Vertical diplopia and oscillopsia due to midbrain keyhole aqueduct syndrome associated with severe cough

Abstract

Purpose: Midline structural defects in the neural axis can give rise to neuro-ophthalmic symptoms. We report a rare case of keyhole aqueduct syndrome presenting after two years of severe cough due to gastroesophageal reflux disease.

Observations: A 58-year-old woman with a 2-year history of daily, severe cough presented to the neuro-ophthalmology clinic with progressive diplopia and oscillopsia. Examination revealed a 1-2 Hz down-beating nystagmus in primary gaze that worsened with left, right, and down gazes. Gaze evoked nystagmus and mild paresis were also seen with up gaze. There was an incomitant left hypertropia due to skew deviation that worsened with right and up gazes and improved with down gaze. She also had a right-sided ptosis and a 3 mm anisocoria not due to cranial nerve 3 paresis or Horner's syndrome. Brain magnetic resonance imaging showed a 1.5 mm × 11.7 mm × 6 mm midline cleft in the ventral midbrain communicating with the cerebral aqueduct, consistent with keyhole aqueduct syndrome. Her nystagmus and diplopia improved with oral acetazolamide treatment, at high doses of 2500-3000 mg per day.

Conclusions and importance: We report the first case of midbrain keyhole aqueduct syndrome with ocular motor and other neuro-ophthalmic manifestations associated with severe cough. Although her cough was effectively treated and intracranial pressure measurement was normal, her ophthalmic symptoms continued to progress, which is common in previous cases reported. Treatment with acetazolamide led to significant improvement, supporting the use of acetazolamide in this rare condition.

Keywords: Cerebrospinal fluid; Down-beating nystagmus; Keyhole aqueduct syndrome; Mesencephalic cleft; Midbrain cleft; Syringobulbia; Syrinx.

Fig. 1

Brain magnetic resonance imaging demonstrating a 1.5 mm wide by 11.7 mm long by 6 mm tall keyhole aqueduct. A. Images from axial T₁–weighted spoiled gradient-recall (SPGR) sequence with gadolinium enhancement of a 55-year-old control (left) and a 58-year-old female with keyhole aqueduct syndrome (right arrow). Images are 1 mm thick. B. Images of sagittal T₂–weighted fast imaging employing steady-state acquisition (FIESTA) sequence from 58-year-old control (left) and patient (right arrows). Images are 0.8 mm thick.