Head Injury (Adult)

• There have been several Clinical Decision Rules (CDRs) developed for the use of CT in minor head injury with various recommendations 1-6 including the Canadian CT Head Rule (CCHR), New Orleans Criteria (NOC) and the NICE guidelines 5

• The most validated and commonly used CDRs are the Canadian CT Head Rule (CCHR) and the New Orleans Criteria (NOC); the CCHR is more widely recommended 7-11

• These are used to stratify adult patients with minor head trauma into risk categories (risk of the need for neurosurgical intervention or clinically important brain injury)

• The published evidence is that the use of CDRs can safely, but only modestly , reduce the use of CT scans in minor head trauma by approximately 25% 6. Indeed, one study has shown a slight increase in the usage of CT by the application of the CCHR 12.

Application of the Canadian CT Head Rule: (CCTHR)

Criteria excluding use of CCTHR 6, 13

• Anticoagulant medication or bleeding disorder

• Age <16 years

• Seizure

• Emergency Department GCS score <13

• Obvious penetrating skull trauma

• Obvious depressed skull fracture

• Focal neurological deficit

• Unstable vital signs associated with major trauma

• “Minimal” head injury (no loss of consciousness, amnesia or disorientation; no clear history of trauma as the primary event; injury occurred > 24 hours previously)

Inclusion criteria 14:

CCHR is applied to patients with minor head injury, the definition of which includes 6, 14:

• Loss of consciousness

• GCS13-15

• Confusion

• Amnesia or disorientation

Patients can be divided into high and medium risk of requiring neurosurgical intervention and clinically important brain injury according to the following 6, 14:

High risk factors

• GCS <15 two hours post-injury

• Suspected open skull fracture

• Sign of  base of skull fracture

• Vomiting more than twice

• Age >65 years

Medium risk factors

• Amnesia before impact >30 min

• Dangerous mechanism of injury

• pedestrian struck by motor vehicle

• occupant ejected from motor vehicle

• fall from >3 feet or 5 stairs

• Patients with either of the two medium-risk characteristics could have a clinically important brain injury that would be seen on CT but are not regarded as at risk for needing neurosurgical intervention. The suggestion is that these patients could be managed with CT or close observation depending on local resources 15-17

Background data for Canadian CT Head Injury Rule and New Orleans Criteria

• The Canadian CT Head Rule ( CCHR) is for patients with “minor” or “mild” head injury15 and is the most widely recommended 7-11. The New Orleans Criteria (NOC) is an alternative 18

• The Canadian CT Head Rule 9, 11, 14, 18 was developed to identify patients at high risk of requiring neurosurgical intervention and clinically important brain injury and has been validated in patients >16 years of age with blunt head trauma.8, 11

• The Canadian CT Head Rule (CCHR) was prospectively derived on 3121 patients who had a minor head injury, defined as a GCS of 13 or greater with witnessed loss of consciousness, disorientation or definite amnesia 15-17

• The authors found that patients with minor head injury could be classified into two levels of risk. Those with one of the five high-risk factors are at substantial risk for neurosurgical intervention and CT is considered mandatory in these cases 15-17

• Prospective validation was carried out in Canada and reported a sensitivity of 100% and a specificity of 52.1% for clinically important brain injury 19

• Several studies have found the CCHR to be highly sensitive in identifying injuries requiring neurosurgical intervention (80-100%) with varying degrees of specificity (49.6-80.7%) 3, 9, 11, 14, 18

• A Dutch study of 3181 consecutive patients reported a sensitivity of 100% for predicting neurosurgical intervention, but a sensitivity of only 84.5% for clinically important brain injury. Similarly, a retrospective study of 240 patients in Australia found that two, of ten clinically important, brain injuries would have been missed if the CCHR had been applied 20, 21

• Comparisons between the New Orleans Criteria and the Canadian CT Head Rule have shown:

• Both had 100% sensitivities, but the Canadian CT Head Rule was more specific (50.6% vs 12.7%) and thus could result in fewer CT Scans11

• In a further 2005 study 10, the NOC had a higher sensitivity for neurocranial traumatic findings and for clinically important findings (97.7%-99.4%) than did the CCHR (83.4%-87.2%). Specificities were very low for the NOC (3.0%-5.6%) and higher for the CCHR (37.2%-39.7%). The authors stated that CCHR would identify all cases requiring neurosurgical intervention, and has greater potential for reducing the use of CT scans.

