<prompt> All are reversible causes of dementia except ?HypothyroidismHydrocephalusMeningoencephalitisAlzheimers disease  <response>: Ans. is d i.e., Alzhimers disease Reversible causes of dementia 1 Surgically treatable :- Normal pressure hydrocephalus, brain tumors frontal lobe tumor, meningioma, subdural hematoma due to head injury, hydrocephalus. 2 Medically treatable :- Depression, hypothyroidism, alcohol abuse, vitamin B nfolateNiacin deficiency, any metabolic or endocrine disturbance, neurosyphilis, Hashimotos encephalopathy, Wilsons disease, celiac disease, whipples disease, chronic meningoencephalitis, drugs and toxin toxic dementia. Irreversible causes of dementia :- Alzheimers disease, vascular multi-infarct dementia, Parkinsonism, Huntingtons chorea, Lewy body dementia, Picks disease. 