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Table 16-3. MAJOR CAUSES OF DEMENTIA

* Indicates potentially treatable causes

Infectious

1. *Acute bacterial meningitis
• Diagnosis: Fever, stiff neck; purulent CSF, + gram stain
• Treatment: Appropriate antibiotics
2. *Viral encephalitis
• Diagnosis: Fever, confusion; lymphocytes in CSF
• Treatment: Nonspecific: steroid support; antiviral agent (acyclovir) for herpes simplex encephalitis
3. *Tuberculous meningitis
• Diagnosis: Headache, stiff neck, malaise, weight loss; CSF: pleocytosis (modest, mainly lymphocytes), low glucose, high protein
• Treatment: INH, ethambutol, streptomycin, other antibiotics, and steroids
4. *Cryptococcal meningitis
• Diagnosis: Headaches; CSF as in tuberculous meningitis; demonstration of organisms or antigen in CSF
• Treatment: Amphotericin B and 5-fluorocytosin
5. *Tertiary syphilis (general paresis rarely seen today)
• Diagnosis: CSF; Poor judgment, grandiosity, frontal release signs; Argyll Robertson pupils; cells in CSF; + CSF VDRL
• Treatment: Penicillin
6. Prion infections
1. Creutzfeldt-Jakob disease
• Diagnosis: Dementia, basal ganglia signs, startle myoclonus, etc.
• Treatment: None
2. Kuru
• Diagnosis: . Cerebellar degeneration; dementia late; acquired by eating victims
• Treatment: None
7. Atypical virus infections
1. Subacute sclerosing panencephalitis
• Diagnosis: Dementia, myoclonus: under 20 years old (caused by measles-like virus); high CSF gamma globulin level
• Treatment: None
2. Progressive multifocal leukoencephalopathy
• Diagnosis: Multifocal hemispheric signs usually in immunosuppressed patient (HIV, on immunosuppressive drugs or with malignancy particularly of reticuloendothelial origin)
• Treatment: None

