Lhermitte’s sign

Lhermitte’s sign is a distinctive neurological symptom characterized by a sudden, brief, electric shock-like sensation that radiates down the spine and into the limbs upon flexion of the neck. It serves as an important clinical clue to cervical spinal cord pathology, often associated with demyelinating disorders such as multiple sclerosis. Recognition of this sign is vital for early diagnosis and management of underlying neurological diseases.

Overview of Lhermitte’s Sign

Definition and Description

Lhermitte’s sign, also known as the “barber chair phenomenon,” refers to a transient, shock-like sensation that typically begins in the neck and travels downward along the spine, sometimes extending to the arms or legs. The sensation is usually triggered by neck flexion but can also occur with coughing, sneezing, or sudden head movements. Although brief, the symptom can be distressing and recurrent, often indicating dysfunction of the cervical spinal cord.

Historical Background

This phenomenon was first described by French neurologist Jean Lhermitte in 1924, who observed the symptom in patients with multiple sclerosis and other conditions involving the spinal cord. Over time, it became recognized as a hallmark of cervical cord demyelination, although subsequent studies revealed its occurrence in various other pathological states such as vitamin B12 deficiency and cervical spondylosis. The sign remains an important diagnostic feature in clinical neurology, valued for its specificity in identifying spinal cord involvement.

Epidemiology and Clinical Significance

Lhermitte’s sign occurs most frequently in individuals with demyelinating diseases, particularly multiple sclerosis, where it affects up to one-third of patients at some point in their illness. It may also present in those with cervical spondylotic myelopathy, radiation-induced myelopathy, and metabolic disorders affecting myelin integrity. While the sign itself is not dangerous, its presence often points to underlying spinal cord pathology that requires prompt investigation and management.

Clinically, Lhermitte’s sign provides valuable insight into the functional state of the cervical cord and can guide further diagnostic imaging, particularly magnetic resonance imaging (MRI). Its identification can also help differentiate central nervous system involvement from peripheral causes of sensory disturbance.

Pathophysiology

Mechanism of the Electric Shock Sensation

The characteristic shock-like sensation in Lhermitte’s sign results from abnormal electrical conduction within the demyelinated or compressed fibers of the cervical spinal cord. Neck flexion stretches these fibers, inducing ectopic impulses that travel along the sensory pathways of the dorsal columns. These transient discharges are perceived as an electric shock radiating down the spine and limbs.

Involvement of the Cervical Spinal Cord

The cervical spinal cord, particularly the posterior (dorsal) columns, is most commonly implicated in Lhermitte’s sign. These columns are responsible for transmitting proprioceptive and fine touch sensations. When demyelination, compression, or inflammation affects this region, the altered conduction dynamics lead to heightened excitability and inappropriate transmission of sensory signals.

Role of Demyelination and Axonal Damage

Demyelination plays a central role in the genesis of Lhermitte’s sign. The loss of myelin sheath disrupts normal saltatory conduction, exposing axons to mechanical stress and electrical instability. In multiple sclerosis and other demyelinating diseases, this damage renders the neurons hypersensitive to minor mechanical deformation during neck movement, generating paroxysmal discharges perceived as electric shocks. Chronic demyelination may also lead to secondary axonal injury, further enhancing the likelihood of abnormal signal propagation.

Neuroanatomical Correlates

Neuroimaging and electrophysiological studies indicate that the posterior columns of the cervical spinal cord, particularly between the C2 and C6 levels, are most frequently involved. Lesions in these regions, whether from demyelination, ischemia, or compression, alter the integrity of sensory tracts and lower the threshold for abnormal firing. Functional MRI studies have confirmed hyperactivity in these pathways during neck flexion in patients exhibiting Lhermitte’s sign, supporting its origin in disrupted dorsal column function.

Etiology and Associated Conditions

Lhermitte’s sign is a manifestation of various neurological and systemic conditions that affect the cervical spinal cord, particularly those involving demyelination or mechanical compression. Recognizing the underlying cause is essential for accurate diagnosis and targeted management. The sign itself is not disease-specific but indicates a disruption of normal conduction in the dorsal columns.

