The nucleus prepositus hypoglossi (NPH) and medial vestibular nuclei (MVN) are two closely related neural integrators situated in the brainstem responsible for horizontal conjugate eye movement. Thiamine deficiency, a hallmark of Wernicke’s encephalopathy, affects the MVN to a greater extent. We report a case of impaired horizontal gaze holding post-sleeve gastrectomy secondary to Vitamin B1 deficiency.

A 24-year-old female presented with new onset diplopia on lateral gaze, dizziness, and lower limb distal paraesthesia eight weeks post-sleeve gastrectomy. Examination revealed conjugate eye movements and horizontal gaze-holding failure bilaterally, with intact convergence and vertical gaze. Normal discs were observed on fundoscopy with no retinal haemorrhages, and visual acuity preserved. She had a normal mental state with mild sensory ataxia. Reflexes were present and symmetrical.

The high metabolic requirements of MVN neurons responsible for high acceleration horizontal vestibulo-ocular reflex (VOR) is postulated to account for the selective vulnerability to thiamine deprivation. This case highlights an unusual presentation of disruption in horizontal gaze-holding mechanisms through failure of neural integrators, particularly the MVN, in the setting of Vitamin B1 deficiency with preservation of vertical gaze.