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Axioms In EM

Does Every Minor Head Injury Need a CT Scan?

Peters, Michelle C. MD

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Dr. Peters is a third-year resident in the Emergency Medicine Residency Program at the Drexel University College of Medicine. The residency is one of the oldest emergency medicine programs in the country, training 48 residents at five clinical sites. Further information can be obtained from Richard Hamilton, MD, Program Director, Emergency Medicine Residency Program, Drexel University College of Medicine, 3300 Henry Ave., Philadelphia, PA 19129 or by visiting to the departmental web page at www.mcphu.edu/medschool/depts/em/index.htm.

Some physical findings suggest the need for a scan, but a more definitive maxim may be forthcoming in NEXUS II

In the United States, more than 1.1 million patients seek emergency department evaluation for acute head injury each year. The highest rates occur in children under 5 and adults 85 and older. Head injury can be subclassified into mild, moderate, and severe depending on the Glascow Coma Scale (GCS).

Eighty percent of head-injured patients sustain minor head trauma with a GCS of 14 to 15, 10 percent have moderate head injury with a GCS of 9 to 13, and 10 percent have severe head trauma with a GCS of 8 or less. Of all those evaluated for head trauma, nearly 20 percent are hospitalized and approximately 200,000 die or suffer permanent disability because of their injuries. Approximately 50,000 patients with severe head injury die prior to ever reaching the emergency department.1 In light of these statistics, it is imperative that emergency physicians know how to deal with all types of head-injured patients.

Since the advent of head CT in the 1970s, head trauma patients have been getting scans. Controversy continues, however, over which head trauma patients require CT in the emergency department. The debate is driven by the importance of immediately identifying any patient with a potentially fatal injury vs. the need to control the ever-rising cost of emergency medical care. It is clear that all individuals who sustain major and moderate head trauma need further evaluation with head CT, but experts debate the need for head CT in the minor head trauma patient.

Over the past decade, numerous studies have looked at the utility of head CT in the patient with a minor head injury. Mohanty et al performed a retrospective analysis of 348 adult patients 18 years and older. The criteria for inclusion were GCS of 14 or 15, no decline in neurological status during the first 20 minutes after arrival, absence of any focal, sensory, or motor neurological deficit, absence of the obvious clinical signs of basal skull fracture (e.g., blood in the ears, Battle's sign, and rhinorrhea), and a history of loss of consciousness (LOC). Of the 348 patients studied, there were 12 patients who had abnormal CT scans; however, none developed a new neurological or anatomic extension of the initial CT findings.2

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LOC or Amnesia

Miller et al prospectively studied 1,382 patients of all ages who presented to an urban university Level I trauma center with a GCS of 15 after LOC or amnesia to the event. Of these patients, 84 (6.1%) had abnormal CT findings. The patients with abnormal CT findings were significantly more likely to have signs of head trauma (laceration, contusion, swelling) or nausea or vomiting. Slightly more than half of all the patients in this study (789 or 57%) underwent CT of the head solely based on LOC/amnesia. None of these patients had any of the symptoms studied or physical evidence of a depressed skull fracture.

Of these 789 patients, only 24 (3%) had abnormal CT results, and no patient required medical or surgical interventions.3

Haydel et al conducted a two-phase study. In the first phase, they evaluated 520 patients as a derivation set to determine which clinical features predicted a brain injury as detected on CT scan. Minor head injury was defined as loss of consciousness in patients with normal findings on a brief neurologic examination (normal cranial nerves and normal strength and sensation in the arms and legs) and a score of 15 on the Glasgow Coma Scale, as determined by a physician on the patient's arrival at the emergency department.

Patients were considered to have lost consciousness if a witness or the patient reported loss of consciousness or if the patient could not remember the traumatic event. Patients with isolated deficits in short-term memory and an otherwise normal score on the Glasgow Coma Scale were considered to have a normal score on the scale. All patients included in the study underwent CT scanning. The patients who declined CT, had concurrent injuries that precluded the use of CT, or reported no loss of consciousness or amnesia for the traumatic event were excluded from the study.

