Lhermitte’s sign feels like a sudden electric shock that shoots down your spine and into your arms and legs when you bend your neck forward. The sensation is brief, lasting only a few seconds, but it can be startling and sometimes painful. It’s sometimes called the “barber chair phenomenon” because tilting your head forward (like you would in a barber’s chair) is the classic trigger.
The Sensation Itself
People who experience Lhermitte’s sign consistently describe it the same way: an electrical shock or lightning-bolt feeling that starts at the base of the skull or upper neck and races downward. The shock travels along the spine and can branch out into the arms, legs, or both. Some people feel it more as intense tingling or buzzing rather than outright pain, but the electrical quality is the defining feature. It doesn’t feel like a muscle cramp, a pinched nerve, or a typical headache. It feels like something zapping through your spinal cord, because that’s essentially what’s happening.
The whole thing is over in a few seconds. There’s no lingering ache or residual numbness from the sensation itself, though some people experience it many times throughout a single day. Each episode is its own brief, sharp event.
What Triggers It
The most common trigger is bending your head forward, chin toward chest. But several other movements can set it off too:
- Coughing
- Sneezing
- Yawning
- Any sudden neck flexion
What these movements share is that they all stretch or shift the spinal cord slightly within the neck. If the nerve fibers there are damaged or irritated, that mechanical stretch is enough to fire off abnormal electrical signals, which your body interprets as a shock running down your spine. People who experience frequent episodes sometimes start unconsciously avoiding certain head positions to prevent triggering it.
Why It Happens
Lhermitte’s sign occurs when the protective insulation around nerve fibers in the upper spinal cord is damaged. Healthy nerve fibers are wrapped in a fatty coating that keeps electrical signals traveling smoothly along their intended paths. When that coating is stripped away or compromised, the exposed nerves become hypersensitive. Bending the neck stretches those vulnerable fibers just enough to generate a burst of rogue electrical activity, which you feel as that characteristic shock.
This is why the sensation has that unmistakable “electrical” quality. It’s not a metaphor. The nerves are literally misfiring.
Conditions That Cause It
Multiple sclerosis is the condition most commonly associated with Lhermitte’s sign, and it’s often the first thing people worry about when they experience it. Studies have found widely varying prevalence rates among MS patients, ranging from around 4% to 33% depending on the population studied. Interestingly, research published in a 2014 study found it was actually more common in people with neuromyelitis optica (a related but distinct condition), affecting about 20.5% of those patients compared to 4.3% of MS patients in that particular study.
But MS is far from the only cause. Vitamin B12 deficiency can produce Lhermitte’s sign, though this is considered rare. In reported cases, the sign was sometimes the very first symptom of low B12, appearing before any other neurological complaints. The good news is that B12-related cases can improve with supplementation.
Other possible causes include cervical spondylosis (age-related wear on the neck vertebrae compressing the spinal cord), spinal cord injuries, tumors pressing on the upper cord, and radiation therapy to the neck or upper chest area. Cervical disc herniations can also produce similar symptoms if they compress the cord in the right spot.
How It’s Managed
Treatment depends entirely on the underlying cause. If a B12 deficiency is responsible, correcting the deficiency can resolve the symptom. If a structural problem like a herniated disc is compressing the cord, addressing that compression is the priority.
For people whose Lhermitte’s sign stems from MS or another condition where the nerve damage can’t be easily reversed, management focuses on reducing the frequency and intensity of episodes. Medications originally developed for nerve pain are the most commonly used options, with variable results. Some people find meaningful relief, while others get only partial improvement.
A soft cervical collar is a surprisingly practical tool. By gently limiting how far you can flex your neck forward, a collar prevents the movement that triggers the shock in the first place. In one reported case of spinal cord compression, wearing a neck collar eliminated the symptom entirely for over a year. It’s not a cure, but for people who are getting shocked dozens of times a day, it can make a real difference in quality of life.
What It Doesn’t Mean
Experiencing Lhermitte’s sign once or twice doesn’t automatically mean you have MS or any serious neurological disease. It is, however, a signal that something is irritating the nerve fibers in your upper spinal cord, and that’s worth investigating. The range of possible causes spans from the easily treatable (a vitamin deficiency, a compressed disc) to the more complex (MS, other autoimmune conditions). The sign itself is the same regardless of the cause. What changes is the underlying reason and the path forward.