• Multiple Sclerosis: This is the most common cause of Lhermitte’s sign. Demyelinating plaques in the cervical spinal cord interfere with normal signal transmission, producing the characteristic electric shock sensation. The symptom may appear transiently during relapses or persist in chronic stages.
• Cervical Spondylotic Myelopathy: Degenerative changes in the cervical spine, including osteophyte formation and intervertebral disc protrusion, can compress the spinal cord. Such mechanical stress induces abnormal impulses in the dorsal columns, mimicking demyelinating pathology.
• Vitamin B12 Deficiency (Subacute Combined Degeneration): Deficiency of vitamin B12 leads to demyelination of both the dorsal and lateral columns of the spinal cord. Patients often experience Lhermitte’s sign in addition to gait disturbances, paresthesia, and weakness.
• Radiation-Induced Myelopathy: Exposure of the cervical spine to radiation, often during cancer therapy, can result in delayed demyelination and necrosis. Lhermitte’s sign may develop months after treatment as a transient or progressive symptom.
• Trauma or Cervical Cord Compression: Physical injury or herniated discs that cause stretching or compression of the spinal cord may trigger Lhermitte’s phenomenon. It is typically associated with neck movement and may resolve as the injury heals.
• Post-Infectious and Autoimmune Myelitis: Inflammatory processes following infections such as Epstein–Barr virus, or autoimmune disorders like neuromyelitis optica spectrum disorder, can cause acute demyelination leading to Lhermitte’s sign.
• Chemotherapy-Related Neurotoxicity: Certain chemotherapeutic agents, including cisplatin and cytarabine, have neurotoxic effects that can damage spinal cord pathways, resulting in transient sensory disturbances like Lhermitte’s sign.
• Other Less Common Causes: Rarely, conditions such as Behçet’s disease, systemic lupus erythematosus, or syringomyelia can also present with Lhermitte’s sign when cervical cord involvement occurs.

Identifying the precipitating condition through a detailed history, neurological examination, and imaging is vital to differentiating reversible causes from progressive pathologies.

Clinical Features

Characteristic Sensation

Lhermitte’s sign is classically described as a brief, electric shock-like or tingling sensation that begins in the neck and radiates down the spine, sometimes extending to the limbs. The sensation typically lasts only a few seconds and may occur spontaneously or with specific movements. The experience is often startling but not usually painful.

Precipitating Factors

The sign is most often triggered by flexion of the neck, which stretches the cervical spinal cord and stimulates demyelinated or compressed fibers. Other provoking factors may include:

• Sudden head movements or neck rotation
• Coughing, sneezing, or straining (Valsalva maneuver)
• Fatigue, stress, or overheating, especially in patients with multiple sclerosis
• Postural changes or prolonged flexion of the neck

Duration, Frequency, and Severity

The episodes of Lhermitte’s sensation are usually brief, lasting less than two seconds, but can recur multiple times daily depending on neck activity. The intensity varies among patients, ranging from mild tingling to a sharp electric jolt. While transient in many cases, chronic forms may persist for months or years in demyelinating diseases.

Associated Neurological Symptoms

Lhermitte’s sign often occurs in conjunction with other neurological deficits depending on the underlying condition. These may include:

• Numbness or paresthesia in the hands and feet
• Weakness or spasticity of the limbs
• Impaired proprioception and balance
• Visual disturbances in demyelinating diseases such as multiple sclerosis
• Bladder or bowel dysfunction in advanced spinal cord involvement

Impact on Daily Activities and Quality of Life

Although the symptom itself is not life-threatening, recurrent episodes of Lhermitte’s sign can cause discomfort, anxiety, and postural avoidance behaviors. Patients may limit neck movement to prevent triggering sensations, which can affect mobility and occupational activities. Persistent symptoms can also lead to sleep disturbances and reduced quality of life, particularly in individuals with chronic neurological disease.

