Pontine tuberculoma presenting as a true-localising abducens palsy.

Abstract

An immunocompetent woman in her early 30s presented with a 3-day history of nausea, vomiting and horizontal diplopia. Examination revealed left-sided abducens paresis, with normal visual acuity, pupillary reactions and fundus. There was no papilloedema, neck rigidity or positive neurological signs. Magnetic resonance imaging (MRI) showed a central pontine T2 hypointense ring-enhancing lesion causing compression of the fourth ventricle. Magnetic resonance spectroscopy showed a lipid lactate peak leading to a diagnosis of pontine tuberculoma. The diagnosis was supported by a positive Mantoux and interferon-gamma release assay. There was no other systemic focus of tuberculosis. She was then started on antitubercular therapy (ATT) for 18 months. After 8 months of ATT, a repeat MRI showed a decrease in the volume of the tuberculoma. This case exemplifies a unique case of isolated abducens palsy in the absence of features of raised intracranial tension, which could localise the lesion to the pons.