MR imaging of vertebrobasilar vascular disease

Headache in Intracranial and Cervical Artery Dissections

Dissection refers to a tear in the wall of an artery, with the two main types being intracranial or extracranial. Dissections tend to occur most commonly in the young, sometimes secondary to trauma involving the neck. To confirm a dissection, some type of vessel imaging is necessary, including magnetic resonance angiography (MRA), computed tomography angiography (CTA), or angiography. The most common presentation of a dissection (especially extracranial) is pain, usually head and neck pain along with a Horner's syndrome. Patients may also present with ischemic symptoms, including transient ischemic attack (TIA) or stroke, which may also be a complication of a dissection. Although headache is a common presentation, there is little research into phenotype or long-term outcomes. There are a number of case reports detailing the phenotypes of headaches that may be present in dissection, including a migraine-like or hemicrania-like headache. Dissections are usually treated with some type of anti-platelet or anti-coagulation, although there are only a few randomized controlled trials. In a new acute headache, dissection is an important diagnosis to keep in mind.

Cerebrovascular Dissections—A Review Part I: Spontaneous Dissections

Spontaneous cerebrovascular dissections are subintimal or subadventitial cervical carotid and vertebral artery wall injuries and are the cause of as many as 2% of all ischemic strokes. Spontaneous dissections are the leading cause of stroke in patients younger than 45 years of age, accounting for almost one fourth of strokes in this population. A history of some degree of trivial trauma is present in nearly one fourth of cases. Subsequent mortality or neurological morbidity is usually the result of distal ischemia produced by emboli released from the injury site, although local mass effect produced by arterial dilation or aneurysm formation also can occur. The gold standard for diagnosis remains digital subtraction angiography. Computed tomography angiography, magnetic resonance angiography, and ultrasonography are complementary means o evaluation, particularly for injury screening or treatment follow-up. The annual rate of stroke after injury is approximately 1% or less per year. The currently accepted method of therapy remains antithrombotic medication, either in the form of anticoagulation or antiplatelet agents; however, no class I medical evidence exists to guide therapy. Other options for treatment include thrombolysis and endovascular therapy, although the efficacy and indications for these methods remain unclear.

Carotid and vertebral artery dissections: clinical aspects, imaging features and endovascular treatment

Extracranial arterial dissections are a recognised cause of stroke, particularly in young adults. Clinical diagnosis may be difficult, and the classical triad of symptoms is uncommon. Imaging plays a pivotal role in the diagnosis of extracranial arterial dissections, and this review provides a detailed discussion of the relative merits and limitations of currently available imaging modalities. Conventional arteriography has been the reference standard for demonstrating an intimal flap and double lumen, which are the hallmarks of a dissection, and for detecting complications such as stenosis, occlusion or pseudoaneurysm. Noninvasive vascular imaging methods, such as ultrasound (US), magnetic resonance angiography (MRA) and computed tomography angiography (CTA) are increasingly replacing conventional angiography for the diagnosis of carotid and vertebral dissections. Ultrasound provides dynamic and "real-time" information regarding blood flow. Source data of MRA and CTA and additional cross-sectional images can provide direct visualisation of the mural haematoma and information about the vessel lumen. Anticoagulation to prevent strokes is the mainstay of medical treatment, but randomised trials to define the optimal treatment regime are lacking. Surgery has a limited role in management of dissections, but endovascular procedures are gaining importance for treatment of complications and if medical management fails.

Heralding manifestations of basilar artery occlusion with lethal or severe stroke

BACKGROUND

Basilar artery occlusion usually causes severe disability or death. Until the recent developments in local intra-arterial or systemic intravenous fibrinolysis, interest in early diagnosis was low because there was no satisfactory treatment. Thus there is little information about the initial phase of the disease.

OBJECTIVE

To report on the early clinical features and patterns of evolution of severe symptomatic basilar artery occlusion.

METHODS

24 patients with established basilar artery occlusion (confirmed by angiography or at necropsy) were reviewed retrospectively, focusing on the early clinical aspects and time course of the disease.

RESULTS

The most common initial symptoms were motor deficits (16/24, including facial palsies), articulatory speech difficulties (15/24), vertigo, nausea or vomiting (13/24), and headaches (10/24). The most frequent objective initial findings were motor deficits (22/24), facial palsies (19/24), eye movement abnormalities (15/24), lower cranial nerve deficits (15/24), altered level of consciousness (12/24), and bilateral extensor plantar responses (9/24). Onset of the disease was gradual in nearly all patients and in half the warning signs were present for up to two months before the final stage. Headaches and visual disturbances were early signs, while speech difficulties and motor deficits were late signs. Once permanent neurological deficits were present, the final illness was reached within six hours in 41%, between six and 24 hours in 32%, and in two to three days in 27%.

CONCLUSIONS

All the patients reviewed presented some symptoms and signs pointing to brain stem involvement. Only 8% (2/24) had an acute course with no adequate warning signs.

[Basilar artery dissection: case report]

We report a case of basilar artery dissection. MRI and angiographic study could ascertain the diagnosis.

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.

