Fibromuscular dysplasia: what the radiologist should know: a pictorial review

Abstract

Fibromuscular dysplasia (FMD) is an idiopathic, segmentary, non-inflammatory and non-atherosclerotic disease that can affect all layers of both small- and medium-calibre arteries. The prevalence of FMD is estimated between 4 and 6 % in the renal arteries and between 0.3 and 3 % in the cervico-encephalic arteries. FMD most frequently affects the renal, carotid and vertebral arteries, but it can theoretically affect any artery. Radiologists play an important role in the diagnosis of FMD, and good knowledge of FMD’s signs will certainly help reduce the delay between the first symptoms and diagnosis. The common string-of-beads aspect is well known, but less common presentations also have to be considered. These less common imaging findings include vascular loops, fusiform vascular ectasia, arterial dissection, aneurysm and subarachnoid haemorrhage. These radiologic presentations should be known by radiologists in order to diagnose possible FMD, particularly when present in young females or when associated with personal or familial hypertension, to reduce the delay between the onset of the first symptom and the final diagnosis. The patients have to be referred to specialised FMD centres for dedicated management.

Teaching Points

• Fibromuscular dysplasia is not a rare disease.

• Radiologists should recognise less common presentations to orient specific management.

• Vascular loops, fusiform vascular ectasia and a “string-of-beads” aspect are typical presentations.

• Arterial dissection, aneurysm and subarachnoid haemorrhage are less typical radiologic presentations.

Fibromuscular Dysplasia of Cervical and Intracranial Arteries

Fibromuscular dysplasia is an uncommon, segmental, nonatherosclerotic arterial disease of unknown aetiology. The disease primarily affects women and involves intermediate-sized arteries in many areas of the body, including cervical and intracranial arteries. Although often asymptomatic, fibromuscular dysplasia can also be associated with spontaneous dissection, severe stenosis that compromises the distal circulation, or intracranial aneurysm, and is therefore responsible for cerebral ischaemia or subarachnoid haemorrhage. Fibro-muscular dysplasia affects middle and distal portions of the internal carotid and vertebral arteries, and occasionally, intracranial arteries. Several pathological and angiographic patterns exist. The most frequent pathological type is medial fibromuscular dysplasia, which is associated with the ‘string of beads' angiographic pattern. Unifocal lesions are less common and can be associated with several pathological subtypes. The pathophysiology of the disease is widely unknown. Fibromuscular dysplasia may in fact result from various causes and reflect a non-specific response to different insults. The poor knowledge of the natural history and the lack of randomised trials that compared the different treatment options do not allow any satisfactory judgement to be made regarding the need for or the efficacy of any treatment.

Clinical presentation and surgical management of dissecting posterior inferior cerebellar artery aneurysms: 2 case reports

Intracranial dissection presenting with subarachnoid hemorrhage (SAH) most commonly involves the vertebral artery. The natural history of this lesion suggests frequent early rehemorrhage and need for urgent treatment. Isolated dissection of the posterior inferior cerebellar artery (PICA) is very rare. We present 2 cases of isolated PICA dissections presenting with SAH. Both patients were middle-aged men who presented with transient loss of consciousness, severe headache, and cranial neuropathies. Initial angiography showed dilatation and narrowing of PICA consistent with dissection and aneurysm formation. The vertebral arteries were normal and there was no other cause for the SAH. Repeat angiography 2 weeks after admission revealed significant enlargement of the aneurysmal dilation of the dissected segment of PICA in both patients. Both patients were treated operatively. One patient had clip reconstruction of the PICA with preservation of flow through the PICA. Follow-up angiography one year later showed no recurrence. The other patient underwent direct surgical trapping and resection of the dissected segment of PICA after passing balloon occlusion testing at the vertebral-PICA junction. Both patients have more than 2 years of clinical follow-up and remain well. Isolated PICA dissection seems to have a less ominous natural history compared to vertebral artery dissection. These lesions need to be followed carefully for evidence of aneurysmal enlargement. Direct surgical reconstruction of the dissected segment may be possible. Balloon occlusion testing may be very helpful in determining if the involved PICA segment can be sacrificed.

