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Organic brain syndrome (OBS) is a general term that refers to diseases (usually not psychiatric disorders) that cause decreased mental function.

OBS is common in the elderly. It is not a part of the normal aging process, however.

OBS is not a separate disease, but is a general term used to describe physical conditions that can cause mental changes.

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 causing pressure on brain (chronic 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
  • Creutzfeldt-Jacob disease
  • Diffuse Lewy Body disease
  • Huntington's disease
  • Multiple sclerosis
  • Normal pressure hydrocephalus
  • Parkinson's disease
  • Pick's disease
  • Senile dementia, Alzheimer's type
• Dementia due to metabolic causes
• Drug and alcohol-related conditions
  • Alcohol withdrawal state
  • Intoxication, drug abuse, or alcohol use
  • Long-term effects of alcohol, Wernicke-Korsakoff syndrome
  • Withdrawal from drugs (especially sedative-hypnotics and corticosteroids)
• Infections
  • Any sudden onset (acute) or long-term (chronic) infection
  • Blood poisoning (septicemia)
  • Swelling of the brain (encephalitis)
  • Swelling of the lining of the brain and spinal cord (meningitis)
• Other medical disorders
  • Cancer
  • Kidney disease
  • Liver disease
  • Thyroid disease (high or low)
  • Vitamin deficiency (B12 and others)

Other conditions that may be related to organic brain syndrome include:

• Depression
• Neurosis
• Psychosis

Symptoms can differ based on the disease. In general, organic brain syndromes cause:

• Agitation
• Confusion
• Long-term loss of brain function (dementia)
• Severe, short-term loss of brain function (delirium)

Tests depend on the disorder, but may include:

• Blood tests
• Electroencephalogram (EEG)
• Head CT scan
• Head MRI

Treatment depends on the disorder. Many of the disorders have mainly supportive care to assist the person in areas where brain function is lost.

Medications may be needed to reduce aggressive behaviors that can occur with some of the conditions.

See the specific disorder. Some disorders are short-term and treatable, but many are long-term or get worse over time.

People with OBS often lose the ability to interact with others or function on their own.

Call your health care provider if:

• You have been diagnosed with organic brain syndrome and you are uncertain about the exact disorder.
• You have symptoms of this condition.
• You have been diagnosed with OBS and your symptoms become worse.

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

Updated by: Luc Jasmin, MD, PhD, Departments of Anatomy & Neurological Surgery, University of California, San Francisco, CA. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.