No abstract

OBJECTIVE This study was conducted to investigate the success rate of using the facial motor evoked potential (FMEP) of orbicularis oculi and oris muscles for facial nerve function monitoring with use of a stepwise protocol, and its usefulness in predicting facial nerve outcome during cerebellopontine angle (CPA) surgeries. METHODS FMEPs were recorded intraoperatively from 60 patients undergoing CPA surgeries. Transcranial electrocortical stimulation (TES) was performed using corkscrew electrodes positioned at hemispheric montage (C3/C4 and CZ). The contralateral abductor pollicis brevis muscle was used as the control response. Stimulation was always applied contralaterally to the affected side using 1, 3, or 5 rectangular pulses ranging from 200 to 600 V with 50 μs of pulse duration and an interstimulus interval of 2 ms. Facial potentials were recorded from needles placed in the orbicularis oculi and oris muscles. RESULTS FMEP from the orbicularis oris and oculi muscles could be reliably monitored in 86.7% and 85% of the patients, respectively. The immediate postoperative facial function correlated significantly with the FMEP ratio in the orbicularis oculi muscle at 80% amplitude ratio (P = .037) and orbicularis oris muscle at 35% ratio (P = .000). FMEP loss was always related to postoperative facial paresis, although in different degrees. CONCLUSION FMEPs can be obtained reliably by using TES with 3 to 5 train pulses. Stable intraoperative FMEPs can predict a good postoperative outcome of facial function. However, further refinements of this technique are necessary to minimize artifacts and to make this method more reliable.

✓ The ventriculus terminalis is a small cavity inside the conus medullaris that is formed during the embryonic development. Previous reports regarding cystic lesion of the ventriculus terminalis (CLVT) in adults have detailed a broad and diversified distribution in terms of clinical symptoms, clinical evolution, neurological findings, and treatment. Therefore, nonstandardized management has led to unsatisfactory outcomes. Thus, the authors propose a new classification system in which the clinical presentation is taken into account to standardize the cases and facilitate the proper management of these lesions. Two more cases are described. The literature was reviewed, dividing the patients into 3 groups by clinical presentation as follows: CLVT Type I, patients with nonspecific neurological symptoms or nonspecific complaints; CLVT Type II, presence of focal neurological deficit; and CLVT Type III, presence of sphincter disturbances (bowel or bladder dysfunction). Two patients were classified as CLVT Type I, 3 as CLVT Type II, and 12 as CLVT Type III. In Type I, no improvement was observed in clinical evaluation after surgery, and stable symptoms were achieved with clinical management. In Type II, 2 patients had total improvement and 1 had subtotal improvement after surgery. Finally, in Type III, 92% of the patients improved postoperatively; among these 33% presented with total improvement. Only 1 case in this group was handled conservatively and no improvement was documented. This new classification is useful to group the patients into 3 clinical types to provide guidance as to the best management options. Treatment for the Type I lesion seems to be best conducted conservatively, whereas Types II and III seem to be best handled surgically.