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V. TYPES OF DEMENTIA
Cortical and sub cortical dementiaDementia may be associated with multiple sub cortical or cortical infarcts and clinical features vary according to that. Distinguishing features of sub cortical and cortical Dementia:Non-Alzheimer’s dementia basically means sub-cortical dementia. Some distinguishing features of sub cortical and cortical dementia are as follows:
Reversible Dementia and Non reversible dementia1. Reversible dementiaReversible dementia – is a term used in the medical literature to describe a dementia that as a specific treatable cause. In the past, dementia has implied a progressive or irreversible course. Potentially reversible dementia syndromes include those arising from inflammatory processes e.g. encephalopathy caused by systemic lupus erythematosus (SLE) , infections such as syphilis ; or toxic conditions (e.g. Alcohol abuse) that produce memory loss and abnormal frontal lobe functions ( Cummings 1987) . Metabolic related dementia such as hypothyroidism or hyperthyroidism and nutritional syndromes such as Vitamin B12 and rotate deficiencies may also be reversible with appropriate therapy. It is estimated that 30% to 40% of persons with memory disturbances have a reversible and there fore treatable dementia. Although most of the patients will have physical disorders, Psychiatric disturbances such as depression are a significant challenge in the differential diagnosis. Treatment of such conditions as depression , drug – induced dementia , infections and metabolic disturbances leads to complete restoration off functioning with prompt diagnosis and appropriate treatment the dementia can be reversed. 2. Non-reversible dementiaWhen a reversible cause of intellectual impairment can’t be identified, the clinical diagnosis is presumed to be a nonreversible dementia many diseases can produce a progressive and nonreversible dementia. Most of these are rare and can affect adults of all ages with older individuals more likely to be affected when dementia does occur in a younger person it have been associated with suicide (margo and Finkel 1990) . The most common nonreversible dementia are Alzheimer’s disease, Parkinson’s disease , Huntington’s disease, pick’s disease , Creutzfeldt – Jakob disease and multi – Infard dementia, transient ischomic attack (TIAs) are included in the category because they can lead to a disabling cerebral infarction . Pre senile dementia and senile dementia:1) Pre–Senile dementia –It resembles that of senile dementia except that disorders occurs in younger age group The onset of disease occurs in people of 40s and 50s and people with this disease live an average 11 years after the onset of disease. 2) Senile dementia- It occurs usually after the age of 65 yrs. Due to degenerative bring changes as accompanied by a clinical picture of mental deterioration. I. Types of dementia according to underlying etiology.A. Dementia in Alzheimer’s disease
Alzheimer’s disease was
first described by Alois Alzhemer , a German neurologist in
1906. Alzheimer’s disease is a primary degenerative cerebral disease of
unknown etiology, with characteristic neuropathological and neurochemical
features. The onset can be in middle adult life or even earlier but the
incidence is higher in later life. In cases with onset before the age of
65-70 years there is the likelihood of a family history of dementia , a more
rapid course and prominence of features of parietal and temporal lobe
damage, including dysphasia or dyspraxia , general impairment of higher
cortical function . There are characteristic changes in the brain: a marked reduction in the population of neuron, particularly in the hippocampus, appearance of neurofibrillary tangles, neurotic plagues, which consist largely of amyloid. Marked reduction in the enzyme chorine acetyl transference in acetylcholline it self.
Sign and symptoms
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Four A’s of Alzheimer’s Disease |
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1. Amnesia: inability to learn new information or to recall previously learned information. 2. Agnosia: failure to recognize or identify objects despite intact sensory function. |
3. Aphasia: language disturbances that can manifest in both understanding and expressing the spoken word. 4. Apraxia: inability to carry out motor activities despite intact motor function (e.g. ability to grab a doorknob but not knowing what to do with it.) |
B). VASCULAR DEMENTIA
Vascular dementia is distinguished from dementia in Alzheimer’s type by history of onset. There is a history of transient ischaemic attacks with brief impairment of consciousness, fleeting pareses or visual loss. Cerebrovascular accidents cause impairment of memory and thinking becomes apparent. Onset in later life can be abrupt in ischaemic episode or gradual emergences. The dementia is result of infraction of brain due to vascular disease including hypertensive cerebrovascular disease. Vascular dementia is the second commonest type of dementia. This disorder arises earlier between 50 – 60 years of age, but more prevalent between ages 60-70 years. It is slightly more common in male than in females.
Clinical Features
· The patient develops multiple episodes of cerebral ischaemia which may or may not be apparent.
· Impairment of cognitive function.
· Memory disturbances.
· Intellectual deficits-
· Focal Neurological sign changes.
· There may be aphasias, disarthria, and dysphagia.
· There may be headache, dizziness, faintness , weakness, sleep disturbance and personality changes.
· Insight and judgment may be preserved.
· An abrupt onset or a step wise deterioration.-
· Seizure occurs in 20 percent of cases.
1) Vascular Dementia of acute onset:
This dementia develops rapidly (i.e. usually within one month but with in no longer than 3 months) after a succession of strokes or a single large infarction.
2) Multi-infract dementia:
This is more gradual in onset than the acute form, following a number of minor ischaemic episodes which produce an accumulation of infarcts in the cerebral parencyma.
