Faculty Bibliography

Previous studies which have measured acoustic-reflex responses to bone-conducted signals have not effectively differentiated reflex responses from artifacts. A convenient method for identifying such artifacts was developed and employed on some acoustic-reflex measures for bone-conducted signals. The findings indicated that artifacts result when a frequently-used acoustic admittance meter (Grason-Stadler 1720B) and a conventional bone vibrator were used to measure reflex responses for tonal and noise-activating signals. It was suggested that the method be employed in future studies which investigate the acoustic reflex in response to bone-conducted signals.

The growth function of the acoustic stapedius reflex was measured in subjects with normal hearing and sensorineural hearing loss of cochlear origin. The effects of age and magnitude of hearing loss were controlled. Activating stimuli were 500, 1000, and 2000 Hz tones and broadband noise. Stapedius muscle activity was inferred from acoustic impedance measures in the contralateral ear. The mean growth functions for tones were essentially linear in log-log plots with the rate of growth equal for the two groups. The mean growth function for the noise signal was curvilinear for the normal hearing groud had linear for the hearing loss group. Comparison of slope functions derived from the fitted data indicated that the rate of reflex growth for the noise signal, over a limited range above reflex threshold, is greater in ears with cochlear lesions than normal ears. For higher level noise signals, however, the rate of reflex growth is similar for normal and pathological ears. The effect of a cochlear lesion on the input-output function of the cochlea for both tonal and noise stimuli is to maintain the rate of reflex growth but shift the function along the intensity axis of a tonal signal and the response axis for a noise signal.

Tympanometry was performed before and after producing specific lesions in the middle ears of cats. The lesions selected for study included stapes fixation, ossicular discontinuity, and scarred tympanic membranes. Stapes fixation resulted in marked increases in middle ear impedance, easily detected with tympanometry. Ossicular discontinuity resulted in complex tympanometric shapes which were easily accounted for by simple interactions between acoustic resistance and reactance. The complex shapes that occurred in normal and abnormal ears with pressure changing from negative to positive resulted from more complicated interactions. Large surgical incisions in the posterior-superior quadrant of the eardrum were quite visible at otoscopy but could not be detected tympanometrically one month after surgery.

At present there is no single surgical approach that is ideally suited to rehabilitation of the paralyzed face. Dynamic reconstruction and neural reconstitution are usually preferred to static methods, except under special circumstances. Experience with over 150 autogenous facial-nerve grafts using epineural suture technique has resulted in return of movement in 95% of properly selected patients. When grafting is not feasible, as in the obliterated central facial nerve, hypoglossal-facial-nerve crossover is a simple and powerful source of reinnervation, usually resulting in minimal intraoral crippling and mild mass movement. A newer procedure, the cross-face nerve graft, is an alternative to hypoglossal crossover, although it results in less axonal input and longer regenerative time. In cases of long-standing facial paralysis with muscle atrophy, temporalis and masseter transfers are dependable and may sometimes be combined with a nerve graft.

The temporal bone findings in a case of hemifacial microsomia are described with photographs. The right facial hypoplasia was associated with anophthalmia and microtia on the same side. The right petrous bone was hypoplastic and showed total superior dehiscence of the internal acoustic meatus. Th otic capsule was deformed with an underdeveloped cochlear modiolus grossly deficient in spiral ganglion population. The spiralling cochlear shell showed partial deficiency of the interscalar septum between the middle and apical coils. The cochlear duct was shorter than that on the normal side; the organ of Corti however was normal. The vestibular system did not show any structural abnormality except for the degeneration and reduction of the Scarpa's ganglion cells and nerve fibers. An additional interesting fact was that the facial nerve was totally absent in the temporal bone except for its nervus intermedius component