HNS58 To CT Or Not To CT In Traumatic Head Injury

Question 1

Traumatic brain injury

Answer 1

• very frequent problem
• associated huge health care burden
• 2 at risk groups:
  1. Young children
  —> leading cause of death and disability
  —> associated with high societal cost as a result of both death and disability
  2. Elderly
  —> increasing incidence of fall-related TBI due to population aging
  —> highest rates of TBI-associated death and hospitalisation

Question 2

Age, Gender, TBI of Paediatric TBI (1-15 yo)

Answer 2

Gender:
- Male > Female: 2x risk TBI, 4x risk fatal TBI

Age distribution:

• Male: Bimodal distribution (高低高, 1-15) (15 years old due to sports injury)
• Female: Positively skewed distribution (越黎越低)

Question 3

Common causes of TBI in children

Answer 3

Preventable causes:

1. Falls at home (39%)
2. Motor vehicle accidents (11%)
3. Unknown causes (5%)
4. Assault (4%)

Mechanisms of injury vary widely by age
—> Increased number of sports injuries in teenage males

Question 4

Paediatric TBI in HK

Answer 4

Incidence: 1.7 per 1000
Overall mortality: 0.6%

Major cause:

1. Fall at home (infants, school children)
2. Traffic-related accidents (older children)

Question 5

Mechanism of brain trauma

Answer 5

1. Primary damage
   - direct focal impact due to sudden acceleration / deceleration within cranium
2. Secondary injury
   - alteration in cerebral blood flow
   - alteration in ICP

Question 6

Sequelae of TBI

Answer 6

• Highly variable
• Depends on affected neuroanatomy and functional impairment
• Vast majority mild in severity
• 2% with persisting / lifelong disability —> significant personal, financial, social consequences

Question 7

Importance of proper initial management

Answer 7

Prevent secondary injury from complications of brain injury
—> Significantly improve mortality and morbidity
—> Reduce hospital stay
—> Reduce health care costs

Question 8

***Role of neuroimaging in TBI

Answer 8

1. Acute setting
   - Determine **presence + extent of injury —> Identify cerebral / cranial problems
   - Determine **severity + ***operability
   - Inform surgical planning
   —> provide anatomical localisation and navigation information
   —> determine extracranial landmarks to help plan skin incision
   —> guiding placement of burr holes when necessary
2. Chronic setting
   - Identify chronic **sequelae
   - Provide important **prognostic indicators
   - Guide **rehabilitation
   - Help to decide **aggressiveness of treatment

Question 9

Role of plain skull XR

Answer 9

• very low diagnostic value
• generally do not give any additional informational that would lead to treatment changes
• Skull fracture -ve:
  —> very low risk of Intracranial haematoma that requires neurosurgical intervention
• Skull fracture +ve:
  —> present in ~5% of skull XR in mild TBI (doesn’t mean surgery in 97% of patients)
• Many researchers recommend abandoning plain XR of head in diagnosing traumatic injuries (e.g. Royal College of Radiologists)

Question 10

***Benefits of conventional CT vs MRI

Answer 10

• More ***available
• Requires ***shorter imaging time
• ***Easier to perform on patients who are agitated / ventilator support / in traction
• Superior in evaluating bones and detecting ***acute subarachnoid / acute parenchymal haemorrhage
• Initial imaging modality of choice during first 24 hours after injury

Question 11

***Common abnormalities finding on CT in TBI

Answer 11

1. Fracture
2. Epidural haemorrhage
3. Subdural haemorrhage
4. Contusion
5. Multiple lesions
6. Subarachnoid haemorrhage

Question 12

***Problems of routine neuroimaging in TBI

Answer 12

1. Not all head trauma patients require neuroimaging
   - <10% minor head injuries have positive findings on CT
   - <1% require neurosurgical intervention
2. Costly
   - opportunity cost of scanner time may be used for patients with other indications

—> Importance of proper identification of small number of patients that would benefit from neuroimaging

Question 13

Defensive medical practice

Answer 13

• Tests and procedures primarily driven by fear of malpractice liability rather than medical indications
• Choosing an aggressive patient management styles even though conservative management was considered medially acceptable by experts
• Varies considerably across clinical situations
• A/E department are most at risk due to quick pace, lack of patient-physician relationship, and patient expectations and demands

Question 14

Potential consequences and Solutions of Defensive medical practice

Answer 14

Potential consequences:

• Costly to health care system
• Unnecessary additional health risks (radiation, contrast, invasive procedures)
• Emotional / stress issues

Solution:
- Use of Evidence-based medicine to inform hospital polices and procedures

Question 15

***Indications for CT in patients with minor head injury

Answer 15

• Previous study: 520 patients with minor head injury —> 36 (6.9%) had positive scans
• ***ALL patients with positive CT have >=1 of following:
  1. Headache
  2. Vomiting
  3. >60 yo
  4. Drug / alcohol intoxication
  5. Deficits in short-term memory
  6. Physical evidence of trauma above clavicles
  7. Seizure
• ALL patients who require operative intervention had >= 1 above risk factors
• CT abnormalities in no-risk-factor group were not clinically significant

