Lhermitte’s sign is a neurological symptom characterized by a sudden, brief sensation that affects the spine and often travels to the limbs. This phenomenon is classified as a paroxysmal symptom, meaning it occurs in short, intense bursts triggered by a specific action. The experience is not a diagnosis in itself but rather an indication of underlying changes within the central nervous system.
Describing the Electric Sensation
The hallmark of Lhermitte’s sign is its distinct quality, most frequently described as a fast, intense, and uncomfortable electrical jolt. People often compare the feeling to a sudden, powerful electric shock or a sharp, forceful buzzing sensation that shoots through the body. This sensation typically begins in the neck or upper spine and rapidly propagates downward, extending through the back and sometimes into the arms, legs, fingers, or toes.
The intensity of this shock-like feeling can range from a strange, momentary tingling to a painful, startling burst of energy. Despite its intensity, the sensation is remarkably transient, usually lasting only a few seconds before disappearing completely. While the feeling is uncomfortable, its sudden nature can be distressing, and it can recur multiple times throughout the day.
The Specific Triggering Movement
The sensation of Lhermitte’s sign is almost exclusively provoked by a specific physical action: neck flexion. This movement involves bending the head forward, bringing the chin toward the chest. The phenomenon is sometimes informally called the “barber chair sign” because it can be triggered when the head is tilted forward suddenly.
The sensation immediately stops once the head is returned to a neutral, upright position, demonstrating the direct link between the movement and the neurological response. While neck flexion is the primary trigger, other actions that momentarily jar or stretch the spinal cord may also initiate the shock. These secondary triggers can include sudden movements like coughing, sneezing, or yawning.
Why This Sensation Occurs
Lhermitte’s sign results from damage to the nerve fibers within the cervical spinal cord, the segment that runs through the neck. The underlying mechanism involves a disruption of the myelin sheath, the protective, insulating layer that surrounds nerve axons. When the myelin is damaged, the nerve is left exposed and hypersensitive to physical manipulation.
The damage is often localized to the posterior columns of the spinal cord, which transmit sensory information. Bending the neck forward causes a mechanical stretching or compression of the spinal cord tissues. This stretch irritates the demyelinated nerve fibers, causing them to fire an abnormal electrical signal. This process is comparable to a frayed electrical wire sending a short circuit when stretched, which the brain interprets as the intense shock sensation.
The most common condition associated with this symptom is Multiple Sclerosis (MS), where the immune system mistakenly attacks the myelin. However, Lhermitte’s sign can also occur with other conditions that affect the spinal cord, such as radiation myelopathy, transverse myelitis, cervical spondylosis, or a severe vitamin B12 deficiency. The presence of the sign suggests central nervous system involvement, requiring further medical investigation.
Managing Daily Life with Lhermitte’s Sign
Management of Lhermitte’s sign centers on preventative strategies and, when necessary, pharmacological intervention to calm nerve hyperexcitability. The most immediate and effective measure is to consciously limit the neck movements that provoke the sensation. Maintaining good posture, especially when sitting or using electronic devices, can help reduce the frequency of unintentional neck flexion.
Some individuals find that wearing a soft cervical collar or neck brace can be helpful, as it physically restricts the range of motion that triggers the electrical feeling. Physical therapy can also be beneficial by teaching exercises to improve neck strength and awareness, further supporting a neutral head position. Incorporating relaxation techniques like meditation or deep breathing may also help, as emotional stress and fatigue can sometimes lower the threshold for nerve firing.
For people who experience Lhermitte’s sign frequently or severely, a physician may prescribe certain medications to stabilize the nerve membranes. Anticonvulsant drugs, such as Gabapentin, Pregabalin, or Carbamazepine, are often used to treat neuropathic pain by slowing the excessive firing of irritated nerves. These medications help to dampen the abnormal electrical signals, making the nerves less responsive to the stretch caused by neck movement.