[Basilar ectasia and stroke: imaging features in 21 cases]

Ectasia of the basilar artery (EB) may cause different clinical manifestations, and its analysis by imaging methods is fundamental. We tried to analyse radiological aspects in 21 patients with stroke and EB. In all of them, diagnosis could be done by computed tomography. However, magnetic resonance was the most complete diagnostic method for the evaluation of the relationship between EB an surrounding structures.

Vertebral artery occlusion associated with cervical spine trauma. A prospective analysis

STUDY DESIGN

Radiographs and charts of 61 patients sustaining cervical spine trauma were studied prospectively to determine the incidence of vertebral artery injuries and possible correlative factors. Statistical analysis was conducted using chi-square testing of a two-way classification system.

OBJECTIVES

To elucidate the incidence of vertebral artery injuries associated with cervical spine trauma, and to determine the value of various factors in predicting the existence of a vertebral artery injury.

SUMMARY OF BACKGROUND DATA

During a 7-month period, 61 patients (41 male patients, 20 female; average age, 40.3 years) with cervical spine trauma were studied.

METHODS

All patients admitted to the authors' hospital with cervical spine injuries underwent magnetic resonance imaging and magnetic resonance angiography of their cervical spine. All magnetic resonance angiographies were examined for vertebral artery injury. Data on demographics and the injury were recorded.

RESULTS

Complete disruption of blood flow through the vertebral artery was demonstrated by magnetic resonance angiography in 12 of the 61 patients (19.7%). Ten of the 12 patients (83%) had either flexion distraction or flexion compression injuries. Age, sex, mechanism of injury, neurologic impairment, and associated injuries were not statistically significant in predicting the presence of a vertebral vessel occlusion.

CONCLUSION

The findings in this study may support the need for vertebral vessel evaluation in selective patients, particularly those with flexion injuries and with neurologic symptoms consistent with vertebral artery insufficiency syndrome that do not correlate with the presenting bone and soft-tissue injuries.

Treatment of dissecting basilar artery aneurysm by flow reversal

Dissecting aneurysm of the basilar artery is a rare but increasingly recognized entity, with a frequently fatal or morbid outcome. Unlike the well established proximal occlusion and trapping approaches to vertebral artery dissections, surgical intervention for basilar lesions has been limited to wrapping techniques for arterial wall reinforcement. We report a case of midbasilar dissecting aneurysm successfully treated by clipping the proximal basilar artery below the level of the anterior inferior cerebellar arteries, allowing retrograde flow via the posterior communicating arteries to provide continued basilar perfusion. With the growing recognition of basilar dissection and pseudoaneurysm formation there is a need for improved therapeutic options. We suggest that definitive treatment can be achieved using the principle of proximal occlusion and flow reversal, and review the pertinent literature on basilar artery dissection.

Hyperdense basilar artery. An early computed tomography sign of thrombosis

Noncontrast computed tomographic scans (CT scans) may show a hyperdense basilar artery before a brainstem infarct is visualized. This early sign should assist clinicians in confirming the diagnosis of basilar artery thrombosis. In a review of admission records of 750 patients with acute cerebrovascular disease from July 1991 to June 1993, at Saint Louis University Hospital, 20 patients were identified with clinical signs of nonlacunar, vertebrobasilar distribution infarction. Eight of these had pontomesencephalic ischemia. Their neuroimaging studies and medical records were evaluated. Four patients with acute clinical signs of pontomesencephalic infarction were found to have a hyperdense basilar artery on CT scans. The scans of 2 patients were excluded because of dolichoectasia; in the other 2 patients, the basilar artery appeared normal on the CT scan. The hyperdense basilar artery was detected within the early hours of neurological symptoms and often was the only detectable abnormality on the scan. In 3 patients extensive brainstem infarcts subsequently developed and they died. Basilar artery thrombosis was confirmed by pathological study in all these patients. In the fourth patient basilar artery occlusion and a large pontine infarct were evident by magnetic resonance imaging and angiography. A hyperdense basilar artery is a common feature on CT scans of patients presenting with an early clinical diagnosis of thrombosis. Untreated, the hyperintense basilar artery often portends a poor prognosis. Its ready recognition should guide further interventional studies and treatment.

Imaging in acute basilar artery thrombosis

The aim of this study was to review the imaging features in acute (< 24 h) basilar artery thrombosis. CT and MR studies in 11 patients with clinical diagnosis of acute basilar artery thrombosis were retrospectively reviewed. MR angiography was obtained in 4 patients. Correlation with clinical symptoms was performed. Multiple cranial nerve palsies and hemiparesis were the most common clinical symptoms at presentation. CT revealed hyperdense basilar arteries (n = 7) and hypodensities in the posterior circulation territory (n = 8). In one instance, the infarction was hemorrhagic. MR imaging showed absence of flow void within the basilar in 6 patients and MRA (using both PC and TOF techniques) confirmed absence of blood flow in 4 basilar arteries. One week after presentation, 5 patients died. Autopsy was obtained in 1 case and confirmed the diagnosis of basilar artery thrombosis. Basilar artery thrombosis has fairly typical imaging features by both CT and MR. MRA may be used to confirm the diagnosis. Prompt recognition may lead to early thrombolytic treatment and may improve survival.

