Schizophrenia
In people with psychosis, the premier cause of auditory hallucinations is schizophrenia, and these are known as auditory verbal hallucinations (AVHs). In schizophrenia, people show a consistent increase in activity of the thalamic and striatal subcortical nuclei, hypothalamus, and paralimbic regions; confirmed by PET and fMRI scans. Other research shows an enlargement of temporal white matter, frontal gray matter, and temporal gray matter volumes (those areas crucial to both inner and outer speech) when compared to control groups. This implies that functional and structural abnormalities in the brain, both of which may have a genetic component, can induce auditory hallucinations.Auditory verbal hallucinations attributed to an external source, rather than internal, are considered the defining factor for the diagnosis of schizophrenia. The voices heard are generally destructive and emotive, adding to the state of artificial reality and disorientation seen in psychotic patients. The causal basis of hallucinations has been explored on the cellular receptor level. The glutamate hypothesis, proposed as a possible cause for schizophrenia, may also have implications in auditory hallucinations, which are suspected to be triggered by altered glutamatergic transmission.Studies using dichotic listening methods suggest that people with schizophrenia have major deficits in the functioning of the left temporal lobe by showing that patients do not generally exhibit what is a functionally normal right ear advantage. Inhibitory control of hallucinations in patients has been shown to involve failure of top-down regulation of resting-state networks and up-regulation of effort networks, further impeding normal cognitive functioning.Not all who experience hallucinations find them to be distressing.
Cerebral amyloid angiopathy (CAA) is a form of angiopathy in which amyloid beta peptide deposits in the walls of small to medium blood vessels of the central nervous system and meninges. The term congophilic is sometimes used because the presence of the abnormal aggregations of amyloid can be demonstrated by microscopic examination of brain tissue after staining with Congo red. The amyloid material is only found in the brain and as such the disease is not related to other forms of amyloidosis. Signs and symptoms
CAA is associated with brain hemorrhages, particularly microhemorrhages. Since CAA can be caused by the same amyloid protein that is associated with Alzheimers dementia, brain bleeds are more common in people who have a diagnosis of Alzheimers disease. However, they can also occur in those who have no history of dementia. The bleeding within the brain is usually confined to a particular lobe and this is slightly different compared to brain bleeds which occur as a consequence of high blood pressure (hypertension) – a more common cause of a hemorrhagic stroke (or bleeding in the brain). Causes
CAA has been identified as occurring either sporadically (generally in elderly populations) or in familial forms such as Flemish, Iowa, and Dutch types. In all cases, it is defined by the deposition of amyloid beta (Aβ) in the leptomeningal and cerebral vessel walls.