Metabolic

1. Lack of substrate
1. *Tissue hypoxia
1. Low blood PO2
• Diagnosis: Cyanosis; blood gases
• Treatment: Oxygen, respiratory support; treat infection and spasm
2. Severe anemia
• Diagnosis: Hemoglobin, hematocrit
• Treatment: Tranfusion, etc.
3. Decreased perfusion
1. Decreased cardiac output
• Diagnosis: Hypotension; signs of congestive failure
• Treatment: Appropriate cardiac medications or fluids for hypovolemia; treatment of septic shock, etc.
2. Arterial obstruction
• Diagnosis: Usually focal signs
• Treatment: Support, anticoagulation if progressive without hemorrhage
3. Increased viscosity (polycythemia)
• Diagnosis: Hematocrit
• Treatment: Phlebotomy
2. *Hypoglycemia
• Diagnosis: Varied clinical picture: often dizziness, syncope; but may have focal signs or seizures; low blood glucose; 5-hour glucose tolerance test to rule out reactive hypoglycemia
• Treatment: IV glucose
3. *Nutritional deficiency
1. Vitamin B12 deficiency
• Diagnosis: Pernicious anemia and/or spinal cord involvement (not always present); lab: low serum B12 levels; positive Schilling test; achlorhydria (usually)
• Treatment: IM vitamin B12 administration
2. Thiamine deficiency
• Diagnosis: Wernicke's encephalopathy; confusion, amnesia, truncal ataxia, disconjugate eye movements; fatal if untreated: Korsakoff's psychosis (residual of Wernicke's): amnesia, confabulation
• Treatment: IM/IV thiamine; vitamin treatment is only partially, if at all, effective for Korsakoff's
2. Endocrine
1. *Hypothyroidism
• Diagnosis: Myxedema, hung-up reflexes, hypothermia; high TSH, low T4, etc.; hyponatremia
• Treatment: Thyroid hormone replacement
2. *Hyperthyroidism
• Diagnosis: Weight loss, tremor, etc.; high T4, etc.
• Treatment: Thyroid suppressants; surgery
3. *Cushing's disease
• Diagnosis: Hypertension, diabetes, Cushingoid features; hypokalemia; high cortisol
• Treatment: Surgery
4. *Parathyroid abnormalities
1. Hyperparathyroidism
• Diagnosis: Hypercalcemia (lethargy, etc.)
• Treatment: Treat hypercalcemia; remove parathyroids
2. Hypoparathyroidism
• Diagnosis: Hypocalcemia; diffuse, soft tissue calcification; tetany
• Treatment: Vitamin D
3. Pseudohypoparathyroidism
• Diagnosis: Hypocalcemia, skeletal abnormalities, basal ganglia calcification, tetany unusual despite very low calcium levels
3. Electrolyte imbalance
1. *Hyponatremia (water intoxication), inappropriate antidiuretic horome secretion, renal sodium wasting
• Diagnosis: Lethargy, seizures, low serum sodium
• Treatment: Water-restriction; hypertonic saline (sometimes)
2. *Hypercalcemia
• Diagnosis: Lethargy, confusion; high serum calcium
• Treatment: Lower calcium (phosphate, steroids, mithromycin, etc.); treat underlying condition
3. *Hypomagnesemia
• Diagnosis: Confusion, seizures; in setting of persistent diarrhea (especially in infants), or of IV therapy without Mg supplements; serum Mg may not reflect deficiency; calcium usually also low
• Treatment: Magnesium sulfate
4. *Hypocalcemia
• Diagnosis: Confusion; tetany seizures; serum calcium low
• Treatment: Replace calcium; treat underlying condition
5. *Hyperosmolar coma
• Diagnosis: High blood glucose, severe dehydration with associated electrolyte abnormalities
• Treatment: Fluids, insulin
4. Toxic
1. Endogenous
1. *Hypercapnia (pulmonary insufficiency)
• Diagnosis: Signs of respiratory insufficiency, asterixis
• Treatment: Assist respirations, pulmonary toilet; antibiotics
2. *Hepatic encephalopathy
• Diagnosis: Lethargy, dementia, asterixis; hyperventilation with respiratory alkalosis (?central); high serum ammonia; high CSF glutamine; if chronic may see dementia plus choreiform movements and dystonia
• Treatment: Treat infections, gastrointestinal bleeding (when present); cleanse bowel (neomycin enemas, acetic acid enemas, lactulose), L-dopa
3. *Renal insufficiency
• Diagnosis: Multifocal myoclonus, seizures, asterixis; signs of uremia; high BUN, creatinine
• Treatment: Treat primary disease; dialysis
4. *Acidosis
• Diagnosis: Hyperventilation, low pH
1. Diabetic ketoacidosis
• Diagnosis: Hyperglycemia, ketosis
• Treatment: Fluids, insulin, bicarbonate
2. Lactic acidosis
• Diagnosis: Acidosis without hyperglycemia, seen with sepsis, shock, idiopathic
• Treatment: Treat underlying cause; bicarbonate
5. *Wilson's disease
• Diagnosis: Dystonia, choreiform movements; cirrhosis; high liver copper, low ceruloplasm; high urine copper excretion
• Treatment: Copper-binding agent (penicillamine), low copper diet, liver transplant?
6. *Hyperlipidemia
• Diagnosis: Greatly increased serum cholesterol and triglycerides
• Treatment: Lower serum lipids
7. Limbic dementia (remote effects of carcinoma)
• Diagnosis: Memory loss, agitation; may have cerebellar or brain stem signs
• Treatment: None
2. Exogenous toxins
1. *Drugs
• Diagnosis: Serum levels, history
1. Hypnotics
• Diagnosis: Ataxia, dementia, lethargy, comatose
• Treatment: Reduce dose slowly if comatose; fluids, respiratory and blood pressure support; dialysis when appropriate; benzodiazepine antagonists (with caution for acute withdrawal)
2. Aspirin
• Diagnosis: Metabolic acidosis plus respiratory alkalosis
• Treatment: Fluids; alkalinize urine
3. Anti-convulsants
• Diagnosis: Ataxia, dementia, lethargy
• Treatment: Reduce dose
2. *Toxins: Methanol, ethylene glycol, old paraldehyde
• Diagnosis: Severe metabolic acidosis, blindness with methanol, hippurate crystals in urine with ethylene glycol
• Treatment: Bicarbonate; ethanol for methanol intoxication

