Case Report Basilar Artery Thrombus vs. Fenestration: A Differential Diagnostic Challenge in Acute Ischemic Stroke Paola Palazzo, MD, Michael Ruff, BS, Michael J. Lyerly, MD, Andrei V. Alexandrov, MD From the Department of Neurology, School of Medicine, University of Alabama Hospital, Birmingham, AL (PP, MJL, AVA); Department of Neurology, Campus Bio-Medico University, Rome, Italy (PP); University of Missouri School of Medicine, Columbia, MO (MR); Birmingham Virginia Stroke Center, Birmingham, AL (MJL).

ABSTRACT We present a case of a man presenting with vertigo and nausea who was found to have multifocal infarcts in the posterior circulation on magnetic resonance imaging (MRI). An magnetic resonance angiography (MRA) demonstrated focal widening and central signal dropout in the distal vertebral artery consistent with arterial fenestration. Transcranial Doppler ultrasonography showed turbulent flow and a spike waveform suggestive of an intra-luminal thrombus. This was confirmed by computed tomography (CT) angiography. Following the initiation of dual antiplatelet therapy, the signal abnormalities on transcranial doppler (TCD) resolved suggesting dissolution of the thrombus. This case highlights the diagnostic pitfalls that may arise when relying on only one modality for assessing intracranial vasculature and the importance of clarifying the diagnosis of basilar thrombosis or fenestration.

Keywords: Ischemic stroke, basilar fenestration, transcranial doppler. Acceptance: Received March 20, 2013, and in revised form June 20, 2013. Accepted for publication June 30, 2013. Correspondence: Address correspondence to Andrei V. Alexandrov, MD, Department of Neurology, University of Alabama at Birmingham, 1813 6th Avenue South, RWUH M226, Birmingham, AL 35294. E-mail: [email protected]. Paola Palazzo and Michael Ruff contributed equally to this article. J Neuroimaging 2014;24:607-609. DOI: 10.1111/jon.12069

Introduction Vertebrobasilar thrombosis is a life threatening cause of acute ischemic stroke. Prompt diagnosis is fundamental, as recognition may lead to specific treatments that may improve functional outcome and survival.1 Correct diagnosis is not always simple, especially in cases of small arterial thrombi that lead to a paucisymptomatic clinical presentation. Arterial fenestration can resemble an arterial thrombus on diagnostic imaging.2 Basilar artery (BA) fenestration is the most common intracranial arterial fenestration having an incidence of up to 5.26% in the general population.3 It results from incomplete fusion of primitive embryologic vessels.4 Typically, fenestration occurs at the proximal end of the BA at the confluence of the vertebral arteries.5 Here, we report a case of basilar thrombus initially misdiagnosed as an arterial fenestration and demonstrate the importance of multimodal imaging techniques to make the correct diagnosis.

Case Presentation A 59-year-old right-handed Caucasian male with a history of borderline hypertension and osteoarthritis presented with acute onset of nausea and dizziness. He complained of vertigo with unsteadiness and an episode of emesis. He reported an acute onset of difficulty seeing things to his right three weeks before, which he had attributed to eye irritation. Neurological exami-

Copyright

nation showed mild dysarthria, dysmetria in the left limbs and a right superior quadrantanopsia. Non-contrast brain CT scan showed diminished attenuation in the left occipital lobe and posteromedial right temporal lobe, suggesting a subacute left PCA infarction (Fig 1A). The patient was admitted to a stroke unit and antiplatelet therapy with aspirin was initiated. The following day his vertigo symptoms had largely resolved. Brain MRI showed several additional small acute ischemic lesions in the right cerebellar hemisphere and in the left superior vermis as well as sub-acute infarction in the left occipital lobe with extension into the corpus callosum (Fig 1B, C). Magnetic resonance angiography (MRA) showed a focal widening and central signal dropout in the left distal vertebral artery with appearance suggestive of fenestration (Fig 1D). An occlusion of the left PCA at the beginning of the P3 segment was also noted. The patient underwent intracranial vessel evaluation by means of transcranial Doppler, which revealed turbulent flow (bruit with randomly appearing spectra speckles above the waveform outline) in the left distal vertebral/proximal BA at the depth of 85 mm. Also, a spike waveform toward the probe was found at the same depth suggesting the presence of an intraluminal thrombus as opposed to a congenital anomaly (Fig 2A). This suspicion was confirmed with CT angiography, which revealed two small filling defects, one at the basilar tip, as well as the larger one within the proximal BA, immediately distal

◦ 2013 by the American Society of Neuroimaging C

607

Fig 1. (A) Non-contrast brain CT scan: previous infarct in the left occipital lobe. (B) MRI: diffusion restriction and (C) ADC map correlation compatible with acute ischemic lesion in the left superior cerebellar vermis. (D) MRA: focal widening and central signal dropout at the vertebrobasilar junction with appearance “suggesting fenestration.” (E) CTA reconstruction: no evidence of thrombus. (F) CTA source image: filling defect within the proximal BA, immediately distal to the confluence of the vertebral arteries, concerning for thrombus.