Diagnostic Evaluation

The diagnosis of Lhermitte’s sign is primarily clinical, based on the patient’s history and the characteristic description of the electric shock sensation induced by neck flexion. However, identifying the underlying cause requires a comprehensive neurological examination supported by imaging and laboratory investigations. The goal of diagnostic evaluation is to confirm cervical cord involvement, determine the etiology, and guide appropriate management.

Clinical Assessment and Elicitation of the Sign

The clinician can elicit Lhermitte’s sign by gently flexing the patient’s neck while observing for a sudden shock-like sensation radiating down the spine or limbs. The sign should be assessed with caution, especially in individuals with cervical instability or trauma. A detailed medical history, including onset, triggers, frequency, and associated symptoms, helps in differentiating between mechanical and demyelinating causes.

Neurological Examination Findings

A full neurological examination is essential to evaluate for additional spinal cord or systemic involvement. Key findings may include:

• Increased deep tendon reflexes and spasticity suggestive of upper motor neuron involvement
• Loss of vibration and position sense indicating dorsal column dysfunction
• Weakness or sensory changes in the limbs, pointing toward cervical myelopathy
• Optic neuritis or visual field deficits in demyelinating disorders like multiple sclerosis
• Ataxia, paresthesia, or other sensory disturbances in metabolic causes such as vitamin B12 deficiency

Imaging Studies

Magnetic resonance imaging (MRI) is the gold standard for evaluating patients presenting with Lhermitte’s sign. It provides high-resolution visualization of the spinal cord and surrounding structures, allowing differentiation between demyelinating, compressive, or inflammatory etiologies.

• MRI of the Cervical Spine: Typically reveals hyperintense lesions on T2-weighted images in demyelinating disorders such as multiple sclerosis or areas of compression in cervical spondylosis. It also helps assess the extent of structural deformity, herniated discs, or spinal stenosis.
• Brain MRI for Demyelinating Lesions: In suspected multiple sclerosis, MRI of the brain may show characteristic white matter plaques in periventricular, juxtacortical, or infratentorial regions. The presence of both spinal and brain lesions supports the diagnosis.

Laboratory Investigations

Laboratory studies are used to identify metabolic, autoimmune, or infectious causes contributing to cervical cord dysfunction. Common investigations include:

• Vitamin B12 and Folate Levels: Deficiencies in these vitamins are associated with subacute combined degeneration of the spinal cord, often presenting with Lhermitte’s sign and other sensory symptoms.
• Autoimmune and Infectious Panels: Testing for markers such as antinuclear antibodies, aquaporin-4 antibodies, or viral serology helps in detecting systemic autoimmune diseases or post-infectious myelitis.
• Inflammatory Markers: Elevated erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP) may suggest inflammatory or infectious processes affecting the spinal cord.

Neurophysiological Tests

Evoked potential studies, such as somatosensory evoked potentials (SSEPs), can assess conduction delays within the dorsal column pathways. These tests are especially useful when imaging findings are inconclusive, providing functional evidence of spinal cord demyelination or conduction block.

Differential Diagnosis

Several neurological conditions can mimic Lhermitte’s sign or produce similar paroxysmal sensations. Differentiating between these disorders is crucial for accurate diagnosis and treatment. The table below summarizes key differences among common differential diagnoses.

Condition	Characteristic Features	Distinguishing Points
Cervical Radiculopathy	Pain or tingling radiating from the neck into one arm following a dermatomal pattern	Usually unilateral; caused by nerve root compression; not typically shock-like or triggered by neck flexion
Peripheral Neuropathy	Distal sensory loss, burning pain, and weakness in a stocking-glove distribution	Originates in peripheral nerves; unaffected by neck movements
Myelitis without Demyelination	Inflammatory spinal cord lesions causing sensory and motor deficits	Symptoms are often continuous rather than transient electric shocks
Other Paroxysmal Sensory Phenomena	Brief tingling or burning sensations without mechanical triggers	Can occur in multiple sclerosis but not associated specifically with neck flexion

Accurate differentiation relies on correlating clinical history, physical examination findings, and neuroimaging results. While Lhermitte’s sign is highly suggestive of cervical spinal cord involvement, confirming the underlying pathology ensures targeted and effective treatment.

