Temporal bone histopathological study of Noonan syndrome.

Four temporal bone specimens, obtained from three individuals 1--6 years of age with Noonan syndrome (NS), were studied histopathologically. All four specimens were accompanied by similar inner ear abnormalities including the reduced number of spiral ganglion cells, enlarged lateral semicircular canal, and dislocated endolymphatic sac and vestibular aqueduct. The mean population of spiral ganglion cells (15,699 cells) was approximately half of those (32,978 cells) in four age-matched control cases. In addition, they had several middle ear abnormalities including the remaining mesenchyme and dehiscence of the facial canal. To our knowledge, this is the first report to describe the histopathological temporal bone findings in patients with NS. We discuss the implications of the observed abnormalities with regard to clinical issues.