Spontaneous Dissection of the Extracranial Vertebral Artery: Indications and Long-Term Outcome of Surgical Treatment

Spontaneous dissection of the vertebral artery (VA) is usually managed medically. The objective of this report was to describe 10 patients treated surgically for spontaneous dissection of the VA. Seven men and three women with a mean age of 52.5 +/- 11.3 years were treated between December 1978 and January 2001. In eight cases the presenting symptom was neck pain. Transient ischemic attack or completed stroke in the vertebrobasilar distribution followed in nine cases. In the remaining case, symptoms resulted from irritation of the superior roots of the brachial plexus. Dissection was located in one segment of the VA in seven cases and two contiguous segments in three cases. Lesions involved aneurysm in seven cases, tight stenosis in two, and occlusion in one. The decision to perform surgery was made because of either continued symptoms despite maximal anticoagulation therapy or the presence of an aneurysm causing recurrent thromboembolism or threatening rupture. In eight cases the revascularization procedure consisted of bypass from the carotid artery to the distal VA. In the remaining two cases revascularization was achieved by transposition of the VA directly onto the common or internal carotid artery. Postoperative recovery was uneventful in all cases. No further neurological events were observed in any patient at a mean follow-up of 96.9 +/- 66 months (range, 12-216 months). Long-term resolution of vertebrobasilar symptoms was achieved in all cases, including one patient whose bypass occluded at 6 months. From these results we conclude that surgical treatment is the method of choice for spontaneous dissection of the extracranial VA associated with continued vertebrobasilar symptoms despite maximal medical therapy or with an expanding aneurysm. The most useful technique is bypass to the distal VA. Morbidity is low and long-term outcome is excellent.

Delayed Occlusion after Internal Carotid Artery Dissection under Heparin

Internal carotid artery dissection (ICAD) is a frequent etiology of stroke in the young. Immediate anticoagulation with unfractionated heparin is the most frequent treatment. A theoretical side effect of unfractionated heparin is an increase in the intramural hematoma resulting in hemodynamic cerebral infarction. We studied 20 patients with ICAD. All patients were immediately treated with unfractionated heparin. Activated partial thromboplastin time (aPTT) ratios were measured twice daily. We prospectively monitored the course of ICAD with repeated ultrasound in hospital. Unexpectedly, delayed ICA occlusion was noted in 5 patients under treatment. One of these developed a watershed infarct. We then analyzed the aPTT ratios over the first 6 days after diagnosis. Patients with delayed occlusion had significantly higher aPTT ratios (2.6 +/- 0.4 vs. 2.0 +/- 0.5, p < 0.05). Within the limits of a partially retrospective design, our study seems to support the notion that unfractionated heparin can increase the intramural hematoma. Our findings further justify a randomized clinical trial to resolve the anticoagulant/antiplatelet debate.

Embolic cerebellar infarction caused by spontaneous dissection of the extracranial vertebral artery--two case reports

Spontaneous dissection of the extracranial vertebral artery (VA) may cause ischemic stroke in the posterior circulation. A 22-year-old female and a 38-year-old male presented with sudden onset of vertigo and nausea without trauma. Angiography was initially interpreted as normal, but retrospective examination disclosed extracranial VA dissection in the V3 segment in both cases. Arterial dissection resulting in embolic stroke in the territory of the ipsilateral posterior inferior cerebellar artery was highly suspected. Both patients were treated conservatively without sequelae. Careful angiographic interpretation is important for the diagnosis of extracranial VA dissection. Spontaneous extracranial VA dissection should be suspected in young patients presenting with ischemic stroke but without predisposing risk factors or associated trauma.

Spontaneous vertebral artery dissection mimicking acute vertigo. Case report

A patient with acute vertigo, and normal findings on neurologic examination, was found to have vertebral artery dissection (VAD). This case shows that the clinical picture of VAD can mimic vertigo of labyrinthine (i.e, peripheral) origin.

