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Archived Issues of Radiology Rounds
MGH Department of Radiology Website
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Headache - When is Neuroimaging Needed?
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| Note: Updated issue available (October 2006) |
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The
vast majority of patients that come to see their physician complaining
of headache have primary headache disorders, such as migraine, cluster,
and tension type headaches and no identifiable pathology. Since
neuroimaging will not have any bearing on the treatment of primary
headaches, there is no reason to order a head scan for these patients.
However, it is not always easy to rule out a secondary headache, which
may be a symptom of life threatening disease, and it is tempting to err
on the side of caution. As a result, there is a high referral rate for
neuroimaging, most of which result in either normal scans or show
incidental abnormalities that in turn cause anxiety and lead to
unnecessary additional tests (see box).
For example, patient expectations or medicolegal concerns were cited as
the primary reason for 17% of those referred in a Canadian study in
which approximately 3% of patients with headache were referred for
neuroimaging. Most of this cohort (85%) had no neurological
abnormalities. In 49% of these patients, the referring physician
suspected an intracranial tumor. However, the yearly incidence of brain
tumors is only 49 per 100,000 in the USA and only about 8% of those
have an isolated headache as a first and only symptom. |
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| (A) |
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(B) |
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(A) Head CT without contrast shows diffuse subarachnoid hemorrhage.
(B)
Subsequent CT angiographic image (with contrast agent) in the same
patient demonstrates an anterior communicating artery aneurysm.
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Neuroimaging for Headache: Diagnostic yield from 3026 patients with normal neurological exam (Evans, 1996)
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| Brain tumor |
0.8%
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| Arteriovenous malformation |
0.2%
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| Hydrocephalus |
0.2%
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| Aneurysm |
0.3%
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| Sub-dural hematoma |
0.2%
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Stroke, including chronic ischemic processes *
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1.2%
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*Unlikely to be cause of headache
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When should Neuroimaging be Considered for an Isolated Headache?
The
US Headache Consortium, the American College of Emergency Physicians,
and the American College Of Radiology have all conducted extensive
studies of the literature to come up with some recommendations for
neuroimaging for patients with headache. Based on the accumulated
evidence, they have concluded that screening patients with isolated
headache by CT or MRI is generally not warranted. They also recommend
that the pain response to therapy not be used as the sole diagnostic
indicator of the underlying etiology of an acute headache.
The specific instances of isolated headache for which neuroimaging
should be considered include "thunderclap" headache (a sudden
excruciating headache that reaches its maximal intensity within
seconds), headache radiating to the neck, temporal headache in an older
individual, and new onset headache in patients with HIV, cancer, or in
those who are in a population at high risk for intracranial disease.
Neuroimaging in Non-Isolated Headaches
Patients
who present with a thunderclap headache and abnormal findings in a
neurological examination should undergo emergent non-contrast head CT
scan since these symptoms may be indicative of a cerebrovascular event
(usually subarachnoid hemorrhage or intracerebral hemorrhage).
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When a non-acute headache (one that has occurred for at least 4 weeks
during a patient’s life) is accompanied by an abnormal neurological
examination, there is a three-fold increase in the likelihood of
finding significant intracranial pathology (e.g. brain tumor,
arteriovenous malformation, hydrocepahlus). Significant neurological
findings that suggest an intracranial abnormality include papilledema,
visual field deficits, unilateral loss of sensation, weakness, or
hyperflexia, and altered mental status. Neuroimaging should be
considered in these cases. However, the significance of some other
symptoms is not clear, including a headache that is worsened by the
Valsalva maneuver, causes awakening from sleep, is progressively
worsening, or is a new headache in an older person.
