What are the possible causes of numbness and tingling in the left arm?

Causes of Numbness and Tingling in the Left Arm

Immediate Life-Threatening Causes Requiring Emergency Evaluation

New onset left arm numbness requires immediate emergency evaluation to rule out acute stroke or acute arterial occlusion—both are life-threatening conditions requiring intervention within minutes to hours to prevent permanent disability or death. 1

Acute Stroke

• The combination of left arm numbness with facial weakness or speech disturbance has a 72% probability of stroke 1, 2
• Isolated hemibody sensory loss (numbness alone) still represents high stroke risk 1, 2
• 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
• Brain MRI with diffusion-weighted imaging must be performed immediately to detect acute ischemic changes and differentiate ischemic from hemorrhagic stroke 1, 2
• CT angiography or MR angiography from aortic arch to vertex should be performed to evaluate carotid and vertebral artery disease 1, 2

Acute Arterial Occlusion

• Check bilateral radial pulses and blood pressure in both arms immediately—if pulse is absent or blood pressure unmeasurable on the left side, this indicates acute arterial occlusion requiring immediate vascular surgery consultation 1, 2
• Assess the "6 P's": Pain, Pallor, Pulselessness, Paresthesias (numbness), Poikilothermia (cool limb), Paralysis 1, 2
• A blood pressure difference >20 mmHg between arms confirms significant arterial compromise 2
• Outcome depends entirely on time to reperfusion—immediate thrombectomy/embolectomy is required 1, 2

Spinal Metastases with Cord Compression

• In patients with known cancer, new radiating pain or numbness in the arms can indicate spinal metastases with myelum compression 3
• Alarm symptoms include decreased strength in the arms, difficulty controlling the arms, numbness or tingling radiating down from chest, and inability to walk with legs giving way 3
• Full spinal column MRI should be performed within 12 hours if there is clinical suspicion of myelum or cauda compression 3

Common Non-Emergent Causes

Peripheral Nerve Entrapment Syndromes

Nerve compression syndromes—specifically carpal tunnel syndrome, cervical radiculopathy, ulnar nerve entrapment, and thoracic outlet syndrome—are the most common causes of unilateral arm numbness and tingling in non-emergent presentations. 4, 5

Carpal Tunnel Syndrome

• Results from median nerve compression at the wrist 5
• Presents with decreased pain sensation and numbness in the thumb, index, and middle fingers 5
• Symptoms are reproduced by wrist hyperflexion and median nerve percussion 5
• Volar splinting and steroid injection often ameliorate symptoms 5

Ulnar Nerve Entrapment

• Causes decreased sensation of the little finger and ulnar aspect of the ring finger, along with intrinsic muscle weakness 5, 6
• Can occur at the elbow (cubital tunnel syndrome) or at the wrist (ulnar tunnel syndrome) 5
• Manifests with neuropathic pain, numbness, tingling, and possible motor deficits in the ulnar distribution 6

Radial Tunnel Syndrome

• Occasionally accompanies inflammation of the common wrist extensors and lateral epicondylitis ("tennis elbow") 5
• A radial nerve block can help exclude concomitant radial tunnel syndrome in patients with lateral epicondylitis symptoms 5

Cervical Spine Pathology

Cervical Radiculopathy

• Results from nerve root compression due to disc herniation, foraminal stenosis, or degenerative spondylosis 4
• New or progressive arm numbness with neck pain requires consideration of cervical radiculopathy 4
• Most cases resolve spontaneously or with conservative treatment 4
• MRI is the most sensitive test for detecting soft tissue abnormalities, though it has high false-positive rates in asymptomatic individuals 4

Cervical Myelopathy (Critical Red Flag)

• Symptoms with decreased leg strength, unsteady gait, or radiating numbness from chest/groin suggest cervical myelopathy and require urgent evaluation 4
• Bilateral symptoms with motor weakness or severe dysautonomia are warning signs 4

Systemic and Metabolic Causes

Diabetes, hypothyroidism, vitamin B12 deficiency, alcohol use, and certain medications can cause peripheral neuropathy, though these typically produce bilateral symmetric symptoms rather than isolated left arm involvement. 4, 5

• Risk factors for nerve entrapment include diabetes, smoking, alcohol consumption, rheumatoid arthritis, and hypothyroidism, although these disorders typically produce bilateral symptoms 5
• Assessment should include glucose/HbA1c, thyroid function, vitamin B12, and renal function 4

Chemotherapy-Induced Peripheral Neuropathy (CIPN)

In patients with cancer history receiving neurotoxic chemotherapy:

• Taxanes and platinum-based agents commonly cause numbness, tingling, and pain in a stocking-glove distribution 3
• The neuropathy is primarily sensory, with numbness and tingling appearing earlier and more prominently than pain 3
• Paclitaxel-induced symptoms are more prominent in lower extremities, while oxaliplatin-induced symptoms are initially more severe in upper extremities 3
• Duloxetine is recommended for patients with neuropathic pain, numbness, and tingling 3, 7

Musculoskeletal Trigger Points

• Trigger points in the infraspinatus and teres minor can reproduce upper extremity numbness and tingling 8
• Compression of these trigger points may reproduce shoulder pain and arm numbness symptoms 8
• Clinicians should consider trigger point referral when examining patients with abnormal sensation, especially when a more common cause cannot be identified 8

Critical Red Flags Requiring Urgent Evaluation

• Acute onset, rapidly progressive, or multifocal paresthesias require urgent evaluation to exclude Guillain-Barré syndrome or vasculitis 4
• Bilateral symptoms with motor weakness or severe dysautonomia 4
• Symptoms with decreased leg strength, unsteady gait, or radiating numbness from chest/groin suggesting cervical myelopathy 4
• New back or neck pain with radiating arm pain in cancer patients (possible spinal metastases) 3

Common Pitfalls to Avoid

• Do not assume left arm numbness is always cardiac-related—while myocardial infarction commonly causes left arm discomfort, other diagnoses including seizures can present similarly 9
• Do not rely solely on conventional x-rays, CT scans, or bone scintigraphy to exclude spinal metastases—full spinal column MRI is required 3
• Do not dismiss isolated sensory symptoms as benign—isolated hemibody sensory loss still represents high stroke risk 1, 2
• Do not overlook bilateral pulse and blood pressure checks—this simple maneuver differentiates stroke from acute arterial occlusion 1, 2