The Specificity and Sensitivity of CT Angiography and
MR/MR Angiography Compared to Conventional
Angiography in Vertebral Artery Dissection remains
uncertain.
Clinical Problem: A 23 year old male presents to the emergency department after a one
week history of neck pain, and a 3 hour history of uncoordinated gait. You would like to
rule out a vertebral artery dissection but you do not want to submit your patient to the
risks of a conventional angiogram.
Clinical Question: What is the sensitivity and specificity of CT/CTA and MR/MRA as
compared to conventional angiography as a gold standard in the diagnosis of vertebral
artery dissection?
Search Strategy:
MEDLINE: (X-ray Computed Tomography [MeSH] OR Magnetic Resonance Imagine
[MeSH]) AND (carotid artery dissection [MeSH] OR vertebral artery dissection [MeSH])
limit to English, Human and Diagnosis (sensitivity/specificity/optimized).
Resulted in 187 hits: 2 papers compared CT angiogram (CTA) to conventional
angiogram in craniocervical artery dissection. (3,4). We reviewed the paper by Chen as
it focused on vertebral artery dissection.
EMBASE: Artery Dissection [MeSH] AND (Internal Carotid Artery OR Vertebral
Artery) AND (Computer Assisted Tomography OR Nuclear Magnetic Resonance
Imaging) AND Angiography.
Resulted in 35 hits. None relevant.
PUBMED: Searched “Dissection MR Artery Diagnosis”. Resulted in 256 hits. Ten papers evaluated CTA and Time of Flight MRA and MRI in
diagnosis of craniocervical artery dissection.
Among papers that investigated the utility of MRA in the diagnosis of craniocervical
artery dissection using modern day techniques, namely T1-weighted fat-suppression
sequence and time of flight MRA, only two papers were found which were in English and
accessible at our institution (1 and 2). The paper by Leclerc focused on vertebral artery
dissection and was selected for review.
COCHRANE LIBRARY: Search “dissection” revealed no relevant results
All relevant papers and review articles were reviewed for relevant references. The
Neuroradiology group at University Hospital, London, Ontario, Canada was approached
regarding any papers not retrieved in the above search.
The Evidence:
1. Leclerc (1999) – Retrospective analysis of 16 patients with 18 vertebral artery
dissections diagnosed by conventional angiogram. Of these, 10 patients with 12
dissections underwent MR within a week of having conventional angiogram and within 2
weeks from onset of symptoms. Two radiologists interpreted the MRI’s.
2. Chen (2004) - Retrospective analysis of 17 patients with vertebral dissection and 17
age/sex matched controls with symptomatic stroke (type of stroke was not defined) who
all underwent CT angiogram and conventional angiogram. CTA’s were performed
within 3 days of conventional angiogram. Two blinded radiologists interpreted CTA’s
and resolved disagreements by consensus.
Clinical Bottom Lines:
1. The spectrum of patients used in both articles was not appropriate as there was no
diagnostic uncertainty.
3. In the setting of vertebral artery dissection, MRI/MRA techniques may be of high
diagnostic sensitivity [92%]. This value is likely inflated due to the confirmation
of dissection prior to testing with MRI/MRA. The specificity is not known based
on this evidence.
4. In the setting of vertebral artery dissection, CT angiography techniques may be of
high diagnostic sensitivity [100%] and specificity [98%]. These values are likely
inflated due to the confirmation of dissection prior to testing with CTA.
5. Conventional angiogram was chosen as the gold standard in the diagnosis of
vertebral artery dissection, but this may not be the ideal test. Although expert
opinion that MR with fat saturation + MRA is better than conventional angiogram
in diagnosing vertebral artery dissection, this is not demonstrated in any single
paper that we found.
Data:
Leclerc: MRI compared to Conventional Angiogram in the Diagnosis of Vertebral
Artery Dissection:
Conventional Angiogram
Positive
Negative
11
0
MRI/ MRA
Positive
1
0
Negative
Sensitivity = 92% (95% CI 76-107); Specificity and LRs cannot be calculated.
Chen: : CTA compared to Conventional Angiogram in the Diagnosis of Vertebral
Dissection:
Conventional Angiogram
Positive
Negative
19
1
CTA
Positive
0
48
Negative
Sensitivity = 100% (95%CI 100-100)), Specificity=98% (95%CI 94-102),
LR+=49(95%CI 7-341), LR- = cannot be calculated
Comments on Leclerc:
1. The MRI’s and MRA’s were not performed in an appropriate spectrum of patients
as the patients selected for the study all had conventional angiographically proven
dissections. Therefore there was no diagnostic uncertainty.
2. It is not clear if radiologists who read the MRI’s and conventional angiograms
were blinded.
3. The study did not assess a combination of MRI and MRA together compared to
conventional angiogram in diagnosing vertebral artery dissection.
4. In the initial few days following dissection, the intramural hematoma will consist
mainly of deoxyhemoglobin, which is isointense to adjacent muscle and will not
be as readily appreciated as the methemoglobin which forms subsequently. We do
not know exactly how early patients in this trial were tested.
5. Some follow up MRA’s were not done within a reasonable time period (often
years apart) and so this component of the paper was not considered here.
6. Conventional digital subtraction angiography may not be the best gold standard.
Comments on Chen:
1. The CT’s were not performed in an appropriate spectrum of patients as the
patients selected for the study were highly likely to have a dissection given the
inclusion criteria.
2. The use of a control group was not appropriate in this case.
3. Two radiologists interpreting CTA were blind to results of conventional
angiogram and clinical presentation and resolved disagreements by consensus.
4. Conventional digital subtraction angiography may not be the best gold standard.
References:
1. Leclerc X. Lucas C. Godefroy O. Nicol L. Moretti A. Leys D. Pruvo JP. Preliminary
experience using contrast-enhanced MR angiography to assess vertebral artery structure
for the follow-up of suspected dissection. [Journal Article] Ajnr: American Journal of
Neuroradiology. 20(8):1482-90, 1999 Sep.
2. Oelerich M. Stogbauer F. Kurlemann G. Schul C. Schuierer G. Craniocervical artery
dissection: MR imaging and MR angiographic findings. [Journal Article] European
Radiology. 9(7):1385-91, 1999.
3. Elijovich L. Kazmi K. Gauvrit JY. Law M. The emerging role of multidetector row CT
angiography in the diagnosis of cervical arterial dissection: preliminary study. [Journal
Article] Neuroradiology. 48(9):606-12, 2006 Sep. UI: 16752137
4. Chen CJ. Tseng YC. Lee TH. Hsu HL. See LC. Multisection CT angiography compared
with catheter angiography in diagnosing vertebral artery dissection. [Clinical Trial.
Comparative Study. Journal Article. Research Support, Non-U.S. Gov't] Ajnr: American
Journal of Neuroradiology. 25(5):769-74, 2004 May. Key Words: vertebral artery dissection, angiography, MRA, CTA, conventional
angiography, dissection, diagnosis, vertebral artery, cerebral vascular disorders
Appraiser: Neema Kasravi and the UWO Evidence Based Neurology Group
Date Appraised: April 15, 2008
Evidence Based Neurology Group
University of Western Ontario