Numbness

Background

Sensory Homunculus.

Dermatomes — anterior

Dermatomes — posterior

• Numbness (paresthesias/hypoesthesia) is a common ED complaint
• Key EM role: distinguish central causes (stroke, spinal cord compression) from peripheral causes
• Pattern of numbness is the most important clue to localization

Clinical Features

Localizing by History and Physical

• Distribution: unilateral face + arm + leg = cortical (stroke); bilateral distal = peripheral neuropathy; dermatomal = radiculopathy; stocking-glove = polyneuropathy
• Onset: acute (minutes-hours) = vascular; subacute (days-weeks) = inflammatory; chronic = metabolic/degenerative
• Associated weakness: combined motor + sensory = more concerning for central or cord lesion
• Sensory level: band-like numbness at a specific dermatome level = spinal cord pathology

Red Flags

• Acute onset unilateral numbness (stroke until proven otherwise)
• Saddle anesthesia + urinary retention (cauda equina syndrome)
• Sensory level on trunk (spinal cord compression)
• Rapidly ascending numbness/weakness (Guillain-Barré syndrome)
• Numbness + bilateral leg weakness (cord compression)

Differential Diagnosis

Peripheral neuropathy

• Peripheral nerve syndromes (mononeuropathy)^
  • Acute trauma
  • Chronic nerve entrapment
• Mononeuritis multiplex^^
  • Acute
    • Diabetes mellitus
    • Polyarteritis nodosum
    • Connective tissue diseases (e.g., SLE, rheumatoid arthritis)
  • Chronic
    • Multiple compressive neuropathies
    • AIDS
    • Sarcoidosis
    • Acromegaly
    • Leprosy
    • Lyme disease
    • Idiopathic
• Associated with autonomic features
  • Alcohol use disorder
  • Amyloidosis
  • Chemotherapy-related neuropathy
  • Chronic nitrous oxide abuse
  • Diabetes mellitus
  • Heavy metal toxicity
  • Porphyria
  • Primary dysautonomia
  • Vitamin B12 deficiency
• Associated with pain
  • Alcohol use disorder
  • Amyloidosis
  • Chemotherapy (heavy metal toxicity)
  • Diabetes mellitus
  • Idiopathic polyneuropathy
  • Porphyria
  • Paraneoplastic syndrome
  • Vitamin B1 or B12 deficiency
  • Arsenic toxicity
  • Thallium toxicity

^A condition in which a single nerve is damaged or compressed.
^^A condition where damage to at least two separate peripheral nerves results in a painful, asymmetric, and asynchronous presentation of sensory and motor deficits.

By Localization

Level	Distribution	Facial	Pain
Brain/cortex	Unilateral	Often	No
Spinal cord	Bilateral	No	Possible
Nerve root	Dermatomal/unilateral	No	Yes
Peripheral nerve	Specific nerve territory	Possible	Yes
Polyneuropathy	Distal symmetric	No	Often

Central

• Stroke/TIA: acute onset, unilateral, often with other deficits
• Spinal cord compression: bilateral, sensory level, weakness (see Epidural compression syndromes)
• Transverse myelitis, MS

Peripheral

• Guillain-Barré syndrome: ascending weakness + paresthesias, areflexia
• Radiculopathy: dermatomal, often with pain
• Diabetic neuropathy: distal, symmetric, stocking-glove
• Carpal tunnel / ulnar neuropathy: specific nerve distribution
• Cauda equina syndrome: saddle anesthesia, urinary retention, bilateral leg symptoms

Evaluation

• Thorough neurologic exam: sensory testing (light touch, pinprick, proprioception), motor strength, reflexes, gait
• Acute unilateral: CT/CTA head → stroke protocol
• Bilateral with sensory level: emergent MRI spine (cord compression)
• Saddle anesthesia: emergent MRI lumbar spine, bladder scan for post-void residual
• Ascending weakness: LP for GBS (albuminocytologic dissociation), respiratory monitoring
• BMP, CBC, glucose, TSH, B12 for polyneuropathy workup (can be outpatient)

Management

• Stroke: activate stroke protocol (see Stroke)
• Cord compression: IV dexamethasone, emergent neurosurgery/oncology, emergent MRI
• Cauda equina: emergent MRI, surgical consultation
• GBS: ICU if respiratory compromise, IVIG or plasmapheresis, neurology consultation
• Peripheral neuropathy: outpatient workup unless acute/progressive
• Radiculopathy: pain management, outpatient follow-up unless red flags

Disposition

• Admit: stroke, spinal cord compression, cauda equina, GBS, acute rapidly progressive symptoms
• Discharge: stable peripheral neuropathy, chronic radiculopathy, isolated carpal tunnel — with neurology follow-up if new
• Return precautions: weakness, difficulty walking, urinary/bowel changes, worsening or spreading numbness

See Also

• Focal neurologic deficits
• Weakness
• Stroke
• Cauda equina syndrome
• Guillain-Barré syndrome