179], either hemi-group, bilateral temporal lobe lesions are a risk factor sphere [180], and the occiptal lobe [181] have been for the development of psychotic symptoms.
reported in musical hallucinosis. However, multiple vascular lesions suggested by white matter hyperinten-sities on neuroimaging are also common associations Musical hallucinosis
[173, 182]. The presence of central vascular lesions One of the most interesting forms of isolated audi-may represent the additional risk factor that distin-tory hallucinosis is musical hallucinosis. Musical hal-guishes patients with musical hallucinosis from those lucinosis can be defined as the perception of music with deafness without these symptoms. It is possible without the presence of an external musical stimu-that vascular lesions may disconnect afferent inputs or lus in which the subject maintains insight. Although cortical networks increasing the threshold for sponta-these phenomena have been described in psychotic illneous activity. The wide variety nature and location ness, epilepsy, and a variety of brain lesions including of lesions in the auditory system that may result in intracerebral haemorrhage [170], they more often are musical hallucinosis mirrors the heterogeneous lesions seen in elderly patients with acquired deafness [171].
associated with complex visual hallucinations [183].
Some authors have reported patients with musi-Unfortunately, there is little evidence available to cal hallucinosis later developing auditory hallucina-guide treatment apart from the appropriate treat-tions characteristic of schizophrenia [172]. However, ment of the underlying lesion. Pharmacological treat-musical hallucinosis is most commonly seen in per-ments are usually ineffective; most authors recom-sons with hearing loss, advanced age, brain disease, mend audiological assessment and appropriate ampli-cognitive impairment, female gender, and social isola-fication [172] when deafness is the trigger. Progno-tion. Although the relative importance of each of these sis is usually guarded with musical hallucinosis per-factors is not well understood [173], deafness is one of sisting and worsening as deafness progresses. Evolu-the most common associations.
tion to AHs and paranoid delusions characteristic of Mechanisms underlying the generation of musilate onset schizophrenia-like illnesses have also been cal hallucinosis remain poorly understood. The most reported [184].
compelling neurobiological model is one of spontaneous activity arising in a deafferented auditory sys-
Secondary olfactory and gustatory
tem, which is then involved in recognition of stimulus by a cortical pattern recognition system [174].
hallucinations
During normal listening to patterned sound such as The literature relating to gustatory hallucinations music, auditory input is processed by two mechanisms, occurring in organic disorders consists mainly of case which operate in a hierarchical manner. The pattern reports in which the nature of the experiences varies is first perceived, and then encoded into memory or considerably. In contrast, the olfactory experiences of recognized. It is possible that reduced auditory input patients with a range of “organic” pathologies are much because of deafness allows spontaneous activity within more uniform in their quality. As described by patients
31
the system. This may take the form of positive feed-with epilepsy, the perceived smells are unpleasant and Introduction – Section 1
usually of burning, rotting, fecal, or other organic patients of color. The black African description of the material. Patients who describe olfactory or gustatory hallucinations was often related to death or decay. Nde-hallucinations are likely to describe or exhibit other tei and Singh [188] identified olfactory hallucinations symptoms depending on the underlying condition.
in 25% (13/51) of Kenyan patients with schizophrenia Isolated hallucinations in either modality are very rare but
reported in musical hallucinosis. However, multiple vascular lesions suggested by white matter hyperinten-sities on neuroimaging are also common associations Musical hallucinosis
[173, 182]. The presence of central vascular lesions One of the most interesting forms of isolated audi-may represent the additional risk factor that distin-tory hallucinosis is musical hallucinosis. Musical hal-guishes patients with musical hallucinosis from those lucinosis can be defined as the perception of music with deafness without these symptoms. It is possible without the presence of an external musical stimu-that vascular lesions may disconnect afferent inputs or lus in which the subject maintains insight. Although cortical networks increasing the threshold for sponta-these phenomena have been described in psychotic illneous activity. The wide variety nature and location ness, epilepsy, and a variety of brain lesions including of lesions in the auditory system that may result in intracerebral haemorrhage [170], they more often are musical hallucinosis mirrors the heterogeneous lesions seen in elderly patients with acquired deafness [171].
associated with complex visual hallucinations [183].
Some authors have reported patients with musi-Unfortunately, there is little evidence available to cal hallucinosis later developing auditory hallucina-guide treatment apart from the appropriate treat-tions characteristic of schizophrenia [172]. However, ment of the underlying lesion. Pharmacological treat-musical hallucinosis is most commonly seen in per-ments are usually ineffective; most authors recom-sons with hearing loss, advanced age, brain disease, mend audiological assessment and appropriate ampli-cognitive impairment, female gender, and social isola-fication [172] when deafness is the trigger. Progno-tion. Although the relative importance of each of these sis is usually guarded with musical hallucinosis per-factors is not well understood [173], deafness is one of sisting and worsening as deafness progresses. Evolu-the most common associations.
tion to AHs and paranoid delusions characteristic of Mechanisms underlying the generation of musilate onset schizophrenia-like illnesses have also been cal hallucinosis remain poorly understood. The most reported [184].
compelling neurobiological model is one of spontaneous activity arising in a deafferented auditory sys-
Secondary olfactory and gustatory
tem, which is then involved in recognition of stimulus by a cortical pattern recognition system [174].
hallucinations
During normal listening to patterned sound such as The literature relating to gustatory hallucinations music, auditory input is processed by two mechanisms, occurring in organic disorders consists mainly of case which operate in a hierarchical manner. The pattern reports in which the nature of the experiences varies is first perceived, and then encoded into memory or considerably. In contrast, the olfactory experiences of recognized. It is possible that reduced auditory input patients with a range of “organic” pathologies are much because of deafness allows spontaneous activity within more uniform in their quality. As described by patients
31
the system. This may take the form of positive feed-with epilepsy, the perceived smells are unpleasant and Introduction – Section 1
usually of burning, rotting, fecal, or other organic patients of color. The black African description of the material. Patients who describe olfactory or gustatory hallucinations was often related to death or decay. Nde-hallucinations are likely to describe or exhibit other tei and Singh [188] identified olfactory hallucinations symptoms depending on the underlying condition.
in 25% (13/51) of Kenyan patients with schizophrenia Isolated hallucinations in either modality are very rare but
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