Life-threatening bilateral internal carotid artery and unilateral vertebral artery total occlusion presenting with dizziness: a case report.

Introduction: It is well known that whereas bilateral occlusion is less common, unilateral internal carotid artery blockage happens regularly. Asymptomatic to fatal ischemic stroke can be the clinical presentation, depending on whether there is adequate collateral blood flow. Internal carotid artery occlusion is often associated with significant neurologic events, both at the time of initial occlusion and during follow-up. Case presentation: The authors describe a patient's experience of dizziness followed by a fall. The hyperdense position of the basilar artery near its bifurcation was identified following a computed tomography (CT) scan. Furthermore, the pons, midbrain, and medial parts of the right temporal lobe showed numerous small hypodensities suggestive of an ischemic injury. The patient had medical treatment without surgery after it was determined that they had bilateral internal carotid arteries and a blocked right vertebral artery. After taking dual anti-platelet therapy for 5 days, the patient recovered without incident and was discharged from the hospital. Discussion: In a young patient with bilateral internal carotid arteries occlusion (BICAO), the authors highlighted the significance of prompt diagnosis of stroke-like symptoms, diagnostic possibilities, and treatment options. Options for diagnosis include brain MRI and CT head to check for ischemia and CT angiography (CTA) head and neck to assess for artery obstruction. Options for treatment include severe medical and surgical treatments, such as carotid endarterectomy, stent implantation, or balloon angioplasty, or medical management alone, such as dual anti-platelet medication and thrombolysis. Conclusion: BICAO is associated with a grave prognosis and significant cerebrovascular complications. High-quality studies are needed to establish the best treatment strategy, considering the complex and individualized nature of the condition.

Anatomical and surgical considerations for Bow Hunter's syndrome in an elderly patient.

Bow Hunter's syndrome (BHS) is an uncommon condition characterized by impingement of one of the two vertebral arteries induced by cervical rotation, causing symptomatic vertebrobasilar insufficiency of the posterior cerebral circulation. We report a case of BHS in an 84-year-old male. Two months following a motor vehicle accident, the patient presented to an urgent care facility with subsequent transfer to the emergency department with complaints of lightheadedness upon right-lateral head movement. A cerebral angiogram demonstrated mild focal stenosis in the dominant left vertebral artery at the C2 level when in neutral position with significant worsening of the stenosis in the right-lateral head position with absent anterograde flow, consistent with BHS. Resultantly, the patient was referred for neurosurgery and successfully underwent placement of right-sided C2-C4 postero-lateral instrumentation and left-sided C2-C3 laminar screws projected towards the right side. This case highlights the importance of imaging in BHS diagnosis and guidance for treatment, as well as the need for a surgical standard of care for BHS patients.

Bow hunter's syndrome due to an anomalous right vertebral artery origin and contralateral absence: a case report and literature review.

BACKGROUND: Bow Hunter's syndrome (BHS), also known as rotational vertebral artery occlusion (RVAO), is a rare condition characterized by dynamic vertebrobasilar insufficiency due to position-dependent occlusion of the vertebral artery (VA). In the existing literature, most cases of BHS are attributed to osteophytic compression originating from the occipital condyle or within the transverse foramen, often accompanied by anatomical abnormalities of the VA. However, cases presenting solely with VA anomalies in the absence of any cervical vertebral structural abnormality are rare. This case report presents a unique instance of BHS in a 56-year-old male, attributed to the anomalous origin of the right VA and the absence of the left VA, without cervical structural abnormalities. CASE PRESENTATION: The patient exhibited symptoms like episodic dizziness and vertigo, which were exacerbated by rightward head rotation and alleviated upon returning to a neutral position. Diagnostic evaluation, including digital subtraction angiography, revealed that the right VA originated from the right common carotid artery and compression-induced stenosis of the right VA during head rotation. Conservative management, including avoidance of certain head movements and anti-arteriosclerosis medication, led to symptom resolution over a two-year follow-up period. CONCLUSIONS: This report contributes to the understanding of BHS by highlighting a rare vascular anomaly presentation and incorporates a review of 14 similar case reports in the literature describing that an anatomical abnormality of the VA is mainly responsible for the pathology of BHS in the absence of cervical vertebral anomalies, thus emphasizing the need for careful diagnostic and management strategies.

