Dementia

Differential Overview

❑ Alzheimer disease

❑ Multi-infarct dementia

❑ Depression

❑ Drugs

❑ Parkinson disease

❑ Frontal lobe dementia

❑ Vitamin B₁₂ deficiency

❑ HIV encephalopathy

❑ Korsakoff syndrome

❑ Brain tumor

❑ Normal pressure hydrocephalus

❑ Chronic subdural hematoma

❑ Neurosyphilis

❑ Creutzfeldt-Jakob

❑ Wilson disease

Diagnostic Approach

Many patients are concerned about age-related forgetting of details, a normal phenomenon. This usually results from decreased attention. The fact that they recognize and worry about this distinguishes them from patients with early dementia. Normal forgetting preserves vocabulary and spelling and improves with cues. For example, patients with Alzheimer disease cannot recall a list of related words any better than random words. Patients with dementia on the other hand have difficulty with one or more of the following: learning and retaining new information (e.g., remembering events); handling complex tasks (e.g., balancing a checkbook); reasoning (e.g., inability to cope with unexpected events); spatial orientation (e.g., getting lost in familiar places); language (e.g., word finding); and/or behavior.

Subtle impairments in memory, attention, and concentration are often easily compensated for and therefore hard to pinpoint. Impaired judgment and abstraction on increasingly simple matters and personality changes (notably irritability) are usually noted first. The time course of onset is helpful in distinguishing dementia from delirium, but acute exacerbations of an underlying dementia that mimic delirium are common with drugs and acute physical illness.

The Mini Mental State Exam (MMSE) measures across domains of cognitive function: memory, executive function, attention, language, praxis, and visuospatial ability. A total score of less than 24/30 suggests dementia or delirium. Scores of 20 to 24 suggest mild impairment; 16 to 19, moderate; and 15 or below, severe. It also provides a quantitative assessment useful in following the course of the disease or response to therapy.

Mini-Cog Repeat three objects, Clock Drawing Test (hands at 8:20), then recall three objects. Suggestive of dementia when either 0/3 objects are recalled or when 1 to 2 are missed and CDT is abnormal.

Clinical Findings

Alzheimer disease  There is a progressive, smooth decline, with aphasia, apraxia, and agnosia. Personality change, ranging from progressive passivity to hostility or paranoia, may be an early manifestation. “Frontal release signs,” including palmomental reflex and snout, are usually found. Early dysphasia predicts a rapid cognitive decline. Patients with advanced disease will exhibit increased muscle tone and clonus.

Multi-infarct dementia  Cognitive impairment will occur in a stepwise fashion, usually associated with focal neurological deficits. An underlying cause such as atrial fibrillation, poorly controlled hypertension, diabetes, or carotid
vascular disease with bruit will usually be evident. The Hachinski Ischemia Score helps differentiate: abrupt onset—2, stepwise deterioration—1, fluctuating mental status—2, nocturnal confusion—1, personality preserved—1, depression—1, somatic complaints—1, emotional lability—1, hypertension—1, history of stroke—2, focal signs—2, angina—1. A score of 7 or more suggests a high probability of multi-infarct dementia.

Depression  Altered mood, self-blaming, anhedonia, disordered sleep, and initiation fatigue are clues. Usually, the patient will recognize the depression.

Drugs  Dementia may be caused or worsened by anticholinergics, antiparkinson agents, antidepressants, nonsteroidal anti-inflammatory drugs, antihistamines, narcotics, steroids, H2-blockers, and substances of abuse.

Parkinson disease  Patients with Parkinson disease have a sixfold increased risk of developing dementia. Typical clinical features will be present, such as rigidity, bradykinesia, resting tremor, and gait disorder. Masked facies on presentation portends an increased subqequent risk. Because visual hallucinations and delusions are a prominent feature, dementia may be difficult to separate from side effects of levodopa. Dementia with Lewy bodies is more common in this setting, characterized by daytime drowsiness, staring into space for long periods, and disorganized flow of ideas.

Frontal lobe dementia  Typically there will be disinhibited behavior and impairment in executive function (e.g., goal setting and planning). Pick disease presents with repetition of words or phrases (echolalia) or abundant unfocused speech (logorrhea).

Vitamin B₁₂ deficiency  Dementia is associated with peripheral neuropathy (distal “pins and needles”) and pallor (macrocytic anemia). There will often be a family history of pernicious anemia or other autoimmune disease. Affected posterior columns will produce a decrease in position and vibration sense, and affected lateral columns increase deep tendon reflexes with upgoing toes. Motor weakness and spasticity may develop, with a stiff to ataxic gait.

HIV encephalopathy  The patient is usually known to be HIV-infected or has risk factors. Impaired memory, poor concentration, decreased reaction time, lack of spontaneity, weakness, and ataxia are often present. Cryptococcal or toxoplasmal meningitis and CNS lymphoma can produce cognitive dysfunction in AIDS and thus confuse the differential.

Korsakoff syndrome  There will be a history of advanced alcohol abuse. The patient is suggestible, confabulates, and has an inability to remember new information despite normal recall, attention span, and level of consciousness.

Brain tumor  Papilledema and focal neurological signs are usually present. Frontal tumors can be relatively silent but are recognized by abulia, bradykinesia, shuffling gait, anosmia, and frontal release signs. Rapid progression of cognitive dysfunction can be found with cerebral edema.

Normal pressure hydrocephalus  The classic triad includes dementia, gait disorder (slow, shuffling, wide-based, ataxic), and incontinence, in the absence of a history of subarachnoid hemorrhage, meningitis, or head injury.

Chronic subdural hematoma  Early features are headache, drowsiness, and strange behavior in an elderly patient. Focal signs come later. A history of head trauma may not be obtained; thus, a high index of suspicion is needed.

Neurosyphilis  An Argyll Robertson pupil (accommodates but does not react), optic atrophy, tabes dorsalis, and a remote history of a chancre are clues. General paresis produces a spastic quadriparesis.

Creutzfeldt-Jakob  Myoclonus is always present, and cerebellar signs are often found.

Wilson disease  Extrapyramidal signs, a golden (Kayser-Fleischer) ring in the iris, and hepatic dysfunction are important clues.

Pictures

Book Source Details

• Book Title: Field Guide to Bedside Diagnosis
• Author(s): David S. Smith
• Year of Publication: 2007
• Copyright Details: Field Guide to Bedside Diagnosis, Copyright © 2007 Lippincott Williams & Wilkins.

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Copyright Details: Field Guide to Bedside Diagnosis, Copyright © 2008 Williams & Wilkins.

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More About This Book: Title: Field Guide to Bedside Diagnosis Authors: David S. Smith Publisher: Lippincott Williams & Wilkins Copyright: 2007 ISBN: 0-78178-165-5

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