Regional cerebral blood flow during tinnitus: a PET case study with lidocaine and auditory stimulation

Brain imaging of tinnitus has suggested central correlates of tinnitus perception. This study presents positron emission tomographic (PET) measurements of regional cerebral blood flow (rCBF) in a female tinnitus patient with bilateral left dominant tinnitus. Lidocaine infusion (75 mg during 5 min (0.2 mg/kg/min)) resulted in a 75% reduction of tinnitus and a temporary abolition of the dominant tinnitus in her left ear. Regional CBF was measured in four conditions: i) at rest while concentrating on tinnitus, ii) following maximum effect of lidocaine, iii) during sound stimulation, and iv) the following day at rest while concentrating on tinnitus. Subtraction analyses showed that tinnitus was associated with increased rCBF in the left parieto-temporal auditory cortex, including the primary and secondary auditory cortex with a focus in the parietal cortex (Brodmann areas 39, 41, 42, 21, 22). Activations were also found in right frontal paralimbic areas (Brodmann areas 47, 49 and 15). Sound stimulation resulted in bilateral activation of auditory areas. It is suggested that tinnitus is processed in primary, secondary and integrative auditory cortical areas. Tinnitus perception may involve areas related to auditory attention, while emotional processing relates to temporofrontal paralimbic areas.