A subdural effusion is a collection of cerebrospinal fluid (CSF) trapped between the surface of the brain and the outer lining of the brain (the dura matter). If this fluid becomes infected, the condition is called a subdural empyema.

A subdural effusion is a rare complication of meningitis caused by bacteria. Subdural effusion is more common in infants.

Subdural effusion may also occur after head trauma.

Symptoms may include:

• Outward curving of a baby's skull's soft spot (bulging fontanelle)
• Abnormally wide spaces in the bony joints of a baby's skull (separated sutures)
• Increased head circumference
• Low energy (lethargy)
• Persistent fever
• Seizures
• Vomiting
• Weakness or loss of movement on both sides of the body

The health care provider will perform a physical exam and ask about the symptoms.

To detect the subdural effusion, tests that may be done include:

• CT scan of the head
• Head size (circumference) measurements
• MRI scan of the head
• Ultrasound of the head

Surgery to drain the effusion is often necessary. In rare cases, a permanent drainage device (shunt) is needed to drain fluid. Antibiotics may need to be given through a vein.

Treatment may include:

• Surgery to drain the effusion
• Drainage device, called a shunt, left in place for a short time or longer time
• Antibiotics given through a vein to treat the infection

Full recovery from a subdural effusion is expected. If nervous system problems continue, they are generally due to the meningitis, not the effusion. Long-term antibiotics are usually not needed.

Complications of surgery may include:

• Bleeding
• Brain damage
• Infection

Contact your provider if:

• Your child has recently been treated for meningitis and symptoms continue
• New symptoms develop

De Vries LS, Volpe JJ. Bacterial and fungal intracranial infections. In: Volpe JJ, Inder TE, Darras BT, et al, eds. Volpe's Neurology of the Newborn. 6th ed. Philadelphia, PA: Elsevier; 2018:chap 35.

Kim KS. Bacterial meningitis beyond the neonatal period. In: Cherry JD, Harrison GJ, Kaplan SL, Steinbach WJ, Hotez PJ, eds. Feigin and Cherry's Textbook of Pediatric Infectious Diseases. 8th ed. Philadelphia, PA: Elsevier; 2019:chap 31.

Nath A. Meningitis: bacterial, viral, and other. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 384.