Prospective analysis of diplopia after anterior temporal lobectomy for mesial temporal lobe sclerosis

Object. In this prospective study the authors investigated the incidence and natural history of postoperative diplopia in patients undergoing anterior temporal lobectomy (ATL) and amygdalohippocampectomy for medically intractable mesial temporal lobe epilepsy. Methods. Forty-seven patients scheduled for ATL for medically refractory seizures were examined preoperatively, 2 to 7 days postoperatively, and 3 to 6 months postoperatively. Ophthalmological examination including pupillary measurements, stereoacuity measurements, palpebral fissure measurements, vertical fusional amplitudes, Lancaster red green testing, visual field testing, and alternate cover testing was performed. Antiepileptic drug levels were monitored. Nine (19%) of 47 patients developed diplopia postoperatively. The diplopia was caused by trochlear nerve palsy in every case. No oculomotor nerve dysfunction was documented. Trochlear nerve function recovered completely in all patients within 3 to 6 months postoperatively. Conclusions. Postoperative diplopia following ATL occurs more often than previously thought and is primarily due to trochlear nerve dysfunction. Awareness of this transient complication is important in preoperative patient counseling.