not just a relic of 20th-century neurology. In today’s era of AI-assisted imaging and advanced antibody testing, it remains a valuable clinical clue. For the pediatric neurologist, it is a crucial tool that enhances the physical examination, prompts timely investigation, and, in cases of MRI-negative myelitis, may be the only evidence guiding the diagnosis. As we incorporate machine learning into spinal cord analysis, Lhermitte sign continues to remind us that the patient’s subjective “zap” is often the most direct way to locate the lesion.

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