Subdural effusion

A subdural effusion is a collection of pus beneath the outer membrane covering the brain that follows aggressive forms of bacterial Meningitis.

Causes, incidence, and risk factors 

A subdural effusion is a rare complication of bacterial meningitis. Subdural effusion is more common in meningitis caused by Hemophilus influenzae and in infants.

Some signs of effusion are similar to those of meningitis, but these follow the disease rather than accompany it. In infants, signs include fever, Lethargy, bulging fontanelles, separated sutures, and increasing head circumference. The effusion may cause fever to persist past the expected time after antibiotic treatment.

Increased pressure on the brain due to the effusion can cause Lethargy, Vomiting, and seizures.


  • Bulging fontanelles  
  • Separated sutures  
  • Increased head circumference  
  • Persistent fever  
  • Vomiting  
  • Seizures  
  • Lethargy  
  • Weakness

Signs and tests 

There is often a history of recent bacterial meningitis. Tests include the following:

Surgical drainage of the effusion is often necessary. Rarely, a permanent drainage device (shunt) is required to drain fluid if fluid is persistent and causes recurrent problems. Treatment with intravenous antibiotics may be necessary.

Expectations (prognosis) 
Full recovery from the effusion is expected. If there are lasting neurological problems, these are generally caused by the meningitis, not the effusion. Extended use of antibiotic therapy is usually necessary.


Complications from surgery include bleeding, infection, and damage to underlying brain structures, which can result in temporary or permanent neurologic deficits.

Seizures may occur after bacterial meningitis and may require prolonged treatment with medications.

Calling your health care provider 
Call your health care provider if your child has recently been treated for meningitis and symptoms persist or if new symptoms develop.

Johns Hopkins patient information

Last revised: December 3, 2012
by Levon Ter-Markosyan, D.M.D.

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