Vascular disease

1. *Strokes (multiinfarct dementia)
• Diagnosis: Focal signs or story, CT scan or MRI positive with completes strokes
• Treatment: Controversial (see chap. 19)
2. *Hypertensive encephalopathy
• Diagnosis: Papilledema, proteinuria, diastolic blood pressure usually above 120; headache, cortical visual loss
• Treatment: Lower blood pressure
3. *Vasculitis (lupus, etc.)
• Diagnosis: Dementia with or without focal signs; may or may not have other systems involved; high sedimentation rate almost always
• Treatment: No effective treatment for most; steroids used and proved effective only for giant cell cranial arteritis
  

Mechanical

1. *Mass lesions
1. Neoplasms
• Diagnosis: Focal signs, except in "silent areas" (i.e., frontal lobes); positive brain scan (over 80%); CT scan and MRI positive in most
• Treatment: Surgery, XRT, Chemotherapy (depending on the type); steroids if edema
2. Subdural hematoma
• Diagnosis: Often headache, lethargy; mild focal signs; history of trauma (not always); increasing CSF protein; positive brain scan; positive CT scan
• Treatment: Surgery
3. Intracerebral hematoma
• Diagnosis: Focal signs, usually; if hematoma is subcortical, in a silent area (less than 10% of spontaneous intracerebral hematomas), focal signs may be minimal; CT scan positive
• Treatment: Surgery (in rare cases)
2. *Hydrocephalus
• Diagnosis: If acute: headache, lethargy, increased intracranial pressure. If chronic: dementia, gait disorder (frontal "apraxic" and spastic gait), and urinary incontinence; normal CSF dynamics, but look for changes indicative of chronic meningitis; CT scan with minimal cortical atrophy and enlarged ventricular system
• Treatment: CSF shunt; appropriate antibiotics or chemotherapy if chronic meningitis of infections or neoplastic origin

"Degenerative" diseases

1. Without elementary neurologic findings
1. *Alzheimer's disease
• Diagnosis: Memory loss usually prominent early; very common, the usual senile dementia; CT scan positive
• Treatment: Symptomatic agents, ?Vitamin E
2. Pick's disease
• Diagnosis: Same; not clinically separable from Alzheimer's: can only be separated pathologically; very rare in United States
• Treatment: None proven
2. Demyelinating disease
1. *Multiple sclerosis
• Diagnosis: Evidence clinically of lesions separated in time and space; dementia common late in illness; frequently high CSF gamma globulin percentage of total CSF protein
• Treatment: High dose steroids briefly in acute exacerbations; disease modifying drugs (see Chpt. 14)
2. Schilder's disease
• Diagnosis: Usually in children; dementia most prominent sign, but soon cortical blindness, long-tract signs, etc.
• Treatment: None
3. Inborn errors of metabolism
1. Lipid storage diseases
• Diagnosis: Tay-Sachs, etc.
• Treatment: None
2. Metachromatic leukodystrphy
• Diagnosis: Dementia, peripheral neuropathy; absent arylsulfatase A
• Treatment: None
3. *Amino acidurias (many of them)
• Diagnosis: Variable, urine for amino acids
• Treatment: Restrictive diet for many
4. Prominent basal ganglia or cerebellar signs.
1. *Parkinsonism
• Diagnosis: Typical basal ganglia signs (see chaps. 8 and 18)
• Treatment: L-dopa (does not help dementia), amantidine, dopamine agonists
2. Huntington's chorea
• Diagnosis: Dementia may precede chorea; family history (autosomal dominant)
• Treatment: None, control behavioral symptoms, genetic counseling
3. Some spinocerebellar degenerations
• Diagnosis: Cerebellar, posterior column, pyramidal, and peripheral nerve disease depending on which variant (Friedreich's ataxia most common example)
• Treatment: None
4. Myoclonic epilepsy (certain forms)
• Diagnosis: Progressive form with Lafora's inclusion bodies produces dementia
• Treatment: None; control seizures
5. Parkinson-dementia complex (Guam)
• Diagnosis: May be associated with ALS
• Treatment: None