Thirteen-and-a-half Syndrome Secondary to the Brainstem Cavernoma

"Thirteen-and-a-half" is a newly described clinical syndrome characterized by the combination of the one-and-a-half syndrome with fifth and seventh cranial nerve nuclei involvement (1^1/2 + 5 + 7 = 13^1/2). To the authors' knowledge, this is the first report of the thirteen-and-a-half syndrome secondary to pontine cavernoma and, overall, only the second reported case of this syndrome in the literature till date.

A 20-year-old man presented with the clinical features suggestive of the thirteen-and-a-half syndrome, explained radiologically by pontine cavernoma. We operated him using a suboccipital transvermian approach and he is doing well at 2.5 years follow-up. Interestingly, his one-and-a-half syndrome has partially improved to left horizontal gaze palsy.

The clinical appreciation of the thirteen-and-a-half syndrome precisely localizes the lesion to ipsilateral dorsal pontine tegmentum. Neurosurgeons must be aware of the newly described "one-and-a-half- plus" syndromes as they help in a better understanding of pathoanatomy caused by different disease processes in the brainstem.