Microsurgical Management of Midbrain Cavernous Malformations: Predictors of Outcome and Lesion Classification in 72 Patients.

BACKGROUND: Due to the complex segmental organization of the brainstem, it is preferable to study midbrain cavernous malformations (MCMs) separately from pontine and medullary lesions. OBJECTIVE: To evaluate clinical results after microsurgical removal of MCMs, assess predictors for outcome and introduce a topographical classification of MCMs. METHODS: A retrospective study was conducted on consecutive patients who underwent MCM resection. Clinical parameters before and after surgery, morphological CM features, surgical approaches and outcomeswere analyzed. MCMs were classified according to their exact location within the midbrain and their axial and sagittal extension. RESULTS: The authors reviewed 72 patients (35 male). Lesions varied in size between 4 and 55 mm. The vast majority of patients benefited from surgery. The mean modified Rankin Scale (mRS) decreased significantly from 1.6 at admission to 1.3 at discharge and to 0.7 at follow-up (6-247 mo postoperatively). Five patients (6.9%) suffered from delayed hypertrophic olivary degeneration as visualized on magnetic resonance imaging. One male suffered from early postoperative re-bleeding that required surgical hematoma evacuation. There were no severe long tract impairment or other disabling complications, no delayed re-bleedings, and no surgical mortality. CONCLUSION: We present a new topographic classification of MCMs that may be useful for predicting the occurrence of postoperative eye movement disorders. Other predictors of persistent oculomotor disturbances are time interval between onset of symptoms and surgery, and patient's age over 40 yr. Early surgery is recommendable in patients with oculomotor disturbances. MCM size over 18 mm, patient age over 40 yr, and poor mRS at admission are important predictors for the long-term outcome.