Preoperative functional assessment of auditory cortex in adult cochlear implant users.
OBJECTIVE
To explore functional neuroanatomical responses to auditory stimulation before and after implantation.


METHODS
A prospective study of three cochlear implant candidates (pure-tone averages of 90 dB HL or greater bilaterally and hearing in noise test [HINT] performances of <40%) in which regional cerebral blood flow (rCBF) was assessed using single photon emission computed tomography (SPECT).


METHODS
Candidates watched a 15-minute videotaped story under four conditions: audio presented monaurally in the right and left ears (aided), audio presented binaurally (aided), and visual-only presentation of the story. Five minutes into each story, 20 to 25 mCi of technetium 99m (99mTc) hexamethyl-propyleneamine-oxime (HMPAO) (Ceratec; Nycomed Amersham, Princeton, NJ, U.SA) was injected over a 30-second period to ensure that subjects were unaware of tracer administration. Subjects were scanned for 20 minutes using a PRISM 3000 gamma camera (Picker International, Cleveland, OH, U.S.A.). Data were normalized and co-registered, and subtraction images were compiled. Subtraction images contrasted activation patterns generated under the visual-only control condition to the auditory activation states acquired monaurally and binaurally.


RESULTS
Right and left ear monaural stimulation in normal hearing subjects resulted in significant bilateral activation of Brodmann areas 41, 42, 21, 22, and 38. Although substantial intersubject response variability was noted, subjects generally failed to bilaterally activate these areas under monaural hearing aid presentations; however, bilateral activation of areas 41 and 22 was noted under binaural presentations.


CONCLUSIONS
Despite relatively similar hearing losses in each ear, significant differences in preoperative auditory cortex activation were observed between ears. These data suggest that functional brain imaging provides a useful tool for exploring the responsiveness of the auditory cortex in cochlear implant candidates.
Roland
P S
PS
Department of Otolaryngology, University of Texas Southwestern Medical Center, Dallas 75390-9035, USA.
Tobey
E A
EA
Devous
M D
MD
D000161:Acoustic Stimulation; D000328:Adult; D000368:Aged; D001301:Audiometry, Pure-Tone; D001303:Auditory Cortex / Q000000981:diagnostic imaging / Q000503:physiopathology*; D001309:Auditory Threshold / Q000502:physiology; D002560:Cerebrovascular Circulation / Q000502:physiology; D003054:Cochlear Implants; D005260:Female; D005625:Frontal Lobe / Q000503:physiopathology; D015902:Gamma Cameras; D006309:Hearing / Q000502:physiology; D006310:Hearing Aids; D006312:Hearing Loss, Bilateral / Q000503:physiopathology / Q000628:therapy; D006319:Hearing Loss, Sensorineural / Q000503:physiopathology / Q000628:therapy; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D009622:Noise; D011300:Preoperative Care; D011446:Prospective Studies; D019275:Radiopharmaceuticals; D013067:Speech Perception / Q000502:physiology; D013382:Subtraction Technique; D019690:Technetium Tc 99m Exametazime; D015899:Tomography, Emission-Computed, Single-Photon
D019275:Radiopharmaceuticals; D019690:Technetium Tc 99m Exametazime