What causes numbness followed by tingling in the left hand and arm?

Acute Evaluation for Left Hand and Arm Numbness Followed by Tingling

You must immediately seek emergency evaluation to rule out acute stroke or acute arterial occlusion, as new onset left arm numbness requires urgent assessment within hours to prevent permanent disability or death. 1

Immediate Emergency Assessment Required

Time-critical evaluation is mandatory because:

• Patients presenting within 48 hours with unilateral numbness have a 10% risk of completed stroke within the first week, with highest risk in the first 48 hours 1, 2
• If numbness is accompanied by facial weakness or speech disturbance, there is a 72% probability of stroke 1, 2
• Even isolated arm numbness alone represents high stroke risk and requires same-day emergency department assessment 1

Critical First Steps in Emergency Department

The following must be performed immediately upon arrival:

Vascular Assessment

• Check radial pulse on the left arm and measure blood pressure in both arms 1, 2
• A blood pressure difference >20 mmHg between arms or absent pulse indicates acute arterial occlusion requiring immediate vascular surgery consultation 2
• Assess the "6 P's": Pain, Pallor, Pulselessness, Paresthesias (numbness), Poikilothermia (cool limb), Paralysis 1, 2

Neurological Examination

• Perform Cincinnati Prehospital Stroke Scale assessment including facial droop, arm drift, and speech abnormalities 2
• Test for accompanying facial numbness, weakness, or speech changes 1, 2

Mandatory Imaging Within 24 Hours

Brain MRI with diffusion-weighted imaging is the preferred initial test to detect acute ischemic changes and must be performed immediately 1, 2

If MRI is unavailable:

• Obtain CT head without contrast to rule out hemorrhage 1, 2
• This imaging differentiates ischemic from hemorrhagic stroke, which fundamentally changes treatment 1

Vascular imaging is also required:

• CT angiography or MR angiography from aortic arch to vertex to evaluate carotid and vertebral artery disease 1
• Carotid ultrasound to identify extracranial carotid stenosis >70% requiring carotid endarterectomy 1, 2

Treatment Based on Diagnosis

If Stroke/TIA is Confirmed

Dual antiplatelet therapy (aspirin + clopidogrel 75 mg) should be initiated for the first 21 days in patients with symptomatic carotid stenosis not undergoing revascularization, followed by long-term single antiplatelet therapy 1, 2

If Acute Arterial Occlusion is Confirmed

• Immediate vascular surgery consultation for thrombectomy/embolectomy is required as outcome depends entirely on time to reperfusion 1, 2

Alternative Diagnoses Only After Stroke is Ruled Out

If emergency evaluation excludes stroke and vascular occlusion, consider these conditions:

Carpal Tunnel Syndrome (Most Common)

• Characterized by numbness and tingling in thumb, index, middle, and radial ring fingers 3
• The Durkan maneuver (firm digital pressure across carpal tunnel) is 64% sensitive and 83% specific 3
• Electrodiagnostic testing is >80% sensitive and 95% specific for diagnosis 3
• First-line treatment: wrist splinting or steroid injection 3
• Surgical carpal tunnel release for patients not responding to conservative therapy 3

Cubital Tunnel Syndrome

• Presents with numbness in ring and small fingers, plus hand weakness 4
• Second most common compression neuropathy in upper extremity 4
• Ulnar nerve decompression can alleviate symptoms and prevent muscle atrophy 4

Cervical Radiculopathy or Peripheral Neuropathy

• Consider if bilateral symptoms or "stocking-and-glove" distribution 5
• Assess for diabetes, thyroid dysfunction, vitamin deficiencies 5
• For neuropathic pain with numbness and tingling, duloxetine is first-line pharmacologic treatment 6, 5
• Physical activity should be offered for neuropathy symptoms 6, 5

Critical Pitfalls to Avoid

Do not assume this is a benign peripheral nerve problem without emergency evaluation - the combination of left-sided symptoms with any facial involvement or speech change has a 72% stroke probability 1, 2

Do not delay imaging for electrodiagnostic testing - if stroke is suspected, brain imaging must occur immediately, not after EMG/NCS 1, 2

Do not dismiss isolated numbness - even without weakness or other symptoms, isolated hemibody sensory loss represents high stroke risk 1