Exploring vertebral artery stump syndrome: An overlooked cause of posterior ischemic strokes. A narrative review of current management options.

INTRODUCTION: Stump syndrome is defined as a clinical syndrome resulting from a distal intracranial vessel embolic stroke due to an extracranial vessel occlusion. Similar to the anterior circulation, the recurrence of ischemic strokes in territories supplied by the posterior circulation in the presence of vertebral artery occlusion is termed Vertebral Artery Stump Syndrome (VASS). MATERIAL AND METHODS: We conducted a literature review, identifying 72 patients with transient ischemic attacks (TIAs) or ischemic strokes attributed to VASS, according to Kawano criteria. We categorized all patients in two groups focusing on the therapeutic management those who underwent primary medical treatment and those who received endovascular or surgical treatment either in acute or chronic phase. RESULTS: In the anticoagulant therapy group, only 1 patient had a stroke recurrence. Among the 4 on antiplatelets, all had recurrences, but 3 benefited from switching to anticoagulants or endovascular therapy. In the endovascular therapy group, worse outcomes were linked to acute large vessel occlusion. Endovascular treatment of the vertebral artery, in a chronic phase, was explored in literature for recurrent TIAs or minor strokes suggesting that this could be a viable therapeutic alternative when medical treatment failed in preventing recurrence of ischemic stroke. CONCLUSIONS: Some studies suggest that anticoagulant medical therapy may be beneficial for VASS and endovascular therapy has also been reported for selected patients. However, data on treatment outcomes and prognosis are still underreported, making treatment decisions challenging. Randomized Controlled Trials are needed to establish the optimal treatment approach.

[A case of suspected vertebral artery stump syndrome assessed by CT angiography].

A 55-year-old man developed ischemic stroke in the bilateral cerebellar hemispheres and bilateral occipital lobes. He was admitted to our hospital 17 months later with recurrent ischemic stroke in the posterior circulation. The left vertebral artery (VA) was occluded on brain magnetic resonance angiography but was visualized with a delay on continuous three-phase CT angiography (CTA). Conventional angiography confirmed a to-and-fro blood flow pattern at the distal end of the left VA, therefore the patient was diagnosed with VA stump syndrome (VASS). VASS is a recurrent posterior circulation ischemic stroke caused by thrombi in an occluded unilateral VA. VASS should be suspected in patients with unilateral VA occlusion and repeated posterior-circulation ischemic stroke. The diagnostic criteria for VASS include confirmation of VA occlusion and the presence of an antegrade flow component at the distal end. In this case, the presence of collateral circulation in the VA was suspected based on CTA findings, leading to the diagnosis of VASS. It was thus suggested that devising the imaging method of CTA may help diagnose VASS.

The morphology of occlusion stump for endovascular recanalization in non-acute vertebral ostial occlusion.

PURPOSE: Non-acute vertebral ostial occlusion (VOO) is a debilitating condition with significant mortality and morbidity rates. However, currently, there is no consensus on the optimal treatment strategy for VOO. This study aims to examine the feasibility, effectiveness, and safety of endovascular recanalization in patients with VOO. METHODS: We conducted a retrospective review of data from 21 consecutive patients with VOO who underwent endovascular recanalization between May 2018 and August 2023. The patients were divided into two groups based on a new angiographic classification proposed by Gao et al. Type I (tapered stump group) included patients with non-acute extracranial vertebral artery ostial occlusion presenting a tapered occlusion stump. Type II (nontapered stump group) consisted of patients with a nontapered occlusion stump. We collected data on recanalization rates, perioperative complications, and follow-up outcomes. RESULTS: Our analysis included data from a total of 21 patients (22 lesions) with a mean age of 64.6 ± 10.6 years. The technical success rate was 66.7 % (14/21), and the rate of periprocedural complications was 14.3 % (3/21). The success rate of transitioning from the tapered stump group to the nontapered stump group was 90.9 % (10/11) and 40 % (4/10), respectively (P = 0.024). The perioperative complication rate for type I and type II patients was 18.2 % (2/11) and 10 % (1/10), respectively. Among these patients, 18 cases underwent endovascular recanalization using transfemoral access, while 3 patients underwent transradial access after failed transfemoral access, with successful outcomes for two patients. CONCLUSIONS: This study suggests that endovascular recanalization may offer a safe, effective, and feasible treatment option for VOO patients. Additionally, the proposed angiographic classification may serve as a useful guide in selecting suitable candidates for surgery.

