Dementia
has many causes, but Dementia of the Alzheimer’s type and vascular dementia
together represent as many as 75 percent of all cases. Other causes of
dementia are Pick’s disease. Creutzfeldt Jakob disease. Huntington’s
disease, Parkinson’s disease, Human Immunodeficiency Virus (HIV) and Head
trauma.
CAUSES OF
DEMENTIA
Degenerative
disease of the central Nervous System.
Vitamin intoxication – vitamin A , Vitamin D – Paget’s disease
Traumatic Causes :-
Severe single head injury
Repeated head
injuries in boxers and others.
Infections
and related conditions: -
Encephalitis of any cause
Neurosyphilic
Chronic Meningitis
Cerebral Sarcoidosis
Cysticercosis
AIDS and AIDS related complex.
Toxic Causes :-
Alcohol
Poisoning with heavy metals – lead, arsenic,
thallium, mercury, carbon
monoxide.
Drug and alcohol withdrawal of anoxiolytic sedative
drugs, amphetamine.
Anoxia:-
Anemia
Post –
anesthesia
Cardiac arrest
Chronic respiratory failure
Degenerative Causes
Senile Dementia
It occurs usually after the age of 65 years
due to degenerative brain changes as accompanied by a clinical picture of
mental deterioration.
Types
of Senile dementia.
Simple deterioration:- In this patient gradually loses
contact with environment poor memory, tendency to reminiscence, intolerance
of change, disorientation, restlessness, insomnia, and failure of judgment.
This is the commonest psychotic reaction in about 15% of the entire group of
senile dementia.
Paranoid reaction:- Gradual formation of delusion . he feels
that his relatives are turned against him and are trying to rob or kill him
.
The presbyophrenic type:- Characterized by
jovial
mood, marked impairment of memory , restlessness and excitability .
Depressed and agitated type:- Severally depressed and
agitated , suffers from hypochondrical and Nihilistic delusion .expresses
morbid ideas about cancer, syphilis and other diseases . Has marked poverty
of ideas.
Delirious and contused type: -Shows severe mental clouding,
which make him restless, contused, resistive and incoherent. Completely
disoriented to time, place and person.
All
these type of senile dementia deteriorate and the patient becomes asocial
and bedridden . He is reduced to a vegetative life.
Pre-senile Dementia
It resembles
that of senile dementia except that disorders occurs in younger age group.
Alzheimer’s
disease:- Dementia of insidious onset and slowly progressive course due to
specific lesions in the brain – stem, hippocampus, parietal and frontal
cortex The first sign are usually impairment of memory for recent events and
inability to process information. Individual thinking becoming limited,
inability to retain new information. The pattern of interference occurs
according to the area of Brain is affected, Hippocampal damage cause memory,
impairment, parietal lobe of brain damage cause difficulty in use of words
or knowing the name of common objects also cause dyspraxia, frontal lobe
damage cause impaired ability to behave appropriately, leading to
tactlessness, disinhibition and loss of finer feelings, speech is also
affected.
Usually
developing age of Alzheimer's disease is between 40 to 50 yrs. Rapid
progression with severe brain and mental deterioration, accompanied by over
activity, emotional distress and agitation, frequent development of aphasia
death occurs between 2 and 10 yrs of sickness, usually an average of 4
years. The patient should be hospitalized treatment is symptomatic.
Genetic
factors:-
Although the cause of dementia of the Alzheimer’s type remains unknown,
progress has been made in understanding the molecular basis of the amyloid
deposits that are a hallmark of the disorder’s neuropathology, some studies
have indicated that as many as 40% of patients have a family history of
dementia of the Alzheimer’s type thus, genetic factors are presumed to play
a part in the development of the disorder, at least in some cases.
Additional support for a genetic influence is the concordance rate for
monozygotic twins, which is higher than the rate for dizygotic twins. (43%
Vs 8%, respectively) In several well-documented cases, the disorder has been
transmitted in families through an autosomal dominant gene, although such
transmission is rare.
