Brain Swelling

Medically Reviewed By William C. Lloyd III, MD, FACS
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What is brain swelling?

A variety of conditions are known to cause brain swelling, which is enlargement of the brain due to excessive fluid collection in the chambers, or ventricles, of the brain or the accumulation of fluid within the brain tissue itself.

Excess fluid in the ventricles of the brain leads to a condition known as hydrocephalus. The fluid exerts outward pressure on the brain tissue, pressing it into the skull. In the skull of an infant or small child, where there are soft areas known as fontanelles and sutures between the bony plates that have not yet hardened, the head can increase in size.

Fluid collection within the brain tissue, called cerebral edema, can result from numerous causes, including infections, trauma, stroke, brain tumors, certain toxic substances, complications of diabetes, chemical imbalances, abuse of opioids, extreme high blood pressure (malignant hypertension), or high altitude sickness.

Symptoms of brain swelling include headache, dizziness, nausea, numbness or weakness, loss of coordination or balance, loss of the ability to see or speak, seizures, lethargy, memory loss, incontinence, or altered level of consciousness. In infants, the fontanelles ("soft spots") may bulge, the head may increase in size, cries may be high-pitched or shrill, and irritability or feeding difficulties may occur.

Brain swelling causes ongoing damage to the brain tissue, so it needs to be treated as quickly as possible to save as much brain tissue as possible. Seek immediate medical care (call 911) for head trauma, significant high altitude sickness, high fever accompanied by neck stiffness or rigidity, severe headache, known ingestion of toxins, bites from poisonous animals or insects, or symptoms suggestive of brain swelling.

What other symptoms might occur with brain swelling?

Brain swelling may accompany other symptoms, which vary depending on the underlying disease, disorder or condition. Symptoms that frequently affect the brain may also involve other body systems.

Symptoms of infection that may occur along with brain swelling

Brain swelling may occur as a result of an infection. Other symptoms suggestive of infection that are known to cause brain swelling include:

  • Confusion or loss of consciousness

  • Fever

  • Gait abnormality

  • Headache

  • Imbalance

  • Malaise or lethargy

  • Neck stiffness or rigidity

  • Rash

  • Seizures

Symptoms of chemical imbalances or toxic exposures that may occur along with brain swelling

Brain swelling may occur as a result of toxic exposures or chemical imbalances. Other symptoms of toxic exposures or chemical imbalances that could accompany brain swelling include:

  • Abdominal pain

  • Abnormal heart rhythm such as rapid heart rate (tachycardia) or slow heart rate (bradycardia)

  • Confusion or loss of consciousness

  • Difficulty breathing or rapid breathing

  • Difficulty speaking

  • Dry skin or changes in skin color

  • Feeling very thirsty

  • Frequent urination

  • Fruity breath

  • Hallucinations

  • Muscle weakness

  • Nausea with or without vomiting

Other symptoms that may occur along with brain swelling

Depending upon the age of the individual and the cause of the swelling, brain swelling may accompany other symptoms including:

  • Bulging of the soft spots on top of the head (fontanelles) in infants or small children

  • Difficulty with memory, thinking, talking, comprehension, writing or reading

  • Dizziness

  • Droopy eyelid

  • Flaccid limbs

  • High-pitched or shrill cries in infants or small children

  • Impaired balance and coordination

  • Increased head size in infants or small children

  • Irritability, fussiness, poor feeding, and sleepiness in infants and young children

  • Lethargy

  • Loss of vision or changes in vision

  • Muscle weakness

  • Numbness or tingling in arms or legs

  • Paralysis

Serious symptoms that might indicate a life-threatening condition

Brain swelling may be a symptom of a life-threatening condition that should be immediately evaluated in an emergency setting. Seek immediate medical care (call 911) if you, or someone you are with, have any of these life-threatening symptoms including:

  • Abnormal pupil size or nonreactivity to light

  • Change in level of consciousness or alertness such as passing out or unresponsiveness

  • Change in mental status or sudden behavior change such as confusion, delirium, lethargy, hallucinations or delusions

  • Flaccid limbs

  • Garbled or slurred speech or inability to speak

  • High fever (higher than 101 degrees Fahrenheit)

  • High-pitched, shrill cries in an infant or small child

  • Irritability, fussiness, poor feeding, and unusual sleepiness in infants and young children

  • Paralysis or inability to move a body part

  • Seizure

  • Stiff or rigid neck

  • Sudden change in vision, loss of vision, or eye pain

  • Trauma to the head

  • Worst headache of your life

    What causes brain swelling?

    A variety of different conditions are known to cause brain swelling, and, in some instances, the cause may not be known. Brain swelling can take two forms, hydrocephalus, in which fluid collects in the ventricles and the swelling occurs from the inside outward, and cerebral edema, in which the fluid collects in the brain tissue and the swelling is generalized.

    Causes of brain swelling related to hydrocephalus

    The causes of brain swelling in which excess fluid collects in the ventricles of the brain (hydrocephalus) are not always known but may include:

    • Birth defects
    • Brain or spinal cord injury
    • Brain or spinal cord tumor
    • Complications of birth
    • Cysts or tumors
    • Genetic abnormalities
    • Infection
    • Normal pressure hydrocephalus

      Causes of brain swelling related to cerebral edema

      Brain swelling related to cerebral edema can be caused by a number of conditions including:

      • Brain tumors
      • Chemical imbalances
      • Diabetic ketoacidosis (a life-threatening complication of diabetes)
      • Exposure to certain toxins
      • Head trauma
      • High altitude sickness
      • Infection
      • Malignant hypertension (severe high blood pressure)
      • Opioid abuse
      • Stroke

      Serious or life-threatening causes of brain swelling

      In some cases, brain swelling may be a symptom of a serious or life-threatening condition that should be immediately evaluated in an emergency setting. These include:

      • Brain or spinal cord injury
      • Brain or spinal cord tumor
      • Diabetic ketoacidosis (a life-threatening complication of diabetes)
      • Exposure to certain toxins
      • Head trauma
      • High altitude sickness
      • Infection
      • Malignant hypertension (severe high blood pressure)
      • Opioid abuse
      • Stroke

      Questions for diagnosing the cause of brain swelling

      To diagnose your condition, your doctor or licensed health care practitioner will ask you several questions related to your brain swelling including:

      • What specific symptoms have you noticed?
      • Did anything such as an injury or illness precede the symptoms?
      • Have you checked your blood sugar?
      • Have you been exposed to any toxic substances?
      • Have you recently traveled from a low altitude to a higher altitude?
      • What medications are you taking?

      What are the potential complications of brain swelling?

      Because brain swelling can be due to serious diseases, failure to seek treatment can result in serious complications and permanent damage. Once the underlying cause is diagnosed, it is important for you to follow the treatment plan that you and your health care professional design specifically for you to reduce the risk of potential complications including:

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      Medical Reviewer: William C. Lloyd III, MD, FACS
      Last Review Date: 2021 Jan 11
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      THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
      1. NINDS traumatic brain injury information page. National Institute of Neurological Disorders and Stroke. http://www.ninds.nih.gov/disorders/tbi/tbi.htm.
      2. Hydrocephalus. PubMed Health, a service of the NLM from the NIH. http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0002538/
      3. Bope ET, Kellerman RD (Eds.) Conn’s Current Therapy. Philadelphia: Saunders, 2013.
      4. Domino FJ (Ed.) Five Minute Clinical Consult. Philadelphia: Lippincott Williams & Wilkins, 2013.
      5. Tierney LM Jr., Saint S, Whooley MA (Eds.) Current Essentials of Medicine (4th ed.). New York: McGraw-Hill, 2011.