Neurovascular considerations in patients with Down syndrome and moyamoya syndrome.

In this article, we describe a rare and complex case of moyamoya syndrome in a 7-year-old boy with Down syndrome and atlantoaxial subluxation. The patient presented with an ischemic stroke in the left hemisphere and cervical cord compression with increased cord edema. Diagnostic digital subtraction angiography revealed unique patterns of vascular involvement, with retrograde flow through the anterior spinal artery, ascending cervical artery, occipital artery, and multiple leptomeningeal arteries compensating for bilateral vertebral artery occlusion. This case underscores the underreported phenomenon of upward retrograde flow through the anterior spinal artery in bilateral vertebral artery occlusion. We address the rare manifestation of posterior circulation involvement in moyamoya syndrome, highlighting the importance of considering atlantoaxial instability as a contributing factor, as the absence of atlantoaxial stability is a risk factor for vertebral artery dissection. This study contributes valuable insights into the intricate relationship of moyamoya syndrome, Down syndrome, and atlantoaxial instability, urging clinicians to consider multifaceted approaches in diagnosis and treatment. It also emphasizes the potential significance of the anterior spinal artery as a compensatory pathway in complex vascular scenarios.

Vertebral Artery Dissection: A Case Report and Review of the Literature.

Arterial dissection is the result of blood entering along the intima-media plane through a breach produced either spontaneously or traumatically. Cervical arterial dissections are an important cause of acute ischemic stroke in children, young adults, and patients with cranio-cervical traumatic injuries. Arterial dissections occur either spontaneously, in genetic diseases, the most important association being with fibromuscular dysplasia. In most of the cases dissection involve the extracranial portions of the internal carotid and vertebral arteries. Magnetic resonance with T1 fat-saturation (T1 FS) sequence of the cervical region or computed tomography (CT) with computed tomography angiography (CTA) shows a very high sensitivity and specificity in the diagnosis of cervical artery dissections. Therapeutic options are still debatable in patients with acute ischemic stroke and vertebral or carotid artery dissection.

Case report: Retrograde endovascular recanalization of vertebral artery occlusion with non-tapered stump via the deep cervical collateral.

Introduction: Vertebral artery (VA) occlusive disease is the major cause of posterior circulation ischemic stroke. Endovascular recanalization has been reported as a feasible treatment for patients with symptomatic VA occlusion refractory to optimal medical therapy. However, VA occlusion with non-tapered stump exhibits a low technique success rate when treated by antegrade endovascular therapy because of increased difficulty in passing the guidewire into the occluded segment. Herein, we presented a novel endovascular approach to recanalize chronically occluded VA with a non-tapered stump using a retrograde method via the deep cervical collateral, which has not been reported before. Case presentation: The present case was a patient with VA ostial occlusion with non-tapered stump and distal severe stenosis of the left VA who had recurrent posterior circulation transit ischemic attacks under optimal medical therapy. CT angiography demonstrated proximal non-tapered occlusion and distal severe stenosis of the left VA, and that the right VA did not converge with the left VA into basilar artery. Endovascular treatment was recommended and performed on this patient. However, antegrade endovascular recanalization of the left VA origin occlusion failed because the micro guidewire was unable to traverse the occluded segment. Fortunately, robust collateral from the deep cervical artery to the V3 segment of the left VA developed, in which we advanced the micro guidewire to the V3 segment of the left VA and reversely passed the micro guidewire through the occluded segment. Then, the occlusion and stenosis of the left VA were successfully resolved with angioplasty and stenting. After the procedure, the patient reported no neurological symptoms under medical therapy during 3-month follow-up. Conclusion: Antegrade endovascular recanalization of VA occlusion with a non-tapered stump is a challenge. The retrograde endovascular method via the cervical collateral may be an alternative for this type of VA occlusion, which requires further exploration.

Acute isolated vertigo with vertical up-beating nystagmus: A rare case of nucleus intercalatus of Staderini ischemia.