Fig 2. (A) Baseline TCD: turbulent flow with minimal flow reversal in the proximal BA (depth 90 mm) and spike waveform (arrow). (B) TCD at discharge: normal blood flow pattern in the BA (depth 85 mm). to the confluence of the vertebral arteries, both concerning for intraluminal thrombi. The filling defects were not noted on the 3D reconstruction as contrast obscured the intraluminal defects (Fig 1E, F). The patient was loaded with clopidogrel in addition to his daily aspirin. The following day a repeat transcranial Doppler

608

did not show any turbulent flow, bruit, or reversal of flow, findings suggestive of thrombus dissolution with no underlying stenosis (Fig 2B). Transthoracic echocardiogram showed no obvious thrombus or vegetation and telemetry monitoring was unremarkable. The patient was discharged the same day on dual anti-platelet therapy, and scheduled for transesophageal

Journal of Neuroimaging Vol 24 No 6 November/December 2014

echocardiogram and 1-month event detection with continuous cardiac rhythm monitoring to evaluate a potential cardiogenic source of his thrombus.

Discussion Our case highlights an important diagnostic challenge in the differentiation of anatomic variation and an in situ lesion. Recently, atherothrombotic lesions received renewed attention with the development of high resolution MRI and the implementation of computed tomography angiography (CTA) protocols in emergent assessments of patients with basilar ischemia.6, 7 Power motion-mode transcranial doppler (TCD) may further augment standard TCD findings of posterior circulation disturbances including thrombosis.8 Even though we did not perform these high resolution MRI techniques, we did compare multiple vascular imaging modalities and ruled out an anatomic variation through real-time assessment of hemodynamics. In particular, the presence of turbulence and its resolution over time on dual antiplatelet therapy correlated with CT angiographic findings of filling defects consistent with a thrombus. Evidence of intracranial vascular disease by a single modality should ideally have confirmatory testing. Current guidelines from the American Society of Neuroimaging note that abnormalities on TCD should be confirmed with angiography.9 Our study demonstrates that MRA and even CTA also have pitfalls in the diagnosis of intracranial vascular disease. Physicians should be knowledgeable of the limitations of various these imaging modalities and the advantages of TCD to complement MRA or CTA to accurately determine the nature of the vascular abnormality.

Conclusion This case illustrates complimentary use of multi-modal imaging in the assessment of a potentially life-threatening BA thrombus, initially diagnosed as an arterial fenestration. Transcranial Doppler was useful as a non-invasive diagnostic tool that un-

veiled hemodynamic changes at the thrombus location concordant with axial CTA image. Had only the MRA or CTA 3D reconstruction images been used as proof of vessel patency, the thrombus could have been missed and less aggressive treatment options could have been chosen in this patient.

The authors report no relevant disclosures related to this report.

References 1. Mattle HP, Arnold M, Lindsberg PJ, et al. Basilar artery occlusion. Lancet Neurol 2011;10:1002-1014. 2. Yim NY, Ha HI, Park JH, et al. Agenesis of bilateral internal carotid artery associated with basilar artery fenestration mimicking intraarterial thrombus: a case report. Vascular Endovasc Surg 2010;44:6974. 3. Wollschlaeger G, Wollschlaeger PB, Lucas FV, et al. Experience and result with postmortem cerebral angiography performed as routine procedure of the autopsy. Am J Roentgenol Radium Therapy Nucl Med 1967;101:68-87. 4. Dodevski A, Lazareska M, Tosovska-Lazarova D, et al. Basilar artery fenestration. Folia Morphol 2011;70:80-83. 5. Uchino A, Saito N, Okada Y, et al. Fenestrations of the intracranial vertebrobasilar system diagnosed by MR angiography. Neuroradiology 2012;54:445-450. 6. Ng KW, Venketasubramanian N, Yeo LL, et al. Usefulness of ct angiography for therapeutic decision making in thrombolyzing intubated patients with suspected basilar artery thrombosis. J Neuroimag: Official J Am Soc Neuroimag 2012;22:351-354. 7. Turan TN, Rumboldt Z, Brown TR. High-resolution MRI of basilar atherosclerosis: three-dimensional acquisition and flair sequences. Brain Behav 2013;3:1-3. 8. Tsivgoulis G, Sharma VK, Hoover SL, et al. Applications and advantages of power motion-mode doppler in acute posterior circulation cerebral ischemia. Stroke; J Cerebral Circulat 2008;39:11971204. 9. Alexandrov AV, Sloan MA, Tegeler CH, et al. Practice standards for transcranial doppler (TCD) ultrasound. Part II. Clinical indications and expected outcomes. J Neuroimag: Official J Am Soc Neuroimag 2012;22:215-224.

Palazzo et al: Basilar Artery Thrombus vs Fenestration

609

Basilar artery thrombus vs. fenestration: a differential diagnostic challenge in acute ischemic stroke.

We present a case of a man presenting with vertigo and nausea who was found to have multifocal infarcts in the posterior circulation on magnetic reson...
320KB Sizes 0 Downloads 0 Views