What is the best approach to manage an elderly patient with giddiness and recurrent vomiting, with a brain MRI ruling out posterior circulation stroke?

Management of Elderly Patient with Giddiness and Recurrent Vomiting with Negative MRI for Posterior Circulation Stroke

Despite a negative MRI, maintain high clinical suspicion for posterior circulation stroke and pursue comprehensive evaluation including vascular imaging and consideration of repeat MRI, while simultaneously managing symptoms and investigating alternative causes. 1

Understanding the Clinical Challenge

This presentation is particularly treacherous because:

• Posterior circulation strokes frequently present with non-specific symptoms including dizziness, nausea, and vomiting without focal neurological deficits, making them easily missed 2
• MRI can be falsely negative in approximately 50% of small posterior fossa ischemic strokes within the first 48 hours, particularly in the brainstem 1
• The NIHSS can be 0 in posterior circulation strokes where symptoms are limited to headache, vertigo, and nausea only 2
• 75-80% of patients with acute vestibular syndrome from posterior circulation infarct have no focal neurologic deficits 3

Immediate Next Steps

1. Perform Focused Clinical Assessment

Examine for subtle posterior circulation signs:

• Look for truncal ataxia (the most common neurological sign in NIHSS 0, DWI-positive patients) 2
• Assess for nystagmus patterns, visual field defects, and cranial nerve abnormalities 2
• Perform HINTS examination (Head Impulse, Nystagmus, Test of Skew) if trained, which has 100% sensitivity for detecting stroke when properly performed 4, 3, 5

Key predictors that increase likelihood of missed stroke on initial imaging:

• Combined neurological symptoms (odds ratio 16.72) 1
• Central oculomotor signs (odds ratio 2.8) 1
• Focal abnormalities on examination (odds ratio 3.3) 1

2. Obtain Vascular Imaging Immediately

Order CT angiography (CTA) or MR angiography (MRA) of the head and neck to evaluate for large vessel occlusion or significant stenosis, as vascular imaging may identify occlusions even when parenchymal changes are not yet visible 1, 2

• CTA provides rapid assessment and is appropriate for urgent evaluation 1
• MRA is preferred if patient has renal insufficiency or contrast allergy 1
• Vertebral and basilar artery stenosis ≥70% is an independent predictor of recurrent stroke (hazard ratio 7.91) 6

3. Schedule Delayed MRI

Arrange repeat MRI brain with diffusion-weighted imaging in 3-7 days after symptom onset, which significantly improves detection of initially missed strokes 1

• Request thin-cut high-resolution DWI sequences specifically 7
• This is critical as early MRI sensitivity for posterior circulation stroke is only 46% compared to 100% for HINTS examination by trained practitioners 3

Assess for High-Risk Features

Evaluate vascular risk factors that increase stroke probability:

• Older age 2
• Hypertension 4, 3
• Atrial fibrillation 2, 4, 3
• History of repeated TIAs within 3 months (hazard ratio 15.4 for recurrent events) 6
• Non-whirling type of dizziness 2, 4

Symptomatic Management

For intractable nausea and vomiting potentially related to area postrema involvement:

• Consider metoclopramide 10 mg four times daily 8, 7
• Add ondansetron 8 mg every eight hours 7
• These medications are specifically effective for area postrema syndrome, which can result from posterior circulation stroke affecting the dorsal medulla 7

Investigate Alternative Diagnoses

If vascular imaging is negative and repeat MRI remains negative, consider:

Peripheral Vestibular Causes

• Perform Dix-Hallpike maneuver for BPPV (look for 5-20 second latency, torsional upbeating nystagmus, symptoms resolving within 60 seconds) 4, 3
• Assess for vestibular neuritis if acute persistent vertigo with normal neurologic exam 2, 4

Other Central Causes

• Brainstem lesions (tumors, demyelination) can present with isolated vomiting without other neurological signs 9
• Consider MRI with gadolinium contrast if not already performed to evaluate for mass lesions 9

Medication Review

• Antihypertensives, sedatives, anticonvulsants, and psychotropic drugs are leading causes of chronic vestibular syndrome 3

Critical Pitfalls to Avoid

• Do not assume normal neurologic examination excludes stroke - most posterior circulation stroke patients lack focal deficits 3
• Do not delay treatment decisions when clinical suspicion remains high despite negative imaging 1
• Do not rely on CT instead of MRI - CT has very low diagnostic yield (<1%) for isolated dizziness and misses most posterior circulation infarcts 3
• Do not overlook the need for vascular imaging - vessel occlusion may be present before parenchymal changes are visible 1
• Do not dismiss symptoms as "just vertigo" - approximately 4% of isolated dizziness cases are due to stroke 2, 4, 3

Ongoing Management

Continue standard stroke prevention measures if vascular etiology suspected:

• Initiate or optimize antiplatelet therapy 6
• Aggressive vascular risk factor modification 2
• Close follow-up given that patients with dysphagia (hazard ratio 4.16) and multisector infarcts (hazard ratio 5.38) have higher recurrence risk 6