Chapter 120. Subdural Hematoma Aspiration in the Infant

Extra-axial fluid collections in children are classified as symptomatic and asymptomatic. Symptomatic, chronic extra-axial fluid collections have been variously classified as hematomas, effusions, or hygromas with differing definitions associated with each. It has been proposed that they all be classified together as extra-axial fluid collections because their appearance on CT scan and the treatment is identical.1 Symptomatic, chronic extra-axial fluid collections usually show ventricular compression and flattening or obliteration of the cerebral sulci on CT scans. Benign subdural fluid collections usually appear as a hypodensity over the frontal lobes with dilatation of the interhemispheric fissure, cortical sulci, and Sylvian fissure. The ventricles are usually normal or slightly enlarged with no evidence of transependymal flow.

Seizures, a large head, vomiting, irritability, depressed level of consciousness, and lethargy are common presenting symptoms of a symptomatic extra-axial fluid collection. The physical examination reveals a full fontanel, macrocephaly, fever, lethargy, hemiparesis, retinal hemorrhages, generalized increased tone, or gaze paresis. Markwalder has done an excellent review of the pathophysiology and experimental studies of chronic subdural hematomas.2

The majority of extra-axial fluid collections result from head trauma. Other causes include bacterial meningitis (postinfectious) and the placement of a ventriculoperitoneal shunt. The etiology of intracranial hemorrhage and extra-axial fluid collections are quite varied (Table 120-1). Acute and chronic subdural fluid collections are common problems during infancy. Males are affected more commonly than females. A clear history of injury or trauma should be sought in the presence of an acute or chronic subdural hematoma. Consider the possible etiology of child abuse if a history of injury is not forthcoming or if the history does not make sense. It is incumbent upon the medical team to rule out abuse. This may require a period of inpatient observation, social services consultation, a radiographic skeletal survey, a bone scan, and possibly an ophthalmological assessment. The presence of retinal hemorrhages in association with a subdural fluid collection is highly suspicious for child abuse. Admission to the hospital for further observation is warranted if child abuse cannot be ruled out. The presence of congenital anomalies may predispose the child to subdural hematoma formation.

Percutaneous removal of the subdural fluid is useful in diagnosing an active infection and rapidly lowering the intracranial pressure in the symptomatic patient. Repeated removal of the fluid by percutaneous aspirations has been advocated by some Neurosurgeons for definitive treatment of chronic extra-axial fluid collections.3,4 Subdural fluid collections in infants have a tendency to increase in size, are often bilateral, can be difficult to diagnose, and are most often seen in children under the age of 2 years. The combination of CT and MRI is usually diagnostic.

A subdural aspiration (or tap) is usually performed by puncturing the anterior fontanel. However, it can also be approached through the coronal suture as well as through the soft cranium. The diamond-shaped anterior fontanel is formed by the junction of the sagittal, coronal, and frontal sutures (Figure 120-1). It measures approximately 4 cm in the anteroposterior plane and 2.5 cm in the transverse plane. The bones of the infant calvarium are separated by connective tissue bands referred to as sutures. The fontanels are readily palpable at the junctions of the sutures. Six of the fontanels are located at the corners of the two parietal bones. Two of these, the anterior and posterior fontanels, are in the midline.

The anterior fontanel, the largest of the neonatal fontanels, is utilized for percutaneous subdural aspiration. The diamond-shaped anterior fontanel is formed by the junction of the sagittal, coronal, and frontal sutures (Figure 120-1). It measures approximately 4 cm in the anteroposterior plane and 2.5 cm in the transverse plane. The posterior fontanel is at the junction of the lamboidal and sagittal sutures. In general, the anterior fontanel has usually closed by 18 months of age but can be patent up to the age of 2 years. The posterior fontanel usually closes earlier in life and is usually complete by 6 weeks of age.

The anterior fontanel is composed of connective tissue and easily perforated with a spinal needle. Continued advancement of the needle would then perforate the underlying dura, allowing the tip of the needle to rest within the subdural space. Traversing the dura is usually associated with a definite change in resistance as the subdural space is entered. Successful entry of the tip of the needle into the subdural fluid collection can be confirmed by removal of the stylet and observing spontaneous drainage from the needle hub. The anterior fontanel is readily palpable and bulging in cases of symptomatic chronic extra-axial fluid collections. The lateral extent of the anterior fontanel is continuous with the coronal suture (Figure 120-1).

