Patients, treatment policy and data collection

This retrospective, single-centre study was performed as part of an authorised institutional audit against national guidance (Interventional procedure guidance 429). Included were all patients with symptomatic intracranial vertebral or basilar artery stenoses treated endovascularly between 1 January 2006 and 3 February 2012. Patients were selected for invasive treatment in an interdisciplinary meeting and remained under the care of stroke neurologists. All patients had ≥70% symptomatic stenoses deemed to be at high risk of recurrent ischaemic events due to at least two of the following:

• Occlusion or hypoplasia of the contralateral vertebral artery.

• Posterior communicating arteries of a size unlikely to sufficiently collateralise the vertebral arteries.

• Recurrent ischaemic events in the territory of the stenosed artery despite BMT.

Clinical data regarding presentation and follow-up were obtained from patients’ notes. The National Institutes of Health Stroke Scale (NIHSS) score was estimated from the details of the neurological examination and classified into mild stroke (NIHSS 0–5), moderate stroke (NIHSS between 6 and 14) and severe stroke (NIHSS >14). Procedure details, complications and imaging follow-up were collected and assessed via the patients’ notes and images.

All surviving patients also underwent a standardised phone interview to obtain information on vascular events during follow-up and to assess their current functional status.

Procedures

All procedures were performed under general anaesthesia. All patients commenced dual antiplatelet therapy (75 mg of aspirin and 75 mg of clopidogrel) at least 5 days before the procedure. The dual antiplatelet therapy was generally continued for 1 year postprocedure, after which one antiplatelet agent was stopped. Patients received a bolus of 5000 units of heparin during the procedure. Platelet function inhibition was not tested.

All procedures were performed by the same operator (WK). The choice of the procedure (stent or angioplasty) and the stent type was at the discretion of the operator. All stents and balloons were CE-marked for treatment of arterial stenoses. No protection system was used. Follow-up imaging was performed according to the clinician’s discretion.

Descriptive statistical analyses were performed with SPSS Software V.24. Fisher’s exact test was used to compare categorical variables. P≤0.05 was considered statistically significant.

Clinical presentations and conditions prior to procedures

All patients presented with symptomatic high-grade (≥70%) intracranial posterior circulation stenoses. Of these patients, 16 were treated following recurrent transient ischaemic attacks (TIAs), all having previously experienced either a brainstem, cerebellar or occipital infarction, except for 1 patient with only recurrent TIAs. Seven patients were treated following recurrent infarctions of either the brainstem, cerebellum or thalamus or occipital hemispheres. One patient was treated following disseminated infarcts in the posterior circulation following a previous posterior circulation TIA. Five patients were treated after their first event but regarded as of high recurrence risk due to the anatomy. Of these, three patients had occipital infarctions and two patients had disseminated posterior circulation infarcts. One patient presented with subarachnoid haemorrhage due to a flow-related aneurysm of the posterior communicating artery. The neurological deficits as assessed by the NIHSS were mild in the majority of patients; three patients had moderate deficits, and in one of these patients this was due to the residuals of a previous middle cerebral artery infarction.

The mean time from the index event to the procedure was 102 days (2–455). The majority (18, 60%) of patients were treated after a recurrent event despite BMT. Fourteen patients were treated in the first month after the index event, and of these eight experienced a recurrent event prior to treatment. The mean time from the most recent event to treatment was 39 days (2–160), and 14 patients were treated within 2 weeks of their most recent event.

Twenty-two patients (73.3%) underwent multimodal imaging for assessment of the underlying vessel pathology. Eight patients (26.7%) were investigated with one imaging modality. Magnetic resonance angiography (MRA) was used in 26 patients (86.7%), DSA in 22 (73.3%) and Computed tomography angiography (CTA) in 8 (26.7%).

The size of the posterior communicating arteries was assessed with the best imaging available for this purpose: Digital subtraction angiography (DSA) in 22 patients and CTA in 8 patients.

All patients treated for symptomatic intracranial stenoses of a vertebral artery showed concomitant significant changes in the contralateral vertebral artery. In 13 patients (54%) the contralateral vertebral artery was occluded, in 3 (12.5%) severely stenotic and in 7 (29%) hypoplastic. In one patient, the contralateral vertebral artery ended as a posterior inferior cerebellar artery.

