Perception of audio-frequency vibrations by profoundly deaf subjects after fenestration of the vestibular system.

A survey is given of the literature on the sensitivity of the vestibular system to audio-frequency sound and vibration in animals. It is also shown that responses to such stimuli can be evoked in man. On the basis of these results it was decided to perform a fenestration of the horizontal semicircular canal in three profoundly deaf volunteers, with normal sensitivity of the vestibular system. The first results are promising: the threshold for audio-frequency vibration in the operated ears improved markedly. Furthermore, the subjects reported perception of environmental sounds using a bone conductor hearing aid.

Hearing thresholds of normal and fenestrated deaf pigeons. A behavioural study on hearing with the vestibular organ.

Hearing thresholds were measured for 5 normal pigeons with the heart-rate conditioning method. After extirpation of the membranous cochlea on both sides and fenestration of the lateral canals, hearing thresholds were measured again with the same method at 250, 750 and 1500 Hz. Hearing thresholds found in this way for deaf fenestrated pigeons correspond very well to threshold values for the "Tullio effect". Electrical activity in the vestibular nerve evoked by sound is thought to be the origin of these phenomena.

Cochlear implant versus vestibular stimulation. Communication.

Results obtained with cochlear electrode implants in totally deaf patients indicate that this means of transmitting auditory information can be of great help in lipreading and remote sound contact. However, using an alternate approach involving fenestration of the labyrinth and acoustical stimulation of the vestibular nerve, we generated a signal in an animal model superior in quality to that generated by electrical stimulation of the cochlea of the cat. This communication raises the question of whether a vestibular signal could be processed so that a deaf person could hear and identify sounds.

Responses of pigeon vestibular nerve fibers to sound and vibration with audiofrequencies.

Single unit recordings were made from the nerve branch innervating the crista in the horizontal semicircular canal of a pigeon. The vestibular organ was either stimulated with sound through the ear canal or with a vibrator in contact with the membraneous ampulla roof. Units responding to sound or vibration showed tuning with a best frequency of approximately 0.7 kHz. The average low-frequency slope of the tuning curves is--16 dB/oct; the average high-frequency slope 20 dB/oct. The threshold amplitude for vibrator stimulation is 30 nm. This value comes close to the calculated threshold value for cupula deflection in the human semicircular canal.

A possible method to study transient effects of ototoxic agents on the vestibular system.

A method is described in which the direct influence of anoxia and ototoxic agents on the vestibular system can be studied. After fenestration of the lateral semicircular canal in pigeons, a vestibular whole nerve action potential (VAP) could be recorded during acoustic stimulation. The cochlear whole nerve action potential (CAP) was recorded simultaneously. The influence of ototoxic agents and anoxia upon the amplitude of these action potentials was studied.

Secondary syphilis of the facial nerve.

A 37-year-old woman had peripheral facial palsy. It took nearly two weeks to establish the syphilitic origin. This rare disease is discussed with reference to nine cases reported in the literature since 1945. The prognosis is good with early antibiotic therapy.

Sensitivity of the vestibular system to acoustic stimuli.

Cochlea-deprived pigeons were placed on a rotating platform and stimulated with sound after fenestration of the lateral canal. The whole nerve action potentials evoked by the sound stimulus were suppressed by the rotatory stimulus. The time course of this suppression makes the lateral crista the most acceptable site of generation of the action potential. In another type of experiment, single unit responses were recorded from the lateral ampullary nerve during stimulation with sound. Phase-lock of the response to the stimulus was best for frequencies fom 0.5 to 1 kHz.

Vestibular and cochlear responses to acoustic transients. Some properties of whole-nerve action potentials in pigeons.

In a previous paper attention was drawn to the possibility of introducing the labyrinth as an organ for sound perception. Behavioural responses of the guinea pig as well as electrophysiological results in the pigeon indicated that fenestration of the labyrinth might be an alternative to cochlear implants. In this paper gross electrode electrophysiological responses to transient acoustic stimuli in the pigeon are further analysed and the influence of fenestration of the lateral canal and cochlea extirpation upon these responses was studied. The vestibular AP generated by sound stimuli could, among other things, be distinguished from the cochlear AP by its shorter latency. The dynamic range of this vestibular AP is at least 30 dB. The largest vestibular responses were obtained for stimulus frequencies below about 1.5 kHz. A simple hydromechanical model to explain the observed responses is discussed.

Acute facial paralysis: a virological study.

A serological study using the complement fixation reaction for herpes zoster virus (HZV) and herpes simplex virus (HSV) was carried out on 120 patients with Bell's palsy and 5 with Ramsay-Hunt syndrome. Three Bell's palsy patients (2.5%) showed a significant HZV antibody titre rise. In no case was a rise of HSV antibody titre observed. Two Ramsay-Hunt patients showed a significant rise of HZV antibody titre. Rise of HSV antibody titre was not observed in this group either. The Monosticon test to exclude infectious mononucleosis, proved to be negative in all cases of Bell's palsy. In 2 cases of Bell's palsy, a biopsy specimen for virus isolation was obtained during a decompression operation. No virus could be cultured from the epineurium of the first patient. That of the second patient was found to contain HSV type I. There was no serological evidence of a HSV antibody titre rise.

Evidence for sound perception with the labyrinth.

A report is presented of experiments on guinea pigs and pigeons concerning behavioural and electrophysiological responses of the labyrinth to sound. In the guinea pigs the cochlea was destroyed on both sides by CO2 laser radiation and fenestration of the lateral semicircular canal was done. In the pigeons the cochlea was removed before fenestration. On account of the results obtained, fenestration of the lateral canal in patients with bilateral total cochlear loss can be considered as an alternative to monopolar cochlear implants.

Viral lesions of the respiratory tract compared to iatrogenic trauma.

A comparison between the mucosal pathology of the respiratory tract in cases of viral infections and of iatrogenic trauma after bronchoscopy and tantalum bronchography indicates that the respiratory mucosa has a very high degree of resistance against infection after trauma and is capable of rapid regeneration as long as the production of mucus continues and the surface remains moist. Viral infection might primarily inhibit mucus production and open the road to secondary infection.

Scanning electron microscopic study of the organ of Corti in normal and sound-damaged guinea pigs.

A method was evolved by which the organ of Corti could be examined in its entirety with the scanning electron microscope, the organ meanwhile retaining its spiral form. This made it possible to assess traumatic effects on the cochlea and qualify lesions in terms of extent, localization and pattern. It was also found possible eventually to cut the same specimen into sections for cellular and subcellular studies. The number of guinea pigs examined totalled 91, divided into three groups. The first group was used to study the anatomy of the organ of Corti with special reference to normal variations and artifacts. Unmistakable indications were found that the longest stereocilia of the inner hair cells are linked to the tectorial membrane. The animals of the second group were exposed to pure tones of high intensity, whereupon, lesions of the organ of Corti were described according to intensity, time, and frequency. Three different types of otologic drills were used to perform mastoidectomies on temporal bones and on the cadaver. The noise produced was analyzed as to intensity and frequency range. It was found that the drill with the lowest rpm (and highest torque) produced the highest noise intensities, at levels which can be traumatic to the human organ of hearing. The animals of the third group were exposed to the amplified noise produced by otologic drills of three different types. The resulting lesions in the organ of Corti were examined by the method described for scanning electron microscopy and compared. In spite of the wide variation in individual lesions, patterns of degeneration of three different types could be distinguished. The high-speed and the very-high-speed drill inflicted less damage on the organ of Corti than the low-speed drill. It is therefore advised to refrain from using the latter drill in prolonged operations.