Objective:

N/A

Background:

Isolated downgaze palsy is rare amongst gaze pathologies. Anatomic localization of vertical gaze is an evolving topic. According to medical literature, vertical gaze is mediated by midbrain nuclei, rostral interstitial nucleus of medial longitudinal fasciculus (riMLF) and interstitial nucleus of Cajal (INC). There have been reports on involvement of both up gaze and downgaze palsies in bilateral thalamic lesions and reports of a unilateral thalamic lesion causing bilateral up gaze palsy. Bilateral thalamic lesions have also been shown to cause isolated downgaze palsy. We present a rare case of isolated downgaze palsy in a patient with an acute pretectum paramedian midbrain and left thalamic infarction.

Design/Methods:

N/A

Results:

A 48-year-old Asian male with history of hypertension presented with acute altered mental status, decreased arousal, and vomiting. He was stabilized but continued to have fluctuations in arousal. He had difficulty focusing on nearby objects and compensated with head posture by tilting his head backwards. Neurological examination demonstrated a complete isolated downgaze palsy. Vertical vestibular ocular reflex was absent and convergence was intact. Brain MRI showed acute left thalamic and pretectum paramedian midbrain infarctions. MRA showed segmental occlusion of the left vertebral artery V1 segment. Daily Aspirin and Plavix with risk factor modifications were implemented. Etiology of infarcts was surmised to be related to posterior circulation atherosclerosis. 

Conclusions:

Isolated downgaze palsy is a rare presentation of stroke. Our case aids in understanding the topographical associations and neuronal projections of gaze palsies. Medical literature supports that the riMLF projects to elevator muscles bilaterally for up-gaze pursuit and ipsilaterally for down-gaze pursuit. Our case adds to the literature that a pretectal paramedian midbrain and unilateral thalamic lesions can cause an isolated downgaze palsy.