Of the 520 patients in the first phase, 36 (6.9%) had positive scans. All patients with positive CT scans had one or more of seven findings:

1. Headache (defined as any head pain, diffuse or local).

2. Vomiting.

3. Over age 60.

4. Drug or alcohol intoxication.

5. Deficits in short-term memory.

6. Physical evidence of trauma above the clavicles (any external evidence of injury, including contusions, abrasions, lacerations, deformities, and signs of facial or skull fracture)

7. Seizure.

Of these criteria, three clinical findings (deficits in short-term memory, drug or alcohol intoxication, and physical evidence of trauma above the clavicles) were significantly associated with a positive CT scan. If patients without the combination of these three findings had not undergone CT scanning, the number of scans would have been reduced by 31 percent, although abnormalities would have been missed in two additional patients for an overall sensitivity of 94 percent.

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Predictive Value

In the second phase of the study, the seven criteria were used on 909 subsequent patients, of which 57 (6.3%) had positive scans. All patients with a positive CT scan had at least one of the seven clinical criteria. In addition, there were 212 patients in whom none of the findings was present, and all these had negative scans. The presence of all seven findings had a sensitivity of 100 percent (95% confidence interval, 95–100%) for identifying patients with positive CT scans.

The absence of all seven findings had a negative predictive value of 100%. Application of these criteria would have reduced the use of CT by 22 percent. Of the 1429 patients in phases 1 and 2 combined, 93 had positive CT scans. Cerebral contusions and subdural hematomas were the most common injuries, findings consistent with the results of other studies. Only six patients (0.4%) underwent neurosurgery, which is consistent with the results of other studies.

One limitation of this study is the lack of follow-up. It is possible that some patients with a negative CT scan had their scans misread or developed problems at a later date, including intracranial bleeding. Nonetheless, most studies have concluded that patients with minor head trauma and normal findings on both neurologic examination and CT scanning can be safely discharged from the emergency department.4

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NEXUS II

Perhaps a more conclusive answer will be elucidated in the National Emergency X-Radiography Utilization Study II (Nexus II). This is a multicenter, prospective, observational study of ED patients with blunt trauma designed to derive a decision rule for CT imaging of patients with blunt head trauma. This study, conducted in 21 different emergency departments across the United States and Canada, will enroll more than 10 times as many patients with head trauma as any currently published study. It should be able to answer definitively questions about the validity and reliability of clinical criteria as a preliminary screen for blunt head trauma.5

Minor head trauma is an extremely common entity seen in most emergency departments, yet the recommendations on the care of these patients vary greatly. Many trauma centers elect to scan all patients with LOC or amnesia after head trauma. This can be a very time-consuming and costly practice. The above studies have shown that not all patients with minor head trauma require head CT because very few will have intracranial pathology, and fewer still will require neurosurgical or medical intervention.

Most practitioners would like to be sure to detect all intracranial injuries, even if only for diagnostic purposes. It is possible to reduce the number of CT scans by one-quarter by limiting them to patients with minor head injury with LOC or amnesia and the seven clinical findings in the Haydel study (see chart).

In all other patients, it seems safe to forego head CT in patients with minor head trauma, even if they have had a loss of consciousness or amnesia. According to one estimate, even a 10 percent reduction in the number of CT scans in patients with minor head injury would save more than $20 million per year.6 For the moment, while it is not axiomatic that every minor head injury needs a CT scan, a more definitive maxim may be forthcoming in NEXUS II.

Axioms in Emergency Medicine is written specifically for emergency medicine residents to dispel myths and misconceptions about different clinical entities. The column is written each month by a resident from the Emergency Medicine Residency Program at MCP Hahnemann School of Medicine in Philadelphia.

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References

1. Marx JA, et al. Rosen's Emergency Medicine Concepts and Clinical Practice. Fifth Edition, Mosby, St. Louis, MO 2002, pp 298–299.

2. Mohanty SK, Thompson W, Rakower S. Are CT scans for head injury patients always necessary? J Trauma 1991;31:801.

3. Miller EC, Derlet RW, Kinser D. Minor head trauma: Is computed tomography always necessary? Ann Emerg Med 1996;27:290.

4. Haydel MF, Preston CA, Mills TJ, Luber S, Blaudeau E, DeBlieux P. Indications for computed tomography in patients with minor head injury. N Engl J Med 2000;343:100.

5. Mower WR, Hoffman JR, et al. Developing a clinical decision instrument to rule out intracranial injuries in patients with minor head trauma: Methodology of the NEXUS II investigation. Ann Emerg Med 2002;40:505.

6. Remus WR, Wippold FJ II, Erickson DD. Practical selection criteria for noncontrast cranial computed tomography in patients with head trauma. Ann Emerg Med 1993;22:148.

© 2003 Lippincott Williams & Wilkins, Inc.

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