What is the most likely diagnosis and urgent management for left‑sided neck and mandibular paresthesia accompanied by intermittent nausea and gait instability?

Urgent Evaluation for Posterior Circulation Stroke

This presentation of left-sided neck and jaw paresthesia with nausea and balance instability requires immediate neuroimaging with MRI brain without contrast to exclude posterior circulation stroke, which can present with isolated cranial nerve symptoms and gait instability in 75-80% of cases without focal motor deficits. 1, 2

Critical Red Flags Present

Your symptom constellation includes multiple concerning features that mandate urgent evaluation:

• Unilateral cranial nerve distribution paresthesia (left neck and mandibular region) suggests involvement of lower cranial nerves (CN IX-XII) or their nuclei in the medulla 1
• Balance instability indicates possible brainstem or cerebellar pathology 1, 2
• Nausea is a common autonomic feature of both peripheral and central vestibular lesions, but combined with other symptoms raises concern for central pathology 2, 3

Most Likely Differential Diagnoses

High Priority: Central Nervous System Pathology

Posterior circulation stroke or transient ischemic attack is the most critical diagnosis to exclude, as approximately 25% of acute vestibular syndrome cases have cerebrovascular disease, rising to 75% in high vascular risk cohorts 1, 2, 3. Key features supporting this:

• Multiple lower cranial nerve involvement (CN IX-XII) suggests medullary or jugular foramen pathology 1
• Gait instability with nausea indicates possible lateral medullary syndrome (Wallenberg syndrome), typically from posterior inferior cerebellar artery occlusion 1
• 75-80% of posterior circulation stroke patients have no focal neurologic deficits initially, making this diagnosis easily missed 2, 3

Jugular foramen syndrome (Vernet, Collet-Sicard, or Villaret syndrome) can cause variable patterns of CN IX-XII palsies with neck involvement 1. Etiologies include:

• Paragangliomas, schwannomas, or meningiomas
• Infection or leptomeningeal processes
• Internal carotid artery dissection (can cause isolated CN XII palsy or multiple lower cranial nerve involvement) 1

Reversible cerebral vasoconstriction syndrome (RCVS) should be considered if there is associated severe headache, as it can present with neurologic deficits, nausea, and ataxia 4

Moderate Priority: Peripheral Nerve Pathology

Numb chin syndrome describes sensory neuropathy in the mandibular division of the trigeminal nerve and can be caused by malignancy, particularly when presenting as an isolated symptom 5. However, your symptoms extend beyond a single nerve distribution.

Vestibular paroxysmia from neurovascular compression of CN VIII can cause episodic vertigo and balance issues, though typically does not cause neck/jaw paresthesia 6

Lower Priority (Less Likely Given Presentation)

• Benign paroxysmal positional vertigo (BPPV) causes brief episodes (<1 minute) triggered by head position changes, not persistent symptoms with paresthesias 1, 2
• Vestibular neuritis causes acute persistent vertigo but would not explain unilateral neck/jaw numbness 2, 3

Immediate Diagnostic Workup

Essential First-Line Imaging

MRI brain without IV contrast is mandatory and should include: 1, 2

• Diffusion-weighted imaging (DWI) to detect acute posterior circulation infarcts (sensitivity 4% vs <1% for CT) 2
• High-resolution sequences through the posterior fossa, posterior skull base, and medulla 1
• Evaluation of the jugular foramen and hypoglossal canal 1

Do NOT rely on CT head, as it has extremely low diagnostic yield (<1%) for isolated dizziness and misses most posterior circulation infarcts 2, 3

Additional Imaging to Consider

MRI or CT angiography of head and neck if initial MRI shows no acute infarct but clinical suspicion remains high, to evaluate for: 1, 4

• Vertebrobasilar insufficiency
• Internal carotid or vertebral artery dissection
• Vascular malformations or RCVS

MRI cervical spine only if red flags suggest spinal cord pathology, though not first-line for this presentation 2

Physical Examination Priorities

Perform focused neurologic examination looking for: 1

• Cranial nerve testing: Assess CN IX-XII function (gag reflex, palate elevation, tongue deviation, shoulder shrug)
• HINTS examination (Head Impulse, Nystagmus, Test of Skew) if trained in the technique—100% sensitive for stroke when performed by experts 2, 3
• Cerebellar testing: Finger-to-nose, heel-to-shin, gait assessment 1
• Horner's syndrome signs: Ptosis, miosis, anhidrosis (suggests lateral medullary syndrome) 1
• Hearing assessment: Sudden unilateral hearing loss is a red flag requiring urgent imaging 2, 3

Critical Management Pitfalls to Avoid

• Never assume normal neurologic exam excludes stroke—75-80% of posterior circulation stroke patients have no focal deficits 2, 3
• Do not delay imaging for "observation"—posterior circulation strokes can progress rapidly 1, 2
• Avoid attributing symptoms to "benign vertigo" without proper evaluation—this symptom pattern is atypical for BPPV 1, 2
• Do not order CT instead of MRI when stroke is suspected—CT misses most posterior circulation infarcts 2, 3

Immediate Actions Required

1. Obtain MRI brain without contrast with DWI sequences emergently 1, 2
2. Neurology consultation for evaluation and management if imaging shows acute pathology 1
3. Assess vascular risk factors: hypertension, diabetes, age >50, prior stroke, atrial fibrillation 2, 3
4. Monitor for progression of neurologic symptoms, particularly development of dysarthria, dysphagia, or motor weakness 1