The canadian CT head rule study for patients with minor head injury: Rationale, objectives, and methodology for phase I (derivation)

Abstract

Head injuries are among the most common types of trauma seen in North American emergency departments, with an estimated 1 million cases seen annually. “Minor” head injury (sometimes known as “mild”) is defined by a history of loss of consciousness, amnesia, or disorientation in a patient who is conscious and talking, that is, with a Glasgow Coma Scale score of 13 to 15. Although most patients with minor head injury can be discharged without sequelae after a period of observation, in a small proportion, their neurologic condition deteriorates and requires neurosurgical intervention for intracranial hematoma. The objective of the Canadian CT Head Rule Study is to develop an accurate and reliable decision rule for the use of computed tomography (CT) in patients with minor head injury. Such a decision rule would allow physicians to be more selective in their use of CT without compromising care of patients with minor head injury. This paper describes in detail the rationale, objectives, and methodology for Phase I of the study in which the decision rule was derived. [Stiell IG, Lesiuk H, Wells GA, McKnight RD, Brison R, Clement C, Eisenhauer MA, Greenberg GH, MacPhail I, Reardon M, Worthington J, Verbeek R, Rowe B, Cass D, Dreyer J, Holroyd B, Morrison L, Schull M, Laupacis A, for the Canadian CT Head and C-Spine Study Group. The Canadian CT Head Rule Study for patients with minor head injury: rationale, objectives, and methodology for phase I (derivation). Ann Emerg Med. August 2001;38:160-169.]

Introduction

Head injuries are among the most common types of trauma seen in North American emergency departments with an estimated 1 million cases seen annually.¹ Some of these patients die or suffer serious morbidity requiring months of hospitalization and rehabilitation. Many others, however, are classified as having a “minimal” or “minor” head injury. Patients with “minimal” head injury have not experienced loss of consciousness or amnesia and rarely require admission to hospital. “Minor” head injury (sometimes known as “mild”) is defined by a history of loss of consciousness, amnesia, or disorientation in a patient who is conscious and talking (ie, with a Glasgow Coma Scale [GCS]² score of 13 to 15.³ A typical review of head injury patients admitted to a neurosurgical service found that 5% of cases were “severe” (GCS score <8), 11% were “moderate” (GCS score 8 to 12), and 84% were “minor” (GCS score 13 to 15).⁴

Although most patients with minor head injury can be discharged without sequelae after a period of observation, in a small proportion of patients, their neurologic condition deteriorates and requires neurosurgical intervention for intracranial hematoma.5, 6, 7, 8 Neurosurgeons and emergency physicians alike are well aware of the phenomenon of patients who “talk and deteriorate” and that the key to saving these patients is early diagnosis of intracranial hematoma followed by early surgery.⁹ During the 1970s, it became apparent that excess mortality and delayed diagnosis could be reduced in head injury by early use of computed tomography (CT).5, 6, 8 At the same time, plain skull radiography has been discouraged because of its very low yield in minor head injury and because of the greater utility of CT in moderate and severe head injury.¹⁰

In recent years, the use of CT for minor head injury¹¹ has become increasingly common, particularly in North America. In 1992, an estimated 270,000 CT scans of the head were performed in US EDs for head injury.¹² Typical US hospital charges for unenhanced CT range from US$500 to US$800, suggesting a national total cost of US$135 million to US$216 million. The US yield of CT for intracranial lesions in minor head injury has been estimated to be from 0.7% to 3.7%.4, 13, 14, 15, 16 Conversely, 96.3% to 99.3% of CT scans performed in the United States for patients with minor head injury would be expected to be normal and therefore to not alter management. More selective use of this expensive high-technology investigation for patients with minor head injury could lead to significant reductions in North American health care costs.

There is, however, considerable disagreement in the literature as to the indications for CT in the large number of head trauma cases classified as “minor.”17, 18 In North America, opinions are divided into 3 groups. The first, composed primarily of neurosurgeons, believe that CT scanning is indicated for all patients with minor head injury.3, 18, 19, 20, 21, 22, 23, 24, 25, 26 Stein and Ross,²¹ who are both US neurosurgeons, have recently written, “We recommend routine and immediate cranial CT scanning of all head injury patients who have lost consciousness or are amnestic, even if all other physical findings are normal.” The American College of Surgeons teaches that, “Except for patients with trivial head injuries, all head-injured patients require CT scanning at some time.”²⁵ The second group, composed of neurosurgeons, emergency physicians, and radiologists, recommend a very selective approach to use of CT scanning in minor head injury.15, 17, 27, 28, 29, 30, 31, 32, 33, 34, 35 This group also points out that even a normal CT scan in the ED does not preclude the later development of intracranial hematoma.36, 37 Taheri, a neurosurgeon from Louisiana, et al¹⁵ write: “…safe discharge without universal computed tomographic evaluation or admission is possible and cost-efficient.” The third group offer no clear or unambiguous recommendations for use of CT scanning in minor head injury cases and often suggest that more studies are required.11, 13, 38, 39, 40, 41, 42, 43 Levitt,⁴² a US emergency physician, writes, “I hope that further research will define good management guidelines to aid those of us treating these patients.”

European authors describe a very selective approach to CT scanning for minor head injury cases. In Italy, CT is only recommended if a fracture has been demonstrated on skull radiography.16, 44, 45 In Denmark, CT is rarely ordered and then only by a neurosurgeon.46, 47 In the United Kingdom and Spain, CT is only recommended for cases with documented skull fracture, focal neurologic deficit, or deterioration in mental status.14, 48, 49

Without the support of widely accepted guidelines, North American emergency physicians are likely to follow the conservative approach of ordering CT scans for most patients with minor head injury seen in EDs. This approach, previously described for ankle and knee injury patients, is fostered by the nature of ED practice: high case volumes, brief physician-patient contact, uncertain follow-up, and fear of medicolegal repercussions.50, 51, 52 There is a clear need for valid and reliable guidelines to allow physicians to be more selective in their use of CT without compromising care of patients with minor head injury.