What could be causing a shocking sensation and numbness in both hands when I flex my neck fully?

Lhermitte's Sign: Cervical Spinal Cord Pathology

You are describing Lhermitte's sign—an electric shock sensation radiating from the neck down the spine and into the extremities with neck flexion—which indicates cervical spinal cord pathology requiring urgent MRI evaluation. 1, 2

Immediate Diagnostic Approach

Obtain urgent MRI of the entire cervical spine with and without gadolinium contrast within 24-48 hours. 3 This is the single most critical diagnostic test, as your symptoms suggest:

• Cervical myelopathy from spinal cord compression (disc herniation, stenosis, or tumor) 2
• Central cord syndrome pattern, which classically presents with bilateral hand numbness and burning dysesthesias in the forearms 1, 2
• Spinal cord injury without fracture/dislocation (SCIwoFD), particularly if you have underlying cervical stenosis or degenerative changes 1

The MRI protocol must include T1-weighted sequences pre- and post-contrast, T2-weighted sequences, and fat-suppressed sequences to evaluate for compressive lesions, intramedullary pathology, or demyelinating disease. 3

Critical Red Flags Requiring Emergency Evaluation

Seek immediate emergency department evaluation if you develop any of the following:

• Progressive weakness in arms or legs 2, 3
• Difficulty with balance or walking 2
• Loss of bowel or bladder control 2
• Saddle numbness (numbness in the groin/perianal area) 2
• Worsening bilateral hand weakness or inability to grip objects 1

These symptoms indicate potential spinal cord compression requiring neurosurgical decompression within 24-48 hours for optimal recovery. 3

Why This Matters

Lhermitte's sign occurs when the spinal cord is irritated or compressed, causing abnormal electrical discharges that travel down sensory pathways with mechanical stress (neck flexion). 2 The bilateral hand numbness you describe suggests involvement of the cervical spinal cord at the C3-C7 level, where central cord pathology preferentially affects upper extremity function. 1, 2

Time is critical—compressive myelopathies causing progressive neurological deficits require decompression within 24-48 hours for optimal recovery. 3 Metabolic failure occurs at the mitochondrial level when spinal cord compression impairs blood flow and oxidative metabolism, leading to progressive sensory and motor deficits. 2

Common Pitfalls to Avoid

• Do not rely on plain X-rays or CT scans alone—full spinal column MRI is mandatory to exclude spinal cord pathology. 2
• Do not delay imaging if you have any lower extremity symptoms, progressive weakness, or bowel/bladder changes, as these indicate more severe cord compression. 1, 2
• Avoid excessive neck flexion until imaging is completed, as repeated mechanical stress on a compressed spinal cord can worsen injury. 2

Additional Workup

While awaiting MRI, your physician should obtain:

• Complete neurological examination documenting upper and lower extremity strength, reflexes, and sensory distribution 3
• Serial neurological examinations every 2-4 hours if symptoms are progressive 3
• Neurosurgical consultation if imaging reveals compressive lesions 3

If MRI shows spinal cord signal changes from C3-C7 with canal narrowing, this confirms cervical myelopathy requiring urgent intervention. 1