A method for the direct electrical stimulation of the auditory system in deaf subjects: A functional magnetic resonance imaging study

Abstract

Purpose: To develop a safe functional magnetic resonance imaging (fMRI) procedure for auditory assessment of deaf subjects. Materials and Methods:A gold-plated tungsten electrode has been developed which has zero magnetic susceptibility. Used with carbon leads and a carbon reference pad, it enables safe, distortion-free fMRI studies of deaf subjects following direct electrical stimulation of the acoustic nerve. Minor pickup of the radio frequency (RF) pulses by the electrode assembly is difficult to eliminate, and a SPARSE acquisition sequence is used to avoid any effects of unintentional auditory nerve stimulation. Results:The procedure is demonstrated in a deaf volunteer. Activation is observed in the contralateral but not the ipsilateral primary auditory cortex. This is in sharp contrast to studies of auditory processing in hearing subjects, but consistent with the small number of previous positron emission tomography (PET) and MR studies on adult deaf subjects. Conclusion:The fMRI procedure is able to demonstrate whether the auditory pathway is fully intact, and may provide a useful method for preoperative assessment of candidates for cochlear implantation.

A method for direct thalamic stimulation in fMRI studies using a glass-coated carbon fiber electrode

“…The recent use of deep brain electrical stimulation in human fMRI studies shows that it should be possible to perform safe functional MR imaging by modifying not only the tip region of the electrode, but also the arrangement of the electrodes, connecting wires, and coil (Gleason et al, 1992;Berthezene et al, 1997;Obler et al, 1999;Tronnier et al, 1999;Alwatban et al, 2002;Rezai et al, 2002). One of the concerns about MR compatibility is the interaction between the electrode and the time-varying magnetic field in the presence of a conducting loop (Tenforde, 1986).…”

Functional Magnetic Resonance Imaging of Activation in Subcortical Auditory Pathway

“… 1,2 Activation in the primary and secondary auditory cortices has been consistently detected using fMRI in normal‐hearing adults and children as well as in hearing‐impaired patients. 3–11 Despite the detailed information available on fMRI of the auditory cortex activation, only a few studies have evaluated activation in the subcortical auditory pathway. 12,13 …”

Testing the Diagnostic Value of Electrical Ear Canal Stimulation in Cochlear Implant Candidates by Functional Magnetic Resonance Imaging

“…Cortical activation upon unilateral electrical stimulation of the auditory nerve in bilaterally or unilaterally deaf subjects has been mainly observed bilaterally in PET and fMRI studies [Alwatban et al, 2002;Berthezene et al, 1997;Tschopp et al, 2000]. With normal-hearing subjects, however, unilateral acoustic stimulation evoked strong contralateralization of cortical fMRI response, and a binaural stimulation evoked a nearly balanced activation [Ito et al, 2004;Scheffler et al, 1998].…”

“…fMRI activation of the primary auditory cortex has been demonstrated during electrical stimulation of the promontory [Alwatban et al, 2002;Berthezene et al, 1997;Schmidt et al, 2003] as well as during ECS [Hofmann et al, 1999;Knaus et al, 2000]. Promontory stimulation induced activation in the contralateral auditory cortex in 85% of deaf patients who reported auditory sensations, whereas only 25% of patients without auditory sensations showed comparable activations [Schmidt et al, 2003].…”

“…Cortical activation after electrical stimulation of the auditory nerve in deaf adults has been observed predominantly in the contralateral and to a lesser degree also in the ipsilateral auditory cortex [Alwatban et al, 2002;Berthezene et al, 1997;Neumann et al, 2002;Schmidt et al, 2003].…”