Hearing music inside our heads is frequent, however some hear it more vividly, constantly and involuntarily. Musical Hallucinations (MH), first described by Baillarger in 1846, are a complex type of auditory hallucination characterized by perception of melodies, music, or songs.

This work aims to review the literature considering MH.

Pubmed and Google Scholar search using MeSH term “musical hallucinations”

MH occurs in 0.16% of the population. They´re usually perceived as frightening or annoying. Proposed mechanisms include spontaneous activity triggered by sensory deprivation from hearing impairment, like in visual hallucinations in Charles Bonnet syndrome, and some authors even include MH as a subtype of this syndrome. Indeed, 60% of all patients with MH have hearing impairment or deafness. Other less frequent causes include focal brain lesions involving the auditory pathway and cortex, temporal epilepsy, metabolic or drug intoxication. Psychiatric conditions are uncommon but not impossible, especially in affective disorders. MH most frequently consist in familiar tunes, sometimes of personal significance, religious songs (especially in older patients), childhood songs, folk and popular songs from the radio - suggesting that musical perception is never unlearned but represents a “parasitic memory”, an unchangeable memory feature which can be experienced by relevant neuronal circuit stimulation. Most patients with MH were reported to have no extraordinary musical skills.

MH are rare and strongly associated with hearing loss, though investigation of other causes should be sought. Treating the underlying cause is important but remission is not guaranteed.

No significant relationships.

Similar to visual hallucinations in visually impaired patients, auditory hallucinations are often suggested to occur in adults with hearing impairment. However, research on this association is limited. This observational, cross-sectional study tested whether auditory hallucinations are associated with hearing impairment, by assessing their prevalence in an adult population with various degrees of objectified hearing impairment.

Hallucination presence was determined in 1007 subjects aged 18–92, who were referred for audiometric testing to the Department of ENT-Audiology, University Medical Center Utrecht, the Netherlands. The presence and severity of hearing impairment were calculated using mean air conduction thresholds from the most recent pure tone audiometry.

Out of 829 participants with hearing impairment, 16.2% (n = 134) had experienced auditory hallucinations in the past 4 weeks; significantly more than the non-impaired group [5.8%; n = 10/173; p < 0.001, odds ratio 3.2 (95% confidence interval 1.6–6.2)]. Prevalence of auditory hallucinations significantly increased with categorized severity of impairment, with rates up to 24% in the most profoundly impaired group (p < 0.001). The corrected odds of hallucination presence increased 1.02 times for each dB of impairment in the best ear. Auditory hallucinations mostly consisted of voices (51%), music (36%), and doorbells or telephones (24%).

Our findings reveal that auditory hallucinations are common among patients with hearing impairment, and increase with impairment severity. Although more research on potential confounding factors is necessary, clinicians should be aware of this phenomenon, by inquiring after hallucinations in hearing-impaired patients and, conversely, assessing hearing impairment in patients with auditory hallucinations, since it may be a treatable factor.