Curriculum · Neurology
Alzheimer disease
What it is
Alzheimer's disease is the most common cause of dementia. It usually starts by forgetting recent events and progresses with deterioration of the activities of daily living such as bathing and eating. It is steadily progressive memory impairment: short-term memory, then long-term memory, then social graces, over a chronic and insidious course. Cognitively: aphasia, apraxia and agnosia, with memory and executive function impairment, visuospatial and language deficits, and behavioral and psychological changes.
Causes and risk
Down syndrome has early onset Alzheimer's disease as a late complication, with hypothyroidism, atlantoaxial instability and acute lymphoblastic leukaemia.
How it is diagnosed
Rule out the reversible organic causes first: hypothyroidism, B12 deficiency, HIV and syphilis infection. Review the medication chart and assess for substance misuse. Set it against the other dementias:
- Vascular: stepwise cognitive deterioration, with abrupt cognitive deficits which plateau for a period of time and then a sudden onset of further deficits, hypertension, previous stroke or transient ischemic attack
- Lewy body: fluctuating attention and alertness, parkinsonism with rigidity and tremor, visual hallucinations, and increased sensitivity to the extrapyramidal side effects of antipsychotics
- Frontotemporal (Pick): personality and behavioural changes early in the disease, with disinhibition, perseveration and apathy
- Normal pressure hydrocephalus: gait instability, urinary incontinence and ventriculomegaly; confirm with a high volume lumbar puncture and follow-up assessment, and treat with ventricular shunting
On CT, late-stage disease shows diffuse cortical and subcortical atrophy. The diagnosis itself is clinical, with MMSE or MoCA alongside it, and MRI shows cortical atrophy that is temporal and parietal. The frontotemporal one is drawn more fully elsewhere: Pick's disease, under 65y, with personality and behavior before memory, disinhibition and hyperorality, and frontal and temporal lobe atrophy on MRI.