Neuroscience · Year 2 · from Neuroscience
Case 2: Weber Syndrome - Midbrain Stroke
Patient Presentation
Demographics: 65-year-old female
Chief Complaint: Double vision and right-sided weakness
History of Present Illness: A 65-year-old woman with poorly controlled diabetes, hypertension, and a recent diagnosis of atrial fibrillation (not yet on anticoagulation) experienced sudden onset of double vision and right-sided weakness while watching television. Her daughter noticed that her left eye was deviated outward and she could not move it inward. The patient also has right-sided facial droop and weakness of her right arm and leg.
Physical Examination:
- Vital signs: BP 162/94, HR 92 (irregular), RR 14
- General: Awake, alert, left eye visibly deviated
- Neurological:
- Mental status: Alert, oriented, normal cognition
- Cranial nerves:
- LEFT CN III palsy: Complete ptosis, eye deviated "down and out" (superior oblique and lateral rectus unopposed), dilated pupil (6 mm) non-reactive to light; right pupil 3 mm reactive
- Right lower facial droop (upper motor neuron pattern - forehead spared)
- Motor: Right arm 3/5; right leg 3/5; left side 5/5
- Tone: Increased on right
- Reflexes: Right-sided hyperreflexia; right Babinski present
- Sensory: Intact
- NIHSS: 12
Workup:
- CT head: No hemorrhage
- MRI brain: Acute infarct in left ventral midbrain (cerebral peduncle and CN III fascicle)
- CT angiography: Patent basilar artery; posterior communicating artery aneurysm excluded
- Echocardiogram: Dilated left atrium, no thrombus visualized
Diagnosis: Weber syndrome (left ventral midbrain infarct) - cardioembolic etiology (atrial fibrillation)
Treatment:
- IV thrombolysis not given (outside window)
- Aspirin bridging to anticoagulation
- Anticoagulation with apixaban started after appropriate interval
- Eye patch for diplopia management
- Physical therapy for hemiparesis
- Glycemic and blood pressure optimization
- Partial recovery of CN III function over months; persistent mild hemiparesis
Clinical Pearl: Weber syndrome localizes to the ventral midbrain (basis pedunculi) and produces an ipsilateral CN III palsy with contralateral hemiparesis. The lesion affects the CN III fascicle as it exits the midbrain ventrally and the adjacent cerebral peduncle carrying the corticospinal tract. The "crossed" motor pattern (ipsilateral CN III, contralateral body) is characteristic of brainstem lesions. Other midbrain syndromes include Benedikt syndrome (CN III palsy plus contralateral tremor/ataxia from red nucleus involvement) and Claude syndrome (CN III plus contralateral ataxia from superior cerebellar peduncle involvement). The pupil is typically involved in Weber syndrome because the parasympathetic pupillary fibers travel on the outside of CN III.