Neuropathology
:- The classic gross neuroanatomical observation of a brain from a patient
with Alzheimer’s disease is diffuse atrophy with flattened cortical sulci
and enlarged cerebral ventricles.
Neurotransmitters:- The neurotransmitters that are most often implicated in the pathophysiological condition of Alzheimer’s disease are acetylcholine
and norepinephrine, both of which are hypothesized to be hypoactive
in Alzheimer’s disease. The decrease in nor epinephrine activity in
Alzheimer’s disease is suggested by the decrease in norepinephirine
containing neurons in the locus ceruleus found in some pathological
examinations of brains from people with Alzheimer’s disease. Two other
neurotransmitters implicated in the pathophysiological condition of
Alzheimer’s disease are the Neuro active peptides somatostain and
corticotropin , both of which have been decreased in Alzheimer’s disease.
Familial Multiple System Taupathy with
Presenile Dementia
A recently
discovered type of dementia, familial multiple system taupathy, shares some
brain abnormalities found of people with Alzheimer’s disease. The gene that
causes the disorder is thought to be carried on chromosome 17. The symptoms
of the disorder include short-term memory problems and difficulty
maintaining balance and walking. The onset of disease occurs in people's
’40s and 50s and people with the disease live an average 11 years after the
onset of symptoms.
Multi-infarct
Cause
The primary
cause of multi-infract dementia is presumed to be multiple cerebral vascular
disease, resulting in a symptom pattern of dementia. It is most common in
men, especially those with pre existing hypertension or other cardiovascular
risk factors the disorder affects primarily small and medium size cerebral
vessels , which under go infraction and produce multiple parenchyma lesions
spread over wide areas of the brain . The cause of the infarctions may
include occlusion of the vessels by arteriosderotic plaque or thromboemboli
from distant origins. An examination of a patient may reveal carotid bruits,
funduscopic abnormalities enlarged cardiac chambers.
Pick's
Disease
Pick’s
disease is characterized by a preponderance of atrophy in the front temporal
regions. These regions also have neuronal loss, gliosis, and the presence
of neuronal pick’s bodies, which are masses of cytoskeletal elements. Pick's
bodies are seen in some postmortem specimens but are not necessary for the
diagnosis. It is most common in men, especially those who have a
first-degree relative with the condition. Pick’s disease is difficulty to
distinguish from Alzheimer’s type, although the early stages of pick’s
disease are more often characterized by personality and behavioral changes,
with a relative preservation of other cognitive functions. Features of
Kluver – Bucy syndrome (such as hypersexuality, placidity and hyperorality)
are much more common in pick’s disease than in Alzheimer’s disease.
Lewy
Body Disease
Lewy body disease is a dementia clinically similar to Alzheimer’s disease
and often characterized by hallucinations, parkinsonian features and
extrapyramidal signs, lewy inclusion bodies are found in the cerebral
cortex. The exact incidence is unknown. These patients show marked advance
effects when given antipsychotic medications.
Huntington's
Disease
Huntington’s
disease is classically associated with the development of dementia. The
dementia seen in this disease is the sub cortical type of dementia,
characterized by more motor abnormalities and fewer language abnormalities
than in the cortical type of Dementia. The dementia of Huntington’s disease
exhibits psychomotor slowing and difficulty with complex tasks, but memory,
language and insight remain relatively intact in the early and middle stages
of the illness. As the disease progress, however, the dementia becomes
complete; the features distinguishing it from dementia of the Alzheimer’s
type are the high incidence of depression and psychosis, in addition to the
classic choreoathetoid movement disorder.
Parkinson's
Disease
It is
characterized by Brady Kinesis, rigidity, hyperkinesias is evident in
slowness in initiating and executing motor acts. The unblinking face is mask
like, writing is cramped and the gait is slow and shuffling with difficulty
in starting and turning associated movements are lacking.
Decreased
motivation and spontaneity fatigability and feeling of depression are very
common. There will be disturbance in other neurological condition which
presenting symptom of the disorder.
