Cortical perfusion response to an electrical stimulation of the auditory nerve in profoundly deaf patients: study with technetium-99m hexamethylpropylene amine oxime single photon emission tomography

Abstract

Brain activation procedures associated with single photon emission tomography (SPET) have recently been developed in healthy controls and diseased patients in order to help in their diagnosis and treatment. We investigated the effects of a promontory test (PT) on the cerebral distribution of technetium-99m hexamethylpropylene amine oxime (99mTc-HMPAO) in 7 profoundly deaf patients, 6 PT+ and one PT-. The count variation in the temporal lobe was calculated on 6 coronal slices using the ratio (Rstimulation-Rdeprivation)/Rdeprivation where R = counts in the temporal lobe/whole-brain count. A count increase in the temporal lobe was observed in all patients and was higher in all patients with PT+ than in the patient with PT-. The problems of head positioning and resolution of the system were taken into account, and we considered that the maximal count increment was related to the auditory cortex response to the stimulus. Further clinical investigations with high-resolution systems have to be performed in order to validate this presurgery test in cochlear implant assessment.

Use of time differences in normal hearing – cortical processing of promontorial stimuli

“…An auditory sensation of the stimulus is believed to demonstrate the responsiveness of auditory neurons (House and Brackmann, 1974) and hence to predict the probable success of the planned implantation. However, the exact nature of the correlation between the promontory test result and the underlying neuronal competence is unknown (Smith and Simmons, 1983), and the signiWcance of a negative test is controversial (Luxford, 1989;Scao et al, 1993;Schmidt et al, 2003). Many centers have limited their use of this test to subjects with severe ossiWcating labyrinthitis, or a history of trauma or retrocochlear surgery (Gantz et al, 1993).…”

“…In a recent study, we demonstrated that right temporal activation (posterior and anterior) is correlated with the ability temporally to parse transmitted phonemes in cochlear implant users relying primarily on temporal cues (Mortensen et al, submitted). However, to identify pre-operative predictors of postoperative results, it is potentially important to combine electrical evaluation of the auditory system with functional neuroimaging (Scao et al, 1993;Truy, 1999).…”

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

“…A rather uniform bilateral activation of the temporal cortex after pure tones and electrical stimuli, was reported by Le Scao et al (7)(8)(9). On the contrary, PET investigations and previous personal studies with SPET, proved an asymmetrical cortical stimulation, with a statistically significant higher increase in contralateral regions (2)(3)(4)6).…”

SPET monitoring of auditory cortex activation by electric stimulation in a patient with auditory brainstem implant

“…Various authors have supported the reliability and usefulness of single photon emission tomography (SPET) in investigating auditory cortex activation in normal and hearing-impaired subjects [2,3,6,15,16,21]. In this paper the features of ABI-induced activation of the auditory cortex were studied by means of SPET.…”