Vertebral webs, less commonly known as vertebral diaphragms, are a very rare vascular pathology of the vertebral artery thought to be an intimal variant of fibromuscular dysplasia. They may be a cause of ischaemic stroke.

Epidemiology

Vertebral webs are exceedingly rare, but possibly under-diagnosed. They are at least ten times rarer than carotid webs ^1,7. One 2017 review of 96 patients with vascular webs causing ischaemic stroke, found that vertebral webs made up only 7% of all vascular web cases ¹. In another 2020 case series of 41 patients with cervical artery webs found on CT angiography, only one patient (2.4%) had a vertebral web ⁷.

Clinical presentation

Vertebral webs clinically manifest as either ischaemic stroke or transient ischaemic attack of the posterior circulation, especially in young patients ^1-6. Unless causing symptoms of ischaemia, vertebral webs are otherwise asymptomatic (unlike dissection).

Pathology

Similar to a carotid web, a vertebral web is thought to be a very rare variant of fibromuscular dysplasia ^1,2,4, although this seems to be inferred from histopathological analyses of carotid webs. The web is a thin, linear, shelf-like membrane that extends from the vertebral artery wall into the vessel lumen ^1-5. The location of the web within the vertebral artery is variable, with one series reporting the V3 segment to be a common location ², however, cases have been described in the V1 ^1,8, V2 ^6,9, and V4 ⁵ segments as well. Again, similar to carotid webs, it is likely that stasis of blood distal to the web can lead to thrombus formation, which can embolise distally causing posterior circulation ischaemic stroke.

Radiographic features

Given vertebral webs are very rare, radiological descriptions are few. Angiographic studies, including Doppler ultrasound ³, CT angiography ^3,7-9, MR angiography ⁵, and the gold standard digital subtraction angiography ^1-4,6,8,9, show similar findings, of a shelf-like, linear, thin, and smooth filling defect of the vertebral artery. Furthermore, on digital subtraction angiography, pooling or stagnation of contrast within the web is seen ⁴. In one case incorporating MR vessel wall imaging, there may be contrast enhancement of the web ⁵, however, this may not be seen in all cases ⁴.

Treatment and prognosis

Optimal management of vertebral webs is not known. Cases in the literature are variably managed with pharmacological (e.g. antiplatelet agents) and/or endovascular (e.g. vertebral artery stenting) therapies ^1-6.

Differential diagnosis

• spontaneous vertebral artery dissection flap

  • may be difficult to distinguish radiologically given the variable location of vertebral webs, but in vertebral web there is no intramural haematoma or pseudoaneurysm ⁴

  • a clinical history of neck pain or trauma would suggest against a vertebral web ⁴

• normal kink in vertebral artery morphology ³

• atherosclerotic plaque

  • may have associated calcifications

See also

• carotid web

• fibromuscular dysplasia