Cochlear pathology following experimental ablation of the vestibular labyrinth

Does endoscopic surgery reduce recurrence of the petrous apex cholesteatoma?

The aim of this study is to present the clinical symptoms, complications and treatments of the petrous apex cholesteatoma and is to describe the current role of oto-endoscopy. This was a retrospective non-randomized study of 14 petrous apex cholesteatoma surgeries performed between 1994 and 2012. Petrosectomy was performed according to the location of the cholesteatoma, hearing level of the patients and facial nerve function. Oto-endoscopy was used in the petrous apex and the cerebellopontine angle for residual cholesteatoma. 14 patients, seven were men and seven women were included in this study between 1994-2012. The most common symptom was hearing loss (85.7 %) and tinnitus (50 %) at the presentation. During the surgeries, it was observed that cholesteatoma involved most frequently facial nerve, dura and labyrinthines. Labyrinthectomy, middle cranial fossa approach and petromastoidectomy was performed to these patients. Four of six patients operated without the endoscope assistance between 1994-2006 had recurrences after the operation. These patients were re-operated and in the follow up, there was no recurrence. In the endoscopy assisted surgery, there was no recurrence observed (significance level p = 0.014). The most common complication after the surgery was hearing loss (42.8 %) but it was not significant after surgery (p > 0.05). The petrous apex and mastoid cavity was obliterated with fat tissue in eight patients while six patients were exteriorized to follow the recurrence and it was insignificant in recurrences (p > 0.05) CONCLUSION: Endoscope-assisted surgery allows to remove residual the cholesteatoma around the carotid artery, dura and facial nerve in the petrous apex resulting in less invasive surgery and less recurrence in blind spots.

Chronic perilymphatic fistula: experimental model in the guinea pig

Chronic perilymphatic fistulas were created in guinea pig cochleas using silicone rubber tubing placed into the scala tympani through the round window. Fistula patency was determined by fluorescein perfusion into cerebral spinal fluid. Fistula were found to be patent in 6 of 6 animals at 7 days and 8 of 13 animals at 28 days. Analysis of ABRs revealed threshold increases of 10 to 15 dB across all frequencies at 1 hour and 7 days. However, thresholds returned to pre-fistula levels by 28 days. Animals with acute fistulas (simple laceration of the round window) had similar threshold increases at 1 hour; however, recovery to baseline levels occurred by day 7. Control animals with intact round windows did not have threshold shifts. Scanning electron microscopy revealed hair cell loss localized to the apical and basal turns of the cochlea. The morphologic changes observed occurred acutely (within 7 days) and were not progressive, despite the presence of a fistula. Hair cell loss or degeneration did not correlate with hearing loss.