Vertebral artery hypoplasia: frequency and effect on cerebellar blood flow characteristics.
OBJECTIVE
Vertebral artery hypoplasia (VAH) is supposed to be a risk factor for posterior circulation ischemia (PCI), particularly in the territory of the posterior inferior cerebellar artery (PICA). The aim of our study was to determine whether VAH impedes perfusion in the dependent PICA territory even in the absence of manifest PCI.


METHODS
VA diameter was retrospectively measured in 934 consecutive patients who underwent whole-brain multimodal computed tomography because of suspected stroke. VAH was defined by a diameter of ≤2 mm and an asymmetry ratio of ≤1:1.7 of both VAs. We performed blinded computed tomography perfusion reading in patients with VAH without PCI (MRI-confirmed) and in control patients (ratio 1:2) with normal VAs. Four different perfusion maps were evaluated for a relative hypoperfusion in the PICA territory.


RESULTS
VAH was found in 146 of 934 patients (15.6%). It was more frequent on the right side (66.1%). Of 146 patients, 59 without PCI qualified for computed tomography perfusion analysis. Depending on the perfusion map, ≤42.4% (25/59) of patients with VAH, but only 7.6% (9/118) without VAH, showed an ipsilateral PICA hypoperfusion (P<0.001). Sensitivities in patients with VAH were as follows: time to drain 42.4% (25/59)>mean transit time 39.0% (23/59)>cerebral blood flow 25.4% (15/59). Cerebral blood volume was never affected.


CONCLUSIONS
VAH is a frequent vascular variant that can lead to a relative regional hypoperfusion in the PICA territory. Additional research should clarify the pathophysiological role of VAH in PCI.
From the Department of Clinical Radiology (K.M.T., A.B.B., W.H.S., M.A., M.F.R.), Department of Neurology (C.O., A.S., L.v.B.), Institute for Stroke and Dementia Research (C.O.), and Department of Neuroradiology (H.J.), Ludwig-Maximilians-University of Munich Hospitals, Munich, Germany.
Kolja M
KM
Thierfelder
Alena B
AB
Baumann
Wieland H
WH
Sommer
Marco
M
Armbruster
Christian
C
Opherk
Hendrik
H
Janssen
Maximilian F
MF
Reiser
Andreas
A
Straube
Louisa
L
von Baumgarten
D000368:Aged; D000369:Aged, 80 and over; D002531:Cerebellum / Q000098:blood supply*; D002533:Cerebral Angiography; D002539:Cerebral Arterial Diseases / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000503:physiopathology; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging / Q000295:instrumentation / Q000379:methods*; D055420:Perfusion Imaging; D012189:Retrospective Studies; D020521:Stroke / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000503:physiopathology; D014057:Tomography, X-Ray Computed; D014711:Vertebral Artery / Q000002:abnormalities / Q000000981:diagnostic imaging / Q000503:physiopathology*; D014715:Vertebrobasilar Insufficiency / Q000000981:diagnostic imaging / Q000503:physiopathology*
brain infarction, posterior circulation; brain ischemia; perfusion imaging; risk factors; stroke