A subdural aspiration is performed for diagnostic purposes as well as for rapid decompression of subdural fluid collections, whether acute or chronic. Perform a subdural aspiration in the young child with a subdural fluid collection and radiographic signs of elevated intracranial pressure, a depressed level of consciousness, and/or a changing level of consciousness.5 Other indications to perform a subdural aspiration include the clinical signs and symptoms associated with elevated intracranial pressure: bulging fontanelles, coma, cranial nerve palsies, hemiparesis, hypotonia, irritability, lethargy, posturing, seizures, somnolence, and vomiting (repeated or intractable). Aspiration of extra-axial fluid collections can reduce intracranial pressure dramatically. Subdural aspiration of fluid allows for culture and sensitivity, identification of microorganisms, and aids in the selection of bacterial specific antimicrobial agents if an infectious etiology is considered to be the cause of the extra-axial fluid collection.

The main contraindications to performing a subdural aspiration include localized infections of the scalp, patients who are coagulopathic or thrombocytopenic, children over the age of two, children who have an absence of the anterior fontanel as a result of premature closure, a solid clot that is not liquefied, and children with congenital anomalies of the skull or brain. This procedure should not be performed by those unfamiliar with the technique and its complications. Consult a Neurosurgeon, if available, prior to performing this procedure. Repeated aspirations are rarely indicated as blood or fluid reaccumulation often requires the placement of a drain or a surgical procedure by a Neurosurgeon.

• Sterile skin prep kit
• Povidone iodine or chlorhexidine solution
• Sterile gloves and gown
• Face mask with an eye shield or goggles
• Sterile drapes
• 1% or 2% lidocaine, with or without epinephrine
• 18 to 22 gauge, 1.5 in. spinal needle or angiocatheter
• Tincture of benzoin
• Cotton swab
• Bandage
• Bundling blanket
• Commercially available immobilization device
• Syringe for aspirating fluid
• Sterile specimen containers
• Culture bottles or swabs
• IV extension tubing, optional

All of the basic equipment can be found in commercially available pediatric lumbar puncture kits. The kit needs to be supplemented with personal protective equipment and skin antiseptic.

The patient should be fully monitored with a noninvasive blood pressure cuff, pulse oximetry, cardiac monitor, and end-tidal carbon dioxide monitor (if available). Obtain a CT scan of the head to determine the presence of an extra-axial fluid collection, the location and extent of the fluid collection, the type of fluid (e.g., blood, pus, etc.), and to rule out the presence of a mass. Obtain a complete blood count (hemoglobin, hematocrit, and platelet count) and a coagulation profile (PT, PTT, and INR) to ensure that the patient is not thrombocytopenic or coagulopathic.

Explain the procedure to the parents and/or guardian of the child if time permits. Obtain an informed consent to perform the procedure. Place the patient supine on a stretcher. The child may need to be restrained to prevent movement during the procedure. Bundling an infant in a blanket and placing their head close to the edge of the bed facilitate aspiration. An alternative is to use a commercially available immobilization device (e.g., Papoose board). The aid of an assistant to hold the child's body with the head straight and upright is recommended if the child is restless. Some children may require the administration of parenteral sedatives or procedural sedation.

This procedure requires strict aseptic technique. Shave the frontal and parietal regions of the child's head. Clean any dirt and debris from the scalp. Identify by palpation the anterior fontanel, the coronal suture, and the lateral margin of the coronal suture. The Emergency Physician should don full sterile and personal protective equipment at this point. This should include sterile gloves, a sterile gown, a face mask with an eye shield or goggles, and a cap. Apply povidone iodine or chlorhexidine solution to the skin over the entire scalp and allow it to dry. Ensure that the solution is not allowed to drain onto the baby's face or eyes. Apply sterile drapes leaving the frontal and parietal regions of the skull exposed. A local anesthetic agent is usually not required but may be used at the Emergency Physician's discretion. If used, place a skin wheal using 0.25 to 0.50 mL of 1% or 2% lidocaine at the site the needle will enter the scalp.

Form a Z-tract by gently sliding the scalp skin laterally (Figure 120-2). Insert a 22 gauge spinal needle into the lateral margin of the anterior fontanel, about 2.5 to 3 cm off the midline (Figure 120-2). Advance the spinal needle beneath the frontal bone until the subdural space is penetrated. This is usually within 5 to 8 mm from the skin surface. A loss of resistance is usually appreciated as the dura is penetrated and the subdural space is entered. Do not advance the needle any further. Securely hold the spinal needle so that it does not move (Figure 120-3). An alternative is to insert the needle at a 45° angle to the skin surface, tunnelling it under the scalp and into the subdural space (Figure 120-4). Remove the stylet. Spontaneous drainage is often appreciated. This fluid may appear hemorrhagic. However, it is not uncommon, especially in patients who require multiple aspirations, to drain xanthochromic fluid.

