Lhermitte’s Sign Explained: Causes of Shock Sensations Down Your Spine

Experiencing a sudden, sharp, electric shock-like sensation that travels down your neck, spine, and into your limbs can be a frightening and confusing event. For many, this unique symptom is a mystery. But this sensation has a name, Lhermitte’s sign, and it is a classic indicator that something is irritating or damaging the delicate nerves of your central nervous system.

While Lhermitte’s sign is most famously associated with a serious neurological disease like multiple sclerosis (MS), it can also be a symptom of a number of other conditions, some of which are far more benign.² However, it should never be dismissed. The presence of this symptom is a clear signal that a full medical evaluation is necessary. 

This guide will explain the underlying mechanism of Lhermitte’s sign, detail its various causes from benign to serious, and outline the steps you should take if you experience it.

Lhermitte’s sign is a subjective symptom, meaning it is a sensation that a person feels and reports.³ It is a sudden, brief, and intense electric shock-like feeling that originates in the neck and travels downward into the spine, and often into the arms, legs, or torso.⁴ The key feature of Lhermitte’s sign is that it is triggered by a specific movement: flexing or bending the neck and head forward. ^[1] It can also sometimes be triggered by coughing, sneezing, or yawning.⁶

The sensation is often described as a jolt of electricity, sometimes accompanied by tingling, numbness, or a buzzing feeling.⁷ It is a paroxysmal symptom, meaning it comes on suddenly and lasts for only a moment, but it can be a very distressing and uncomfortable experience.⁸

The underlying cause of Lhermitte’s sign is damage to the myelin sheath, the protective fatty covering that insulates the nerve fibers in the spinal cord. The myelin sheath acts like the plastic insulation on an electrical wire, allowing for a rapid and efficient transmission of nerve signals.⁹

When the myelin is damaged, the nerve is left exposed. This damage can cause the nerve to become overly sensitive to movement. When the neck is flexed forward, the spinal cord and its nerves are stretched. This stretching can irritate the exposed, demyelinated nerve, causing it to “short circuit” or send an abnormal electrical signal. The brain interprets this abnormal signal as the electric shock sensation of Lhermitte’s sign. ^{[2] 10}

While Lhermitte’s sign is a classic symptom of demyelination, the cause of that demyelination can vary greatly in severity.

Lhermitte’s sign is considered one of the most classic and well-known symptoms of Multiple Sclerosis (MS).¹¹ MS is an autoimmune disease in which the body’s immune system mistakenly attacks and damages the myelin sheath in the brain and spinal cord.¹²

• The Link: A person with MS may experience Lhermitte’s sign during a flare-up of the disease, indicating a new or active area of inflammation and demyelination in the spinal cord. It can also be a persistent symptom for people with chronic spinal cord damage. ^[3] The presence of Lhermitte’s sign is often one of the first clues that a person has an underlying demyelinating disease.

While MS is the most common serious cause, other neurological conditions can also damage the spinal cord and lead to Lhermitte’s sign.¹³

• Spinal Cord Compression: Anything that physically puts pressure on the spinal cord can irritate the nerves and trigger the symptom.¹⁴ This can include:
  • Cervical Disc Herniation: A herniated disc in the neck can compress the spinal cord.¹⁵
  • Tumors: A benign or malignant tumor growing near the spinal cord.¹⁶
  • Spinal Stenosis: A narrowing of the spinal canal that puts pressure on the nerves ^[4].¹⁷
• Radiation Myelopathy: This is a rare side effect that can occur months or years after a person has received radiation therapy to the neck or upper back, causing delayed damage to the spinal cord’s myelin.¹⁸
• Transverse Myelitis: An inflammatory condition that damages the myelin sheath of the spinal cord.¹⁹ It can occur as a one-time event or as a symptom of a larger disease process.²⁰

In some cases, Lhermitte’s sign can be caused by conditions that are less likely to be a sign of a progressive neurological disease.

• Vitamin B12 Deficiency: A severe vitamin B12 deficiency can damage the myelin sheath of the nerves, leading to a variety of neurological symptoms, including Lhermitte’s sign. ^{[5] 21} This is a treatable condition.
• Cervical Spondylosis: Degenerative changes in the cervical spine, such as bone spurs or disc changes, can irritate the spinal cord and nerve roots, leading to a temporary or intermittent Lhermitte’s sign.
• Trauma: A past injury to the neck can cause temporary swelling or inflammation that irritates the nerves and triggers the symptom, but the symptom usually resolves as the swelling goes down.

If you experience Lhermitte’s sign, it is a clear indication that a professional medical evaluation is necessary. The key is to get an accurate diagnosis to determine the underlying cause.

1. Consult a Neurologist: Do not dismiss this symptom. It is a sign of a neurological issue and should be evaluated by a neurologist.
2. Diagnostic Workup: Your neurologist will likely order a number of tests to get to the root of the problem:
   • MRI of the Brain and Spine: This is the most important test. An MRI can detect demyelinating lesions (MS), spinal cord compression, or other structural abnormalities. ^[6]
   • Physical and Neurological Exam: Your doctor will test your reflexes, strength, and sensation to look for other signs of neurological dysfunction.
   • Blood Tests: These tests can rule out causes like vitamin B12 deficiency or other inflammatory markers.²³