Nystagmus phenotypes in posterior circulation stroke

Acute vestibular syndrome (AVS) is characterized by sudden, persistent vertigo or dizziness with nausea, vomiting, postural instability, and spontaneous nystagmus. Differentiating peripheral vestibular disorders from posterior circulation stroke remains a major diagnostic challenge in emergency neurology, as vestibulo-cerebellar infarcts may present as "central pseudo-neuritis," mimicking peripheral vestibular disease. Although the HINTS examination is a valuable bedside tool, its reliability depends on the presence and characterization of nystagmus and is reduced in patients without spontaneous nystagmus.

To characterize nystagmus phenotypes in posterior circulation stroke using videooculography (VOG) and to identify features that improve recognition of central vestibular pathology in patients with AVS.

Retrospective single-center descriptive cohort study of 34 patients with posterior circulation stroke confirmed by neuroimaging, who underwent VOG between 2014 and 2026. Eye movements were assessed using VOG and nystagmus features (direction, gaze dependence, fixation suppression, head-shaking responses) were correlated with lesion location.

Thirty-four patients were included; nystagmus was present in 70% (24/35). Of these, 50% showed multiple nystagmus phenotypes and 50% a single pattern. Spontaneous nystagmus (horizontal or vertical) and Head-shaking nystagmus (HSN) both occurred in 62%, while gaze-evoked nystagmus was rare (12%). There was a non-significant trend toward a higher prevalence of HSN in PICA infarctions (OR 4.81) and HSN showed cross-coupled or direction changing features in 80% of patients. No clear correlation was found between the side of the lesion and the direction of nystagmus, nor between fixation and the slow-phase velocity (SPV) of nystagmus.

Nystagmus is a frequent clinical feature of posterior circulation stroke with heterogenous phenotypes. Lesion laterality did not correlate with nystagmus direction, and fixation did not consistently alter SPV. HSN was a frequent sign of central vestibular dysfunction. Performance of the head shaking test may improve detection of central vestibular pathology and complement the HINTS examination in acute vertigo.