{'fraction_non_alphanumeric': 0.02002503128911139, 'fraction_numerical': 0.0037546933667083854, 'mean_word_length': 5.349206349206349, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
The pathogenesis and treatment of cholesteatoma.

Congenital cholesteatoma, which arises from embryonic epidermoid tissue, is rare. In the majority of cases the cholesteatoma is acquired. It may develop as a retraction pocket involving the whole membrane, as a result of migration over the perforation edges or as basal cell invasion behind an intact membrane. There is no evidence for a metaplastic process or a Langerhans' cell mediated origin. Treatment modalities include several methods of either conservative or radical surgery, the main aim being one-stage total eradication of cholesteatoma and simultaneous reconstruction. With appropriate surgical methods recurrence figures after 5 years should remain under 10%. The patient's own tissues are the material of choice in the reconstruction.