Some hear choruses singing folk songs, others hear Mozart or even the Glenn Miller Orchestra -- but there is no music; they are hallucinating. New research in the August 8 issue of Neurology, the scientific journal of the American Academy of Neurology, confirms the region of the brain and condition that causes this rare and bizarre disorder.
Researchers have connected lesions on the dorsal pons, a part of the brain stem, with multiple cases of musical hallucinations. Lesions such as these are most often caused by stroke but can also be the result of tumors, encephalitis, or abscesses.
The case study outlined in this issue of Neurology involves a 57-year-old with symptoms including dizziness and right-sided numbness of his body. An MRI showed a lesion, or abnormal growth, in the dorsal pons which turned out to be an abscess with bacterial meningitis. Antibiotics were administered and the patient improved rapidly.
However, during his recovery, the patient developed continuous auditory hallucinations in his right ear, consisting of men's and children's choruses singing folk songs.
"He only became aware of the hallucinations several hours after they began -- he had expected to find a carnival or celebration in the schoolyard next to the hospital," said study author Eva Schielke, MD, a neurologist at University Hospital Charité in Berlin, Germany. Even though the patient was fully alert and aware he was imagining the sounds, the hallucinations persisted for five weeks. A prolonged antibiotic treatment was eventually successful and the man was released after 11 weeks having almost completely recovered.
Only 10 other cases of musical hallucinations with dorsal pons lesions have ever been reported. In all but one of the cases, patients were alert and aware that they were hallucinating. All patients suffered from severe disorders such as stroke, brain hemorrhage or encephalitis within two weeks of the onset of the lesion.
"A French patient heard popular French chansons, another heard Mozart, and a Canadian patient heard Glenn Miller big band music," said Schielke. "In most cases, the music is familiar to the patient. Our patient, for example, heard folk songs which he liked to listen to before."
Musical hallucinations in non-psychiatric patients are most common in elderly people suffering from chronic and extensive hearing loss. In those cases, it is theorized that sensory deprivation causes the disorder.
This study describes a quick onset of hallucinations with no long-term hearing loss. Researchers have theorized that these types of hallucinations may be triggered by a disruption in communication pathways between the sensory centers in the neocortex of the brain and a bundle of nerve cells and fibers in the brain stem called the reticular formation. The disruption may cause auditory hallucinations by limiting the function of neurons that stop the brain from hallucinating.
