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Pandor A, Goodacre S, Harnan S, et al. Diagnostic Management Strategies for Adults and Children with Minor Head Injury: A Systematic Review and an Economic Evaluation. Southampton (UK): NIHR Journals Library; 2011 Aug. (Health Technology Assessment, No. 15.27.)

Cover of Diagnostic Management Strategies for Adults and Children with Minor Head Injury: A Systematic Review and an Economic Evaluation

Diagnostic Management Strategies for Adults and Children with Minor Head Injury: A Systematic Review and an Economic Evaluation.

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1Background

Description of health problem

Head injuries account for over 700,000 emergency department (ED) attendances every year in England and Wales1 (with about 20% of head-injured patients being admitted to hospital for further assessment and treatment),2 and are responsible for a significant proportion of the ED workload. In the UK, 70–88% of all people who sustain a head injury are male, 10–19% are aged ≥ 65 years and 40–50% are children.1 The severity of head injury is directly related to the mechanism and cause.2 Most minor head injuries (MHIs) in the UK result from falls (22–43%), assault (30–50%) or road traffic accidents (25%).1 Alcohol may also be involved in up to 65% of adult head injuries. Motor vehicle accidents (MVAs) account for most fatal and severe head injuries.3 There are, however, marked variations in aetiology across the UK, particularly by age, gender, area of residence and socioeconomic status.35

Injury severity can be classified according to the patient's consciousness level, as measured on the Glasgow Coma Scale (GCS) when they present to the emergency care services. Most patients (90%) present with a minor injury (GCS 13–15), whereas 10% present with either moderate (GCS 9–12) or severe (GCS 3–8) head injury.6 Patients with a MHI are conscious and responsive, but may be confused or drowsy. Initial management of MHI may involve identification and treatment of other injuries, or first aid for scalp bruising or bleeding, but MHIs are typically isolated so initial treatment is limited to analgesia and reassurance.

The main challenge in the management of MHI is identification of the minority of patients with significant intracranial injury (ICI), especially those who require urgent neurosurgery. Head injury can result in a range of intracranial lesions, including extradural or subdural haematoma, subarachnoid haemorrhage, cerebral contusion or intracerebral haematoma. Although patients with intracranial lesions often present with moderate or severe head injury according to their GCS, some present with apparently MHI. Subsequent progression of the intracranial lesion can result in a decreasing consciousness level, brain damage, disability and even death.

Early identification of an intracranial lesion can reduce the risk of brain damage and death. First, some intracranial lesions (typically extradural haematoma) can rapidly expand if untreated, leading to raised intracranial pressure, brain damage and death. Emergency neurosurgery to evacuate the haematoma and relieve increased pressure can allow most patients to make a full recovery,711 whereas delayed neurosurgery is associated with poorer outcomes.11,12 Second, a proportion of patients with an ICI that does not require urgent neurosurgery (i.e. a non-neurosurgical injury, such as an intracerebral haematoma) will subsequently deteriorate and require critical care support and/or neurosurgery. These patients may have better outcomes if they are admitted to hospital and managed in an appropriate setting.13 We have defined the former group as having ‘neurosurgical’ injuries and the latter as having ‘non-neurosurgical’ injuries. However, it should be recognised that our definition is based upon the emergency treatment required rather than all subsequent treatment. Many patients with injuries that we define as having ‘non-neurosurgical’ injuries will benefit from general neurosurgical care and may require later neurosurgical interventions.

Outcome from head injury can be assessed using the Glasgow Outcome Score (GOS). The scale has the following categories:

  1. dead
  2. vegetative state – unresponsive and unable to interact with environment
  3. severe disability – able to follow commands, but unable to live independently
  4. moderate disability – able to live independently, but unable to return to work or school
  5. good recovery – able to return to work or school.

The scale has subsequently been extended to eight categories by subdividing the severe disability, moderate disability and good recovery categories into upper and lower divisions [known as the extended GOS (GOS-E)].