3) Subcortical vascular dementia
There may be a history of hypertension. There is evidence of foci of ischemic destruction in the deep white matter of the cerebral hemispheres. Which can be suspected on clinical groups and demonstrated on computerized cortex is preserved and this contrasts with the clinical picture, which may closely resemble that of dementia in Alzheimer’s disease.
4) Mixed cortical and sub cortical vascular dementia.
Mixed cortical and sub cortical components of the vascular dementia may be suspected from the clinical features, the results of investigation (including autopsy) or both.
5) Other vascular dementia
-Vascular dementia, unspecified
C. Dementia in other diseases
Cases of dementia due to cause other than Alzheimer’s disease or vascular disease
Onset may be at any time in life, rarely in old age.
1) Dementia in Huntington’s disease
Huntington’s disease is an autosomal dominant disorder caused by a gene which has been localized to the most distal band of the short arm of chromosome 4. Therefore 50% of the children of one affected parent can develop this disorder. Spontaneous mutations can also give rise to sporadic cases in which there is no known family history.
Pathological features
· Microscopically the brain is usually small with reduced mass and there is marked atrophy of the corpus striatum of the basal ganglia, particularly the caudate nucleus, and of the frontal lobes.
· Histological change includes neuronal loss in the cerebral cortex, particularly affecting the frontal lobes, and in the corpus striatum, particularly affecting GABA neurons;
· Biochemical changes include reduced levels of GABA and glutamic acid decarboxylase, and dopamine hypersensitivity.
Clinical features:-
· Males and females are affected equally by Huntington’s disease and the average age of onset is in the 30s.
· Insidious onset of involuntary choreiform movement disorder.
· Involuntary choreiform movements in face, hands, shoulder or in the gait.
· Slurring of speech, extra pyramidal rigidity and epilepsy.
· Psychiatric features include depression, increased risk of suicide and schizophreniform and delusional disorders.
· Insight tends to be retained until a late stage.
· Death usually occurs within 15 years of the onset of symptoms.
Although there is no known cure, phenothiazine antipsychotics in low doses may be given to help with emotional disturbance, while depression may be treated with antidepressants. Involuntary movements may be decreased by giving tetrabenzine. This may act by causing dopamine depletion at never endings, but may cause depression to develop, thereby limiting.
2) Dementia in pick’s disease:-
It occurs in middle life usually between 50 and 60 years, characterized by slowly progressing changes of character and social at deterioration, memory impairment, impairment of intellect and language functions with apathy, euphoria and extra pyramidal phenomena. There will be atrophy of the frontal and temporal lobes, but with out the occurrence of neuritic plaques and neurofibrillary tangus in excess of that seem in normal aging.
Signs ad symptoms
-Onset is slow with steady deterioration.
-A predominance of frontal lobe involvement is evidenced by two or more of the following.
a). Emotional blunting
b). Coarsening of social behaviour
c). Disinhibition
d). Apathy or restlessness
e). Aphasia
-Behavioural manifestations which precede memory impairment.
3) Dementia in Creutzfeldt – Jakob disease
Creutzfeldt-Jakob disease with extensive neurological signs due to specific neuropathological changes that are presumed to be caused by a transmissible agent, onset is middle age or later age typically in the fifth decade, but may be at any adult age. The course is sub acute, leading to death within 1-2 years.
Signs and symptoms
-There is very rapid progression of dementia with disintegration of virtually all higher cerebral functions.
-One or more of the following types of neurological symptoms and signs emerge, usually after or simultaneously with the dementia.
a). Pyramidal symptoms
b). Extra pyramidal symptoms
c). Cerebellar symptoms
d). Aphasia
e). Visual impairment
4) Dementia in Parkinson’s disease
Parkinson’s disease is a disorder of a nucleus of norm cell, deep in the centre of the brain, called the substantianigra. Because of the death of cells in this nucleus there is a reduction in the neurotransmitter dopamine and cause the typical symptoms. The dementia in Parkinsonism develop is thought to be due to reduction in acetylcoline and the evidence in affected of cell death in the nucleus of meynert.
Signs and Symptoms:
-Rigidity
-Shuffling gait
-Mask like face
-Mumbling of speech
-Hypokinesia
-Difficulty in co-ordination
5) Dementia in Human Immunodeficiency Virus (HIV) disease
A disorder characterized by cognitive deficits meeting the clinical diagnostic criteria for dementia. HIV dementia presents with complaints of forgetfulness, slowness, poor concentration and difficulties with problem solving and reading. Apathy, reduced spontaneity and social withdrawal are common and in significant minority of affected cases, psychosis or seizure, tremor, impaired rapid, repetitive movements, imbalance, ataxia, hypertonia, generalized, hyperreflexia, positive frontal release signs and impaired pursuit and saccadic eye movement may present. Children also develop this condition and HIV associated neuro-developmental disorder is characterized by developmental delay, hypertonia, microcephaly and basal ganglia calcification.
6) Alcoholism Dementia
Chronic alcoholics develop a specific recent memory loss called Korsakoff’s syndrome. This is progressive if the person continues to drink or as after a head injury or stroke, some recovery of function may be possible over months or even years. Since it does not affect the over all functions of the cerebrum, Korsakoff’s syndrome is not strictly speaking a dementia. There is evidence that some alcoholics develop a more generalized shrinking of the brain which shows up on CT scanning. This shrinkage is a sign of developing general dementia.