A subdural puncture (commonly referred to as a subdural “tap”) is used to evacuate subdural blood or fluid. This procedure can be performed in infants when an acute or chronic subdural fluid collection is causing the child to experience symptoms of increased intracranial pressure. The procedure also can be used for diagnostic purposes in a child with potentially infected cerebrospinal fluid (subdural empyema and meningitis with effusions).

Neurosurgical consultation should be obtained before this procedure whenever possible. As for the recommended age group, subdural puncture is usually performed in infants, preferably those with an open fontanelle. The procedure can also be performed in patients with fibrous or split sutures (up to approximately 18 months of age). A similar procedure has been described in adults (1).

The subdural space lies beneath the skin, subcutaneous tissue, skull, and dura (Fig. 43.1). The major landmark for a subdural tap is the lateral margin of the anterior fontanelle, which is formed by the coronal suture. Subdural fluid collections can be acute, subacute, or chronic and can result from trauma or infection (2,3). Disruption of the bridging veins that traverse the dura is a major factor leading to formation of a subdural hematoma (4). Dural or sinus tears and repeated needle punctures of the fontanelle also are known causes. Transudates and exudates can occur and may be loculated. Identification of a subdural fluid collection as the etiology of increased intracranial pressure can allow rapid reversal of symptoms with the successful removal of fluid. These collections are best diagnosed by computed tomography (CT) or magnetic resonance imaging (MRI) of the brain.

Physiologic parameters that suggest the therapeutic need for a subdural tap include those signs and symptoms associated with increased intracranial pressure. These include mental status changes, irritability, somnolence, pallor, lethargy, vomiting, full or bulging fontanelle, third or sixth nerve palsies, respiratory irregularity, unconsciousness, coma, posturing, seizures, hypotonia, hemiparesis, and spasticity (see also Chapters 42 and 44). The fluid can be an acute or subacute blood collection from trauma or a transudate or exudate that accompanies a central nervous system infection.

Subdural puncture can be used as a therapeutic and diagnostic tool to verify the presence of fluid, identify the type of fluid, and decrease the intracranial pressure (5,6). This invasive procedure should always be reviewed with a neurosurgical consultant before proceeding if time allows. Imaging of the brain using ultrasound (if the patient has an open fontanelle), CT, or MRI should also be performed before undertaking this procedure whenever possible. MRI of the head prior to the tap can be especially useful in cases of suspected intentional trauma to document the presence and age of the blood collection before evacuation. Repeated subdural taps to remove residual fluid are rarely indicated; reaccumulation of fluid generally warrants drain placement by a neurosurgeon. Contraindications to performing subdural puncture include bleeding abnormalities, overlying infected skin, and age outside the infant-toddler group.