Abstract
Pure-tone audiometry, auditory evoked brainstem response (ABR) and electronystagmographic examination (ENG) were studied before and after microvascular decompression (MVD) in 41 patients with trigeminal neuralgia (TN) and 39 patients with hemifacial spasm (HFS).
Fourteen patie n ts (34.1%) with TN and 16 (41.0%) with HFS suffered from hearing loss postoperatively, while 1 patient (2.4%) with TN and 2 (12.8%) with HFS had a hearing gain after MVD. Latencies of peak V of ABR were longer on the affected side than on the unaffected side before MVD in 6 patients with TN and 3 with HFS. Among these 9 patients, decreased latency of peak V were observed after MVD in 4 patients. Latencies of peak V were increased after MVD in 13 (33.3%) patients with TN and 25 (73.5%) with HFS. Various abnormalities were observed in ENG before MVD in 15 patients (45.5%)with TN and 10 (29.4%) with HFS. Abnormalities in optokinetic nystagmus (OKN)and/or eye tracking test (ETT) were detected before surgery in 7 patients (45.5%) with TN and disappeared after MVD in 5 patients, whereas no abnormality in OKN and ETT was observed in patients with HFS. Postoperative improvements in spontaneous and/or positional nystagmus were observed in 2 patients with HFS.
These postoperative improvements of the abnorm alities in neurotological examinations suggest that the effect of causative vessels extend to the 8th cranial nerve and brain stem, although no patient complained of any otological symptoms before surgery.
