Association of Auditory Charles Bonnet Syndrome with Increased Blood Flow in the Nondominant Brodmann Area 22

Aim: Auditory Charles Bonnet syndrome (aCBS) is characterized by musical hallucinations (MHs) that accompany acquired hearing impairments. This hallucination is the acoustic perception of music, sounds, or songs in the absence of an outside stimulus, and it may be associated with hyperactivity of the superior temporal lobes. Some studies have reported the possibility of improving MH with antiepileptics. To elucidate in detail the brain regions responsible for aCBS, we analyzed the regions that changed functionally after treatment.

Methods: Before and after treatment with carbamazepine (four cases), clonazepam (one case), and a hearing aid (one case), cerebral perfusion single-photon emission computed tomography (SPECT) and the Auditory Hallucination Rating Scale (AHRS) were applied to six patients with hearing-loss-associated MHs.

Results: Cerebral blood flow analysis using SPECT revealed hyperperfusion in Brodmann area (BA) 22-the posterior region of the superior temporal gyrus-in the nondominant hemisphere in all six patients in the pretreatment phase. After treatment, the hyperperfusion region improved in all patients. The area percentages with hyperperfusion in the nondominant BA22 were strongly positively correlated with the AHRS score.

Conclusion: The results suggest that aCBS, which was treatable with antiepileptics or hearing aids, was involved in hyperexcitement in BA22, and that MH strength was correlated with degree of excitement.