Dissection of the vertebral arteries: case report and discussion

Vertebral artery dissection is an unusual condition with potentially protean neurologic presentations. It may occur spontaneously or follow apparently minor neck trauma. Ischemic symptoms related to the posterior circulation ensue and may be due to obstruction or embolization. The ensuing stroke is ischemic, although subarachnoid hemorrhage may be a complication as well. A case of vertebral artery dissection in a young woman who developed symptoms approximately one week after mild neck injury is reported, and the topic is reviewed.

Recurrent syncope and quadriplegia

A 72-year-old man had posturally induced syncopal episodes, followed by quadriparesis, coma, and death. Neuroimaging studies supported the clinical diagnosis confirmed by neuropathological findings.

Subarachnoid hemorrhage without detectable aneurysm. A review of the causes

BACKGROUND

In 15% to 20% of patients with a spontaneous subarachnoid hemorrhage, no aneurysm is found on the first angiogram. This review emphasizes that this group of patients is in fact heterogeneous and describes the clinical features, pattern of hemorrhage on early computed tomographic (CT) scan, prognosis, and proposed management in the several and distinct subsets of these patients.

SUMMARY OF REVIEW

Patients in whom no aneurysm is revealed on the initial angiogram can be subdivided mainly according to the pattern of hemorrhage on an early CT scan. In two thirds of these patients the CT scan shows a perimesencephalic pattern of hemorrhage (ie, blood confined to the cisterns around the midbrain); these patients invariably have a good prognosis, which obviates the need for a second angiogram. Patients with diffuse or anteriorly located blood on CT scan are at risk of rebleeding. In most of these patients the source of hemorrhage is an occult aneurysm, but intracranial artery dissections, dural arteriovenous malformations, mycotic aneurysms, trauma, bleeding disorders, substance abuse, or a cervical origin of the hemorrhage should also be considered. Patients with no blood revealed on an early CT scan but with xanthochromic cerebrospinal fluid are extremely rare. These patients deserve a second reading of the scan for blood in the prepontine cistern, which can be the only site of hemorrhage in perimesencephalic hemorrhage.

CONCLUSIONS

The prognosis and management of patients in whom no aneurysm is found on the initial angiogram depends on the pattern of hemorrhage on the initial CT scan. Patients should no longer be designated with the umbrella term "angiogram-negative subarachnoid hemorrhage."

"Dolichoectatic" intracranial vertebrobasilar dissecting aneurysm

We report five patients with intracranial vertebrobasilar dissecting aneurysms, all of whom had ischemic symptoms. Angiographically, four of the five cases revealed distention and elongation of the vertebrobasilar artery like dolichoectasia and one irregular stenosis, the so-called "string sign". Magnetic resonance imaging disclosed all dolichoectatic dissecting lesions by demonstrating intimal flaps, double lumen, or subacute clot in the false lumen. We also present a successful demonstration of slow flow in the false lumen by gradient refocused magnetic resonance imaging scan with partial flip angle by the cardiac gating method. It is suggested that many of the classical "dolichoectasia" may include dissecting lesions.

Lateral cervical spine dislocation and vertebral artery injury

Although anterior and posterior traumatic displacement of cervical vertebrae are commonly noted, and the devastating neurological deficits associated with these injuries have been amply defined, lateral displacement with fractures has been rarely recognized, and the clinical significance of this injury has been overlooked. This report describes five cases of cervical spine fractures with lateral dislocation. All patients had lateral and anteroposterior cervical spine radiographs as well as cervical angiography or postmortem study demonstrating either complete occlusion or significant impairment of flow of the vertebral arteries. Two cases had traumatic vertebral artery occlusion with secondary medullary and cerebellar infarction resulting in the patient's death. Vertebral artery injury apparently is not uncommon in this particular type of fracture. The diagnosis of these vascular injuries may require angiography or magnetic resonance angiography. A vertebral occlusion or dissection is a problem of considerable complexity, requiring individualized management depending on the patient's symptomatology, location and nature of the injury, and time lapsed since the injury.

Intracranial magnetic resonance angiography

Intraarterial angiography remains the "gold standard" for the evaluation of the intracranial vasculature, but it carries with it the risks of local vascular damage, systemic reactions, transient neurologic deficits, permanent neurologic compromise, and even death. To date, magnetic resonance angiography (MRA) has been applied to a variety of different manifestations of intracranial vascular disease. Presently, MRA studies and flow measurement techniques serve to compliment the more traditional spin-echo evaluation of patients with small aneurysms, arterial and venous occlusions, vascular malformations, and in some cases of neoplastic vascular invasion. Practically, the limitations of these techniques must be taken into account such that the appropriate method is applied to answer a specific clinical question and the acquisition parameters are chosen to maximize the sensitivity and specificity of the study. The intent of this review is to summarize the technical approaches, clinical role, pitfalls, and potential improvements in the MRA techniques as they apply to the intracranial circulation.