Risk factors and precipitating neck movements causing vertebrobasilar artery dissection after cervical trauma and spinal manipulation

STUDY DESIGN

Potential precipitating events and risk factors for vertebrobasilar artery dissection were reviewed in an analysis of the English language literature published before 1993.

OBJECTIVES

To assess the literature pertaining to precipitating neck movements and risk factors for vertebrobasilar artery dissection in an attempt to determine whether the incidence of these complications can be minimized.

SUMMARY OF BACKGROUND DATA

Vertebrobasilar artery dissection and occlusion leading to brain stem and cerebellar ischemia and infarction are rare but often devastating complications of cervical, manipulation and neck trauma. Although various investigators have suggested potential risk factors and precipitating events, the basis for these suggestions remains unclear.

METHODS

A detailed search of the literature using three computerized bibliographic databases was performed to identify English language articles from 1966 to 1993. Literature before 1966 was identified through a hand search of Index Medicus. References of articles obtained by database search were reviewed to identify additional relevant articles. Data presented in all articles meeting the inclusion criteria were summarized.

RESULTS

The 367 case reports included in this study describe 160 cases of spontaneous onset, 115 cases of onset after spinal manipulation, 58 cases associated with trivial trauma, and 37 cases caused by major trauma (3 cases were classified in two categories). The nature of the precipitating trauma, neck movement, or type of manipulation that was performed was poorly defined in the literature, and it was not possible to identify a specific neck movement or trauma that would be considered the offending activity in the majority of cases. There were 208 (57%) men and 158 (43%) women (gender data not reported in one case) with an average age of 39.3 +/- 12.9 years. There was an overall prevalence of 13.4% hypertension, 6.5% migraines, 18% use of oral contraception (percent of female patients), and 4.9% smoking. In only isolated cases was specific vascular disease such as fibromuscular hyperplasia noted.

CONCLUSIONS

The literature does not assist in the identification of the offending mechanical trauma, neck movement, or type of manipulation precipitating vertebrobasilar artery dissection or the identification of the patient at risk. Thus, given the current status of the literature, it is impossible to advise patients or physicians about how to avoid vertebrobasilar artery dissection when considering cervical manipulation or about specific sports or exercises that result in neck movement or trauma.

Proximal balloon occlusion for dissecting vertebral aneurysms accompanied by subarachnoid hemorrhage

Five patients with spontaneous dissecting vertebral aneurysms presenting with subarachnoid hemorrhage were treated with endovascular proximal balloon occlusion after a successful balloon Matas' test. Occlusion was performed in the extracranial portion of the vertebral artery after the potentially dangerous period of cerebral vasospasm. Two patients rebled preoperatively during the waiting period. Although angiograms demonstrated residual aneurysmal dilatation for four of the five patients, postoperative hemorrhages or progression of the dissection were not observed during the 19- to 48-month follow-up period. Only one patient experienced transient postoperative ischemic complication. Although the timing of the procedure and the site of occlusion remain controversial, proximal balloon occlusion of the vertebral artery appears to be a safe and effective therapy for patients with dissecting vertebral aneurysms presenting with subarachnoid hemorrhages. This method provides an important, less invasive alternative for this condition.