Most patients with MHI have no intracranial lesion (or at least no lesion detectable by currently used imaging modalities) and will make a good recovery, although post-traumatic symptoms, such as headaches, depression and difficulty concentrating, are relatively common and often underestimated. There is some evidence that early educational intervention can improve these symptoms,1417 but this does not rely upon initial diagnostic management. Most patients with a MHI and a neurosurgical or non-neurosurgical intracranial lesion will make a good recovery with appropriate timely treatment, although a significant proportion will suffer disability or die.711,18 Failure to provide appropriate timely treatment appears to be associated with a higher probability of disability or death.11,12

The incidence of death from head injury is estimated to be 6–10 per 100,000 population per annum.2 This low incidence is owing to most patients having MHI with no significant intracranial lesion and the good outcomes associated with ICI in patients presenting with MHI when treated appropriately. However, when death or disability does occur following MHI, it often affects young people and, therefore, results in a substantial loss of health utility and years of life. As such outcomes are potentially avoidable, clinicians typically have a low threshold for investigation.

Current service provision

Patients with MHI present to the ED, where a doctor or nurse practitioner will assess them and, if appropriate, arrange investigation. Clinical assessment may consist of an unstructured assessment of the patient history and examination or may use a structured assessment to combine features of the clinical history and examination in a clinical decision rule. Investigations include skull radiography and computerised tomography (CT) of the head. After assessment and investigation, patients may be discharged home, admitted to hospital for observation or referred for emergency neurosurgery. The aim of diagnostic management is to identify as many patients with ICI as possible (particularly those with neurosurgical injury), while avoiding unnecessary investigation or hospital admission for those with no significant ICI.

Guidelines for managing head injury in the NHS were drawn up by the National Institute for Health and Clinical Excellence (NICE) in 200319 and revised in 2007.1 These guidelines use clinical decision rules to determine which patients should receive CT scanning and which should be admitted to hospital. Similar guidelines from the Scottish Intercollegiate Guidelines Network (SIGN) are used in Scotland.20

The NICE guidelines were based upon a literature review and expert consensus. Cost-effectiveness analysis was not used to develop the guidelines, but was used to explore the potential impact on health service costs. The guidelines were expected to reduce the use of skull radiography, increase the use of CT scanning and reduce hospital admissions, thus reducing overall costs. Data from a number of studies have since confirmed that more CT scans and less skull radiography are being performed.2123 However, Hospital Episode Statistics (HES) for England show that the annual number of admissions for head injury increased from 114,769 in 2001–2 to 155,996 in 2006–7. As average length of stay remained relatively constant, bed-days increased from 348,032 in 2001–2 to 443,593 in 2006–7. Figure 1 shows that the increase in admissions has been seen in adults rather than in children.24

FIGURE 1. Head injury admissions in England, 1998–2007.

FIGURE 1

Head injury admissions in England, 1998–2007.

These data suggest that the annual costs of admission for head injury have increased from around £170M to £213M since the guidelines were introduced.

The increase in admissions could be indirectly due to the NICE guidance. If, for example, clinicians were ordering more CT scans, but lacked the ability to interpret them or access to a radiological opinion then this could result in more admissions. However, changes in NHS emergency care occurring around 2003 other than NICE guidance could have been responsible for the increase in admissions. For example, the introduction of a target limiting the time spent in the ED to 4 hours could have resulted in patients being admitted to hospital rather than undergoing prolonged assessment in the ED. Furthermore, a general trend away from surgical specialties and towards emergency physicians in the responsibility for MHI admissions may have changed the threshold for hospital admission.

Description of technology under assessment

Diagnostic strategies for MHI include clinical assessment, clinical decision rules, skull radiography, CT scanning and biochemical markers. Clinical assessment can be used to identify patients with an increased risk of ICI and select patients for imaging or admission. A recent meta-analysis of 35 studies reporting data from 83,636 adults with head injury25 found that severe headache (relative risk 2.44), nausea (2.16), vomiting (2.13), loss of consciousness (LOC) (2.29), amnesia (1.32), post-traumatic seizure (PTS) (3.24), old age (3.70), male gender (1.26), fall from a height (1.61), pedestrian crash victim (1.70), abnormal GCS (5.58), focal neurology (1.80) and evidence of alcohol intake (1.62) were all associated with intracranial bleeding. A similar analysis of 16 studies reporting data from 22,420 children with head injury25 found that focal neurology (9.43), LOC (2.23) and abnormal GCS (5.51) were associated with intracranial bleeding.

