Objective: To discuss the classification of petrous bone cholesteatoma (PBC) and add a subclassification; to review the existing literature and to propose the ideal surgical management of PBC based upon the experience of the largest series published in the literature until now. Study Design: Retrospective analysis. Setting: Quaternary referral neuro-otologic private practice. Materials and Methods: The data of 129 patients who underwent surgery for PBC between 1979 and 2008 were analyzed with respect to the classification, type of the approach used, facial nerve lesion and its management, recurrences and outcome. Results: Out of the 129 PBC cases 64 were supralabyrinthine, 9 infralabyrinthine, 7 infralabyrinthine-apical, 48 massive and 1 apical. The facial nerve was involved in 95% of the cases. Hearing could not be preserved in 82% of the cases due to the extent of the lesions and the surgical approaches used. The internal carotid artery, jugular bulb and the lower cranial nerves were infrequently involved, but demanded careful identification and meticulous care to avoid complications. Obliteration of the cavities provided a safe solution for protection of the exposed dura and the vital neurovascular structures. Recurrences were observed in 5 cases. Conclusion: The classification of PBC is fundamental to choose the appropriate surgical approach; the facial nerve is involved in almost all the cases, radical removal takes priority over hearing preservation and cavity obliteration is important to protect the vital neurovascular structures which may be exposed.

Recent electrocorticography data have demonstrated excessive coupling of beta-phase to gamma-amplitude in primary motor cortex and that deep brain stimulation facilitates motor improvement by decreasing baseline phase-amplitude coupling. However, both the dynamic modulation of phase-amplitude coupling during movement and the general cortical neurophysiology of other movement disorders, such as essential tremor, are relatively unexplored. To clarify the relationship of these interactions in cortical oscillatory activity to movement and disease state, we recorded local field potentials from hand sensorimotor cortex using subdural electrocorticography during a visually cued, incentivized handgrip task in subjects with Parkinson's disease (n = 11), with essential tremor (n = 9) and without a movement disorder (n = 6). We demonstrate that abnormal coupling of the phase of low frequency oscillations to the amplitude of gamma oscillations is not specific to Parkinson's disease, but also occurs in essential tremor, most prominently for the coupling of alpha to gamma oscillations. Movement kinematics were not significantly different between these groups, allowing us to show for the first time that robust alpha and beta desynchronization is a shared feature of sensorimotor cortical activity in Parkinson's disease and essential tremor, with the greatest high-beta desynchronization occurring in Parkinson's disease and the greatest alpha desynchronization occurring in essential tremor. We also show that the spatial extent of cortical phase-amplitude decoupling during movement is much greater in subjects with Parkinson's disease and essential tremor than in subjects without a movement disorder. These findings suggest that subjects with Parkinson's disease and essential tremor can produce movements that are kinematically similar to those of subjects without a movement disorder by reducing excess sensorimotor cortical phase-amplitude coupling that is characteristic of these diseases.

Classification is fundamental to choosing the right surgical approach. Transotic and modified transcochlear approaches hold the key to treating complex cases. Infratemporal fossa approach type B has to be used for extension into the clivus, sphenoid sinus, or rhinopharynx. Internal carotid artery, jugular bulb, and sigmoid sinus involvement should be identified before operation.

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