Takuya Yamakawa

A clinical study on the magnetic stimulation of the facial nerve

Objectives: A clinical study on the usefulness of magnetic stimulation of the facial nerve, with special attention paid to the selection of the coil shape and stimulation procedures. Study Design: The subjects consisted of 55 patients with Bells palsy, 1 patient with a cerebellopontine angle (CPA) tumor, 1 patient with multiple sclerosis (MS), and 30 normal subjects. Three types of coils were used in this study; a 90‐mm large single coil, a 40‐mm small single coil, and a 20‐mm small double coil. Methods: The compound muscle action potentials (CMAPs) and long latency response were evoked by transcranial magnetic stimulation (TMS) with a 90‐mm large single coil. The 40‐mm small single coil was used to test blink reflex by aiming it at the supraorbital nerve as the target site. The subcutaneous activation of the infra‐auricular facial nerve was performed with the 20‐mm double coil. Results: The reproducible CMAP and long latency responses were obtained from normal subjects with TMS. However, responses were observed only in patients with relatively mild Bells palsy. The magnetic stimulation—evoked responses reflected the brainstem function in the patients with a CPA tumor and MS. Conclusion: Although magnetic stimulation remains inferior to conventional electric stimulation in some sense and requires further study, this method is potentially useful because it can stimulate the facial nerve continuously from the cortex to the periphery and can effectively evoke responses reflecting the brainstem function.

A facial nerve study using transcranial magnetic paired stimulation.

OBJECTIVE The purpose of this study was to evaluate the refractory period of the facial nerve by transcranial magnetic paired stimulation (TMPS) with as short interstimulus interval (ISI) as possible. Also, by applying TMPS, the long latency response obtained at the same time was recorded and its neurophysiological characteristics were studied. METHODS (Experiment 1) The subjects comprised of 30 normal volunteers and 19 patients with Bells palsy. The experiments were carried out using two sets of Magstim model 200 and Bistim modules, a large coil measuring 90 mm in diameter with a maximal output of 2.0 tesla (T), and a Neuropack 8 (Nihon Kohden Co., Japan) to control the stimulation and record the electromyographic findings. The amplitude of compound muscle action potentials (CMAP) to the orbicularis oris muscle was studied by TMPS at the parieto-occipital region. The ISI was set at 0.9, 1.1, 1.3, 1.5, 1.7, 1.9 and 2.1 ms in order to measure the refractory periods of the nerve. (Experiment 2) The subjects comprised of ten normal volunteers. The same method as in experiment 1 was carried out. However, this time, the lead electrodes were placed on the orbicularis oculi muscle, similar to that of the blink reflex. The ISI was set at 40, 60, 80, 100, 200, 300, 500, 800 and 1000 ms, and the effects of the facilitation and inhibition were studied. RESULTS (Experiment 1) In normal subjects, when the ISI was less than 1 ms, a significant decrease in the amplitude was noted. In severe palsy cases with House-Brackmann Grade IV-V TMS yielded no response. In two of the cases of House-Brackmann Grade III, the CMAP was obtained. (Experiment 2) The long latency response with TMPS was most strongly inhibited when ISI was 80 ms. CONCLUSION We were able to investigate the refractory periods, the reflex pathway of the facial nerve and the trigeminal nerve including the pons and the medulla oblongata by TMPS.

A Study of the Distribution of Facial Nerve Conduction Velocities by Transcranial Magnetic Stimulation