• In other trials, the CCHR has been found to perform variably better than the New Orleans Criteria (NOC) in trials that have compared the two depending on what particular accuracy measure was analysed. 22, 23 In an external validation of the CCHR and the NOC, the CCHR was found to have a lower sensitivity than the NOC for neurocranial or clinically important CT findings 20

• A 2011 systematic review 8 of several clinical decision rules (CDR) reported that CCTHR had a consistently high sensitivity for identifying injury requiring neurosurgical intervention with an acceptable specificity to allow selected use of CT. CCTHR  is the most widely validated CDR, but its exclusion criteria make it difficult to apply universally (see below).

• The ACR Appropriateness criteria state that “ By design, the New Orleans Criteria is highly sensitive (97.7%–99.4%) for any traumatic finding on CT at the cost of specificity (3.0%–5.6%), whereas the Canadian CT Head Rule accepts lower sensitivity (83.4%–87.2%) for non-neurosurgical traumatic findings in exchange for higher specificity (37.2%–39.7%) and reduced imaging 24”

• Patients who present without loss of consciousness or amnesia are not included by the Canadian CT Head rule, but there is evidence that there is still a risk of intracranial injury if other risk factors from the rule are present. 25 The incidence of intracranial injury in patients with GCS 15 has been reported from 1.6% to 7.5% 26, 27

• The decision to perform imaging on patients with no LOC, amnesia or disorientation and GCS 15 should be based on the judgement of the managing physician after history and examination 

• The evidence in the literature suggests that the probability of life-threatening complications after a normal CT is minimal. 28, 29

• In the great majority of patients with mild head injury  CT will be negative for acute traumatic findings. The evidence is that these  patients can be safely discharged rather than admitted as long as the neurologic examination is also normal (NPV of 100% for neurologic deterioration requiring surgical intervention)24

• There have been some reported cases of patients who have had a normal head CT and subsequently developed an intracranial haematoma. 30, 31

• Clinical caution should be exercised in those on anticoagulation/antiplatelet agents which are associated with an increased risk of developing intracranial haemorrhage following trauma32, 33

• Non-contrast CT is considered the most appropriate first line investigation for patients with head injury 5, 24, 34

• Non-contrast CT Is able to detect scalp, bone, extra-axial haematomas and parenchymal injuries 35

• Many hospitals are now using CT as a means of rapidly determining those patients with minor head injuries who can be safely discharged versus those who need admission or neurosurgical opinion 36-39

• Spiral CT with multiplanar reformatted images have been shown to increase diagnostic accuracy 40, 41 and should be performed when technically feasible

• BCVI is associated with a risk of severe morbidity and mortality

• About two-thirds of patients with BCVI are asymptomatic at presentation 42

• There is a variable latent period after the initial injury. Some patients may not develop symptoms for up to a week after trauma 43

• Appropriate intervention reduces the likelihood of stroke 44

• Therefore, early diagnosis is important

• CT angiography is accepted as the investigation of first choice 45, 46 although some studies have shown that CTA may underdiagnose BCVI 47, 48

• A number of screening guidelines have been published and are reviewed in a 2019 publication 43, but the expanded Denver Criteria 44, 45, 49 (see below) are established as the  most widely used screening guidelines for BCVI

• In a 2014 study 50 the expanded Denver criteria demonstrated a sensitivity and NPV  for detecting BCVI of 97% and 99.6%, respectively

• The Memphis criteria are used in some institutions 49

• The Denver and Memphis criteria can be used in combination 45.

• Screening criteria stress the greater risk of BCVI in high-energy trauma, but it should be noted that in older patients (>65) lower-energy mechanisms may lead to BCVI 45 which may indicate the need for a more liberal approach to investigation in this group of patients, particularly with cervical spine injuries 46.

• A grading scale for BCVI– modified from the Denver scale – has been proposed by Biffl et al 46– see below). The Grade of injury and its description can determine the requirement for observation, or the need for medical or surgical intervention.

