Crossed Brainstem Syndrome of the Tectal Plate's Inferior Colliculus Revealing Quadrigeminal Midbrain Cavernous Malformation.

Cavernous malformations are low-flow fragile vascular lesions prone to extralesional bleeding that can occur in the cerebral hemispheres, the brainstem, or the spinal cord. This paper reports the case of a 32-year-old right-handed man with acute-onset headaches associated with right-sided tinnitus, right-sided hemianesthesia, and binocular diplopia related to cranial nerve IV palsy. Neuroimaging displayed left-sided isolated cavernous malformation of the inferior tectal plate, with evidence of extralesional bleeding. Clinical presentation and neuroimaging features were compatible with inferior colliculus crossed brainstem syndrome. Thanks to clinical improvement and the absence of mass effect on neuroimaging, surgical intervention was delayed. At the 3-month follow-up consultation, symptoms had improved aside from diplopia, which required wearing prism eyeglasses. Tectal cavernous malformations account for 18% of midbrain cavernomas. It was explained that surgical excision using the supracerebellar infratentorial approach would be performed within 2 months after a second extralesional bleeding episode causing disabling symptoms.