Lhermitte’s Sign
Lhermitte’s sign is a sudden, brief sensation that feels like an electric shock traveling down the spine. Damage to the protective covering of nerves in the spinal cord, called myelin, most often causes this symptom. When myelin is harmed, nerve signals don’t travel properly, which leads to the shock-like feeling when the neck bends forward.
French neurologist Jean Lhermitte first described the symptom in the early 20th century, building on earlier work by Pierre Marie. While people often link it to multiple sclerosis, it can also occur with other conditions that affect the upper spinal cord, such as transverse myelitis, spinal cord injury, or vitamin B12 deficiency.
Not all cases come from disease. Sometimes, neck strain, trauma, or treatments like radiation to the neck can trigger the sensation. Knowing the possible causes can help determine whether it signals a serious neurological issue or a temporary, non-disease-related problem.
Definition of Symptom
Lhermitte’s sign is a neurological symptom. People describe it as a brief electric shock-like sensation that moves down the spine. This feeling can also extend into the arms or legs. The sensation often happens when someone bends their neck forward. It may also occur with actions like coughing or sneezing. Each episode usually lasts only a few seconds.
This symptom is a type of paresthesia, which means an unusual skin sensation such as tingling or prickling. In Lhermitte’s sign, the feeling is sudden and travels along the path of the spinal cord.
Key Features of Lhermitte’s Sign
- Type: Neurological symptom
- Sensation: Electric shock-like or tingling
- Trigger: Neck flexion or certain movements
- Duration: Seconds
- Location: Neck, spine, limbs
Lhermitte’s sign is not a disease. Instead, it signals that the spinal cord may be affected by another condition. Most often, it is linked to issues in the cervical spinal cord, such as multiple sclerosis or other structural changes.
Possible Causes / Lhermitte’s Sign Causes
Lhermitte’s sign occurs when something irritates or harms the cervical spinal cord. Often, demyelination—the loss of the myelin sheath around nerve fibers—causes the problem. When myelin is damaged, nerve signals become disrupted, which can trigger the electric shock-like sensation.
Multiple sclerosis (MS) is one of the most common causes. In MS, the immune system damages myelin in the central nervous system. This can create lesions in the neck region that respond to neck movement with abnormal nerve signals. Other inflammatory conditions, such as transverse myelitis and Behçet’s disease, can cause similar nerve injury.
Lupus can also lead to inflammation that affects the spinal cord. Vitamin B12 deficiency can harm the spinal cord, sometimes due to poor diet, absorption problems, or certain health conditions. Structural or mechanical causes include:
- Cervical spondylosis (age-related wear in the neck).
- Disc herniation pressing on the spinal cord.
- Spinal cord tumors or spinal cord compression.
- Arnold–Chiari malformation affecting brain and spinal cord alignment.
Radiation therapy to the neck or chest can cause nerve problems months or years later. Trauma from accidents or sports injuries can also directly injure the spinal cord. The barber chair phenomenon refers to a similar sensation caused by sudden neck extension, especially in people with existing spinal cord issues. Both disease and movement-related strain can trigger Lhermitte’s sign.
Other Non-Disease Causes
Lhermitte’s sign can also happen in people without an underlying disease. Some treatments, devices, or activities may temporarily irritate the spinal cord or nerves. Radiotherapy, including some modern techniques, can sometimes cause this symptom. The effect may appear weeks or months after treatment, especially if the neck area was included.
Some chemotherapy drugs can also be linked to Lhermitte’s sign. These medicines may irritate or harm nerves, causing the electric shock-like sensation when bending the neck. Wearing a neck brace for long periods can change posture and muscle tension. Sometimes, this extra strain on the neck can lead to symptoms. Certain movements, like stretching the neck too far or holding poor posture, may briefly trigger Lhermitte’s sign.
How It Causes the Symptom
Certain movements, usually neck flexion (bending the head forward), can trigger unusual nerve signals in the cervical spinal cord and cause Lhermitte’s sign. When the neck bends, the cervical spine changes position. If myelin—the protective coating around nerve fibers—is damaged, these fibers can send abnormal electrical impulses.
This damage often affects the posterior columns of the spinal cord, which carry sensory information about touch and position. Disruption here can create the brief, shock-like feeling down the spine. Common factors that can lead to this effect include:
- Multiple sclerosis (MS) – a condition that damages myelin.
- Cervical spine injury – trauma that affects spinal cord pathways.
- Vitamin B12 deficiency – which can harm myelin health.
- Radiation therapy – possible long-term spinal cord changes.
The sensation can travel from the neck down the spine and sometimes into the arms or legs. It usually lasts only seconds but can repeat with each neck movement. This effect happens because damaged nerve fibers respond to stretching or movement with abnormal signals, not because of problems with muscles or bones.
Possible Complications
Lhermitte’s sign itself is not usually harmful, but it can be connected to other complications depending on the underlying cause. People with multiple sclerosis (MS) or other spinal cord disorders may face a range of related issues. Nerve pain can become more frequent or intense over time.
This discomfort may interfere with daily activities, especially when the neck is bent forward. Some people experience MS symptoms that worsen when Lhermitte’s sign appears. These can include muscle weakness, balance problems, or vision changes.
Fatigue is a common complication. The sudden electric shock sensation can be draining, and repeated episodes may increase tiredness during the day. Heat and stress may trigger or intensify the symptom. For example, hot weather, a warm shower, or emotional strain can make the sensation more noticeable.
| Trigger | Possible Effect |
|---|---|
| Heat | Increased nerve pain, more frequent shocks |
| Stress | Heightened sensitivity and discomfort |
| Fatigue | Lower tolerance to symptoms |
Ongoing discomfort may make it hard to concentrate or stay physically active, which can affect work, exercise, and social life. If the underlying condition progresses, other neurological symptoms may appear alongside Lhermitte’s sign.
When to Seek Medical Attention
Contact a healthcare provider if you notice new or unexplained episodes of Lhermitte’s sign, especially if you have no known neurological condition. Seek care when the sensation appears alongside other symptoms, such as:
- Numbness or tingling in the limbs
- Weakness or loss of coordination
- Vision changes
- Problems with balance or walking
If you already have a diagnosed condition, such as multiple sclerosis, talk to your doctor if symptoms increase in frequency or intensity. This could mean your condition has changed or your treatment needs adjustment.
Seek urgent medical attention if you experience Lhermitte’s sign after a recent injury to the head, neck, or spine. This may signal structural damage or inflammation that needs prompt evaluation. A short guide to when to call a doctor:
| Situation | Action |
|---|---|
| First-time occurrence with no known cause | Schedule a medical evaluation |
| Worsening or persistent symptoms | Contact healthcare provider soon |
| After trauma to head or neck | Seek urgent medical care |
| With other neurological symptoms | Get prompt assessment |
