Amusia representing impairment of absolute pitch perception due to damage to the middle longitudinal fasciculus: a case report

Absolute pitch (AP) is the ability to identify the pitch of isolated tones without reference to an external pitch. A 21-year-old semi-professional musician with a previous ability for AP developed a left-hemispheric cerebral hemorrhage due to an arteriovenous malformation (AVM). One month after the hemorrhage, she underwent surgery to treat the AVM, resulting in the resolution of her aphasia and right upper limb clumsiness. However, her AP ability was lost. Before the hemorrhage, she could dictate complex music that she listened to, but afterward, she could no longer identify even a single tone. Neuropsychological assessments revealed a decreased retention span for auditory information, slight impairment of environmental sound and speech processing, and difficulty in understanding the auditory presentation of numbers with more than four digits. Neuromusicological assessments with an established battery of tests revealed impairments of chord and timbre perception, alongside the loss of AP ability. Brain computed tomography conducted 9 months after the hemorrhage revealed low-density areas in the middle longitudinal fasciculus, a region associated with language and auditory processing, including AP perception. To our knowledge, this is the first reported case of a patient with AP loss because of a focal brain lesion.