Partial neurolysis of the hypoglossal nerve for selective lingual atrophy in a porcine model.

OBJECTIVES: Obstructive sleep apnea in children is most commonly treated with adenotonsillectomy; however, in cases of significant tongue base prolapse, this may prove inadequate. Surgical procedures used to increase the retroglossal airway have significant morbidities and low patient acceptability. We theorized that effective reduction of the tongue base can be achieved through partial denervation of the hypoglossal nerve, which is easily accessed in the submandibular space with minimal morbidity. METHODS: We performed a prospective, experimental study in which topographic innervation maps of porcine tongue were generated by stimulating the hypoglossal main trunk and peripheral branches. The effects of complete unilateral nerve sectioning on tongue base volume and linear dimensions were measured and compared to the contralateral control side. In the final stage, only the peripheral nerve that was determined as the main supply to the tongue base was sectioned, and the results were compared to those in the matched controls. RESULTS: A medial branch of the hypoglossal nerve was consistently identified as the main motor supply to the tongue base. Complete denervation resulted in a measurable decrease in the volume of the tongue base as compared to that of controls. Partial neurolysis produced inconsistent changes in 2 subjects, with decreases in linear dimensions that were not proportional to the decrease in volume. Histologically, complete denervation was followed by a significantly greater replacement of muscle with fat and connective tissue as compared with partial neurolysis. CONCLUSIONS: There were inconsistent changes in volume and linear dimensions of the tongue base following partial neurolysis of the hypoglossal nerve over the 3-month experimental period.

Multimodality intraoperative monitoring during complex lumbosacral procedures: indications, techniques, and long-term follow-up review of 61 consecutive cases.

OBJECT: The purpose of this study was to examine the neurological outcomes after complex lumbosacral surgery in patients undergoing multimodality neurophysiological monitoring. METHODS: Sixty-one patients were consecutively enrolled in this study. These patients underwent complex intra- and extradural lumbosacral procedures with concomitant intraoperative electromyography (EMG) monitoring of the lower-limb muscles, external anal and urethral sphincters (EAS and EUS), and lower-limb somatosensory evoked potentials (SSEPs). Long-term (minimum 2-year) clinical follow-up data were obtained in all cases. Most patients were treated for spinal/spinal cord tumors (61%) or adult tethered cord syndrome (25%). Recordable lower-extremity SSEPs were reported in 54 patients (89%). New postoperative neurological deficits occurred in only three patients (4.9%), and remained persistent in only one patient (1.6%) at long-term follow-up examination. In only one of these cases was a significant decrease in SSEP amplitude detected. Spontaneous EMG activity was observed in the lower-extremity muscles and/or EAS and EUS in 51 cases (84%). Intraoperatively, EMG demonstrated activity only in the EUS in 5% of patients and only in the EAS in 28%. In seven patients (11%) spontaneous intraoperative EMG activity was observed in both the EAS and the EUS; however, in only three of these cases was EMG activity recorded in both sphincters simultaneously. In addition to spontaneously recorded EMG activity, electrically evoked EMG activity was also used as an intraoperative adjunct. A bipolar stimulating electrode was used to identify functional neural tissue before undertaking microsurgical dissection in 58 individuals (95%). In the majority of these patients, evoked EMG activity occurred either in one (33%) or in two muscles (9%) simultaneously. The presence of electrically evoked EMG activity in structures encountered during microdissection altered the plan of treatment in 24 cases (42%). CONCLUSIONS: The authors conclude that the combined SSEP and EMG monitoring of lower-limb muscles, EAS, and EUS is a practical and reliable method for obtaining optimal electrophysiological feedback during complex neurosurgical procedures involving the conus medullaris and cauda equina. Analysis of the results indicates that these intraoperative adjunctive modalities positively influence decision making with regard to microsurgery and reduce the risk of perioperative neurological complications. Validation of the clinical value of these approaches, however, will require further assessment in a larger prospective cohort of patients.