Posterior inferior cerebellar artery susceptibility sign in lateral medullary syndrome

BM Krishna Vadana, R Adhithyan, C Kesavadas, Veerendra Malik 
 Department of Imaging Sciences and Interventional Radiology, Sri Chitra Thirunal Institute of Medical Science and Technology, Thiruvananthapuram, Kerala, India

Correspondence Address:
Dr. B M Krishna Vadana
Room no. 305, A Block, Men's Hostel Sri Chitra Thirunal Institute of Medical Science and Technology, Thiruvananthapuram, Kerala
India

Full Text

Susceptibility vessel sign is an important sign to localize the thrombosis in a vessel in case of ischemic stroke.

We report a patient with a classical lateral medullary syndrome in which posterior inferior cerebellar artery (PICA) susceptibility sign was very nicely demonstrated in the susceptibility weighted imaging (SWI) on magnetic resonance imaging (MRI) even before computed tomography (CT) angiography was done.

A 41-year-old male patient, who was an occasional alcoholic and smoker, presented with complaints of sudden onset of occipital headache associated with vomiting, ataxia, hemifacial sensory loss on the left side, and blurring of vision. Clinically, posterior circulation stroke was suspected. An emergency MRI with stroke protocol was performed [diffusion weighted imaging (DWI), apparent diffusion coefficient, SWI, fluid-attenuated inversion recovery, and time-of-flight angiography]. On DWI, there was a small acute infarct in the posterolateral aspect of the left medulla. Hence, a diagnosis of lateral medullary syndrome was made. On SWI, there was a curvilinear hypointensity with susceptibility blooming observed along the expected course of the left PICA. CT angiography performed on the next day showed cut-off in the left PICA [Figure 1].{Figure 1}

Ischemic stroke, a neurological emergency, is most commonly caused by thrombosis of the involved vessel. SWI helps in identifying an intra-arterial thrombus. The presence of a higher concentration of deoxyhemoglobin and clot retraction makes acute intra-arterial thrombus paramagnetic, which produces a blooming artifact.[1]

Positive “susceptibility sign” is defined when the diameter of a hypointense vessel exceeds the diameter of the contralateral artery on SWI images.[2] Magnetic properties of hemoglobin vary according to its oxygenation status. Deoxyhemoglobin is a paramagnetic substance whereas oxyhemoglobin is diamagnetic.[3] The intra-arterial thrombus contains more deoxyhemoglobin as compared to flowing blood.

Susceptibility vessel sign is a very useful sign in patients with acute stroke in localizing the site of the intra-arterial thrombus.

Acknowledgements

The authors would like to thank the faculty of the Radiology and Neurology Department of the SCTIMST.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References