Normal-Pressure
Hydrocephalus
Hydrocephalus is an increase in the intracranial cerebrospinal fluid volume
associated with dilatation of the ventricular system. In the case of primary
hydrocephalus an increased volume of CSF with in the cranial cavity can
result from increased formation of CSF, an obstruction to its circulation or
decreased absorption. This is turn leads to raised CSF pressure.
Normal –
pressure hydrocephalus is both obstructive and communicating. It is caused
by an obstruction in the subarachnoid speace which prevents CSF from being
reabsorbed, but allows it to flow in to the subarachnoid space from the
ventricular system.
Hydrocephalus is associated with dilatation of the ventricular system.
In Normal
pressure hydrocephalus the features of raised ICP are generally absent. The
syndrome mainly occurs in the 7th and 8th decads of
life. Varying degrees of cognitive impairment and physical slowness occur.
Other features include unsteadiness of gait, urinary incontinence and
nystagmus. When it caused pre-senile dementia particularly If physical
features are absent, it may prove difficult to differentiate normal –
pressure hydrocephalus from Alzheimer’s disease.
Traumatic Causes
HEAD INJURY
The commonest
cause of head injury is motor vehicle accidents. Acute posttraumatic
psychosis and the chronic Psychological sequence of head injury cause,
cognitive impairment, personality change and neurotic symptoms. A common
consequence of head injury does not deflect the extent of brain damage is
called post concussional or posttraumatic syndrome. Such as head ache
dizziness, emotional liability, anxiety, irritability, sensitivity to noise,
impaired concentration and subjective memory loss, confusion, disorientation
and mood disturbance, also cause defect in memory and calculation, damage to
the frontal lobe maybe followed by personality change towards a pathy and
indifference.
SUBDURAL
HAEMATOMA
Subdural
haematoma commonly caused by head injury arise in association with clotting
disorder, acute haematoma associated with disturbed consciousness up to
extreme of coma and neurological signs cause dementia.
Extracranial
Causes of Dementia
Systemic
conditions may affect neuronal function through the blood stream, producing
a dementia or a sub acute derious syndrome.
ENDOCRINE
DYSFUNCTIONS :-
Endocrinedisorers,
such as hyper and hypothyroidism, addition’s disease, Cushing’s syndrome,
acromegaly hyper and Hypoparathyrodism and diabetes mellitus are all
potential cause of an organic brain syndrome.
CEREBRAL
ANOXIA:-
Cerebral
anoxia arises from any hindrance to the transport of oxygen from the level
of the alveoli to its place of eventual utilization with in neuron,
respiratory failure cardiac failure, suffocation, severe anemia cerebral
vascular disease and metabolic disturbances such hypoglycemia and cyanide,
poisoning are all Important cause
VITAMIN
DEFICIENCY :-
Due to
vitamin deficiency associated with chronic physical and mental illness,
ageing and social disadvantage vitamin B group are associated with
neuropsychiatry symptoms, chronic thiamine deficiency leads to beriberi with
cardiac failure neuropathy and in acute cases Wernicke’s encephalopathy.
Nicotine acid
deficiency leads to pellagra with triad to gastrointestinal disorder,
dementia and psychiatric disturbance like, irritability, anorexia and
emotional instability and delirium, vitamin biz deficiency cause sub acute
combined degeneration of the spinal cord accompanied by a macrocytic anaemia
and progressive dementia.
METABOLIC DISORDER :-
Hepatic
and renal disease, electrolyte and fluid disturbances and acute porphyria.
Hepatic failure is associated with marked neuropsychiatric symptoms. It
cause liver disease is cause consciousness in impaired during episodes of
ecephalopathy concentration and memory impaired.
Electrolyte
abnormalities cause apathy, slowness and withdrawal, which may resemble
dementia.
Drug and Dementia
Reseprine,
Methylopa and phenocetin cause chronic brain syndromes chronic use of
canabis can produce mental and physical sluggishness, disturbance of recent
memory and volition associated with chronic head ache and reversal of sleep
rhythm. Drug use and use of cannabis associated cerebral Atrophy.