The value of CT angiography in patients with acute severe headache; a prospective study

Acute headache may be an isolated symptom of subarchnoid hemorraghe (SAH),
cerebral venouw thrombosis (CVT), reversible cerebral vasoconstriciont syndrome
(RCVS) or carotid dissection. The are serious conditions with high morbidity
and mortality. If a patient presents with acute headache routinely a standard
head CT is performed. If this CT is performed within 6 hours after the start of
the headache, and is evaluated by an experienced neuro-radiologist a SAH is
sufficiently excluded. If this scan is performed after 6 hours sensitivity
drops and a lumbar puncture is still mandatory to exclude SAH. However in using
this method diagnosis like CVT, RCVS or dissection may be missed. For this
reason CT angiography (CTA) of the cerebral arteries is increasingly used in
the MCH and LUMC to exclude both arterial en venous pathology. In current
clinical practice 80% of patients between the hospitals receive a CTA, however
diagnostic value has never been prospectively researched in this patient group.
Also reasons for making this scan vary between neurologist without clear
reasons. This practice is objectionable as complications due to scanning may
occur:
- The iodine contrast that is given for this scan may cause nefropathie in a
small group of patients. Varying percentages have been cited from <1% in
patients without risk factors to 11% in higer risk patients. The risks are
significantly reduced by the use of a local contrast nefropathy protocol which
has been proven to reduce the risk of contrast nefropathie to 1.4%.
- Secondly there is a risk of contrast allergies.
- Finally radiation exposure is raised from 2mSV for a standard head CT tot an
additional 3.5mSv for the CTA. Radiation may be reduced by immediate
performance of the CTA or a more sensible use of CTA in a selected group of
patients.
The diagnostic value of CTA in this patient group has not been proven
unequivocally. Several longitudinal studies have followed patients with acute,
severe headache after a normal head CT and lumbar puncture and found no risk of
raised SAH. however follow times varied greatly and as CTA was not performed
other diagnoses may have been overseen. A recent study shows 6.6% vascular
abnormalities in this patient group after CTA. In recently published data from
our own centre we found 19% vascular abnormlities in patients with a normal
head CT and lumbar puncture. Both percentage are significantly higher than may
be expected in the general population.
As there a re no prospective studies regarding this subject, we hope that this
current study may shed some light on the value of CTA in patients with acute,
severe headache and a normal neurological examination and head CT. We hope to
be able to make a better selection for scanning based on patient
characteristics, thus reducing unecessary diagnostics

Determining the diagnostic value of CTA in patients with acute headache and
normal neurological examination and head CT by performing a prospective study.
Charting patient characteristics in order to more purposefully apply the CTA
and avoid excessive diagnostics.

The study will be a prospetive diagnostic study in two hospitals with
neuro-vascular expertise: the MC Haaglanden en LUMC. We will prspectively
include all patients with acute severe headache who present to the emergency
room and a normal neurological examination. In the current clinical practive
the patients undergo a standard head CT and if necessary an lumbar puncture to
exclude hemorraghe. Between the two hospitals 80% receive a CTA. In the
remaining group the reasons for not performing a CTA is unclear as is the
possible diagnostic yield. In order to avoid indication bias we wish to als
perform CTA on the remaining 20% of patients also.
Patients will be included and asked for consent by the treating physician. For
all patients it will be noted when a phycisian decides to make a CTA or not and
why. The patients in whom the treating phycisian does not see the indication
for CTA, informed consent will be obtained to perform CTA for study purposes.
Should there be a risk of contrast nefropathie patients will be prepared
according to the local IV contrast nefropathy risk protocol. If there are
absolute contra indications patient will be excluded, but data will be noted
for possible follow up and to evaluate the occurence of contra-indications.
Headache charateristics will be inventoried. Differential diagnosis before and
after CTA will be noted to evaluate changes due to CTA performance.

In current clinical practice 80% of pateints with acute severe headache receive
CTA in their diagnostic follow up. The diagnostic yield and value of this
practice is unknown. In this study a further 20% of patients will receive a
CTA. As we hope to include 200 patients, this will amount to 40 patients.
Participation in this study will subject these patients to an added radiation
exposure of 3.5mSv, and also added exposure to iodine contrast fluid via
intravenous injection.
All patients will be subjected to a questionaire lasting approximately 30
minutes. After a year patients will be contacted again for follow up via a
telephone questionaire which will last 10 minutes.
The aim of this study is to more purposefully apply CTA and thus reduce these
risks for future patients. Should CTA prove usefull in this patient group, then
standard head CT may be dismissed as interval diagnostic tool. This would
reduce radiation exposure with 2mSv to an only added 1.5 mSv. As this may be
applied to a selected group based on study result overall exposure may be
reduced in a group in which 80% now receive both standard head CT and CTA
(total 5.5mSv).
Risk of contrast nefropathie will be evaluated according to local nefropathie
protocol and patients will be treated accordingly.
Should pathology be found in the course of this study than patients will
receive necessary follow up and treatment.