The role of intercalatus nucleus of Staderini (INS), the most caudal of the perihypoglossal nuclei, is much debated. Last research seems to suggest that this nucleus plays a role as a vertical eyes movements integrator. The few clinical reports present in the literature that describe isolated lesions of the INS have described patients presenting in acute with up-beating vertical spontaneous nystagmus. Isolated acute lesion of INS is, in fact, much rare, and, without other neurological signs, is exceptional. We present a case of acute isolated vertigo with no other neurological signs or symptoms, due to INS ischemia provoked by vertebral artery stenosis. The patient presented with spontaneous vertical up-beating nystagmus that showed at videonystagmographic recording, a clear exponential decay of angular slow-phase velocity, that is considered a typical sign of neural integrator impairment. This case seems to represent a further confirm that INS is part, as a vertical-to-position neural integrator, of the neural circuit controlling the vertical eyes movements.

Parent artery occlusion for cerebral infarction after spontaneous recanalization in traumatic vertebral artery: A case report.

Background: There is no established treatment strategy for traumatic vertebral artery occlusion that does not require cervical spine repair surgery. Case Description: A 49-year-old man was brought to our hospital with traffic trauma. Fractures were observed in the left lateral mass and transverse process of Atlas and the left vertebral artery was occluded at the level of the foramen transversum of Atlas. No acute cerebral infarction was observed. Because the cervical spinal cord was not compressed by the fracture, no repair surgery was performed. Continuous intravenous heparin and oral aspirin were started for traumatic vertebral artery occlusion. Thereafter, the left vertebral artery spontaneously recanalized, but no cerebral infarction was observed. The patient was discharged home on day 16 of injury. Four days later, however, he was brought to our hospital with nausea and lightheadedness. Acute cerebral infarction was observed in the left posterior inferior cerebellar artery territory and a thrombus in the left vertebral artery V4 segment. Parent artery occlusion was performed to prevent further cerebral infarction due to distal embolization of the thrombus. No further cerebral infarction occurred after the operation and the patient was discharged home with a modified Rankin scale score of 1. Conclusion: In cases of traumatic vertebral artery occlusion without an occlusive mechanism, parent artery occlusion may be considered in terms of recanalization risk, regardless of the need for repair surgery.

Microsurgical revascularization of a symptomatic proximal vertebral artery: pilot experiences from a single center.

Background: Vertebral artery stenosis and occlusion (VASO) is a high-risk factor for posterior circulation stroke. Post-stent restenosis and drug tolerance have facilitated the exploration of microsurgical vascular reconstruction. This study aims to evaluate the safety and efficacy of microsurgical reconstruction of the proximal VA. Methods: Twenty-nine patients (25 men, aged 63.2 years) who had symptoms of posterior circulation ischemia underwent microsurgical revascularization for proximal VASO were retrospectively included in this study. Procedural complications and clinical and angiographic outcomes were reviewed. Results: Twelve, three, and five patients underwent VA endarterectomy, artery transposition, or both, respectively; seven patients underwent vertebral endarterectomy plus stent implantation; and two patients failed surgery because of the difficult exposure of the VA and the occurrence of vascular dissection. The perioperative period-related complications included seven cases of Horner's syndrome, five cases of hoarseness, and one case of chylothorax. No cases of perioperative stroke or death were reported. The mean follow-up period was 28.4 (8-62 months). Most patients improved clinically; however, the vertebrobasilar ischemia symptoms did not decrease significantly in two patients during the follow-up. Moreover, follow-up imaging was performed in all the patients, and no signs of anastomotic stenosis were reported. Conclusion: Microsurgical reconstruction is an alternative option that can effectively treat refractory proximal VASO disease and in-stent stenosis, with a high rate of postoperative vascular recirculation. Prospective cohort studies with larger sample sizes must be conducted to validate the above conclusions.

Non responsible vascular area hyperperfusion syndrome after mechanical thrombectomy for vertebral artery occlusion: A case report.