Endovascular treatment of vertebral artery dissections and pseudoaneurysms

Sixteen patients with dissecting aneurysms or pseudoaneurysms of the vertebral artery, 12 involving the intradural vertebral artery and four occurring in the extradural segment, were treated by endovascular occlusion of the dissection site. Patients with vertebral fistulas were excluded from this study. The dissection was caused by trauma in three patients (two iatrogenic) and in the remaining 13 no obvious etiology was disclosed. Nine patients presented with subarachnoid hemorrhage (SAH), two of whom had severe cardiac disturbances secondary to the bleed. The nontraumatic dissections occurred in seven women and six men, with a mean age on discovery of 48 years. Fifteen patients were treated with endovascular occlusion of the parent artery at or just proximal to the dissection site. One patient had occlusion of a traumatic pseudoaneurysm with preservation of the parent artery. Four patients required transluminal angioplasty because of severe vasospasm produced by the presenting hemorrhage, and all benefited from this procedure with improved arterial flow documented by transcranial Doppler ultrasonography and arteriography. In 15 patients angiography disclosed complete cure of the dissection. One patient with a long dissection of extracranial origin extending intracranially had proximal occlusion of the dissection site. Follow-up angiography demonstrated healing of the vertebral artery dissection but persistent filling of the artery above the balloons, which underscores the need for embolic occlusion near the dissection site. No hemorrhages recurred. One patient had a second SAH at the time of therapy which was immediately controlled with balloons and coils. This patient and one other had minor neurological worsening resulting from the procedure (mild Wallenberg syndrome in one and minor ataxia in the second). Symptomatic vertebral artery dissections involving the intradural and extradural segments can be effectively managed by endovascular techniques. Balloon test occlusion and transluminal angioplasty can be useful adjuncts in the management of this disease.

[Intracranial dissecting aneurysms of the posterior circulation: report of 3 cases and review of the literature]

Dissecting aneurysms of cerebral arteries are unusual causes of stroke. The carotid system is the commonest site of this pathology, the vertebral arteries are less involved and dissection of the basilar artery is rare. The authors report three cases of arterial dissection of the vertebrobasilar system, two of the vertebral arteries and one of the basilar artery. An extensive review of the literature is presented. The clinical picture of dissection of vertebrobasilar system was inespecific but pain was a prominent symptom, though had not occurred in the site of the arteries involved. The pain was suggestive of subarachnoid hemorrhage. Associated or risk factors were mild trauma, migraine and high blood pressure. The angiographic findings were suggestive, however just the "double lumen" has been considered pathognomonic. The prognosis is variable. It was benign in case 3, left sequela in case 2, and case 1 rebleed fatally.

Proximal clipping of dissecting intracranial vertebral aneurysm--effect of balloon Matas test with neurophysiological monitoring. Case report

A case of repeated subarachnoid haemorrhage (SAH) caused by rupture of a dissecting intracranial vertebral aneurysm is reported. The clinical manifestations, angiographic findings, pre-operative assessment with neurophysiological monitoring, and surgery are presented. A review of the literature suggests that this type of intracranial aneurysm is being recognized with increasing frequency in SAH and fatality, and therefore exploration and treatment of vertebrobasilar (V-B) dissecting aneurysms is necessary. We emphasize that a balloon Matas test with monitoring of somatosensory evoked potentials (SEP), auditory brain stem responses (ABR), and its wedge pressure in occluding the vertebral artery before operation are objective assessments of treatment for dissecting intracranial vertebral aneurysm.

Extracranial vertebral artery aneurysm with neurofibromatosis. Endovascular treatment by detachable balloon

An extracranial vertebral artery aneurysm in a patient with neurofibromatosis is described. The aneurysm was treated by endovascular balloon occlusion of the proximal vertebral artery. The details of the therapeutic management are discussed, and the vascular manifestations of neurofibromatosis are reviewed.

Hemodynamic analysis of associated extracranial atraumatic vertebral artery aneurysm and arteriovenous fistula. Case report

A case of atraumatic arteriovenous (AV) fistula of the extracranial vertebral artery associated with an atraumatic aneurysm of the contralateral extracranial vertebral artery is reported. The fistulous lesion was excised after distal and proximal ligation of the vessel. Subsequently, the contralateral aneurysm underwent spontaneous dissolution. Seven cases of extracranial vertebral AV fistulae associated with ipsilateral vertebral artery aneurysms (four traumatic and three as part of vascular dysplastic syndromes) have been reported previously.

