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Headache is most common reason for CT brain scan


Approximately 1 in 4 computed tomography (CT) scans of the brain in Ontario are requested to evaluate patients with headaches. New research from the Institute for Clinical Evaluative Sciences (ICES) shows that few scans will find a potential cause for the headache.

“There is concern about the potential overuse of CT scans for headache in ambulatory care. This study shows that very few scans find a treatable cause for headache. Because of the very small potential risk of cancer from exposure to ionizing radiation, efforts should be made to avoid CT scanning for headache when the likelihood of identifying a cause for the headache is extremely low,” says principal investigator and ICES scientist, Dr. John You.

The study of 3,930 outpatient CT scans done in Ontario in 2005 found:

  • Headache is the most common reason for requesting outpatient CT scans of the brain in Ontario (accounting for approximately 1 in every 4 scans requested)
  •  Scans infrequently find a potential cause for the headache (1 in every 50 scans)
  •  One in every 500 patients scanned for headache (0.2 per cent) is diagnosed with a brain tumour
  • Because of the very small potential risk of cancer from exposure to ionizing radiation, physicians should try to avoid CT scanning for headache when the likelihood of finding a serious cause for the headaches is extremely low
  • Three-quarters of the scans are ordered by family physicians. Although the use of CT scans in Ontario for headache could be more efficient (i.e., the vast majority of scans are not uncovering a secondary cause for the patient’s headaches), several factors suggest that physicians in Ontario are ordering CT scans reasonably responsibly when evaluating patients with headache

“Patients experiencing headaches four or five days per month, such as migraines, very rarely require CT scanning of the brain; in contrast, individuals experiencing daily headaches for months typically require CT scanning of the brain,” says You, who is also an assistant professor of medicine and clinical epidemiology and biostatistics at McMaster University.

Author affiliations: ICES (J.J. You, A. Laupacis, C. M. Bell); Depts. of Medicine and of Clinical Epidemiology and Biostatistics, McMaster University (J. J. You); Cleveland Clinic Canada (J. Gladstone, A. Laupacis); Dept. of Neurology Sunnybrook Health Sciences Centre (J. Gladstone); Dept. of Medical Imaging, Sunnybrook Health Sciences (S. Symons); Dept. of Medical Imaging, U of T (S. Symons); Dept. of Medicine, U of T (A. Laupacis, C. M. Bell, D. Rotstein); Dept. of Health Policy, Management and Evaluation, U of T (A. Laupacis, C. M. Bell); Keenan Research Centre of the Li Ka Shing Knowledge Institute, St. Michael’s Hospital (A. Laupacis, C. M. Bell).

The study “Patterns of care and outcomes after computed tomography scans for headache” is in the October 2010 online issue of The American Journal of Medicine.

ICES is an independent, non-profit organization that uses population-based health information to produce knowledge on a broad range of healthcare issues. Our unbiased evidence provides measures of health system performance, a clearer understanding of the shifting healthcare needs of Ontarians, and a stimulus for discussion of practical solutions to optimize scarce resources. ICES knowledge is highly regarded in Canada and abroad, and is widely used by government, hospitals, planners, and practitioners to make decisions about care delivery and to develop policy.



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