Clinical features have been combined in a number of studies to develop a structured clinical decision rule. Initially, clinical decision rules were developed to determine which patients should be admitted to hospital for observation. More recently, clinical decision rules have been developed to determine which patients should receive CT scanning. A systematic review undertaken for the NICE guidance19 identified four studies of four different clinical decision rules. The studies of the Canadian CT Head Rule (CCHR) criteria26 and the New Orleans Criteria (NOC) rule27 were both high quality, applicable to the NHS and reported 100% sensitivity for the need for neurosurgical intervention. Of the other two studies, one28 reported poor sensitivity and one29 was not applicable to the NHS. On this basis, the NICE guidance adapted the CCHR for use in the NHS and recommended this for adults and children, effectively as the NICE clinical decision rule.19 In 2007, the guidance was updated1 to recommend using a rule developed specifically for children – the Children's Head injury Algorithm for the prediction of Important Clinical Events (CHALICE) rule30 – although a modified version of the original rule continued to be recommended for adults.

Skull radiography can identify fractures that are associated with a substantially increased risk of intracranial bleeding, but cannot identify intracranial bleeding itself. Skull radiography is therefore used as a screening tool to select patients for investigation or admission, but not for definitive imaging. A meta-analysis31 found that skull fracture detected on a radiograph had a sensitivity of 38% and specificity of 95% for intracranial bleeding. More recent meta-analyses in adults25 and children32 reported relative risks of 4.08 and 6.13, respectively, for the association between skull fracture and intracranial bleeding. The NICE guidance only identifies a very limited role for skull radiography and use in the NHS has decreased accordingly.2123

Computerised tomography scanning definitively shows significant bleeding and a normal CT scan effectively excludes a significant bleed at the time of scanning. Magnetic resonance imaging (MRI) can detect some lesions that are not evident on CT,33 but arguably none that is of clinical importance and certainly none that influences early management. CT can therefore be considered as a reference standard investigation for detecting injuries of immediate clinical importance. Liberal use of CT scanning will minimise the risk of missed ICI. However, this has to be balanced against the cost of performing large numbers of CT scans on patients with no ICI and the potential for harm from radiation exposure, particularly in children.

Hospital admission and observation may be used to identify intracranial bleeding by monitoring the patient for neurological deterioration. Although commonly used in the past, the effectiveness of this approach has not been studied extensively and has the disadvantage that neurosurgical intervention is delayed until after patient deterioration has occurred. Hospital admission and observation are usually used selectively, based upon clinical assessment or skull radiography findings. As with CT scanning, the use of hospital admission involves a trade-off between the benefits of early identification of patients who deteriorate owing to ICI and the costs of hospital admission for patients with no significant ICI.

Studies have compared CT-based strategies to skull radiography and/or admission to conclude that CT-based strategies are more likely to detect intracranial bleeding and less likely to require hospital admission.34,35 Both cost analyses based upon randomised controlled trial (RCT) data36 and economic modelling37 suggest that a CT-based strategy is cheaper. However, admission-based strategies may be an inappropriate comparator for cost-effectiveness analyses because they appear to be expensive and of limited effectiveness, particularly if applied unselectively.

More recently, the role of biochemical markers for the identification of brain injury has been investigated. The focus of these research efforts has been on a rule-out test, of high sensitivity and negative predictive value, such that patients with a negative test can be discharged without the radiation exposure associated with CT scanning. The most widely researched biomarker is the astroglial cell S100 calcium-binding protein beta subunit (S100B). Although it has been identified in non-head-injured patients,38 following isolated head injury a measurable concentration less than the currently used cut-off of 0.1 μg/l measured within 4 hours of injury39 has been linked to negative CT scans with a sensitivity of 96.8% and specificity of 42.5%. So far, inconsistency of sensitivity and specificity results has limited its widespread application. The question of clinical applicability and cost-effectiveness has also yet to be addressed adequately. Other biochemical markers, such as neuron-specific enolase (NSE), dopamine and adrenaline, have been studied but less extensively and without validation or consistent results, rendering it impossible to draw any evidence-based conclusions about their utilisation.

© 2011, Crown Copyright.

Included under terms of UK Non-commercial Government License.

Bookshelf ID: NBK100019
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