[A case of cavernous angioma in the lower pons, showing subacute onset of unilateral cranial nerve palsy and segmental sensory disturbance].

We report a 54-year-old man with right abducent nerve palsy, right facial nerve palsy, and left segmental sensory disturbance, which progressed for 2 weeks. He was found to have cavernous angioma in the lower pons. When he visited our hospital, he had right facial palsy, sensory disturbance of left half of the face and left upper limb, and diplopia. He had suffered right abducent nerve palsy 5 years previously and had recently developed hypertension. Neurological examination further revealed right abducent nerve palsy, right peripheral facial nerve palsy, sensory impairment of the left half of the face, and sensory impairment on the left side from C2 to Th3. Magnetic resonance imaging of the head revealed hemorrhage with a rim at the right dorsal part of the lower pons. No abnormalities were identified on cerebral angiography. He was diagnosed as having hemorrhage originating from a cavernous angioma. We assumed that the segmental sensory disturbance was caused by medial involvement of the lateral spinothalamic tract, which is somatotopically arranged: the fibers from the sacral segments being most lateral. The ventral trigeminothalamic tract, right abducent nerve, and right facial nerve were also disturbed. Segmental sensory disturbance usually accompanies a spinal cord lesion. But several cases with similar symptoms following a brainstem lesion have been reported. Most of them had stroke, showing acute onset of illness. Our case showed subacute onset of illness; cranial nerve palsy and segmental sensory disturbance progressed for 2 weeks.