  SCREENING CRITERIA FOR BCVI 44, 45, 49

  	Expanded Denver	Memphis Criteria
  Signs/symptoms
  	Potential arterial haemorrhage from, neck, mouth, nose, ears
  	Expanding cervical haematoma
  	Cervical bruit in patient <50
  	Focal/lateralising neuro deficit	Horner’s syndrome
  	Neuro deficit inconsistent with CT head findings	Unexplained neuro deficit
  	Stoke on imaging
  Risk factors for BCVI
  	High energy transfer mechanism
  	Displaced mid-face fracture (Le Fort II or III)	Unilateral or bilateral  Le Fort II or III
  	Mandible fracture
  	Complex skull fracture/basilar skull fracture/occipital condyle fracture	Skull base fractures involving foramen lacerum
  	Severe Traumatic Brain Injury (TBI) with GCS < 6
  	Cervical spine fracture, subluxation or ligamentous injury at any level	Cervical spine fracture
  	Near hanging with anoxic brain injury
  	Clothesline-type injury or seat belt abrasion with significant swelling, pain, or altered mental status	Neck soft tissue injury (e.g., seatbelt injury or hanging)
  	TBI with thoracic injuries
  	Scalp degloving
  	Thoracic vascular injuries
  	Blunt cardiac rupture
  	Upper rib fractures

  Blunt Cerebrovascular Injury Modified Grading Scale 46

  GRADE	DESCRIPTION
  I	Intimal irregularity or dissection with <25% luminal stenosis
  IIa	Dissection or intramural hematoma with 25–70% luminal stenosis
  IIb	Dissection or intramural hematoma with intraluminal thrombus or >70% luminal stenosis
  IIIa	Pseudoaneurysm <1 cm diameter with <70% luminal stenosis, or hemodynamically insignificant arteriovenous fistula
  IIIb	Pseudoaneurysm ≥1 cm diameter or with ≥70% luminal stenosis
  IV	Complete occlusion
  V	Transection with active extravasation or hemodynamically significant arteriovenous fistula

   

• The NICE (2023) Guidelines state that:

For safety, logistic and resource reasons, MRI scanning should not be the primary investigation for clinically important traumatic brain injury in people who have sustained a head injury. But additional information of importance to prognosis can sometimes be detected using MRI 5

• The ACR Appropriateness criteria state that  MRI as an initial imaging test in mild head trauma (GCS13-15) is not usually appropriate 24

• MRI may be used in the subacute setting to evaluate patients with unexplained neurological deficits 51

• MRI is superior to CT in identifying diffuse axonal or shear injury, small intraparenchymal contusions and trace subdural hemorrhage 52, 53

• Magnetic resonance angiography with Vessel Wall Imaging (VWI) protocol sequences may be used in some patients to assess for arterial injury or venous sinus occlusion

• Disadvantages

• Insensitive to acute subarachnoid or parenchymal haemorrhage, and fracture compared with CT 35, 52

• Limited role in the acute setting due to long acquisition times and difficulty in performing a scan of the critically ill patient who may require life support systems

• Certain absolute contra- indications; e.g. pacemaker

• Traumatic venous injury is often overlooked 43.

• Mechanisms include:

• Tear of the dural sinuses

• Compression of a venous sinus or pial veins due to bleeding or increased pressure

• Epithelial injury with secondary thrombus 54, 55

• Altered flow dynamics, and/or alterations in coagulation secondary to injury56

• Venous sinus gas (and /or increased density) on non-enhanced CT is a marker for venous sinus injury 56, 57.

• Intrasinus gas is heavily associated with skull fractures involving or close to a dural venous sinus 54, 56

• The above signs should prompt consideration of CT venography.

Suggestions have been made to standardise the interpretation of findings on CT in blunt head trauma 58 using the NeuroImaging Radiological Interpretation System (NIRIS) - see below.

The predictive value for the management of patients by a revised version of the NIRIS has been reported 59.

Clinical Decision Rules such as the Canadian Head CT Rule are an adjunct to clinical judgement, but there are some situations where clinical judgement will take precedence regarding the need for brain imaging:

• Elderly patients, particularly those with pre-existing cognitive impairment, in whom it may be difficult to judge the degree of injury-related amnesia or confusion.

• Patients on anticoagulants/ anti-platelet agents. There is no consensus regarding the need for primary imaging in these patients, nor for the need for follow-up imaging following an initial normal CT 60. Some studies have shown a slight increase in delayed bleeding 24 or risk of death 61.

In view of the above an individualised approach based on expert clinical judgement is advised.