Overview – Neurocognitive Disorders, Part 2
Neurocognitive Disorders are a category of mental health disorders that primarily affect cognitive or thinking abilities. They are not developmental conditions but are acquired conditions representing underlying brain pathology that results in a decline in function from a previously attained level of cognitive (mental) functioning. Diagnosis requires that symptoms must be associated with a medical condition and not another mental health problem, and there cannot be evidence of delirium, which is a separate, temporary disorder with similar symptoms.
Two categories are recognized: Mild and Major that exist on a spectrum of cognitive and functional impairment. At the mild Neurocognitive Disorder level, the individual is likely to describe their everyday tasks as being more difficult or as requiring extra time or effort or compensatory strategies. Neurocognitive deficits in mild neurocognitive disorder do not interfere with the capacity for independence in everyday activities, although the individual usually functions at a suboptimal level, with the tasks becoming more fatiguing. A mild Neurocognitive Disorder may or may not progress to a major neurocognitive disorder. A major Neurocognitive Disorder shows a serious decline from a previous level of cognitive performance, interfering with independence in everyday activities, and requiring more assistance with complex activities. Some activities may need to be abandoned altogether.
In Neurocognitive Disorders, Part 1, information on four types of disorders was presented:
- Traumatic Brain Injury
- HIV Infection
- Prion Disease
- Frontotemporal Lobe Degeneration
In Neurocognitive Disorders, Part 2, information on four additional types of disorders are presented, one type each day for four days. These are:
Neurocognitive Disorder Due to Huntington’s Disease
Neurocognitive Disorder due to Huntington’s Disease is a genetic disease that is characterized by loss of control over muscle movement along with severe mood and behavioral changes. Early symptoms include changes to processing speed, organization, and planning. Later symptoms involve motor abnormalities. It is inherited in an autosomal dominant fashion. Every child of a parent with Huntington’s Disease has a 50/50 chance of inheriting the expanded gene that causes the disease. If the child has not inherited this expanded gene, he or she will never develop the disease and cannot pass it on to their children. The abnormal IT15 gene is passed from parent to child and can be determined by blood tests. No cure exists for Huntington’s disease.
Although most adults are diagnosed with Huntington’s disease in middle life or around age 40, cognitive and psychological abnormalities may begin in early adulthood. At time of diagnosis, most patients are in the height of their career and involved in raising families.
Neurocognitive Disorder Due to Alzheimer’s Disease
Neurocognitive Disorder Due to Alzheimer’s Disease is the leading cause of dementia. It is a progressive disorder in which an individual experiences a gradual increase in problems related to cognitive or thinking functions. The production of acetylcholine decreases, which is clinically manifested as progressive memory loss along with associated behavioral symptoms. The likelihood of developing Alzheimer’s Disease is estimated at 5.0 to 10.0 percent in persons in their seventies, and 25 percent for those age 80 and older. Alzheimer’s disease is comorbid with 75 percent of Down Syndrome individuals who over age 65. Early onset of Alzheimer’s Disease can occur in the fifties and sixties, with onset of symptoms in the eighties and nineties.
Cortical atrophy in the brain, amyloid plaques, and tau neurofibrillary tangles are characteristic of Alzheimer’s Disease. These may be observed through neuroimaging or through postmortem histopathology. Symptoms vary based on the individual and the stage of the disease.
- A mild Neurocognitive Disorder due to Alzheimer’s disease may be diagnosed as possible if there is evidence of the presence of a known pathogenic mutation from genetic testing or family history. If no such evidence is available, possible Alzheimer’s disease may be diagnosed if there is clear evidence of decline in learning and memory, the cognitive decline is steadily progressive and gradual, and there is no evidence of mixed etiology.
- A major Neurocognitive disorder due to Alzheimer’s disease may be diagnosed as probable if psychosis, irritability, agitation, combativeness, and wandering in the moderately severe stage with gait disturbance are observed, and dysphagia or difficulty swallowing, incontinence, myoclonus or involuntary muscle spasms, and seizures are observed in the later stages.
Neurocognitive Disorder Due to Prion Disease
Neurocognitive Disorder Due to Prion Disease involves fatal disorders that are in a unique category of mental illness in that the underlying pathology, and frequently the etiology as well, can potentially be determined. They encompass the group of disorders in which the primary clinical deficit of impaired cognitive function is acquired rather than developmental. Two categories are recognized: mild neurocognitive disorders and major neurocognitive disorders (formerly referred to as dementia).
The causative agents are believed to be proteinaceous infectious particles or prions, a type of protein. These pathogenic agents are able to induce abnormal folding of The These causative agents are believed to be proteinaceous infectious particles or prions, a type of protein. specific normal-cellular proteins called prion proteins that are found most abundantly in the brain. The functions of these normal-prion proteins are still not completely understood. The abnormal folding of the prion proteins leads to brain damage and the characteristic signs and symptoms of the disease. Prion diseases are usually rapidly progressive and always fatal. Prions kill neurons by shortening the dendritic spines on neurons that pull information into the cells, which they use to transmit signals to each other.
Prion diseases are transmissible to both humans and animals and are sometimes spread to humans by infected meat products. Scrapie is a type of disease seen in animals. Several types have been identified in humans including Creutzfeldt-Jakob Disease (CJD) and Variant Creutzfeldt-Jakob Disease (vCJD), Bovine Spongiform Encephalopathy (BSE) or Mad Cow Disease, and Chronic Wasting Disease (CWD).
Neurocognitive Disorder Due to Parkinson’s Disease
Neurocognitive Disorder Due to Parkinson’s Disease reportedly was named for James Parkinson, a general practitioner in London during the 19th century who first described the symptoms of the disease. It is a chronic and progressive movement disorder characterized by muscle stiffness, tremor, and a shuffling walk. Later on, changes in mood and behavior and cognitive symptoms of dementia with Lewy Bodies may arise. Not all people with Parkinson’s disease develop dementia, however, and it is difficult to predict who will.
In some studies dementia was reported to occur in approximately 20 to 60 percent of individuals with Parkinson’s disease, with a sixfold risk to develop dementia compared to healthy controls. It is more likely to be present in older individuals or those with more severe or advanced disease. Onset of Parkinson’s disease before the age of 40 is rare. It occurs more commonly in males than in females and impacts all races and ethnic groups.
Parkinson’s Disease is linked with a loss of nerve cells in the substantia nigra of the brain, which leads to a reduction in the brain chemical, dopamine. When dementia was present, neuronal loss and the presence of Lewy Bodies were evident in the substantia nigra at autopsy. When a diagnosis of mild NCD or major NCD due to Parkinson’s Disease is being considered, a distinction must be made from other brain disorders, such as:
- Progressive supranuclear palsy
- Corticobasal degeneration
- Multiple system atrophy
- Neuroleptic-induced parkinsonism when dopamine-blocking drugs are utilized
- Subcortical small vessel disease
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