Biomedical subjects
Publications and source records attributed to J J Zappia.
Papillary cystadenoma lymphomatosum, or Warthin's tumor, is known to have a high rate of multicentricity. An incidence of 5-14% is suggested by the literature. We present a female patient with three discrete masses noted in the superficial lobe of the parotid gland at the time of surgical resection. The epidemiology, histology and pathophysiology of Warthin's tumor is discussed and the need for adequate surgical resection is emphasized.
Leukemic involvement of the temporal bone is not uncommon and may present in a variety of ways including auricular or external canal skin lesions, red or thick tympanic membrane, middle ear effusions, otitis media, hearing loss or mastoiditis. Symptomatic facial nerve involvement, on the other hand, is extremely unusual. We discuss a pediatric patient whose sudden onset facial nerve paresis was the presenting symptom that led to her diagnosis of leukemia. At the time of mastoidectomy, a granulocytic sarcoma or chloroma was noted to be overlying the VIIth nerve.
Ossifying fibromata are rare lesions of the temporal bone. Because the tumors tend to progress and can become clinically massive, early complete resection is advised whenever feasible to prevent clinically evident recurrences and potentially life-threatening complications.
The availability of thin-film multichannel electrodes provides new possibilities for implantation and direct stimulation of the modiolar portion of the auditory nerve. Electrodes in direct contact with the auditory nerve should be functional at lower thresholds and might require fewer remaining neurons for stimulation compared to electrodes in the scala tympani. This strategy would also provide close contact with neural elements subserving a greater frequency range. Implantation of the eighth nerve may also be advantageous in profoundly deaf subjects who lack an implantable scala tympani. In this study we evaluated the effect of surgical implantation and chronic placement of a silicon substrate implant in the modiolar portion of the auditory nerve of the guinea pig. Of six chronically implanted ears, five showed changes limited to the loss of spiral ganglion cells in the canal of Rosenthal, immediately adjacent to the implant. The sixth ear showed more extensive cochlear alteration in a pattern suggestive of vascular injury. In separate acute experiments, implants were placed in the modiolar portion of the auditory nerve and electrophysiologic analysis was performed. Middle latency responses with good morphology were obtained at thresholds below those found with scala tympani implants. Input-output functions exhibited a plateau in response amplitude at stimulus levels below thresholds for seventh or vestibular portion of the eighth nerve. Further modifications of the modiolar portion of the auditory nerve electrode design will include development of an electrode interconnect that will allow chronic implantation with stimulation.
The development of a reproducible unilateral deafness animal model was the primary objective of this study. Because of its importance in the function of cochlear prostheses, the status of the VIIIth nerve was used as the measure of deafness. The effect of a concentrated neomycin solution applied locally to the middle ear of the guinea pig was evaluated. Spiral ganglion cell survival was quantitated at 1, 2, 4, 6 and 10 weeks after exposure. Although the intermediate time periods showed moderate inter-animal variability, by ten weeks, consistent spiral ganglion cell loss was seen with maximum cell loss at the extreme apex (18.8% of control) and base (30.3% of control) and maximum cell survival in the lower middle turns of the cochlear spiral (53% of control).
Silicon micromachining and thin-film technology have been employed to fabricate iridium stimulating arrays which can be used to excite discrete volumes of the central nervous system. Silicon multichannel probes with thicknesses ranging from 1 to 40 microns and arbitrary two-dimensional shapes can be fabricated using a high-yield, circuit-compatible process. Iridium stimulating sites are shown to have similar characteristics to iridium wire electrodes. Accelerated pulse testing with over 8 million 100 microA biphasic current pulses on 8000 microns 2 sites has demonstrated the long-term stability of iridium and activated iridium sites. In vivo tests have been performed in the central auditory pathways to demonstrate neural activation using the devices. These tests show a selective activation both as a function of site separation and site size.
A retrospective study was undertaken to review patterns of treatment and survival for patients with olfactory neuroblastomas at the University of Michigan since the introduction of craniofacial resection in the late 1970s. Recent results were compared to previous reports. Disease-free and overall survival for patients with Kadish stage B tumors were unchanged from prior years. Improvement in both disease-free intervals and overall survival was evident for patients with stage C tumors. Interestingly, in two patients with "unresectable" local disease, complete responses to induction chemotherapy followed by radiotherapy were noted.