title: Positive auditory cortical responses in patients with absent brainstem response.
abstract: OBJECTIVE
  To compare the detectability of the different auditory evoked responses in patients with retrocochlear lesion.
  
  
  METHODS
  The 40-Hz auditory steady state response (ASSR) and the N1m auditory cortical response were examined by magnetoencephalography in 4 patients with vestibular schwannoma, in whom the auditory brainstem response (ABR) was absent.
  
  
  RESULTS
  Apparent N1m responses were observed despite total absence of the ABR or absence except for small wave I in all patients, although the latency of N1m was delayed in most patients. On the other hand, clear ASSFs could be observed only in one patient. Very small 40-Hz ASSFs could be detected in 2 patients (amplitude less than 1fT), but no apparent ASSFs were observed in one patient, in whom maximum speech intelligibility was extremely low and the latency of N1m was most prolonged.
  
  
  CONCLUSIONS
  The N1m response and 40-Hz ASSR could be detected in patients with absent ABR, but the N1m response appeared to be more detectable than the 40-Hz ASSR.
  
  
  CONCLUSIONS
  Combined assessment with several different evoked responses may be useful to evaluate the disease conditions of patients with retrocochlear lesions.
authors.affiliation: Laboratory of Rehabilitative Auditory Science, Tohoku University Graduate School of Biomedical Engineering, 1-1 Seiryo-machi, Aoba-ku, Sendai 980-8574, Japan; Department of Audiology, Tohoku University Graduate School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai 980-8574, Japan; Department of Otolaryngology-Head and Neck Surgery, Tohoku University Graduate School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai 980-8574, Japan. Electronic address: kawase@orl.med.tohoku.ac.jp.
authors.forename: Tetsuaki
authors.initials: T
authors.lastname: Kawase
authors.affiliation: Department of Functional Brain Imaging, Institute of Development, Aging and Cancer, Tohoku University, 4-1 Seiryo-cho, Aoba-ku, Sendai 980-8575, Japan; MEG Laboratory, Kohnan Hospital, 4-20-1 Nagamachi-minami, Taihaku-ku, Sendai 982-8523, Japan.
authors.forename: Akitake
authors.initials: A
authors.lastname: Kanno
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Tohoku University Graduate School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai 980-8574, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Takata
authors.affiliation: Department of Epileptology, Tohoku University Graduate School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai 980-8575, Japan; Department of Electromagnetic Neurophysiology, Smart Ageing International Research Center, Institute of Development, Aging and Cancer, Tohoku University, 4-1 Seiryo-cho, Aoba-ku, Sendai 980-8575, Japan.
authors.forename: Nobukazu
authors.initials: N
authors.lastname: Nakasato
authors.affiliation: Department of Functional Brain Imaging, Institute of Development, Aging and Cancer, Tohoku University, 4-1 Seiryo-cho, Aoba-ku, Sendai 980-8575, Japan.
authors.forename: Ryuta
authors.initials: R
authors.lastname: Kawashima
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Tohoku University Graduate School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai 980-8574, Japan.
authors.forename: Toshimitsu
authors.initials: T
authors.lastname: Kobayashi
mesh_terms: D000161:Acoustic Stimulation; D000368:Aged; D001933:Brain Stem / Q000503:physiopathology*; D002540:Cerebral Cortex / Q000503:physiopathology*; D005072:Evoked Potentials, Auditory; D016057:Evoked Potentials, Auditory, Brain Stem; D005260:Female; D006801:Humans; D015225:Magnetoencephalography; D008297:Male; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000503:physiopathology*
keywords: Auditory evoked field; Auditory steady state response; Magnetoencephalography; N1m; Vestibular schwannoma