Kazuyuki Tashima

Antidromically evoked facial nerve responses in guinea pigs: a basis for clinical applications in patients with facial palsy.

SummaryWe investigated the differences in wave form in antidromically evoked facial nerve responses in guinea pigs with and without facial nerve dysfunction. The antidromic facial nerve responses were evoked with alternative stimulation of positive and negative square-wave pulses of 0.1 ms duration and recorded at the bony fallopian canal near the geniculate ganglion. One hundred responses were summed by a signal processor. The application of alternative stimulations made it possible to eliminate stimulus artifacts and to analyze precisely the waves with latencies shorter than 0.5 ms in the test animals. Normal antidromic facial nerve responses showed a triphasic wave form with two positive and one negative peaks. A blockade of the nerve between the recording and stimulating sites resulted in transformation of the wave into a monophasic one. A proximal blockade to the recording site changed the wave form to a biphasic shape. These findings suggest that the site of an intratemporal facial nerve lesion can be predicted from the wave forms evoked by antidromic facial nerve responses.

Volumetric changes of the aerated middle ear and mastoid after insertion of tympanostomy tubes

Volumetric changes of the middle ear and mastoid were measured monthly by the direct volumetric method in 28 ears from 21 patients (12 children and nine adults) with otitis media with effusion. The mean volumetric increase immediately after the insertion of the tubes was 1.56 ml and was attributed to the volume of effusion aspirated from the tympanic cavity and mastoid antrum. The volume increased significantly for three months (P less than 0.01). The increase was speculated to be due to disappearance of the mucosal edema and of effusion in the tympanic cavity and mastoid. The volumetric changes showed little increase thereafter.

Antidromically Evoked Facial Nerve Response in Guinea Pigs – A Long-Term Follow-Up after Nerve Injury

Conclusion: The present animal experiment supported that the antidromically evoked facial nerve response (AFNR) was useful for the early diagnosis of facial palsy and for assessing its recovery course. Objective: Chronological changes of AFNR latencies after nerve damage were investigated to examine whether or not AFNR latency was suitable as a parameter for the assessment of facial nerve function. Materials and Methods: AFNR were recorded in guinea pigs with and without the total or partial transection of the facial nerve. Chronological changes of AFNR after facial nerve transection were investigated. Results: 48 h after the total transection, the responses almost completely disappeared, and reappeared after 3 weeks. The latencies of the recovered responses were prolonged then but shortened thereafter. Meanwhile, the partial transection did not result in a total loss of AFNR, but in a decrease of the amplitude and prolongation of the latency. One day after the partial transection, the latencies of the responses had already prolonged. From the 3rd to the 7th day, the latencies progressively prolonged, and then shortened by the 14th day.

Antidromically evoked facial nerve response in guinea pigs with partial nerve injury.

Since the most common site of lesion in facial palsy is in the intratemporal course, we need a test to evaluate facial nerve function in the temporal course. Antidromically evoked facial nerve response (AFR) allows real time evaluation of the functional alterations of the facial nerve. Some papers state that the prolongation of latency was demonstrated on the damaged facial nerve [2, 3, 5]. However, there is no chronological study on the prolongation of latency in the damaged facial nerve. The purpose of this study is to show the chronological changes in latencies of this response after nerve damage in guinea pigs.

Neurovascular decompression for hemifacial spasm - Transmastoid approach.

To avoid cochlear and vestibular nerve injury as much as possible, neurovascular decompression for hemifacial spasm via the mastoid was performed. This approach was superior to the classic suboccipital approach with respect to more direct accessibility to the 7th and 8th cranial nerves with less retracting the cerebullum and to minimum chance of subsequent trauma to the 8th cranial nerve. On the other hand, the disadvantages of this approach were less visualization of the cerebello-pontine angle and a more cautious maneuver to prevent CSF leakage. We recommend the transmastoid approach for the cases in which intratemporal tumors can not be ruled out as a cause of the hemifacial spasm.