[A case of reversible deafness in cystic arachnoiditis (author's transl)].

A patient studied preoperatively by a neuro-otological test battery showed signs of an extensive cerebellopontine angle tumour. During the operation dense fibrotic tissue was found extending from the choroid plexus to the right acoustic nerve, which was freed and thus decompressed. Postoperatively, low frequency hearing improved markedly in the right ear. In contrast to the well-known documented cases of successful decompression of the optic nerve it has not been possible up to now to achieve a successful outcome in similar procedures on the acoustic nerve. In the described case the fibrotic lesion had obviously just caused reversible damage to the myelin sheaths of the eighth nerve, which can be interpreted as "neurapraxia" (Seddon, 1943). Further investigations in regard to the systematic elucidation of possibly reversible damage to the acoustic nerve are currently being performed at the IInd ENT department of Vienna University.