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Three Part Question

In [patients presenting to acute care with delayed (>24hrs post injury) mild head injury], when should a [CT head scan] be performed to detect [clinically significant pathology]?

Clinical Scenario

A 30-year-old, normally fit and well man presents with a headache, 36hrs after hitting his head when falling off his ladder. He did not lose consciousness at the time of injury, but now has a bad headache. He has a normal neurological exam. This fits the criteria for a mild head injury according the WHO head injury score. You know that current NICE guidance on imaging in head injuries has only been validated in populations of patients presenting within 24 hours. You wonder if you should request a CT head scan for this patient to look for possible traumatic intracranial pathology.

Search Strategy

Embase (1974 to 2022 June 23)
Ovid MEDLINE(R) ALL (1946 to June 23, 2022)
Cochrane database of systematic reviews (Issue 6 of 12, June 2022):

1 Tomography, X-Ray Computed/ or CT head.mp.
2 head injury.mp. or exp Craniocerebral Trauma/
3 delayed presentation.mp. or Delayed Diagnosis/
4 1 and 2 and 3

Search Outcome

69 papers were identified using the OVID interface (MEDLINE and EMBASE), and 88 papers using Cochrane Library.
Of these, 3x were flagged as being relevant, 2x of which were included in the systematic review by Maricowitz et al, and so not listed below.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Marincowitz et al. 2016 UK	650 adult patients received CT head scans looking for head trauma. 101 (15.5%) presented >24hrs since injury.	Retrospective cohort study	Whether there was a significant traumatic intracranial finding on CT.	Presenting <24hrs: 8.4%. Presenting >24hrs: 9.9%	Single centre, small study (101 CT head scans in patients presenting over 24hrs from injury), retrospective series. Potential for recall bias in patients presenting late. Some patients who did not have CT scans, may have had serious intracranial abnormalities that were missed as they did not re-present to the hospital and so were under-represented in the analysis.
			Whether there was a NICE indication for a CT head scan.	Presenting <24hrs: No indication in 13.7%. Presenting >24hrs: No indication in 28.6%.
			Sensitivity of NICE guidelines for predicting intracranial injury on CT head scan.	Presenting <24hrs: 98% (95% CI 87.0% to 99.9%). Presenting >24hrs: 70% (95% CI 35.4% to 91.9%)
Marincowitz et al. 2015 UK	3x research papers: - 1x retrospective observational (UK) - 1x retrospective observational (USA) - Case series (USA, abstract only)	Systematic review	Percentage of CT head scans in which clinically significant pathology was identified in patients presenting late.	2.21%, 3.1% and 6.8%	Meta-analysis not possible due to low number and heterogeneity of identified studies.

Comment(s)

The current evidence agrees that clinically significant pathology is often picked up on CT head scans of patients who present in a delayed fashion, defined as >24hrs following head injury. However, one recent study by Marincowitz et al. highlighted that the strict application of current NICE guidelines to this population of patients risked both over-investigation, or conversely, missing clinically significant intracranial injuries (30% of the cohort in the study). There is a lack of evidence to support decision models in the population of delayed head injury presentations. Both papers included in this BestBET are written by the same author. More research is needed to understand these presentations and to identify the risk factors that might predict clinically significant intracranial pathology in this group.

Clinical Bottom Line

In patients presenting in a delayed fashion (>24hours) following a mild head injury, strict adherence to the current NICE guidelines risks missing clinically significant intracranial injuries. There is an absence of published evidence on risk factors for injury in this delayed presentation population, and so the three part question can not be answered fully at this time. Local guidance is recommended.

References

1. Carl Marincowitz, Victoria Allgar, William Townend CT head imaging in patients with head injury who present after 24 h of injury: a retrospective cohort study Emergency Medicine Journal 2016; 33:538–542
2. Carl Marincowitz, Christopher Smith and William Townend The risk of intra-cranial haemorrhage in those presenting late to the ED following a head injury: a systematic review Systematic Reviews 2015; 4:165