One-and-a-half syndrome : its presentation, causes and neuroanatomy

Abstract

BACKGROUND: One-and-a-half syndrome involves a combination of an ipsilateral horizontal gaze palsy and an ipsilateral internuclear ophthalmoplegia. This condition is easily missed due to its presentation, but can be the first sign of serious disease. We aim to increase awareness of this syndrome’s presentation and give an insight into the intricate neuroanatomical connections that are affected in it.

CASE PRESENTATION: We present a case of a 39-year-old previously healthy female who presented with a one-week history of diplopia and non-vertiginous dizziness. On examination, a left horizontal gaze palsy with deficits in left abduction and right adduction was noted, accompanied by left adduction weakness and right horizontal disconjugate jerk nystagmus in abduction. A diagnosis of OAHS was made, and she was admitted for further tests. An MRI of her brain revealed multiple hyperintensities throughout, along with an enhancing lesion in keeping with active disease. A diagnosis of Multiple Sclerosis was made and she was given a five-day course of methylprednisolone, with which her vision, and ultimately her gait, improved. She was discharged with outpatient follow-up, to further discuss treatment options for her new diagnosis.

CONCLUSION: Diplopia and vertigo are symptoms that should prompt careful clinical examination with proper attention to ocular motility testing, and subsequent referral to neurology if required. Unnecessary delays in diagnosis and management could ultimately be detrimental to the patient, and being aware of uncommon presentations would go a long way in enhancing patient safety.