The major dementia syndromes include:
Alzheimerís disease
Parkinsonís disease
Lewy body dementia,
Vascular dementia,
Frontal lobe dementia,
Reversible dementia.

DSM-IV criteria for the diagnosis of:

Alzheimerís disease:
Gradual impairment of cognitive function resulting in social or occupational
dysfunction;
Impaired recent memory with one or more of the following: impaired executive
function, impaired visual processing, impairment of skilled motor
activities;
Absence of other psychiatric, neurologic or systemic diseases;
Occurrence of deficits not exclusively in the setting of delirium .



Vascular dementia:
is suggested by the presence of abrupt onset of symptoms
with stepwise deterioration, focal neurologic findings on examination, and
presence of infarcts on CT scan.



Parkinsonís disease:
typical features like rigidity,
tremor and bradykinesia will be evident. The recurrent graphic visual
hallucinations and delusions are the most characteristic feature of associated
dementia.

Frontal lobe dementia:
there is impairment of executive function, behavior
is disinhibited, and cognitive function is normal or minimally abnormal. These
patients donít have insight of their problem.

Reversible causes:
include the followings:
Medication induced
Metabolic disorders like vitamin B12 deficiency,
Thyroid problems,
Hyponatremia, hypercalcemia;
Alcohol related;
Hepatic, and renal dysfunction;
Normal pressure hydrocephalus,
CNS disorders like tumors and hematomas.

The American Academy of Neurology recommends routine non contrast CT/MRI of
the head, vitamin B12 level, and TSH level in all patients with dementia.
Screening for neurosyphilis is done only
when there is high index of suspicion. Test for HIV should be considered in a
high-risk patient, but it is not a routine part of investigations

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