Representative cases

Case 1

An octogenarian patient presented with abrupt-onset unsteadiness and right-sided hearing loss. The patient had a background of diabetes, hypercholesterolaemia, hypertension and was a previous smoker. The initial scan showed an acute right cerebellar infarction and the patient was treated with aspirin (figure 1A). Shortly after the patient had a fall and presented 10 days later with loss of balance. A repeat MRI demonstrated new bilateral cerebellar infarctions, larger on the left, and a small subdural haematoma. A contrast-enhanced MRA demonstrated an occluded left ICA and an occluded right vertebral artery, and the left vertebral appeared to have multifocal stenosis. The patient was then started on dual antiplatelet treatment and transferred to our centre. A diagnostic angiogram confirmed the MRA findings (figure 1B). The day following the cerebral angiogram, the patient had a further brainstem stroke. The patient then underwent an angioplasty (figure 1C,D). This was complicated by further midbrain and thalamic infarction (figure 1E,F) during a spell of low blood pressure the following night. The NIHSS score prestent was 6, and poststent was 9. The patient was discharged to rehabilitation and died 5 years later due to peripheral vascular disease (gangrene); there were no further strokes.

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Figure 1

An octogenarian patient with repeated posterior circulation infarcts and systemic atherosclerosis. (A) The Diffusion weighted imaging (DWI) sequence confirms among others an acute left posterior inferior cerebellar artery (PICA) territory infarct. (B) The diagnostic angiogram confirms a high-grade stenosis of the left vertebral artery at the level of the dura perforation. The right vertebral artery is occluded. These changes were thought to be of atherosclerotic aetiology. The posterior communicating arteries are small. Note the origin of the anterior spinal artery immediately distal to the stenosis. (C) An angioplasty was performed with a Gateway 2.0×15 mm balloon the following day under general anaesthesia. The image shows the balloon across the stenosis. Inflation time was 60 s. (D) Postangioplasty there is better flow across the stenosis. There is some luminal irregularity but no intimal flap. The spinal artery remains patent. (E) The DWI MRI 2 days later shows new bilateral midbrain infarcts. (F) The coronal T2-weighted Fluid attenuated inversion recovery (FLAIR) sequence confirms the presence and locations of the new midbrain infarcts.

Case 2

A patient in the fourth decade of life presented with left facial weakness and right-sided sensory alterations (NIHSS score of 2). Imaging demonstrated occipital and brainstem infarction (figure 2A). Vascular imaging demonstrated an occluded left vertebral and a high-grade right vertebral stenosis (figure 2B,C). The patient was noted to be polycythaemic and had a background of hypertension and smoking. The patient was treated medically, including with phlebotomy. However, the patient had recurrent TIAs with headache, and visual and sensory symptoms. An angioplasty of the right vertebral was performed. The symptoms subsequently settled, but then recurred over the next 2 years. An angiogram demonstrated restenosis of the right vertebral. The patient then underwent a right vertebral artery stent (figure 2D,E). A follow-up angiogram 2 years later showed no restenosis (figure 2F). There were no further events, now 8 years following the index event. The patient has subsequently been diagnosed with diabetes.

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Figure 2

A patient in the fourth decade of life with recurrent posterior circulation events. (A) The diffusion weighted MRI shows an acute posterior cerebral artery (PCA) territory infarct. (B) The contrast magentic resonance angiography (MRA) confirms the occlusion of the left vertebral artery and the high-grade stenosis of the distal right vertebral artery. (C) The diagnostic angiogram under general anaesthesiashows the short but very severe stenosis of the right vertebral artery immediately before joining the basilar artery. (D) The stenosis was initially treated with angioplasty but symptoms recurred. Therefore, a drug-eluting coronary stent (Promus Element 2.25×8 mm) was deployed 18 months later. This image shows the stent placed across the stenosis causing distortion of the anatomy. (E) The immediate result after stent placement is satisfactory. (F) The 2-year follow-up angiogram shows no restenosis. The patient has remained asymptomatic for 8 years.

Procedures and complications

Stenoses of the intracranial vertebral artery were treated in 24 patients (80%), and stenoses of the basilar artery in 6 (20%). No significant differences in complications, technical success, restenosis and outcome were found between these two groups. The left vertebral artery was more frequently affected (13 vs 11).

