HNS58 To CT Or Not To CT In Traumatic Head Injury Flashcards
Traumatic brain injury
- 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
Age, Gender, TBI of Paediatric TBI (1-15 yo)
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)
Common causes of TBI in children
Preventable causes:
- Falls at home (39%)
- Motor vehicle accidents (11%)
- Unknown causes (5%)
- Assault (4%)
Mechanisms of injury vary widely by age
—> Increased number of sports injuries in teenage males
Paediatric TBI in HK
Incidence: 1.7 per 1000
Overall mortality: 0.6%
Major cause:
- Fall at home (infants, school children)
- Traffic-related accidents (older children)
Mechanism of brain trauma
- Primary damage
- direct focal impact due to sudden acceleration / deceleration within cranium - Secondary injury
- alteration in cerebral blood flow
- alteration in ICP
Sequelae of TBI
- Highly variable
- Depends on affected neuroanatomy and functional impairment
- Vast majority mild in severity
- 2% with persisting / lifelong disability —> significant personal, financial, social consequences
Importance of proper initial management
Prevent secondary injury from complications of brain injury
—> Significantly improve mortality and morbidity
—> Reduce hospital stay
—> Reduce health care costs
***Role of neuroimaging in TBI
- 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 - Chronic setting
- Identify chronic **sequelae
- Provide important **prognostic indicators
- Guide **rehabilitation
- Help to decide **aggressiveness of treatment
Role of plain skull XR
- 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)
***Benefits of conventional CT vs MRI
- 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
***Common abnormalities finding on CT in TBI
- Fracture
- Epidural haemorrhage
- Subdural haemorrhage
- Contusion
- Multiple lesions
- Subarachnoid haemorrhage
***Problems of routine neuroimaging in TBI
- Not all head trauma patients require neuroimaging
- <10% minor head injuries have positive findings on CT
- <1% require neurosurgical intervention - 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
Defensive medical practice
- 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
Potential consequences and Solutions of Defensive medical practice
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
***Indications for CT in patients with minor head injury
- 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
***Criteria for need of imaging in Minor head injury
- ***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 - ***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
Minor vs Major head injuries
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
Amnesia
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
Vomiting and headache
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
Ethanol / Drug intoxication
In New Orleans criteria
Up to 8% ethanol intoxicated patients may had intracerebral injury
- impaired sensoria and judgment increased likelihood of ***severe mechanisms of injuries
- ***brain atrophy in chronic abuser increased susceptibility to insult
- alcohol / drugs of abuse may ***potentiate effect of TBI on neurons / vasculature
Age (>60 and infants)
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
Anticoagulation / Coagulopathies
- 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
***Basal skull fracture
4 important signs:
- ***Haemotympanum (blood in middle ear)
- **Raccoon eyes (periorbital ecchymosis, skull fracture at **anterior cranial fossa)
- ***CSF otorrhea / rhinorrhea
- **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)
***Limitations of conventional CT
- CT findings may **lag behind actual intracranial damage
- examinations performed within 3 hours of trauma may underestimate injury —> **repeat imaging - 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
Benefit of MRI vs CT
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
Cranial CT for mild TBI in China
- No existing criteria for selecting mild TBI to CT
- almost all TBI patients undergo cranial CT in A/E department
Summary
- 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