Introduction: There are currently no published reports of hyperperfusion syndrome in the non responsible vascular area after mechanical thrombectomy for acute cerebral infarction with large vessel occlusion. Here, we report a case of hyperperfusion syndrome in the blood supply area of the right middle cerebral artery after mechanical thrombectomy for acute cerebral infarction after vertebral artery occlusion. Patient concerns: A 21-year-old woman developed left vertebral artery occlusion, for which she received mechanical thrombectomy and successful recanalization of her occluded cerebral vessel. Subsequently, the patient became extremely agitated, with high blood pressure and headache. Diagnosis: Two hours after the operation, bedside transcranial Doppler ultrasound examination found that the cerebral blood flow velocity of the M1 segment of the right middle cerebral artery was more than twice that of the left middle cerebral artery. Combined with the symptoms, signs and examination results of the patient, hyperperfusion syndrome in the blood supply area of the right middle cerebral artery was considered. Interventions: The patient was administered sedation, and her pressure and ventricular rate were strictly controlled. She was no longer agitated, and her headache was significantly relieved at 36 hours after the operation. Outcomes: On the 5th day after the operation, the blood flow velocity of her right middle cerebral artery decreased to normal level, and the patient recovered well. Conclusion: In this case, after mechanical thrombectomy, such patients with acute posterior circulation cerebral infarction can experience hyperperfusion syndrome in the non responsible vascular area of the anterior circulation. Bedside transcranial Doppler cerebral blood flow examination can identify the hyperperfusion state of cerebral vessels in a timely manner and effectively guide treatment.

[Clinical Effect of Surgical Reconstruction of Extracranial Vertebral Artery].

Objective To evaluate the effect of surgical reconstruction of extracranial vertebral artery and to summarize the experience. Methods The clinical data of 15 patients undergoing surgical reconstruction of extracranial vertebral artery from September 2018 to June 2022 were collected.The operation methods,operation duration,intraoperative blood loss,operation complications,and relief of symptoms were retrospectively analyzed. Results Eleven patients underwent vertebral artery (V1 segment) to common carotid artery transposition,two patients underwent endarterectomy of V1 segment,two patients underwent V3 segment to external carotid artery bypass or transposition.The operation duration,intraoperative blood loss,and blocking time of common carotid artery varied within 120-340 min,50-300 ml,and 12-25 min,with the medians of 240 min,100 ml,and 16 min,respectively.There was no cardiac accident,cerebral hyperperfusion syndrome,cerebral hemorrhage or lymphatic leakage during the perioperative period.One patient suffered from cerebral infarction and three patients suffered from incomplete Horner's syndrome after the operation.During the follow-up (4-45 months,median of 26 months),there was no anastomotic stenosis,new cerebral infarction or cerebral ischemia. Conclusion Surgical reconstruction of extracranial vertebral artery is safe and effective,and individualized reconstruction strategy should be adopted according to different conditions.

Cerebellar Ischemic Stroke Secondary to Rotational Non-Dominant Vertebral Artery Occlusion (RVAO): A Rare Complication Following Supratentorial Surgery.

Non-traumatic vertebrobasilar stroke syndrome is rare. Many etiological mechanisms have been described over the years, with the dynamic occlusion of one vertebral artery following head rotation (RVAO) being one of them. We report the case of a patient undergoing surgery for supratentorial metastasis, who postoperatively developed a cerebellar ischemic stroke secondary to RVAO. Postoperative imaging showed a right hypoplastic VA; so, a transient occlusive mechanism was thought to be responsible for the postoperative cerebellar stroke. Although rare, RVAO can occur following head rotation during patient positioning for neurosurgical procedures.

Embolic stroke induced by rotational persistent 1st intersegmental artery compression.

A 45-year-old man suffered multiple cerebral infarctions in the vertebrobasilar artery territory, followed by second stroke against conservative treatment. Radiological examinations revealed intra-arterial defect in left persistent 1st intersegmental artery (PFIA) at C1 level, suggesting mural thrombus, and mechanical compression of left PFIA at the level with head rotation to the right clearly revealed by reconstructed 3-dimensional radiological images, but no findings of atlantoaxial instability. One month after the second stroke, posterior fixation was performed. Postoperative course was uneventful without subsequent stroke for 24 months. This unique case demonstrated that PFIA might associate with cerebral stroke as a clinical condition of bow hunter's stroke even in middle age. Reconstructed 3-dimensional radiological images might be useful for clear demonstration of the pathophysiology in this complex clinical entity.