Ten patients (33.3%) were treated with a stent, 13 (43.3%) with angioplasty and 5 (16.7%) with a combination of both. In two patients (6.7%) access to the stenosis failed without procedure-related complications. Of these two patients, one died 9 months later of non-stroke-related morbidity. The second patient sustained a further posterior circulation stroke 10 months later and then further carotid distribution infarctions.

One patient (3.3%) died after a procedural basilar artery rupture.11 Two patients with prior stroke had strokes within 24 hours of the procedure, with NIHSS scores ranging from 7 to 11 preprocedure and an NIHSS score 6 after treatment.

One patient suffered a guidewire vessel perforation during the attempted treatment of a vertebral artery stenosis, from which he recovered without attributable deficit in spite of being on dual antiplatelet medication. In the treated vessel sections, no perforator territory infarct was encountered.

Two patients (6.7%) had asymptomatic complications (dissection and pseudoaneurysm of the treated vertebral arteries).

Figure 3 shows the Kaplan-Meier curves showing 10-year survival free of risk of death, recurrent posterior stroke, or any recurrent posterior stroke or TIA.

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Figure 3

Kaplan-Meier curves of the 10-year risk of death, recurrent posterior stroke, or any recurrent posterior stroke or transient ischaemic attack (TIA). (A) Death, (B) recurrent stroke of the posterior circulation, and (C) any recurrent stroke or TIA of the posterior circulation.

A self-expanding stent (Wingspan) was used in two patients. Otherwise, various balloon-mounted and drug-eluting coronary stents were deployed (Pharos, Taxus, Promus Element and Xience). Gateway or Maverick balloons were used for angioplasty. There was no significant correlation between the type of procedure or type of stent and vessel patency (p=0.59), outcome (p=0.4), complication rate (p=0.34), or stroke or death within 30 days postprocedure (p=0.48).

Postdischarge follow-up

The median clinical follow-up time was 7 years (range 1–11). Of the 30 patients, 7 died, including 1 who died from the procedure. One patient died of pneumonia 10 months after the procedure. Three patients died from various malignancies. Two patients died from vascular events, one due to gangrene 5 years later and the second from an intracerebral haemorrhage 9 years later.

Twenty-three patients are still alive. No patients were lost to follow-up (table 1). Three patients (10%) had further posterior circulation strokes and two patients (6.7%) a TIA during follow-up. Of these three patients with recurrent strokes, one was in a patient in whom the attempted treatment failed; this patient later also had a right middle cerebral artery infarction. In the second patient, recurrent stroke occurred at 6 months after discontinuation of dual antiplatelet therapy (remaining on a single antiplatelet); following this event all patients were treated with dual antiplatelet treatment for a minimum of 1 year. The third patient had a recurrent stroke 2 months after treatment. Of the TIA recurrences, one is described in the case report above, and the second occurred 2 years following vertebral artery stenting that had been complicated by infarction; the patient was not considered well enough to undergo further intervention. He has been free of further cerebrovascular events since, although he has had myocardial ischaemia. A further patient had a new infarction in the posterior circulation on imaging but no clinical correlate. In addition, two patients experienced strokes in the distribution of the right middle cerebral artery.

The Modified Rankin Scales (MRS) obtained during the telephone interviews were as follows: nine patients had MRS 0, eight had MRS 1, four had MRS 2, no patient had MRS 3 and one had MRS 4.

All but one patient was followed up with imaging. The median imaging follow-up time was 12 months (IQR 3.6–36). Nine patients had multimodal follow-up, while 17 underwent only one study. Twenty-two patients were imaged with MRA and 12 underwent DSA.

The last follow-up study did not show a stenosis in 19 (63%) patients. Recurrent stenoses were found in five patients (16.7%), and in three (10%) an occlusion of the treated artery had occurred. Retreatment was performed in six patients, all with recurrent vertebral artery stenosis, two of whom were symptomatic and the other four patients were treated for recurrent asymptomatic stenoses.

Three patients (10%) previously treated with stenting underwent Percutaneous Transluminal Angioplasty (PTA), and the other three (10%), previously treated with PTA, had a stent inserted.