Spiral ganglion neurons (SGNs) require both pre-and postsynaptic contacts to maintain viability. BDNF, chlorphenylthiocAMP, and depolarization (veratridine

To estimate the prevalence of "incidental" acoustic neuromas (ANs) in the population at large.Design: An intracranial magnetic resonance imaging (MRI) database of 46414 patients presenting to the University of California, San Francisco (UCSF), without known audiovestibular complaints was searched retrospectively from July 1995 to February 2003. Seventy percent of these MRIs included gadolinium, and none was specifically targeted through the internal auditory canal. A medical chart review of 688 patients with acoustic neuromas presenting to UCSF between 1980 and 1999 was searched for sex distribution.Setting: Tertiary care university medical center.Results: Eight patients with incidental AN were discov-ered. This figure suggests that undiagnosed ANs may be present in at least 0.02% of the population. Three patients were found to have audiovestibular symptoms on inquiry after diagnosis. Audiometry revealed asymmetry at 4 kHz in only 3 of 7 patients, with an otherwise symmetric audiogram in the remaining patients. Tumor size in this population ranged from 3 to 28 mm. Incidental ANs were more common in men, but ANs were more common in women overall. Conclusions:The prevalence of incidental AN appears to be roughly 2 in 10000 people. This figure indicates that AN may be less prevalent than suggested in previously reported temporal bone studies and more prevalent than suggested by epidemiologic studies.

We describe a timetable of events during programmed cell death (PCD) in neuronal PC12 cells, specifically, Ras signaling, immediate-early gene (IEG) expression, DNA fragmentation and commitment to PCD. Commitment occurs over a period from 10-20 hr after NGF withdrawal. Ras signaling declines rapidly after NGF removal, reaching minimal levels within 2-4 hr, well before the onset of commitment. DNA fragmentation, detected by TUNEL reaction, begins about 24 hr after NGF withdrawal, well after all cells are committed, but coincident with the onset of cell dissolution previously determined by trypan blue exclusion (Mesner et al., 1992). Among the IEGs studied here, c-jun and TIS21 are expressed within 6 hr after NGF withdrawal. Expression of c-fos, egr-1, and TIS11 does not begin until 20 hr after NGF withdrawal. IEG expression generally ends by 24 hr after NGF withdrawal. The IEGs TIS7 and nur77 are not expressed during PCD, yielding a pattern distinct from that following other stimuli. An identical pattern of IEG expression occurs in non-neuronal PC12 cells deprived of serum, although expression begins at 10-14 hr after serum withdrawal. A similar IEG expression pattern was observed in Rat-1 fibroblasts, with various genes expressed 6-18 hr after serum withdrawal. In none of these cell types did expression of the stress-related gene Hsp70 change following trophic factor withdrawal. The distinctive pattern of IEG expression described here should facilitate identification of intracellular regulatory signals active during PCD.

OBJECTIVE: The goal of this study was to evaluate a conservative management strategy of postoperative infection after cochlear implantation. METHODS: A retrospective review of the medical records of 108 cochlear implant patients operated on at the University of California, San Francisco between 1991 and 2000 and 133 cochlear implant patients from the University of Iowa between 1997 and 2000 showed 4 patients with evidence of postoperative infections. The clinical presentation, intervention, laboratory results, and outcome are analyzed in each case. RESULTS: Minimal surgical intervention with limited incision and drainage with prolonged postoperative antibiotics was effective in treating postoperative cochlear implant infections without the need for device removal. Implant function remained unaffected after surgery. CONCLUSION: Postoperative cochlear implant infections can be effectively controlled with limited surgical and prolonged medical management. Chronic implant infections may be explained by a primary immunodeficiency. With appropriate treatment leading to infection control, a conservative management strategy is advocated before consideration of device explantation.

Our experience suggests that GdMRI plays a crucial role in the diagnosis of cochlear pathology associated with sensorineural hearing loss and may directly impact patient management.