title: Auditory nerve is affected in one of two different point mutations of the neurofilament light gene.
abstract: OBJECTIVE
  To define auditory nerve and cochlear functions in two families with autosomal dominant axonal Charcot-Marie-Tooth (CMT).
  
  
  METHODS
  Affected members in two families with different point mutations of NF-L gene were screened with auditory brainstem responses (ABRs). Those with abnormal ABRs were further investigated with clinical, neurophysiological and audiological procedures. The point mutations of NF-L gene involved were Glu397Lys in 8 affected members of the family with AN, and Pro22Ser in 9 affected members of the family without AN.
  
  
  RESULTS
  ABRs and stapedial muscle reflexes were absent or abnormal in affected members of only one family consistent with auditory neuropathy (AN). In them, audiograms, otoacoustic emissions, and speech comprehension were normal. Absent or abnormal ABRs were consistent with slowing of conduction along auditory nerve and/or brainstem auditory pathway. Wave I when present was of normal latency.
  
  
  CONCLUSIONS
  Auditory nerve involvement in the presence of normal cochlear outer hair cell activity is asymptomatic in one of two families with CMT disorder with different point mutations of the NF-L gene. The nerve disorder is consistent with altered synchrony and slowed conduction.
  
  
  CONCLUSIONS
  The absence of "deafness" may reflect the ability of central mechanisms to compensate for the slowly developing auditory nerve abnormalities.
authors.affiliation: Institute of Clinical Neurophysiology, University of Ljubljana, Ljubljana, Slovenia.
authors.forename: Dusan
authors.initials: D
authors.lastname: Butinar
authors.forename: Arnold
authors.initials: A
authors.lastname: Starr
authors.forename: Janez
authors.initials: J
authors.lastname: Zidar
authors.forename: Pantelitsa
authors.initials: P
authors.lastname: Koutsou
authors.forename: Kyproula
authors.initials: K
authors.lastname: Christodoulou
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods; D000293:Adolescent; D000328:Adult; D000368:Aged; D002607:Charcot-Marie-Tooth Disease / Q000235:genetics* / Q000503:physiopathology; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology; D005192:Family Health; D005260:Female; D007839:Functional Laterality; D018698:Glutamic Acid / Q000235:genetics; D006801:Humans; D008239:Lysine / Q000235:genetics; D008297:Male; D008875:Middle Aged; D016900:Neurofilament Proteins / Q000235:genetics*; D017354:Point Mutation / Q000235:genetics*; D011392:Proline / Q000235:genetics; D011930:Reaction Time / Q000502:physiology; D012694:Serine / Q000235:genetics; D000159:Vestibulocochlear Nerve / Q000503:physiopathology*
chemical_list: D016900:Neurofilament Proteins; C044882:neurofilament protein L; D018698:Glutamic Acid; D012694:Serine; D011392:Proline; D008239:Lysine