Plain Radiographs

Plain skull films are rarely used today in pediatric trauma centers. While previously useful for evaluation of fractures, as well as for pneumocephalus, evaluation of bony fragments in depressed, comminuted fractures, and for evaluation of diastatic sutural fractures has been offset by CT, which provides soft tissue assessment as well as excellent cranial vault imaging especially with the more routine use of three-dimensional (3D) reconstruction algorithms. Today the role of the skull radiograph is used primarily as a map for identification of foreign bodies, or to document child abuse.⁷ Plain films, however, still remain helpful to rule out spinal column injury while minimizing radiation exposure to the developing child that would come from a full-body, spine CT study. Since children more often suffer ligamentous injury, a screen with plain x-rays followed by magnetic resonance imaging (MRI) has provided an alternative to the radiation incurred with a full-body scan with mixed efficacy. If the child is awake and particularly uncomfortable due to either limitation to care in the intensive care unit setting or anxiety associated with wearing a rigid cervical collar, flexion/extension radiographs or dynamic fluoroscopic films may be used. Patients with diminished responsiveness are challenging, as actual clearance and collar removal requires radiologic in combination with clinical clearance, and thus there is little indication for cervical clearance in the early period in these patients. MRI for evaluation of ligamentous injury within the first 48 hours of the event can be performed if removal of the collar is necessary for the care of the patient, such as in operative intervention requiring manipulation of the neck. Unfortunately, MRI use has become increasingly popular as a screen, although it may be an unnecessary expense or risk due to frequent need for sedation and limited monitoring ability to obtain the requisite images. Based on extrapolation from recent studies in adult trauma patients, the risk of missing an occult unstable cervical injury in the teenage group with adequate prior static radiographs is less than 1%;^8–11 these data may not apply to the very young pediatric population. In pediatric spine injury, since there is a predominance of upper cervical and occipitocervical pathology in the younger pediatric population, we prefer imaging the cervical spine alone with CT including 3D reconstructions as necessary for initial radiologic clearance. Due to the low incidence of injury, the thoracic and lumbar spine can be imaged by plain radiograph unless a CT is desired for an area of pain or deformity, or the mechanism of injury is significantly violent, such as motor vehicle collision.

Computed Tomography

For TBI, the noncontrasted axial head CT is the imaging modality of choice in pediatric neurotrauma. The scan can be performed very rapidly providing immediate information regarding cranial injury, intra- and extra-axial blood, fractures, ventriculomegaly associated with TBI, and to a less-specific degree, ischemia. The progression of intra- and extra-axial hemorrhagic lesions has been well documented. A repeat CT scan may be obtained within twelve hours if significant blood is present or there is a change in neurologic status. Data have failed to reconcile personal practice bias into standard protocols and practice regarding early repeat CT scanning. Repeat imaging should be conservatively considered given the “trauma” of transport and potential for worsening of hemodynamic instability. In adults, Oertel and colleagues evaluated 142 cases and described hemorrhagic progression by hematoma type as follows: 51% in parenchymal contusions, 22% in epidural hematomas, and 11% of subdural hematomas on 24-hour, follow-up CT scanning.¹² Unique to the pediatric population is the usual absence of anticoagulant use for comorbid conditions; this likely decreases the development of a delayed insult on CT from 85% to 31%.¹³ These results can be applied to the pediatric TBI patient as a general guide in assessing the need for repeat CT evaluation.

Concern has been raised about the effect that ionizing radiation has on the immature central nervous system. Prediction models for the use of CT in mild TBI (Glasgow Coma Scale (GCS) 14 to 15) for the pediatric population have recently been investigated. The estimated rate of lethal malignancies from CT is 1 per 1000 to 1 per 5000 scans with increased risk with younger age.^4,5 Of 14,969 pediatric patients who underwent CT-scanning of the head for suspected TBI and met study parameters, 376 (0.9%) had clinically important TBI (defined as requiring acute intervention including neurosurgery), and only 60 (0.1%) underwent neurosurgery. The negative predictive value is 100% if the following criteria were met: (1) normal mental status, (2) no scalp hematoma except frontal, (3) no loss of consciousness or loss of consciousness for less than 5 seconds, (4) non-severe injury mechanism, (5) no palpable skull fracture, and (6) acting normally per parents. The negative predictive value is equivalent in children over 2 years of age with normal mental status, no loss of consciousness, no vomiting, no severe headache, no evidence of basilar skull fracture, and non-severe injury mechanism. It can be concluded from these data that CT scanning in the low risk TBI pediatric population may be avoided based on provider preference and likelihood of surgery.⁶ Even in the higher risk categories, the authors’ preference is not to repeat imaging unless there is consideration for a change in management strategy, that is, decision making for surgical intervention.

Recently there has been an increased utilization of the so-called “pan scan” including head, cervical spine, chest, abdomen, and pelvis. Tillou and colleagues reported on the effectiveness of the “pan CT scan” in an adult cohort indicating that if any study was omitted, from 311 CT scans, 17 injuries (5.4%) requiring immediate attention would have been missed.¹⁴ We recommend caution and careful consideration of each patient’s mechanism of injury, neurologic status, and age prior to undertaking a “pan scan” to limit the potential radiation exposure; however, this is determined in large part by trauma surgery. With the advent of “pediatric” protocols developed to lower the radiation load without compromising image quality, these studies, especially if limited to the head and cervical spine, can facilitate the care of the patient, reducing time in the radiology department and providing a wealth of information useful for clinical decision making.

