Subjective examination and objectified measurement of trigeminal nerve function with neurovascular compression in trigeminal neuralgia before and after Jannetta microvascular decompression.

The present study investigated a method for the objective assessment of the trigeminal nerve in trigeminal neuralgia with vascular-nerve conflict before and after microvascular decompression. So far, the diagnosis and the assessment of the success of therapy have been largely based on subjective criteria. For this purpose, a collective of ten patients was examined at three points in time. The subjective parameters were collected by means of questionnaires. In addition, a subjective examination of the olfactory ability as well as a comprehensive ENT medical examination and diagnostics were carried out before the operation. Finally, by means of objective olfactometry, the side-separated change of the derived chemo- somatosensory evoked potentials between stimulation by CO2 in the area of the nasal mucosa and registration by EEG on the scalp preoperatively, 7 days postoperatively and in the course after 3 to 6 months was investigated. Two hypotheses have been formulated, which are tested using objective olfactometry. Preoperatively, an extension of the latency times of the diseased side due to the vascular-nerve conflict was suspected, which should adapt to the healthy side in the course of successful surgery. On the other hand, a change in amplitude due to prolonged pressure damage was assumed. One week after surgery, 60 percent of patients were pain-free. One patient reported greater pain than before surgery. In the follow-up measurement, 78 percent of the patients were pain-free. Overall, half of the patients showed a preoperative prolongation of latency on the side affected by trigeminal neuralgia in half of the patients. Postoperatively, there was a median reduction in latency on the diseased side. Already in the course measurement, 63 percent of the patients showed a normalization of the latency period compared to the healthy side. In the synopsis of the three measurement dates, the changes in amplitude provided a recognizable trend towards postoperative recovery. A preoperative increase in latency with simultaneous reduction of amplitude as assumed in the initial hypothesis could not be demonstrated in any of the ten patients. From our point of view, this is due to the extent of the existing pressure damage through the vessel, whereby higher-grade nerve damage does not seem likely. This will be also confirmed with regard to the processes described in the literature in the context of nerve recovery. Overall, the investigation by olfactometry in the evaluation of latent changes of the chemo-somatosensory evoked potential is basically suitable to objectify changes in the context of trigeminal neuralgia preoperatively and after microvascular decompression. However, it requires the investigation of a larger collective and an adjustment of the conduct of the study in order to obtain statistically usable statements. In view of the increasing importance of quality management in medicine, it seems to be a suitable procedure with which the diagnostic criteria can be supplemented and the success of microvascular decompression can be objectified.