Objective: The pathophysiology of monocular elevation deficiency is poorly understood. The goal of this study was to determine the appearance of the extraocular muscles and the oculomotor nerve.
Design: Observational case series.
Participants: Six patients with monocular elevation deficiency.
Methods: Ophthalmologic examination and thin-sectioned magnetic resonance imaging (MRI) at the brainstem level as well as across the orbit in 6 patients were performed.
Main outcome measures: Ocular alignment and movement, extraocular muscles, and the oculomotor nerve on MRI.
Results: One out of 6 patients with monocular elevation deficiency showed focal thickening of the inferior rectus muscle near the orbital apex. The 5 remaining patients showed normal extraocular muscles and the oculomotor nerves on MRI.
Conclusions: Focal thickening of the inferior rectus muscle may partially explain the cause of restricted gaze. In addition, the finding of normal oculomotor nerves might support an underlying deficit in the unilateral center for upgaze as the etiology of monocular elevation deficiency.