Numerous stratagems have been devised to determine what studies should be ordered for which patients. Patients with trivial injuries rarely need a CT scan, and those with severe head injuries obviously need one. Most of the effort centers around identifying the patient who appears to have a minor head injury but maybe harboring or apt to develop a significant intracranial injury. An optimal protocol has not been developed, and a rigorous prospective application and further refinement of published systems is sadly lacking. In view of this state of affairs, the following is presented as a guideline. Patients may be stratified into one of three groups based on the likelihood of intracranial injury as outlined in the following sections 1) 2)
In this group, there is an extremely low likelihood of intracranial injury (ICI) of ≤ 8.5 in 10,000 cases (with 95% confidence level) 3).
CT scan is not usually indicated. Plain SXRs are not recommended: 99.6% of SXRs in this group are normal. Linear non-displaced skull fractures in this group require no treatment, although in-hospital observation (at least overnight) may be considered. Patients in this group who meet the criteria for observation at home may be managed with observation at home with written head-injury discharge instructions.
1. presence of any moderate or high risk criteria which include: GCS ≤ 14, unresponsiveness, focal deficit, amnesia for injury, altered mental status (including those that are significantly inebriated), deteriorating neuro status, signs of basal or calvarial skull fracture
2. assessment prior to general anesthesia for other procedures (during which neurologic exam cannot be followed in order to detect delayed deterioration).
The results of a study of Bodanapally et al. from Department of Radiology , Department of Diagnostic Radiology and Imaging Sciences and Nuclear Medicine, Neurosurgery Baltimore, Maryland, Department of Diagnostic Radiology and Imaging Science Atlanta, Georgia, indicate that virtual high monochromatic (190 keV, thin-section) images combined with standard 120 kV images may provide optimal diagnostic performance for evaluation of patients suspected of TBI 4).
The information supplied by the admission CT scan not only allows for diagnostic screening for potential intracranial injuries requiring acute neurosurgical interventions, but also provides important prognostic information. If better implemented, outcome prediction models could help prioritize resources in the emergency setting. Better outcome prediction could also have the potential to improve TBI research by providing baseline risk stratification in trials and to optimize standardization of cohorts in comparative effectiveness research 7).
The main emergent conditions to rule out (and brief descriptions):
a) extra-axial blood:surgical lesions are usually ≥1cm maximal thickness
● epidural hematoma: usually biconvex and often due to arterial bleeding. May cross dural barriers (unlike SDH) such as falx, tentorium
● subdural hematoma (SDH): usually crescentic, usually due to venous bleeding. May cover larger surface area than EDH (dural adherence to inner table limits extension of EDH). Chronology of SDH: acute = high density, subacute ≈ isodense, chronic ≈ low-density
b) subarachnoid blood(SAH): trauma is the most common cause of SAH. Unlike aneurysmal SAH where blood is thickest near the circle of Willis, traumatic SAH (tSAH) usually appears as high density spread thinly over convexity and filling sulci or basal cisterns. However, when the history of trauma is not clear, a CTA (or arteriogram) may be indicated to R/O a ruptured aneurysm (that might have precipitated the trauma in some cases)
c) intracerebral hemorrhage (ICH): increased density in brain parenchyma
d) hemorrhagic contusion: often“fluffy” inhomogeneous high-density areas within the brain parenchyma, usually adjacent to bony prominences (frontal and occipital poles, sphenoid wing). Typically less well-defined than primary ICH
e) intraventricular hemorrhage: present in ≈ 10% of severe head injuries. Associated with poor outcome; may be a marker for severe injury rather than the cause of the poor out- come. Use of intraventricular rt-PA has been reported for treatment
2. hydrocephalus: enlarged ventricles may sometimes develop following trauma
3. cerebral swelling: the obliteration of basal cisterns, compression of ventricles and sulci.
4. evidence of cerebral anoxia: loss of gray-white interface, signs of swelling
5. skull fractures (best appreciated using bone windows):
a) basal skull fractures (including temporal bone fracture)
b) orbital blow-out fracture
c) calvarial fracture (CT may miss some linear nondisplaced skull fractures)
● linear vs. stellate
● open vs. closed
● diastatic (separation of sutures)
1. Many facilities perform a repeat head CT at 24 hours for patients who are clinically stable but had findings on initial head CT of: traumatic subarachnoid hemorrhage SAH, small subdural hematoma or epidural hematoma, cerebral contusions
2. For patients with severe head injuries:
a) for stable patients, follow-up CTs are usually obtained between day 3 to 5, (some recommend at 24 hrs also) and again between day 10 to 14.
b) some recommend routine follow-up CT several hours after the “time zero”CT(i.e.initial CT done within hours of the trauma) to rule-out delayed EDH, SDH, or traumatic contusions
3. for patients with mild to moderate head injuries:
a) for those with an abnormal initial CT, the CT scan is usually repeated prior to discharge b) stable patients with mild head injury and normal initial CT do not require follow-up CT Urgent follow-up CT: performed for neurological deterioration (loss of 2 or more points on the GCS, development of hemiparesis or new pupillary asymmetry), persistent vomiting, worsening H/A, seizures or unexplained rise in intracranial pressure (ICP) in patients with an ICP monitor.
Retrospective data show that routine CT scanning (in the absence of any clinical deterioration) after mild traumatic brain injury or moderate TBI had no therapeutic (interventional) consequences 12) 13).
On the other hand there is a trend towards routine use for patients with severe TBI but the evidence to support this concept is low. Some authors recommend a cCT scan if clinical signs of neurological deterioration occur 14) , other findings suggest that routine cCT might be beneficial in some subgroups of patients 15) 16). In particular patients with multiple trauma and severe TBI and patients who are endotracheally intubated, mechanically ventilated, and sedated might benefit from routine repeated cCT 17). There is only a single study which investigated the role of a follow-up cCT scan exclusively in unconscious, sedated, and mechanically ventilated patients with severe TBI 18). In those patients early clinical signs of neurologic deterioration are potentially difficult to detect. A change in pupils' status, signs of brain herniation, and seizures are commonly clinical signs of severe brain damage and therapeutic intervention might be too late 19).
Discharge after a repeat head CT and brief period of observation in the Emergency Department allowed early discharge of a cohort of mild TBI patients with traumatic ICH without delayed adverse outcomes. Whether this justifies the cost and radiation exposure involved with this pattern of practice requires further study 20).
The proper classification of these patients is of major importance in situations where a CT is not accessible.
A portable screening device that uses near-infrared spectroscopy (NIRS) technology allows a preliminary estimate of an intracranial hematoma.
The use of the device in a military medical rescue center (Kunduz, Afghanistan) is easy to learn and can be repeatedly used even under emergency room conditions. The technique can be applied in penetrating and blunt TBIs in the absence of an immediately available CT scan in rural areas, preclinically, under mass casualty conditions (e.g., in disaster situations) as well as in humanitarian crises or war zones. Nevertheless, further studies to assess the validity of this device are necessary 21).