What urgent evaluation and management should be undertaken for a 21‑year‑old woman who suddenly developed involuntary eye crossing (convergence spasm) while using her mobile phone, accompanied by generalized dizziness and mild vertiginous sensation?

Urgent Neuroimaging with MRI Brain is Required to Rule Out Posterior Circulation Stroke

This 21-year-old woman presenting with acute involuntary convergence and dizziness requires urgent MRI brain with diffusion-weighted imaging (DWI) to exclude posterior circulation stroke or other central pathology, despite her young age and atypical presentation.

Immediate Clinical Assessment

Perform focused bedside examination looking for:

• Focal neurologic deficits (cranial nerve abnormalities, limb weakness, sensory changes, ataxia)
• Skew deviation using alternate cover test (vertical misalignment suggests brainstem pathology) 1
• Gait testing for cerebellar dysfunction
• Nystagmus pattern (direction-changing or vertical nystagmus indicates central cause)

The convergence spasm itself, while often functional, can mask serious underlying pathology when accompanied by vertigo 1, 2.

Why Neuroimaging Cannot Be Deferred

The combination of convergence abnormality with vertiginous symptoms creates diagnostic ambiguity that mandates imaging:

Critical considerations:

• Acute vestibular syndrome (AVS) with dizziness carries 25% prevalence of posterior circulation stroke, rising to 75% in high-risk cohorts 3
• 11% of patients with acute persistent vertigo but no focal neurologic signs have acute infarct on imaging 3
• Convergence spasm can occur with brainstem lesions affecting the medial longitudinal fasciculus, as documented in multiple sclerosis 4
• Skew deviation (which produces vertical diplopia and can mimic convergence issues) demands immediate brain/brainstem MRI to evaluate for demyelination, stroke, or mass lesions 1

The absence of obvious neurologic deficits does NOT exclude stroke—75-80% of AVS-related infarcts lack focal neurologic deficits 3.

Imaging Protocol

MRI brain with DWI is the gold standard 3:

• Superior soft tissue resolution compared to CT
• DWI detects acute ischemia within minutes
• Include brainstem and cerebellum sequences
• Consider MRA of vertebrobasilar circulation if stroke suspected

Important caveat: Early MRI has 20-50% false-negative rate for small brainstem strokes 5. If clinical suspicion remains high with negative initial MRI, repeat imaging in 24-48 hours or obtain MRA/CTA of posterior circulation.

CT head without contrast is inadequate—it detected acute lesions in only 6% versus 11% with MRI in similar presentations 3.

Differential Diagnosis Framework

Central (dangerous) causes to exclude:

• Posterior circulation stroke/TIA (vertebrobasilar territory) 6, 5
• Brainstem demyelination (multiple sclerosis) 4
• Cerebellar or brainstem mass
• Vertebral artery dissection 3

Peripheral/functional causes (diagnoses of exclusion):

• Functional convergence spasm (most common when isolated) 7, 8, 2
• Vestibular neuritis (but wouldn't cause convergence spasm)
• Vestibular migraine 3

Management Algorithm

1. Immediate: Obtain vital signs, assess stroke risk factors (hypertension, diabetes, smoking, oral contraceptives in young women)

2. Within 1-2 hours: Urgent MRI brain with DWI and brainstem protocol

3. If MRI positive for stroke: Activate stroke protocol, neurology consultation, consider hyperacute intervention if within therapeutic window

4. If MRI negative and symptoms persist: Consider MRA vertebrobasilar system, repeat MRI in 24-48 hours if high suspicion, neurology/neuro-ophthalmology referral 1

5. If imaging negative and symptoms resolve: Neuropsychological evaluation for functional disorder 7, but only after excluding organic pathology

Critical Pitfalls to Avoid

• Do not assume functional etiology based on age alone—young women can have vertebral artery dissection, especially with recent neck manipulation or minor trauma
• Do not rely on normal neurologic exam to exclude stroke 3
• Do not perform only CT—inadequate sensitivity for posterior fossa pathology 3
• Do not delay imaging for psychiatric evaluation—functional convergence spasm is a diagnosis of exclusion requiring negative neuroimaging 1, 7

The mobile phone use is likely coincidental—convergence spasm can be triggered by near work but the accompanying vertigo elevates concern for central pathology 2.