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Auditory hallucinosis consists of abnormal acoustic perceptions that occur in the absence of a corresponding acoustic stimulus while the patient is aware of their non-real nature.1
Musical hallucinosis represents a particular type of acoustic hallucinosis, in which the acoustic perception is formed by music, sounds, or songs. It is frequent in psychiatric diseases and is sometimes reported in sensory neural deafness, but rarely after stroke.1 2 We describe a case of musical hallucinosis in a professional musician with a left subcortical haemorrhagic lesion, presumably caused by a cavernous angioma.
A 35 year old, right handed man was referred to our inpatient department in July 1999 7 days after the onset of a slight clumsiness of his right hand followed by complex acoustic perceptions. The patient had attended a symphonic concert where an orchestral transcription of Wagner's “Siegfried” was played: the patient is a connoisseur of music and a composer. When he returned home, about 1 hour later, his musical hallucinosis started. Auditory perceptions were described by the patient as a symphonic piece of music performed by an orchestra with numerous kettledrums and percussion instruments. It was a rather familiar music, unknown to him, but similar to what he had heard during the concert. The theme was played in a minor tonality with frequent use of drums and other percussion instruments interspersed with string instruments. A chorus played by string instruments accompanied the theme. The patient said that the music resembled a piece by the late German romantic authors (for example, Mahler, Bruckner, and Wagner's latest works). The music was initially low in intensity but progressively increased; it was perceived in the middle of his head as if he was listening with headphones on. Conflicting emotions occurred: he felt that it was the most frightening and terrifying music he had ever heard and strongly desired to push it out of his mind but, on the other hand, he was deeply fascinated and said that he would like to compose such an exciting piece.
The patient said that during his musical hallucinosis he was able to speak, watch, and understand television programs and to go about his normal activities. He reported that during the phenomenon his hearing was normal and he could hear everything going on around him, such as the noise outside the house (for example, from the road) and all the usual noise going on in his own house.
The musical hallucinosis lasted about 90 minutes and afterwards the patient fell asleep; he did not have musical hallucinosis during the next day on awakening and it did not recur during the next 20 months.
Seven days after the episode the patient was admitted to our department. On admission a neurological examination evidenced only a slight motor impairment of the right hand. His hearing sensation was normal on clinical and instrumental examination. No signs of drug or alcohol misuse were evident. Moreover there was no history of psychiatric disorders.
A cranial CT showed a small hyperdense lesion on the left temporal lobe at subcortical level. Brain MRI (fig 1A) evidenced a haemorrhagic lesion involving the left putamen and the external capsula near the insula. The lesion was located next to the acoustic radiation (fig 1 A and B). Cerebral angiography was normal. Three EEG recordings (performed on days 1, 3, and 5 after admission) highlighted only a mild abnormal slow activity at the temporal level, without epileptiform grapho-elements. Audiograms and brain stem auditory evoked potentials were normal.
Transient musical hallucinosis has been described in several situations, such as psychiatric disorders, alcoholism, drug and chemical intoxication, ear and acoustic nerve diseases and, rarely, brain stem lesions mainly involving the tegmentum.1 2Even if musical hallucinosis has been reported in hemispheric lesions2 a clear relation with the central acoustic pathway has never been described.
In our patient the prolonged duration of the episode, the preservation of consciousness and memory, and the absence of epileptiform abnormalities on EEG rule out an epileptic genesis of musical hallucinosis. In patients with sensory-neural deafness musical hallucinosis may be determined by an increased cortical excitability due to a deafferentation phenomena1 or by a spontaneous activation of cerebral areas involved in musical perception.3
In the present case, it might be directly related to the impairment of the acoustic radiation, containing both ascending (excitatory) and descending (inhibitory) fibres. The inhibitory fibres run from thr auditory cortex to lower structures of the central acoustic pathway (medial geniculate nucleus and inferior colliculus) and presumably modulate acoustic perception. The comparison of brain MRI (fig 1 A) and of a corresponding anatomical drawing (fig 1 B) suggests that the lesion just touches the acoustic radiation between the left medial geniculate body and the auditory cortex. Another explanation of such peculiar findings in our patient may derive from a recent hypothesis regarding musical hallucinosis in acquired deafness3: the subcortical lesion may have caused either a disconnection between the primary auditory and the association cortices or an impairment of the “neural networks for the perceptions and imagery of sounds, including the auditory association and the frontal cortex”.3Indeed, the closeness of the lesion to the superior temporal gyrus may interfere with the associative fibres connecting the auditory cortex to the other cerebral areas involved in musical perceptions.
Compared with previously reported cases,1-3 our patient presents several peculiarities. Firstly, the duration of the musical hallucinosis was shorter and the auditory perceptions were heard bilaterally and not lateralised in the opposite ear. Secondly, it occurred in the absence of sensory-neural deafness and might be related to a lesion involving the central acoustic pathway, even at a hemispheric level. This is not in agreement with the notion that complex acoustic hallucinosis is invariably related to damage to the peripheral acoustic pathway or to combined central and peripheral dysfunction.1 2 Thirdly, our report greatly supports the role of the dominant hemisphere in musical processing, by contrast with the accepted notion that musical perception is a specific function of the non-dominant hemisphere.1 4 We can speculate that the musical training of the patient might have determined the shift of musical representation from the non-dominant to the dominant hemisphere.5
Finally, several features of musical hallucinosis in our patient are fascinating. The similarity between the acoustic perceptions and the symphonic music that he had previously heard leads to the hypothesis of an involvement of acoustic memory circuits. The professional experience and the personal sensibility towards symphonic music might both have contributed in the determination of musical hallucinosis influencing the processing of musical sensations.
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