A headache that is accompanied by a fever can be caused by meningitis,
especially if it is accompanied by nuchal rigidity. In these cases, a
head CT is needed to check for hydrocephalus to determine whether it is
safe to do a diagnostic lumbar puncture. This precaution is also
necessary in cases of headache in patients exhibiting signs of
increased intracranial pressure, including papilledema, absent venous
pulsations on funduscopic examination, altered mental status, or focal
neurological deficits. If the CT scan is negative, the opening pressure
is normal, and the CSF analysis does not indicate the presence of
blood, the available evidence suggests that there is no need for an
emergent angiography.
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| Guidelines for Neuroimaging in Patients with Headache1 |
Emergent neuroimaging recommended
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"Thunderclap" headache with abnormal neurological exam
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| Neuroimaging recommended to determine if it is safe to do lumbar puncture |
Headache accompanied by signs of increased intracranial pressure
Headache accompanied by fever and nuchal rigidity
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| Neuroimaging should be considered |
Isolated "Thunderclap" headache
Headache radiating to neck
Temporal headache in an older individual
New onset headache in patient who is
- HIV positive
- has a prior diagnosis of cancer
- is in a population at high risk for intracranial disease
Headache accompanied by abnormal neurological examination, including
papilledema or unilateral loss of sensation, weakness, or hyperflexia
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Neuroimaging not usually warranted
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Migraine and normal neurological exam |
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No recommendation (Some evidence for increased risk of intracranial abnormality, not sufficient for recommendation)
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Headache worsened by Vasalva maneuver, wakes patient from sleep, or is progressively worsening |
| No recommendation (insufficient data) |
Tension type headache and normal neurological exam
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1 From
guidelines developed by US Headache Consortium, the American College of
Emergency Physicians, and the American College of Radiology
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CT or MRI?
Although
MRI has better soft tissue contrast than CT, nearly every life
threatening condition that could cause a headache can be seen on a
non-contrast CT. A few very rare disorders, including venous sinus
thrombosis, and vasculitis can be found by MRI and not CT. However, MRI
can be too sensitive, finding small abnormalities, such as a small
aneurysm or an arachnoid cyst that have no clinical significance.
If an abnormality is found on non-contrast CT, contrast agent will be
administered. The use of contrast CT will be at the discretion of the
radiologist unless the referring physician specifically advises that
contrast agent is contraindicated.
Acknowledgements
Thanks
to Aneesh B. Singhal, M.D., MGH Department of Neurology and Pamela W.
Schaefer, M.D., Neuroradiology Division, MGH Department of Radiology,
for their advice in preparing this issue.
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Scheduling and Reporting
If
emergency neuroimaging is warranted, the patient should be sent to the
Emergency Department at MGH, where a CT will be performed. In other
cases, neuroimaging can be performed at Mass General West Imaging in
Waltham, Mass General Imaging in Chelsea or the main MGH campus and can
be ordered online via the Radiology Order Entry (ROE) system http://mghroe
or by calling 4-XRAY (617-724-9729). Results are made available to
physicians online within 24-48 hours.
Further Information
For further questions on neuroimaging, contact Pamela Schaefer, M.D.
For general questions about web-based Radiology scheduling, call 617-726-0304
For general questions about Radiology Services, call 617-724-4902
This article provided useful information about the appropriate use of imaging studies:
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References
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Maytal, J, Bienkowski, RS, Patel, M and Eviatar, L. (1995) The value of brain imaging in children with headaches. Pediatrics 96: 413-6
Evans, RW. (1996) Diagnostic testing for the evaluation of headaches. Neurol Clin 14: 1-26
Frischberg, B, Rosenberg, J, Matchar, D, McRory, D, Pietrzak, M, Rozen, T and Siberstein, S. (2000). Evidence based guidelines in the primary care setting: Neuroimaging in patients with nonacute headache. (Download pdf)
Clinch, CR. (2001) Evaluation of acute headaches in adults. Am Fam Physician 63: 685-92
American College of Emergency Physicians. (2002) Clinical
policy: critical issues in the evaluation and management of patients
presenting to the emergency department with acute headache. Ann Emerg Med 39: 108-22
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