Extracranial vertebral artery dissections: a review of 13 cases

Clinical and radiologic findings in 13 patients (11 women, 2 men) with extracranial vertebral artery dissection are reported. Dissection was spontaneous in 8 patients, occurred after neck manipulation in 2 and after a potential minor injury to the neck in 3. Six had a history of common migraine, 4 were using oral contraceptives at the time of dissection, and 3 had fibromuscular dysplasia. Dissection was bilateral in 8 patients and associated with carotid dissection in 3. It usually presented with neck or occipital pain preceding basilar ischemic symptoms by a few minutes to 1 month. In 3 patients, transient ischemic attacks were the only manifestation of basilar ischemia, and in 1 patient there was no symptom of basilar ischemia despite bilateral vertebral dissection. In 19 of the 21 dissected vertebral arteries, the angiographic appearance was that of an irregular stenosis, which was associated in 6 arteries with pseudoaneurysmal formation. In 2 patients, 1 vertebral artery was occluded but the contralateral artery showed the typical irregular stenosis. The dissection involved only the third segment in 33%, only the second segment in 24%, and 2 or more segments in 38%. Eleven patients were treated with anticoagulants and 2 with aspirin; 11 recovered without sequelae and 2 had residual deficit. No recurrence was observed (mean follow-up 34 months). At control angiography (n = 12) or ultrasonic study (n = 1), 63% of dissected vertebral arteries had returned to normal, 26% showed marked improvement, and 11% were occluded. Our patient characteristics are compared with those of previously published cases. The validity of the distinction between spontaneous dissection and dissection associated with minor trauma is discussed.

Dissecting aneurysm of the vertebral artery. Report of seven cases and angiographic findings

Seven cases of dissecting aneurysm of the vertebral artery, all appearing to be of fusiform type, are reported. Clinically, all seven cases initially showed symptoms of subarachnoid hemorrhage; however, three of these were associated with Wallenberg's syndrome. The characteristic angiographic findings in these cases were: 1) retention of contrast medium in the aneurysm; 2) the presence of a true (vertebral artery) and false (arterial wall) lumen in the late arterial and/or venous phase; and 3) irregular arterial narrowing proximal and/or distal to the aneurysm. Autopsy findings of one patient supported the angiographic findings. Recently, reports of fusiform aneurysms associated with subarachnoid hemorrhage have been increasing. As dissecting aneurysms are found in the fusiform group, it is very important to analyze serial angiograms in order to choose a method of surgical treatment.

Intracranial dissecting aneurysms of the posterior circulation. Report of six cases and review of the literature

Dissecting aneurysms of the intracranial posterior circulation are unusual lesions that affect otherwise healthy young adults, are difficult to diagnose and manage, and carry a high morbidity and mortality rate. Headache in the suboccipital-posterior cervical region is the most common presenting symptom. The dissection usually occurs between the intima or internal elastic lamina and the media; subadventitial dissection does occur and accounts for the infrequent finding of subarachnoid hemorrhage. A deficit in the inner layers of the vessel is the proposed source of dissection. The angiographic features are inconsistent, although an irregularly narrowed arterial segment with proximal and/or distal dilatation are typical findings. Depending on the location of the dissection, the surgical options are: ligation, trapping, or reinforcement of exposed abnormal portions of the vessel. Anticoagulation therapy is not indicated in the management of this lesion.

A dissecting aneurysm of the vertebral artery

A rare case of dissecting aneurysm of the vertebral artery evidenced by ischemic attacks is reported. The aneurysm was treated by proximal ligation of the artery. There have been no repeated ischemic attacks and bleeding for 20 months. Analysis of 51 cases of vertebral artery aneurysm failed to disclose any comparable case. A review of the literature also revealed that clinically diagnosed dissecting aneurysms of the vertebrobasilar system have been reported rarely. Most of these cases were found at autopsy.

Resection and anastomosis of a cervical vertebral artery aneurysm

A patient with a fusiform aneurysm of the cervical vertebral artery at C-1 presenting with posterior circulation infarctions is reported. Exposure via the posterolateral approach, resection of the aneurysm, and end-to-end anastomosis are described. The authors emphasize the importance of the surgical approach and ability to expose and mobilize a generous portion of the cervical vertebral artery.