F. Tecchio et al., Tonotopic cortical changes following stapes substitution in otosclerotic patients: A magnetoencephalographic study, HUM BRAIN M, 10(1), 2000, pp. 28-38
The aim of the study was to investigate and follow up the tonotopic organiz
ation of the primary auditory cortex in otosclerotic patients before and af
ter corrective surgery. The characteristics of primary auditory cortex acti
vation were studied in ten otosclerotic patients (i.e., subjects suffering
from a conductive hearing loss, prior to and following stapes substitution)
. Magnetoencephalographic recordings of auditory evoked fields by tone-burs
t stimulation at octave frequencies between 250 and 2000 Hz were performed
during monaural stimulation. The brain topography of the main cortical resp
onse (N100m) generators at different tones was studied in patients and comp
ared with ten healthy controls; pre-post-surgical changes were also correla
ted to their clinical outcome following corrective surgery. A significant d
ecrease of the tonotopic extension in the cortical region responsive to the
four explored frequencies was found in patients before surgery with respec
t to the control population At the time of postsurgical follow-up, the tono
topic representation had enlarged and was approaching the dimensions seen i
n normal subjects, although with higher variability. The extent of the enla
rgement of the postoperative tonotopically organized area was directly corr
elated with the postsurgery period duration. Our findings indicate that aud
itory cortical areas of human adults undergo functional reorganization foll
owing peripheral alteration of the sensory input entering the CNS. The rest
riction of the cortical tonotopic region caused by the long-term reduction
of acoustic input is followed by a reorganization within the usual boundari
es following the recovery of auditory function; this process is taking plac
e in a time scale of a few weeks. Hum. Brain Mapping 10:28-38, 2000. (C) 20
00 Wiley-Liss, Inc.