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Michel aplasia

Dr Yuranga Weerakkody and Dr Frank Gaillard et al.

Michel aplasia also known as complete labyrinthine aplasia (CLA) was first described in 1863. It is a congenital abnormality of the inner ear and is characterised by bilateral absence of differentiated inner ear structures (with resultant - and not surprising - anacusis). It is thought to result from failure of development of the otic placode. It is associated with:

abnormal development of the skeletal portions of the second arch
- nondifferentiation of the stapes, with resultant absence of round and oval windows
- abnormal course of the facial nerve
skull base abnormalities
- hypoplasia of the petrous temporal bone; hypoplastic and sclerotic petrous apex may mimic labyrinthitis ossificans
- platybasia
- aberrant course of the jugular veins

It should not be confused with Michel dysplasia

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References

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1. Marsot-Dupuch K, Dominguez-Brito A, Ghasli K et-al. CT and MR findings of Michel anomaly: inner ear aplasia. AJNR Am J Neuroradiol. 1999;20 (2): 281-4. AJNR Am J Neuroradiol (full text) - Pubmed citation
2. Ozgen B, Oguz KK, Atas A et-al. Complete labyrinthine aplasia: clinical and radiologic findings with review of the literature. AJNR Am J Neuroradiol. 2009;30 (4): 774-80. AJNR Am J Neuroradiol (full text) - doi:10.3174/ajnr.A1426 - Pubmed citation