Management and Treatment

Management of Lhermitte’s sign focuses on two main goals: addressing the underlying cause of the symptom and providing symptomatic relief. Since the sign itself is a manifestation rather than a standalone disorder, a comprehensive and individualized treatment plan is essential for optimal outcomes. The approach varies depending on whether the cause is demyelinating, compressive, metabolic, or iatrogenic in nature.

Treatment of Underlying Cause

Identifying and treating the primary condition often leads to improvement or resolution of Lhermitte’s sign. Common therapeutic strategies include:

• Multiple Sclerosis Management: Disease-modifying therapies (DMTs) such as interferon-beta, glatiramer acetate, or monoclonal antibodies (e.g., ocrelizumab, natalizumab) are used to reduce demyelination and prevent relapse. Corticosteroids may be administered during acute exacerbations to limit inflammation and restore conduction.
• Nutritional Supplementation: In patients with vitamin B12 or folate deficiency, parenteral vitamin B12 injections are the treatment of choice, followed by oral maintenance therapy. Early intervention helps reverse neurological deficits and prevent progression.
• Surgical or Conservative Management of Cervical Myelopathy: In cases caused by cervical spondylotic myelopathy, treatment may involve physical therapy, cervical traction, or surgical decompression depending on the degree of spinal cord compression and neurological impairment.
• Management of Radiation-Induced Injury: For radiation myelopathy, corticosteroids and hyperbaric oxygen therapy may help reduce inflammation, although preventive measures such as careful dosing during radiation remain most effective.

Symptomatic Treatment

When the underlying cause cannot be rapidly reversed or if Lhermitte’s sign persists despite treatment, symptomatic management is aimed at reducing nerve hyperexcitability and improving patient comfort.

• Pharmacological Options: Neuropathic pain medications such as gabapentin, pregabalin, carbamazepine, or lamotrigine can help reduce the frequency and intensity of electric shock sensations. These agents stabilize neuronal membranes and inhibit abnormal discharges.
• Physical Therapy and Postural Modifications: Patients may benefit from cervical stabilization exercises, posture correction, and avoidance of excessive neck flexion. Use of a soft cervical collar can minimize neck movement and prevent symptom recurrence.
• Lifestyle Adjustments: Managing fatigue, stress, and body temperature can lessen symptom severity, particularly in individuals with multiple sclerosis where heat sensitivity aggravates neurological symptoms.

Regular follow-up is important to assess symptom progression, adjust medications, and evaluate the response to therapy. Education and reassurance help patients understand the benign nature of the symptom itself, even when the underlying condition requires ongoing care.

Prognosis and Outcomes

The prognosis of Lhermitte’s sign depends largely on the underlying etiology and the effectiveness of its management. In many cases, especially when related to reversible or treatable causes such as vitamin B12 deficiency or transient cervical compression, the symptom resolves completely with appropriate therapy. However, in chronic neurological disorders like multiple sclerosis, the sign may recur intermittently or persist over time.

Natural History of the Condition

Lhermitte’s sign typically appears intermittently and may fluctuate in intensity and frequency. In demyelinating disorders, episodes often correspond with disease activity and may subside during remission. Some patients experience complete resolution, while others report persistent but tolerable sensations that diminish over years.

Factors Influencing Recovery

Several factors influence recovery and prognosis, including:

• Severity and duration of the underlying spinal cord lesion
• Promptness of diagnosis and treatment initiation
• Extent of remyelination or neural repair following inflammation or injury
• Patient adherence to therapy and rehabilitation protocols
• Presence of coexisting neurological or metabolic disorders

Chronic and Recurrent Cases

In chronic cases, particularly those linked to progressive neurological diseases, Lhermitte’s sign may persist despite optimal therapy. Recurrent episodes are more common in patients with cervical spondylosis or multiple sclerosis, where ongoing demyelination or mechanical irritation continues to affect the dorsal columns. Long-term use of neuropathic pain modulators, combined with physical therapy, often provides partial relief and improves quality of life.