Question 16

***Criteria for need of imaging in Minor head injury

Answer 16

1. ***New Orleans criteria
   - apply to those with GCS score 15 (normal)
   - 7 clinical / historical finding which calls for CT after TBI
   記: 阿伯醉左, 頭痛, 嘔, 斷片, 斷鎖骨, 發羊吊
   —> Headache
   —> Vomiting
   —> >60 yo
   —> Drug / alcohol intoxication
   —> Persistent anterograde amnesia (deficits in short-term memory)
   —> Visible trauma above clavicle
   —> Seizure
2. ***Canadian Head CT rules
   - CT required for minor head injury when any one of the following described:
   記: 混亂, 失憶, 13分昏迷
   —> GCS 13/15
   —> Witnessed loss of consciousness
   —> Amnesia
   —> Confusion

• High risk for neurosurgical intervention exists when:
  —> >=65 yo
  —> >=2 episodes of vomiting
  —> GCS <15 two hours after head injury
  —> Suspected open / depressed skull fracture
  —> Signs of **basal skull fracture (haemotympanum, **Raccoon eyes, **CSF otorrhea, **CSF rhinorrhea, ***Battle’s sign)
• Medium risk for brain imaging detection by CT imaging
  —> Amnesia before impact for >= 30 mins
  —> Dangerous mechanism of head impact (pedestrians struck by vehicle, occupant ejected from vehicle, fall from >3 feet / 5 stairs)

—> neither is completely foolproof but is still very useful in guiding clinical decisions

Question 17

Minor vs Major head injuries

Answer 17

Depends on GCS score + Duration of post-traumatic amnesia
Mild: 13-15, <24 hours
Moderate: 9-12, 1-6 days
Severe: 3-8, >= 7 days

However it is difficult to define

Major head injuries (always require imaging):

• worsening level of consciousness (GCS 3-8)
• loss of consciousness for >= 5 mins
• failure of mental status to improve over time
• seizure
• penetrating skull injuries
• focal neurological findings
• signs of basal / depressed skull fracture
• confusion / aggression on examination

Question 18

Amnesia

Answer 18

Included in both New Orleans criteria + Canadian CT head rules

• although transient amnesia is common after mild thread injury
• **longer / more severe amnesic episodes imply greater chance of **haemorrhage
• amnesia lasting >= 30 mins is associated with ***Bilateral cerebral hypoperfusion

Question 19

Vomiting and headache

Answer 19

New Orleans criteria:
- ALL TBI patients with head / vomiting should be imaged

Canadian CT head rules:
- >= 2 episodes of vomiting is considered as high risk factor requiring neurosurgical intervention

However, some study suggested that presence of headache / vomiting were NOT predictive of intracranial haemorrhage in paediatric population

Question 20

Ethanol / Drug intoxication

Answer 20

In New Orleans criteria

Up to 8% ethanol intoxicated patients may had intracerebral injury

1. impaired sensoria and judgment increased likelihood of ***severe mechanisms of injuries
2. ***brain atrophy in chronic abuser increased susceptibility to insult
3. alcohol / drugs of abuse may ***potentiate effect of TBI on neurons / vasculature

Question 21

Age (>60 and infants)

Answer 21

New Orleans criteria
- ALL >60 should be imaged

Canadian CT head rules
- ALL >65 is at high risk for needing neurosurgical intervention

• High incidence of intracranial injuries among infants who have no signs / symptoms
  —> imaging should be pursued more aggressively in ***younger children

Question 22

Anticoagulation / Coagulopathies

Answer 22

• Not well-established if they should affect decision to imaging
• 1 study showed that patients with abnormal clotting studies more likely to have delayed brain injury on CT

Question 23

***Basal skull fracture

Answer 23

4 important signs:

1. ***Haemotympanum (blood in middle ear)
2. **Raccoon eyes (periorbital ecchymosis, skull fracture at **anterior cranial fossa)
3. ***CSF otorrhea / rhinorrhea
4. **Battle’s sign (ecchymosis over mastoid process as a result of extravasation of blood along posterior auricular artery, takes 1 day to develop after injury, fracture at **middle cranial fossa)

Question 24

***Limitations of conventional CT

Answer 24

1. CT findings may **lag behind actual intracranial damage
   - examinations performed within 3 hours of trauma may underestimate injury —> **repeat imaging
2. CT missed approximately 10-20% of abnormalities seen on MRI
   - **image quality issue due to displacement of CT signals near metal objects, bone, calcifications
   - can **miss small amounts of blood that occupy ***widths less than a slice of CT cut because of volume averaging

Question 25

Benefit of MRI vs CT

Answer 25

Superior choice to CT ***48-72 hours after injury

• **Greater sensitivity in subacute / chronic settings
• Ability to detect ***haematomas improves over time as composition of blood changes
• Superior to CT in detecting **axonal injury, **small areas of contusion, subtle neuronal damage
• Better at imaging ***brainstem, basal ganglia, thalamus

Question 26

Cranial CT for mild TBI in China

Answer 26

• No existing criteria for selecting mild TBI to CT

- almost all TBI patients undergo cranial CT in A/E department

Question 27

Summary

Answer 27

• Most TBI are mild and not associated with chronic sequelae
• Indiscriminate use of CT when not clinically indicated are costly and with associated harm
• Careful identification of patients who may benefit from early CT is important