Dementia (Overview)
Definition (DMS-IV):
- Major impairment in memory and learning, plus at least one other domain: handling complex tasts, reasoning ability, spatial ability and orientation, language.
- Significantly interferes with work performance, social activities, or relationships with others.
- Significant decline from previous level of functioning.
- Insidious and progressive onset.
- Not occurring only with delirium, and not better accounted for by other major psych disorders, systemic/neurological disease.
"Mild Cognitive Impairment":
- Various definitions, but basically refers to memory impairment, but with preserved ability to function in daily life. Does carry increased risk for progression to delirium.
Major Dementia Syndromes:
1. Alzheimer’s Disease – most common form of dementia (60-80% of cases), risk increases with age. Diagnosis is primarily clinical (definitive dx confirmed pathologically on autopsy). Earliest deficits are episodic memory for recent events. Keep in mind that neuropsychiatric symptoms are not uncommon (psychosis, aggression, apathy, depression).
2. Vascular Dementia (Multi-infarct Dementia) – as compared to Alzheimer’s, get early prominent deficits in executive function moreso than memory impairment. Other suggestive features include onset of cognitive deficits associated with stroke, abrupt onset of symptoms followed by stepwise deterioration, and neuro exam or imaging consistent with prior CVAs.
** “Mixed Dementia “ = combined AD and Vascular Dementia – fairly common as there is considerable overlap with risk factors and comorbidities **
3. Frontotemporal Dementia – focal atrophy of frontal and temporal lobes. Presents earlier than AD (mean age 57) and rarely after 75. Different phenotypes exist, but basically the distinguishing feature is the prominent behavioral and personality changes, including social disinhibitions. 20-40% of cases are familial.
4. Dementia with Parkinsonism – has various syndromes, all with Parkinson-type features (bradykinesia, resting tremor, cogwheel ridigity, etc).
a. Dementia with Lewy Bodies – hallmarks are persistent visual hallucinations
b. Parkinson’s Disease Dementia – PD is associated with 6x risk of dementia.
c. Progressive Supranuclear Palsy – vertical supranuclear palsy with downward gaze abnormalities
d. Multisystem Atrophy – includes “Shy Drager Syndrome” – autonomic dysfunction with cerebellar and pyramidal signs
5. Reversible Dementia Syndromes – more aptly called “Potentially Reversible. ” Some of these cause more of a delirium picture than dementia.
a. Medication-induced – chronic use of analgesics, anticholinergics, psychotropic meds, sedatives, etc.
b. Metabolic – Vitamin B12 deficiency, Hypothyroidism
c. Depression (“Pseudodementia”)
d. CNS disease – Neoplasms, Chronic Subdural Hematomas, Neurosyphilis, Normal Pressure Hydrocephalus
6. Other – Creutzfeldt-Jackob Disease (prion disease), HIV Dementia
Workup:
- Most important distinction is Dementia vs Delirium. Evaluation of course includes careful history (including meds/drugs), and exam especially focusing on the neuro exam.
- Mini-mental status exam is easy to do and fairly helpful. A score of 24 or less is fairly sensitive (87%) and somewhat specific (82%). Limitations are that it is insensitive for mild dementia, and is influenced by education, language, as well as motor/visual/hearing impairments.
Rough estimate of MMSE scores:
- Mild Dementia – 21-24
- Moderate – 10-20
- Severe – 9 or less
Neuropsychological testing can be done to confirm the diagnosis of dementia.
In addition to routine metabolic labs, the American Academy of Neurology recommends routine B12 and TSH levels in all patients with dementia. Screening for neurosyphilis is not routinely recommended unless there is clinical suspicion (but in practice, most people just order it anyways).
Although this is somewhat controversial, the AAN also recommends neuroimaging with Head CT or MRI in the routine initial evaluation of patients with dementia.
(Chanu Rhee MD, 2/1/11)