Objective: The purpose of this study was to evaluate by the collision method the distribution of nerve conduction velocities (DNCVs) of the facial nerve under transcranial magnetic stimulation (TMS), to better understand its neurophysiological characteristics.Materials and Methods: The subjects were 13 normal volunteers and 3 patients with Bells palsy. The experiments were carried out using Magstim model 200, a large coil measuring 90mm in diameter with a maximal output of 2.0 tesla (T), and a Neuropack 8 (Nikon Kohden, Japan) to control the stimulation and record the electromyographical findings. The labyrinthine segment of the facial nerve within the temporal bone was selected as the site for transcranial magnetic stimulation, and the main trunk of the facial nerve that runs subcutaneously in the parotid region was selected as the site for electric stimulation. The reference electrode of the bipolar lead was placed over the mentalis muscle. The amplitude of compound muscle action potentials (CMAP) to the mentalis muscle was studied by the collision method.Measurement and Results: The peak of DNCV was detected at 22 to 24m/sec in 13 normal volunteers. The data showed a decrease in the number of thicker fibers, which tended to show faster conduction velocities, in Bells palsy patients.Conclusions: We were able to investigate the DNCVs of the facial nerve by TMS. Thicker myelinated fibers may be more susceptible to compression damage. From this finding it can be said that the compression of the nerve results in a state comparable with Bells palsy.

Diagnostic Cytology in Oto-Rhino-Laryngology.

An analysis of 3360 clinical cytological smears prepared in the department of Oto-Rhino-Laryngology from 1981 to 1992 showed:1. Of the total 3360 smears (2029 were obtained by brushing, 1090 by aspiration, 80 by needle puncture, 147 from sputum, and 12 by other means).2. The origin of 697 specimens was an oral lesion, 599 came from the pharynx, 428 from the larynx, 366 from lymphnodes, and 338 from nasal and paranasal areas.3. The 12 years were divided into four periods (I-IV); 610 smears were examined in period I, increasing to 1066 in proportion to the number of ABC (aspiration biopsy cytology) specimens.4. In period I, before the introduction of ABC, smears obtained by brushing accounted for 88.2% and, ABC for only 1.0%. However, in periods II-IV, after the introduction of ABC, the percentages were 50.2% and 43.6%, respectively.5. Of the 786 smears diagnosed as malignant (class IIIb-V) only 4 were false positives (0.5%). The false negative rate could not be determined.6. Of the 693 smears with a cytological diagnosis of suspected carcinoma, 62 were nonepithelial malignant tumors, and 34 were reported only as malignant change. Histological examination showed an incorrect cytological diagnosis in 6 specimens of ABC.7. Although clinical diagnostic cytology is not a substitute for histo-pathological diagnosis, it can meet the demands of clinicians who want microscopic evidence before medical treatment. It is an ideal method of examination which imposes little burden on patients, and it can be used for daily medical examinations.

Case Report of Parotid Gland Calculi.

Parotid grand calculi in a 52-year-old man is reported. The examinations showed swelling of left parotid gland and a palpable small hard mass at the mid portion of the parotid duct and on the left side. CT and Echo were recommended for its diagnosis. CT showed a small high density area, and the Echo showed an acoustic shadow in front of the left parotid gland. The surgical operation was performed with a small external incision in the longitudinal direction along the parotid duct. After the operation, a cut-down tube with a diameter of 1mm was retained in the parotid duct, for preventing stenosis of the parotid duct. The stone was analyzed by infrared spectrometry, and was composed of calcium phosphate and protein.

Bacteriological Study on a New Washer with Running Water for Fiberoptic Endoscopes.

Sterilization of the flexible laryngeal fiberscope was tested with a newly designed washer which uses running water. Its efficacy was studied in 102 patients undergoing endoscopic examinations.The main part of the washer was a cloro-vinyl pipe 16 mm in diameter, into which the fiberscope was inserted, and fresh water was kept flowing for 3 minutes. Statistically, 1.65 strains of bacteria were detected at the tip of the endoscopes immediately after endoscopic examinations.The incidence of the cases which all strains of bacteria detected before washing were disappeared was 83.3%, and the non effective cases by washing were 9.8%. The cases were 24.5% which a few new strains of bacteria never detected pre-washing were appeared postwashing. These strains of bacteria detected after washing were small in quantity and revealed pathologically low grade. The tips of the nasal endoscopes used in patients with epistaxis all had negative occult blood tests after washing for 5 minutes. The use of the washer was considered to be clinicaly effective in the occasion of the continuous endoscopy.