The initial subdural aspiration usually results in spontaneous drainage through the spinal needle. The spontaneous cessation of flow through the needle suggests that the extracranial and intracranial pressures are equalized, not that the fluid has been completely evacuated. If the fluid does not spontaneously drain, carefully and gently apply a syringe to the spinal needle and gently aspirate the fluid. Use minimal negative pressure to just aspirate the fluid collection and prevent pulling the brain or any bridging veins into the needle. Alternatively, apply digital pressure to the anterior fontanelle to increase the flow through the spinal needle. Some Physicians may choose to apply intravenous extension tubing to the spinal needle to allow the subdural fluid to drain away from the patient and directly into the specimen tubes. This is left to the Emergency Physician's preference. Observe the gradual flattening of the anterior fontanel to determine the endpoint for the procedure.6 Generally, on any one occasion, no more than 25 to 30 mL of subdural fluid should be aspirated. Larger volumes, up to 80 mL, have been safely aspirated.7 Remove the spinal needle and apply a bandage.

Consult a Neurosurgeon to evaluate and manage the patient. There are numerous alternatives to the aspiration of the fluid collection. These include observation, burr hole drainage, drainage through an external collecting system, placement of a subdural-to-peritoneal shunt, and a craniotomy. A craniotomy should be performed in patients with a symptomatic nonliquefied clot or extensive membrane development precluding aspiration.

Some Physicians prefer to use an intravenous catheter rather than the spinal needle. Removal of the metal needle leaves a soft Teflon catheter in place that minimizes the risk of injury to the brain or intracranial vascular structures. The use of an intravenous catheter set rather than a spinal needle is left to the discretion of the Emergency Physician.

Monitor the child for a change in their level of functioning after subdural aspiration. Comparison to the child's baseline neurological examination is essential. It is mandatory to document timed serial neurological examinations in the patient's chart. The clinical examination is age-related. It is often prudent to observe the infant in the arms of a parent or healthcare worker while monitoring their level of alertness, facial expression, extraocular movement, pupillary response, and limb movement. Obtain daily head circumference measurements and plot them on a head circumference chart. Note the size and feel of the anterior fontanel. Infection can be prevented with careful attention to aseptic technique. A simple bandage placed over the puncture site is usually sufficient and can be removed 48 to 72 hours after the procedure. Continued spontaneous drainage through the puncture site should be monitored carefully as it poses an infectious risk.

Perform an ultrasound or CT scan of the head to determine if the fluid collection has been adequately drained. Bedside ultrasonography is an effective tool in neonates and young children. Any change in the child's neurological examination requires an emergent head CT scan or ultrasonography to determine if the subdural fluid collection has reaccumulated. Send the aspirated fluid for the appropriate laboratory analysis if an etiology other than an acute traumatic hemorrhage is suspected. This can include a biochemistry analysis (glucose and protein level), cell count and differential, culture (bacterial, fungal, viral, etc.), cytology, and gram stain. Admit the child to the Intensive Care Unit where they can be appropriately monitored and observed.

Injury to the superior sagittal sinus or draining veins is best avoided by inserting the spinal needle 2.5 to 3 cm lateral to the midline. At no time should the trajectory of the needle be in the midline or parasagittal in location. Overpenetration of the spinal needle can result in intracerebral hemorrhage. Have an assistant immobilize the child to prevent them from moving and the needle lacerating the brain or a blood vessel. Persistent leakage of subdural fluid from the puncture site can be the result of insufficient fluid aspiration or failure to use a Z-tract. This complication can also be prevented by tunneling the needle under the scalp prior to penetrating the lateral margin of the anterior fontanel (Figure 120-4). This leakage can usually be controlled with local pressure, head elevation, and rarely by using cotton soaked with tincture of benzoin. Placement of a single suture at the puncture site will usually control continued leakage if less invasive methods fail. Introducing infection into the subdural space has also been reported following a subdural aspiration.8 This is best avoided by maintaining strict aseptic technique.

Acute and chronic subdural fluid collections are common problems during infancy. They are regarded as posttraumatic lesions in the great majority of cases. Birth trauma is sometimes implicated but uncommon. It appears that minor injuries during infancy or even more violent injuries such as infant shaking and/or cranial impact are the inciting events. It is incumbent upon the Emergency Physician to rule out any possibility of child abuse! Report actual or suspected abuse to the appropriate state agency as required by law. Aspiration of extra-axial fluid collections in the symptomatic child can be completed safely with very little risk to the child. Admission and continued observation are mandatory.