What is the diagnosis and management for a 40-year-old male with no significant past medical history (PMH) presenting with intermittent tingling sensations starting from the scalp and radiating down to the arms and legs, lasting approximately 30 minutes, with relief achieved by relaxing his arms?

Lhermitte's Sign (Barber Chair Phenomenon)

Definitive Diagnosis

This patient is experiencing Lhermitte's sign—an electric shock-like sensation radiating from the scalp down the spine and into the limbs, triggered by neck flexion and relieved by relaxing the arms (which extends the neck). This is a classic neurologic sign indicating cervical spinal cord pathology, most commonly demyelination or extrinsic compression 1.

Pathophysiology and Clinical Significance

The tingling sensation starting from the scalp and radiating down to arms and legs, lasting 30 minutes and relieved by arm relaxation (which extends the neck), represents typical Lhermitte's phenomenon 1. This occurs when:

• Neck flexion mechanically irritates the posterior columns of the cervical spinal cord, generating abnormal sensory signals that radiate caudally along sensory pathways 1
• The 30-minute duration suggests sustained neck flexion during activities, with relief occurring when the patient extends the neck by relaxing the arms 1
• This is fundamentally different from pulsatile tinnitus or scalp dysesthesia, as it involves the entire neuraxis from scalp to extremities in a dermatomal pattern 1

Critical Differential Diagnosis

Primary Consideration: Cervical Spinal Cord Pathology

Extrinsic cervical spinal cord compression is the most likely diagnosis in a 40-year-old male with intermittent symptoms 1. Key features include:

• Degenerative cervical spine disease (disk herniation, spondylosis, osteophytic spurring) is the most common cause in this age group 2
• Reverse Lhermitte's phenomenon (induced by neck extension) typically indicates extrinsic compression, while typical Lhermitte's (induced by flexion) can indicate either intrinsic or extrinsic pathology 1
• The intermittent nature and positional relief strongly suggest mechanical compression rather than intrinsic cord disease 1

Secondary Considerations

• Cervical demyelination (multiple sclerosis) is the classic cause of Lhermitte's sign but typically presents with additional neurologic deficits and is less likely to be purely positional 1
• Post-traumatic cervical cord contusion can cause delayed typical Lhermitte's phenomenon, but requires history of neck trauma 1
• Cervical spine tumor or syrinx should be considered if symptoms are progressive or associated with other neurologic findings 3

Immediate Diagnostic Workup

Required Imaging

Order MRI of the cervical spine with and without contrast immediately 3, 1. This is the gold standard for evaluating:

• Cervical spinal cord compression from disk herniation, spondylosis, or tumor 3
• Intrinsic cord signal abnormalities suggesting demyelination or myelopathy 3
• Structural abnormalities at the craniocervical junction 3

Do NOT order temporal bone CT, CTA head/neck, or brain MRI as initial studies—these are indicated for pulsatile tinnitus or focal neurologic deficits, not for Lhermitte's sign 4, 5.

Essential Clinical Evaluation

Perform focused neurologic examination to identify:

• Motor weakness in upper or lower extremities suggesting myelopathy 3
• Sensory level on trunk examination indicating spinal cord lesion level 3
• Hyperreflexia, clonus, or Babinski sign indicating upper motor neuron involvement 3
• Gait abnormalities suggesting spinal cord dysfunction 3
• Bladder or bowel dysfunction indicating severe cord compression requiring urgent intervention 3

Management Algorithm

If MRI Shows Cervical Cord Compression

1. Urgent neurosurgical consultation if there is evidence of significant cord compression, myelomalacia, or progressive neurologic deficits 3
2. Conservative management for mild compression without myelopathy includes:
   • Physical therapy focusing on neck posture and strengthening 2
   • Avoidance of extreme neck flexion positions 1
   • NSAIDs for inflammatory component 2
3. Surgical decompression (anterior cervical discectomy and fusion, laminectomy, or laminoplasty) is indicated for:
   • Progressive myelopathy 3
   • Severe cord compression with signal changes 3
   • Failure of conservative management with persistent disabling symptoms 3

If MRI Shows Demyelinating Lesions

1. Neurology consultation for evaluation of multiple sclerosis or other demyelinating disorders 1
2. Brain MRI with contrast to evaluate for additional demyelinating lesions 3
3. Lumbar puncture for cerebrospinal fluid analysis (oligoclonal bands, IgG index) if demyelination suspected 3

If MRI is Normal

1. Reconsider diagnosis—true Lhermitte's sign with normal cervical spine MRI is rare 1
2. Consider alternative diagnoses:
   • Scalp dysesthesia related to cervical muscle tension (but this doesn't radiate to limbs) 2
   • Peripheral neuropathy (but this doesn't originate from scalp) 6
   • Functional neurologic disorder (diagnosis of exclusion) 7

Symptomatic Treatment While Awaiting Imaging

• Gabapentin 300 mg three times daily, titrated up to 900-1800 mg daily in divided doses, can reduce neuropathic pain from nerve root or cord irritation 2
• Avoid prolonged neck flexion during work, reading, or phone use 1
• Soft cervical collar for short-term use (days, not weeks) may provide temporary relief but should not delay definitive evaluation 2

Critical Pitfalls to Avoid

• Do not dismiss this as "just tingling" or anxiety—Lhermitte's sign is a specific neurologic finding indicating spinal cord pathology that requires imaging 1
• Do not order brain imaging or vascular studies first—the radiation pattern from scalp down the spine localizes pathology to the cervical spinal cord, not the brain or blood vessels 4, 5, 1
• Do not confuse with restless legs syndrome—RLS involves an urge to move the legs that worsens at rest and in the evening, without radiation from the scalp 3
• Do not delay imaging for "conservative trial"—cervical myelopathy can progress irreversibly if cord compression is not identified and treated 3
• Do not attribute symptoms to migraine with aura—migraine aura spreads gradually over 5-20 minutes, lasts less than 60 minutes, and does not radiate from scalp to limbs in a dermatomal pattern 3