[Surgical Removal of a Superior Medial Midbrain Cavernous Angioma through the Anterior Interhemispheric Transcallosal Transforaminal Approach:A Case Report].

A 33-year-old male presented with sudden onset of dysarthria. MRI showed a single round lesion containing hematomas in varying stages combined with venous malformation in the superior midline portion of the midbrain, indicating a midbrain cavernous angioma. Serial follow-up MRI revealed enlargement of the angioma concomitant with worsening of the dysarthria, ataxia, and intention tremor. Preoperative MRI suggested that the angioma consisted of a cystic hemorrhagic lesion with an 18-mm diameter without hydrocephalus. Since the angioma was located just beneath the floor of the midline portion of the third ventricle, we chose an anterior interhemispheric transcallosal transforaminal approach. After callosotomy, the foramen of Monro was widened by dissecting the choroidal fissure, enabling entry into the third ventricle. The lower part of the massa intermedia was cut;the median floor of the third ventricle was dissected and the angioma was removed. After the surgery, only a transient complication of seesaw nystagmus was observed, caused by damage to the interstitial nucleus of Cajal. As the anterior interhemispheric transcallosal transforaminal approach does not damage both forces, this technique may be a safe and useful approach for superior medial midbrain lesions, located just beneath the floor of the third ventricle.