Neurosurgical strike by a coconut 'shell': A rare case of isolated internuclear ophthalmoplegia following closed head injury due to coconut fall

A 24-year-old female patient presented to the casualty following coconut fall on the head a few hours back with acute-onset binocular diplopia maximum on the left gaze and also on looking to the left and downward. Clinical examination revealed no external injuries, focal neurological deficits, or features of raised intracranial pressure. Computed tomography imaging was within normal limits. Hence, she was referred to ophthalmology by the neurosurgeon as a case of suspected partial third nerve palsy. Ocular examination revealed best-corrected visual acuity of 6/6 BE. There was limitation of adduction in the right eye and nystagmus in the left eye on attempted laevoversion. Convergence was absent. Anterior segment and fundus of both eyes were normal. Diplopia charting showed crossed diplopia which was maximum on left gaze. A clinical diagnosis of right anterior internuclear ophthalmoplegia (type-1) was made. It was confirmed by magnetic resonance imaging which revealed acute infarcts in the region of superior pons near right medial longitudinal fasciculus. The patient was treated with occlusion glasses.