What are the possible causes and treatments for numbness on the left side of the neck?

Numbness on the Left Side of the Neck: Evaluation and Management

Immediate Assessment Priority

Isolated neck numbness requires systematic evaluation to exclude serious underlying pathology, particularly cranial nerve involvement, malignancy, or inflammatory conditions, before attributing symptoms to benign mechanical causes. 1, 2

Red Flag Symptoms Requiring Urgent Investigation

You must actively screen for the following concerning features that mandate immediate advanced imaging:

• Constitutional symptoms: Fever, unexplained weight loss, or night sweats 2
• Progressive neurological deficits: Weakness in arms or legs, bilateral symptoms, or symptoms affecting both upper and lower extremities (suggesting myelopathy) 3
• Autonomic dysfunction: New bladder or bowel dysfunction, loss of perineal sensation 3
• Recent lymphadenopathy or difficulty swallowing: May indicate inflammatory, infectious, or neoplastic process 4
• Multiple cranial nerve involvement: Numbness extending to face, difficulty with facial expression, or swallowing problems 1
• Elevated inflammatory markers: If labs show elevated CRP or ESR 4, 2

Differential Diagnosis by Anatomic Distribution

Cervical Nerve Root Involvement (C2-C4)

• C2-C3 distribution: Numbness in the lateral neck and posterior scalp 1
• Cervical radiculopathy: Annual incidence 83 per 100,000; typically presents with neck pain radiating to arm with tingling, though isolated neck numbness can occur 3
• Degenerative disc disease: Common but correlates poorly with symptoms in isolation 4, 5

Cranial Nerve Pathology

• Trigeminal nerve (CN V): Can cause facial and neck sensory abnormalities 1
• Glossopharyngeal nerve (CN IX): Oropharyngeal pain with potential neck involvement 1
• Multiple cranial neuropathies: Lesions at skull base or neck can affect multiple nerves simultaneously due to anatomic proximity 1

Serious Pathology to Exclude

• Malignancy: Primary or metastatic tumors affecting cervical spine or perineural spread from head/neck cancers 1, 2
• Infection: Cervical epidural abscess, meningitis 2
• Vascular causes: Vertebral or carotid artery dissection 2
• Inflammatory conditions: Cervical arthritis, inflammatory myopathies (often with elevated inflammatory markers) 2

Diagnostic Imaging Algorithm

When to Order MRI (High Priority)

MRI of the cervical spine without contrast is indicated if ANY of the following are present:

• Red flag symptoms listed above 4, 3
• Symptoms persisting beyond 4-6 weeks despite conservative management 5
• Focal neurologic symptoms or signs on examination 5
• Clinical suspicion for cranial neuropathy requiring evaluation from brain stem nuclei to end organs 1

For suspected cranial nerve involvement: MRI orbits, face, and neck without and with IV contrast OR MRI head without and with IV contrast are usually appropriate and may be complementary depending on institutional protocols 1

When Plain Radiographs Are Insufficient

• X-rays showing degenerative changes are insufficient for complete evaluation given that such changes are common in asymptomatic individuals and correlate poorly with symptoms 4
• MRI is superior for evaluating soft tissue abnormalities, nerve root compression, inflammatory processes, and infection not visible on X-ray 4, 3

Management Approach

Conservative Management (If No Red Flags Present)

• Exercise therapy: Appears beneficial for neck pain 5
• NSAIDs: Some evidence for muscle relaxants in acute neck pain with muscle spasm 5
• Proprioceptive retraining: Exercises targeting cervical proprioception and muscle coordination are effective for chronic neck pain with sensorimotor disturbances 6

Monitoring Strategy

• If conservative management initiated, reassess in 2-4 weeks 4
• Consider repeat inflammatory markers if initially elevated 4
• Critical threshold: 75-90% of cervical radiculopathy achieves symptomatic relief with nonoperative therapy, but 30-50% with chronic neck pain develop symptoms lasting more than one year 3, 5

Key Clinical Pitfalls

Do not assume benign mechanical cause without excluding serious pathology first. The combination of isolated sensory symptoms in a specific nerve distribution warrants careful evaluation 1, 2. Most neck pain is mechanical/musculoskeletal 2, but isolated numbness—particularly unilateral and in a specific distribution—requires higher suspicion for nerve-specific pathology 1.

MRI findings must be interpreted in clinical context: High rates of abnormal findings exist in asymptomatic individuals, so imaging abnormalities alone do not confirm the pain source 4, 2, 7. However, the presence of red flags mandates imaging regardless 4, 3.

Minimal response to initial therapy is itself a red flag requiring escalation of diagnostic evaluation 4.