Overall, while Lhermitte’s sign can be distressing, it is generally benign and does not signify permanent damage by itself. Early detection and management of the primary cause remain the key to favorable outcomes and symptom control.

Complications and Quality of Life Considerations

Although Lhermitte’s sign is typically a benign and transient symptom, its recurrent or chronic nature can affect patients both physically and psychologically. In some individuals, the anticipation of the electric shock sensation may lead to anxiety, restricted movement, and avoidance of daily activities. Over time, these adaptations can impact mobility, posture, and overall quality of life.

Functional Limitations

Repetitive episodes of Lhermitte’s sign may cause patients to avoid neck flexion or certain physical activities. This can lead to stiffness of the cervical muscles, postural imbalance, and reduced range of motion. In occupational settings that require frequent neck movement, such as desk work or driving, symptoms may interfere with performance and safety. Overcompensation for discomfort can also contribute to secondary musculoskeletal strain in the shoulders and upper back.

Psychological Impact

The unpredictability and recurrence of the shock-like sensations can generate anxiety, stress, and fear of movement, particularly in chronic neurological conditions like multiple sclerosis. Patients may develop hypervigilance toward physical triggers, resulting in social withdrawal or reduced participation in recreational activities. In severe cases, the chronic discomfort may contribute to mood disturbances such as depression, especially when combined with other neurological symptoms.

Rehabilitation Approaches

A multidisciplinary rehabilitation approach can significantly enhance coping and physical adaptation. Physical therapists can design neck stabilization and mobility exercises to improve strength and reduce stiffness, while occupational therapists provide ergonomic adjustments for daily activities. Psychological counseling and relaxation therapies, including mindfulness and cognitive-behavioral therapy, can help patients manage anxiety associated with recurrent symptoms. Patient education is essential to reassure individuals that Lhermitte’s sign, though uncomfortable, rarely indicates worsening disease by itself.

With comprehensive management, most patients can maintain functional independence and resume normal activities with minimal disruption to their quality of life.

Recent Research and Advances

Recent advancements in neuroimaging, neurophysiology, and molecular biology have deepened understanding of the mechanisms behind Lhermitte’s sign and its related pathologies. Research efforts have also focused on improving diagnostic accuracy and developing novel therapeutic strategies to prevent or reverse demyelination within the spinal cord.

Neuroimaging Insights into Demyelinating Lesions

High-resolution MRI and diffusion tensor imaging (DTI) have provided valuable insights into microstructural changes within the cervical spinal cord. Studies using these modalities have demonstrated correlations between dorsal column lesion load and the occurrence of Lhermitte’s sign in multiple sclerosis. Functional MRI has further revealed abnormal activation patterns in sensory pathways during neck flexion, confirming the physiological basis of the symptom.

Biomarkers of Neural Repair and Recovery

Ongoing research is identifying serum and cerebrospinal fluid biomarkers that indicate remyelination and axonal repair. Neurofilament light chain (NfL) levels, for example, serve as indicators of axonal injury, while myelin-associated glycoprotein and oligodendrocyte lineage markers reflect regenerative activity. Such biomarkers may eventually help clinicians monitor therapeutic response and predict recovery from spinal cord lesions associated with Lhermitte’s sign.

Emerging Therapies and Preventive Strategies

Novel pharmacological agents targeting neuroprotection and remyelination are under investigation. Experimental compounds such as clemastine fumarate and anti-LINGO-1 antibodies have shown potential in promoting myelin repair in demyelinating diseases. Advances in stem cell therapy also hold promise for regenerating damaged neural tissues and restoring conduction integrity in the spinal cord. Additionally, neurorehabilitation programs integrating virtual reality and neuromodulation techniques are being explored to retrain neural pathways and reduce symptom recurrence.

These developments represent significant progress in understanding and managing the neural mechanisms underlying Lhermitte’s sign. Continued interdisciplinary research will likely lead to improved diagnostic precision, more effective treatments, and better quality of life for affected individuals.

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