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Neuroradiology Case of the Week

Case 149

Alisa Johnson, Terry Chun, MD and PL Westesson MD, DDS, PhD

Clinical Presentation: The patient is a 31-year-old male with vertigo, nausea, and ataxia. While lifting a heavy weight he heard a popping sound in the neck and he has developed a pontine and right cerebellar stroke.

Radiological Findings:

Right Vertebral Artery Angiogram: Findings revealed a subintimal dissection involving the third portion of the vertebral artery. There is a long, smooth narrowing segment along the anterior and superior aspect of the third portion. The third portion is the segment of the vertebral artery after it exits through the foramen transversarium and crosses over the posterior arch of the atlas.

Left Vertebral Artery Angiogram: The finding is similar to that on the right side - dissection of the third portion of the left vertebral artery. The third portion that courses over the posterior arch of the atlas shows a short segment with smooth narrowing along the anterior and superior aspect indicating dissection.

Clinical Discussion: Vertebral artery dissection accounts for 20% of cervical vascular injuries and is either spontaneous or caused by neck trauma [1]. Trauma to the vertebral artery can be caused by blunt injuries, penetrating or non-penetrating injuries. Spontaneous vertebral artery dissection is more common in middle age females with 30% of cases being bilateral [2]. The symptoms of vertebral artery dissection are often difficult to differentiate from musculoskeletal pain [3]. Clinically, the 70% of patient may present with diffuse headache, neck or occiput pain often with neurological symptoms. Symptoms may be delayed from days to weeks. Neurologic symptoms are often caused by ischemia in the posterior circulation caused by occlusion of the vessel or emboli. Ninety percent of infarcts caused by dissection are thromboembolic rather than hemodynamic [3]. The vertebral artery is most susceptible to dissection at the point where it leaves the foramen transversarium of C2. Within the vessel, the dissection usually occurs between the intima and media, called a subintimal dissection. Subadventitial dissection is less common and occurs between the media and adventitia.
     Most dissections of the vertebral artery will heal spontaneously. Surgery and endovascular treatments are reserved for patients with persistent symptoms of ischemia. The surgical treatments for vertebral artery dissection is ligation of the vertebral artery with an in situ or extracranial-to-intracranial bypass. Endovascular treatment involves a percutaneous balloon angioplasty and placement of one or more metallic stents.

Neuroimaging Discussion: Non-invasive techniques are the primary screening procedures in patients with head and neck trauma.  If vascular injury is suspected additional imaging is done.  In one study, CT angiography has a sensitivity of 100%, specificity of 98%, and accuracy of 98.5%.  The study showed that CT angiography enabled successful diagnosis of all 19 dissected vertebral arteries and 48 of 49 non-dissected vertebral arteries, but misidentified a severe atherosclerotic lesion as an aneurysmal-type dissection [4].
     In another study, T1WI and T2WI in six patients showed cresentic high-signal intensity consistent with an intramural hematoma.  In addition, MR angiograms showed dilation and an intimal flap on source images from contrast-enhanced three-dimensional MR angiography on two patients [5]. This study found MR angiography to be a good diagnostic tool for vertebral artery dissection but found it was difficult to accurately evaluate luminal stenosis and differentiate it from hypoplasia, vasospasm or dysplasia without dissection.
     Catheter angiography is often postponed unless there is evidence of injury on prior imaging or high clinical suspicion of vertebral artery dissection in which case angiography is still considered the standard method of establishing this diagnosis [5].
     Signs on catheter angiogram of vertebral artery dissection:

• Long, irregular luminal narrowing
• Vessel occlusion
• Double lumen or intimal flap
• Pseudoaneurysm formation

References:

1. Osborn AG. Diagnostic Cerebral Angiography, 2nd ed.  Lippincott Williams &Wilkins, Philadelphia, 1999.
2. Morris P. Practical Neuroangiography. Williams & Wilkins, Baltimore. 1997.
3. Schievink WI.  Spontaneous dissection of the carotid and vertebral arteries: review article.  N Engl J Med. 2001 Mar 22;344(12):898-906. [Medline]
4. Chen CJ, Tseng YC, Lee TH, Hsu HL, See LC.  Multisection CT angiography compared with catheter angiography in diagnosing vertebral artery dissection.  AJNR Am J Neuroradiol. 2004 May;25(5):769-74. [Medline]
5. Shin JH, Suh DC, Choi CG, Leei HK.  Vertebral artery dissection:  spectrum of imaging findings with emphasis on angiography and correlation with clinical presentation.  Radiographics. 2000 Nov-Dec;20(6):1687-96. [Medline]