Friday, May 22, 2015

Organic Brain Syndrome and Alzheimer's Disease

Table of Contents


Organic brain syndrome (OBS) is a general term used to describe decreased mental function due to a medical disease, other than a psychiatric illness. It is often used synonymously (but incorrectly) with dementia.

Alternative Names

OBS; Organic mental disorder (OMS); Chronic organic brain syndrome

Causes, incidence, and risk factors

Disorders associated with OBS include:

  • Brain injury caused by trauma
    • Bleeding into the brain (intracerebral hemorrhage)
    • Bleeding into the space around the brain (subarachnoid hemorrhage)
    • Blood clot inside the skull causing pressure on brain (subdural hematoma)
    • Concussion
  • Breathing conditions
    • Low oxygen in the body (hypoxia)
    • High carbon dioxide levels in the body (hypercapnia)
  • Cardiovascular disorders
    • Abnormal heart rhythm (arrhythmias)
    • Brain injury due to high blood pressure (hypertensive brain injury)
    • Dementia due to many strokes (multi-infarct dementia)
    • Heart infections (endocarditis, myocarditis)
    • Stroke
    • Transient ischemic attack (TIA)
  • Degenerative disorders
    • Alzheimer's disease (also called senile dementia, Alzheimer's type)
    • Creutzfeldt-Jacob disease
    • Diffuse Lewy Body disease
    • Huntington's disease
    • Multiple sclerosis
    • Normal pressure hydrocephalus
    • Parkinson's disease
    • Pick's disease
  • Dementia due to metabolic causes
  • Drug and alcohol-related conditions
    • Alcohol withdrawal state
    • Intoxication from drug or alcohol use
    • Wernicke-Korsakoff syndrome (a long-term effect of excessive alcohol consumption or malnutrition)
    • Withdrawal from drugs (especially sedative-hypnotics and corticosteroids)
  • Infections
    • Any sudden onset (acute) or long-term (chronic) infection
    • Blood poisoning (septicemia)
    • Brain infection (encephalitis)
    • Meningitis (infection of the lining of the brain and spinal cord)
  • Other medical disorders
    • Cancer
    • Kidney disease
    • Liver disease
    • Thyroid disease (high or low)
    • Vitamin deficiency (B1, B12, or folate)

Other conditions that may mimic organic brain syndrome include:

  • Depression
  • Neurosis
  • Psychosis



Review Date: 02/06/2010
Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; and Luc Jasmin, MD, PhD, Department of Neurosurgery at Cedars-Sinai Medical Center, Los Angeles, and Department of Anatomy at UCSF, San Francisco, CA. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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