HEAD CT DECISION RULES – WHO TO SCAN? EMC SDMH 2015

Objectives Understand rationale for developing and using a clinical decision rule for Head CT Compare Adult Head CT rules – Canadian CT head Rule; New Orleans Criteria; NEXUS II Compare Paediatric Head CT rules – CHALICE PECARN

MINOR HEAD inJURY Defined as presenting GCS 14-15 Incidence of ‘clinically important’ brain injury ~ 1% Incidence of abnormal head CT ~ 5- 6% Neither ethical nor cost effective to scan everyone US CT rates up to 80% of minor head injury! Rules need to ensure patients are not missed (i.e have high sensitivity) High sensitivity rules generally NOT specific by definition

COMMON HEAD CT RULES CANADIAN CT HEAD RULE NEW ORLEANS CRITERIA NEXUS II Evidence skull # Scalp haematoma Neurological deficit Recurrent vomiting Age > 65 Altered level of alertness Abnormal behaviour GCS < 15 at 2 hrs after injury Suspected open/depressed skull # Signs of basal skull # Vomiting > 1 episode Age > 65 Retrograde amnesia >30 mins Dangerous mechanism Excluded patients on warfarin; abnormal neurological findings, and those with seizures (scanned) Headache Seizure Visible trauma above the clavicles Vomiting Age > 60 Persistent anterograde amnesia Intoxication

HOW Do ThEY PERFORM CCHR and NOC – 99-100% sensitive NEXUS II 97% sensitive CCHR more specific (40-50%) than NOC (12%) and NEXUS (47%) CCHR reduced need for CT by 48% vs NOC (12%) Canadian authors believed introduction of NOC would have increased their baseline scanning rate!

CuRRENT PRACTICE NSW State guideline Increase sensitivity by summing all identified risk factors ?specificity

Paediatric Head CT rules Paediatric assessment potentially more difficult Non-verbal, or poor localisation Minor head injuries common in toddlers! High level of parental anxiety Risk of TBI low however PECARN series – abnormal CT 5.2%, ciTBI 0.9% CHALICE series – abnormal CT 1.2% ciTBI 0.6% Risks from radiation higher than in adults Poorer educational performance Estimated additional risk malignancy 1:1500 in 1 yr old

CHALICE – ‘High Risk’ Criteria MECHANISM AND HISTORY EXAM High speed MVA > 64km/hr Fall >3m High speed impact LoC >5 min Amnesia > 5 min Abnormal drowsiness 3 or more vomits Suspicion of NAI Seizure in non-epileptic GCS <14, or <15 if under 1yr age Suspicion of skull fracture Tense fontanelle Positive focal neurology Bruise swelling or laceration >5cm if <1 yr of age  ANY feature positive treated as indication for CT

PECARN – ‘low risk’ criteria PECARN - <2 yrs old PECARN - >2 yrs old GCS < 15 Altered Mental status Palpable skull fracture CT Head (4.4% risk ciTBI) Non-frontal scalp haematoma LoC > 5s Severe mechanism Car vs pedestrian/bike Fall>1m Head struck by high speed impact Abnormal behaviour per parents  Observe or CT Head (0.9% risk of ciTBI) GCS < 15 Altered mental status Signs of basilar skull fracture CT Head (4.3% risk ciTBI) History of vomiting (>1) LoC Severe mechanism Car vs pedestrian/bike Fall >2 m Head struck by high speed impact Severe headache Observe or CT Head (0.9% risk of ciTBI)

CHALICE VS PECARN Rule –in rule vs Rule-out rule. PECARN only rule externally validated in literature Would you scan a 2 yr old on CHALICE criteria? Recent study at Tertiary Childrens Hospital Australia 19% CT scan rate – 1.4% ciTBI (intervention) CHALICE predicted 46% scan rate (303 children not scanned) – 4 missed positive scans, none requiring intervention. PECARN 100% sensitive, 100% NPV for <2 PECARN 96.8% sensitive, 99.95% NPV for ciTBI >2 CHALICE 98% sensitive, 87% specific in trial (but not validated)

Questions?

SUMMARY Head CT needs to balance risk vs benefit and resource utilization All current Head CT clinical decision rules seem to offer good sensitivity Canadian Head CT rule currently appears to be best clinical decision rule in adults in terms of specificity and efficient resource use PECARN appears to have strongest evidence for utility in ED for pediatric use, but rules not directly comparable Be aware that NSW guidelines tend to be summative of existing rules