Clinical Effect of Surgical Reconstruction of Extracranial Vertebral Artery / 中国医学科学院学报

Objective To evaluate the effect of surgical reconstruction of extracranial vertebral artery and to summarize the experience. Methods The clinical data of 15 patients undergoing surgical reconstruction of extracranial vertebral artery from September 2018 to June 2022 were collected.The operation methods,operation duration,intraoperative blood loss,operation complications,and relief of symptoms were retrospectively analyzed. Results Eleven patients underwent vertebral artery (V1 segment) to common carotid artery transposition,two patients underwent endarterectomy of V1 segment,two patients underwent V3 segment to external carotid artery bypass or transposition.The operation duration,intraoperative blood loss,and blocking time of common carotid artery varied within 120-340 min,50-300 ml,and 12-25 min,with the medians of 240 min,100 ml,and 16 min,respectively.There was no cardiac accident,cerebral hyperperfusion syndrome,cerebral hemorrhage or lymphatic leakage during the perioperative period.One patient suffered from cerebral infarction and three patients suffered from incomplete Horner's syndrome after the operation.During the follow-up (4-45 months,median of 26 months),there was no anastomotic stenosis,new cerebral infarction or cerebral ischemia. Conclusion Surgical reconstruction of extracranial vertebral artery is safe and effective,and individualized reconstruction strategy should be adopted according to different conditions.

Safety of early posterior fusion surgery without endovascular embolization for asymptomatic vertebral artery occlusion associated with cervical spine trauma.

PURPOSE: Vertebral artery occlusion (VAO) is an increasingly recognized complication of cervical spine trauma. However, the management strategy of VAO remains heavily debated. Therefore, the aim of this retrospective study was to investigate the safety of early fusion surgery for traumatic VAO. METHODS: This study included a total of 241 patients (average age 64.7 years; 201 men) who underwent early surgical treatment for acute cervical spine injury between 2012 and 2019. The incidence of VAO, cerebral infarction rates, the recanalization rates, and cerebral thromboembolism after recanalization were retrospectively analyzed. RESULTS: VAO occurred in 22 patients (9.1%). Of the 22 patients with VAO, radiographic cerebral infarction was detected in 4 patients (21.1%) at initial evaluation, including 1 symptomatic medullar infarction (4.5%) and 3 asymptomatic cerebrum infarctions. A patient who experienced right medullar infarction showed no progression of the neurologic damage. Follow-up imaging revealed that the VAOs of 9 patients (40.9%) were recanalized, and the recanalization did not correlate with clinical adverse outcomes. The arteries of the remaining 13 (59.1%) patients remained occluded and clinically silent until the final follow-up (mean final follow-up 33.0 months). CONCLUSION: Despite the lack of a concurrent control group with preoperative antiplatelet therapy or endovascular embolization for VAO, our results showed low symptomatic stroke rate (4.5%), high recanalization rate (40.9%), and low mortality rate (0%). Therefore, we believe that the indication for early stabilization surgery as management strategy of asymptomatic VAO might be one of the safe and effective treatment options for prevention of symptomatic cerebral infarction.

Right cerebellar stroke with a right vertebral artery occlusion following an embolization of the right glomus tympanicum tumor: Case report with literature review.

A 35-year-old female presented with episodes of frequent dizziness, ear fullness, and right ear tinnitus for 12 months. Head imaging revealed a right glomus tympanicum tumor. She underwent pre-operative endovascular embolization of the glomus tympanicum tumor with surgical, cyanoacrylate-based glue. Immediately after the procedure, she developed drowsiness and severe pain in the right temporal region. Further investigations revealed a right cerebellar stroke in the posterior inferior cerebellar artery territory. She was treated with intravenous heparin, followed by one year of oral anticoagulation. With rehabilitation, she significantly recovered from her post embolization stroke. However, the tumor was resected at another institution. Ten years later, follow-up imaging indicated a gradual increase in the size of the glomus jugulare tumor compressing the nearby critical vascular structures. She subsequently received radiation therapy to treat the residual tumor. Currently, she has no neurological deficit, but her mild dizziness, right ear tinnitus, and hearing impairment persist.

A Loop That Matters-An Unusual Case of Bow Hunter's Syndrome.

Bow Hunter's syndrome (BHS), also known as rotational vertebral artery occlusion (VAO), is a rare entity in which vertebral artery is reversibly compressed due to rotation or extension of the head, causing vertebrobasilar insufficiency. Because of VAO, BHS should be considered as a possible life-threatening condition. Diverse aetiologies of BHS may trigger a broad spectrum of non-specific symptoms and may result in frequent misdiagnosis of this disorder in daily clinical practice. Herein, we present a case of BHS caused by previously non-described vascular aetiology.