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Organic brain syndrome



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


Disorders associated with OBS include:

Other conditions that may mimic organic brain syndrome include:


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

Signs and tests

Tests depend on the disorder, but may include:

Support Groups

Expectations (prognosis)

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

Calling your health care provider

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.

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


Treatment depends on the disorder. Many of the disorders are treated mainly with rehabilitation and 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.



Knopman DS. Alzheimer's disease and other dementias. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 425.

Review Date: 2/6/2010
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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