SPET Monitoring of Perfusion Changes in Auditory Cortex following Mono- and Multi-Frequency Stimuli

Summary

Aim: In order to assess the relationship between auditory cortex perfusion and the frequency of acoustic stimuli, twenty normally-hearing subjects underwent cerebral SPET. Methods: In 10 patients a multi-frequency stimulus (250-4000 Hz at 40 dB SL) was delivered, while 10 subjects were stimulated with a 500 Hz pure tone at 40 dB SL. The prestimulation SPET was subtracted from poststimulation study and auditory cortex activation was expressed as percent increments. Results: Contralateral cortex was the most active area with multi-frequency and monofrequency stimuli as well. A clear demonstration of a tonotopic distribution of acoustic stimuli in the auditory cortex was achieved. In addition, the accessory role played by homolateral acoustic areas was confirmed. Conclusion: The results of the present research support the hypothesis that brain SPET may be useful to obtain semiquantitative reliable information on low frequency auditory level in profoundly deaf patients. This may be achieved comparing the extension of the cortical areas activated by high-intensity multifrequency stimuli.

Zusammenfassung

Ziel: Zur Aufklärung der Beziehung von regionaler Perfusion des auditorischen Kortex und Frequenz des akustischen Stimulus wurden 20 Normalpatienten mit Hilfe von Hirn-SPECT untersucht. Methoden: Bei je 10 Patienten wurde ein Multifrequenzstimulus (250-2000 Hz bei 60 dB) bzw. ein Monofrequenzstimulus (500 Hz bei 60 dB) verwendet. Die vor der Stimulation akquirierten SPECT-Daten wurden jeweils von den nach der Stimulation akquirierten SPECT-Daten abgezogen und die aditori-sche Kortexaktivation als prozentuale Steigerung ausgedrückt. Ergebnisse: Der kontralaterale Kortex war das am stärksten aktivierte Areal sowohl bei der Multifrequenz- als auch bei der Monofrequenzstimula-tion. Es konnte eine klare tonotopische Verteilung der akustischen Stimuli im auditorischen Kortex demonstriert werden. Zusätzlich konnte die akzessorische Rolle des homolateralen akustischen Kortex bestätigt werden. Schlußfolgerung: Die Ergebnisse dieser Studie unterstützen die Hypothese, daß Hirn-SPECT semiquantitative Informationen im Niederfrequenzbereich auch bei tauben Patienten liefern könnte. Dies kann erreicht werden durch den Vergleich der Ausdehnung aktivierter kortikaler Areale bei Hochintensität-Multifrequenzstimulation.

Key words

Brain SPET - auditory cortex perfusion - mono- and multi-frequency acoustic stimuli

Schlüsselwörter

Hirn-SPECT - Perfusion des auditorischen Kortex - Mono- und Multifrequenz-akustische Stimuli

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