Magnetic Resonance Imaging

Magnetic resonance imaging in the pediatric trauma population is problematic primarily due to time constraints. The time for examination is significantly longer than the CT and frequently requires sedation in the young to ensure adequate image quality. If the patient is intubated in the field or on arrival to the ED, MRI becomes a more practical modality with extension of sedation, although the decision should be based on a specific question particularly as it relates to the cervical spine. In emergent and urgent settings, the potential benefits of subtler imaging seldom outweigh the screening achieved by CT alone for cranial trauma. This may differ in the cervical spine where bony abnormalities are less common and soft tissue injury may be better imaged by MR. Following the emergent acute phase, it must be recognized that certain implants such as intracranial pressure (ICP) sensors or cranial bolts have to be removed or disconnected to ensure safety from potential further injury or artifact,¹⁵ such as inducible radio frequency heating, movement in the magnetic field leading to further parenchymal damage, or metallic artifact from skin staples, and thus, at this time MR in the acute setting has little efficacy.

In contrast, cervical spine or other spinal injury in a child is often best assessed by MR, although it is often impractical to image the entire spine in the acute setting. The initial screening of patients with clinical exam and CT usually provide a target area for more focused regional imaging. A patient with a spinal fracture and correlating neurologic findings can be better assessed for surgical pathology such as a hematoma or disc protrusion into the canal. As mentioned, since in children most often it is the extent of the ligamentous injury that is being evaluated, T2, FLAIR, or FIESTA sequences provide more information as to the extent of significant ligamentous injury, the potential for instability, and need for surgical intervention.

Remote Imaging/Telemedicine

With the advent of further regionalization for neurotrauma care, patients arriving with a variety of radiographic studies from the initial triage referring hospital is becoming more common. Often various proprietary image software packages for viewing the patient’s studies can be encountered on a daily basis, leading to incompatibility and the need to repeat radiographic assessment in a vulnerable patient population. Teleradiology or the unification of systems under a single compatible program needs investigation to reduce costs and danger to the patient due to delayed intervention. Further, early communication from the primary emergency room to the trauma surgeon and neurosurgeon can commonly guide more appropriate selection of screening images and allow more expedient delivery of care upon arrival. Standardization in the “spokes and hub” model, where the receiving neurosurgeon has reviewed imaging studies remotely or from his office or home, can have substantial impact on timing from arrival to surgery for emergency craniotomies. Since shorter time from injury to surgery has been repeatedly shown to improve outcome dating back to the 1970s, efforts at broadening teleradiographic access along with regionalization of neurosurgical care/emergencies, particularly from rural areas, are likely to be more common in the near future.

External Ventricular Drain Placement

Many institutions have developed protocols to be followed when an EVD is inserted. The major potential risks of ventriculostomy placement are ventriculostomy-related infection (VRI) or insertional hemorrhage. A recent review of VRI indicated that a body of retrospective studies was limited by nonuniform definitions of infection versus colonization versus contamination. It lists, however, the rate of VRI from 0% to 22% among 23 studies with 5733 EVD insertions. The cumulative rate of positive cultures was 8.08% per EVD placed. With an earlier, more stringent definition of VRI in 1988, the incidence of VRI among the 5733 EVD insertions dropped to 6.1%.¹⁷ Most studies have defined VRI as a single positive CSF culture obtained from the ventricular catheter or from CSF drawn via lumbar puncture. To limit this potential complication, prophylactic intravenous antibiotics or antibiotic impregnated catheters have been used. A controlled multicenter, prospective, randomized trial performed by Zabramski et al., showed striking results when antibiotic-impregnated catheters were used. In adult patients randomized to minocycline and rifampin-impregnated versus nonimpregnated drains, the rate of positive CSF cultures dropped from 9.4% to 1.3%, and the colonization rate of the drain dropped from 37% to 18%.¹⁸ In contrast, another prospective, randomized, controlled trial in a single institution established equivalent infection rates among 116 patients comparing antibiotic-impregnated catheters to that of nonimpregnated drains with systemic antibiotics. These investigators concluded that impregnated catheters may diminish the cutaneous opportunistic infections associated with systemic antibiotics without tradeoff of VRI.¹⁹ Technical aspects of insertion have been investigated; it has been showed that extended tunneling of the catheter has no effect on infection rate.²⁰ Risk factors for VRI development have been established in multiple reports, including subarachnoid hemorrhage (SAH), intraventricular hemorrhage (IVH), craniotomy, cranial fracture with CSF leak, ventriculostomy irrigation, concomitant systemic infection, and duration of placement.^21,22 Factors not associated with VRI include hydrocephalus, closed head trauma, tumor, CSF drainage, multiple catheters, and concomitant ICP sensors.²² Most agree that sterile placement with some prophylactic antibiotic coverage whether impregnated or systemic can reduce the potential for VRI.

Less frequent risks of placement include malposition, hemorrhage, and neurologic injury. Almost all of the above studies were performed in the adult population. Generalization to the pediatric population seems appropriate but warrants further study. A recent retrospective study of 96 EVD placements in pediatric patients reported complication rates of infection (9.4%), malposition (6.3%), hemorrhage (4.2%), and obstruction (3.1%).²³