Stenting of Symptomatic Atherosclerotic Lesions in the Vertebral or Intracranial Arteries (SSYLVIA): study results

BACKGROUND AND PURPOSE

Stroke rates in patients with symptomatic intracranial stenosis may be as high as 10% to 24% per year on medical therapy. This multicenter, nonrandomized, prospective feasibility study evaluated the NEUROLINK System for treatment of vertebral or intracranial artery stenosis.

METHODS

Patients were 18 to 80 years old with symptoms attributed to a single target lesion of > or =50% stenosis. Patients received 5 neurological examinations before and in the year after the procedure, and another angiogram at 6 months.

RESULTS

In 61 patients enrolled, 43 (70.5%) intracranial arteries (15 internal carotid, 5 middle cerebral, 1 posterior cerebral, 17 basilar, 5 vertebral) and 18 (29.5%) extracranial vertebral arteries (6 ostia, 12 proximal to the posterior inferior cerebellar artery [PICA]) were treated. In the first 30 days, 4 patients (6.6%) had strokes and no deaths occurred. Successful stent placement was achieved in 58/61 cases (95%). At 6 months, stenosis of >50% occurred in 12/37 (32.4%) intracranial arteries and 6/14 (42.9%) extracranial vertebrals, 4 in the vertebral ostia. Seven (39%) recurrent stenoses were symptomatic. Four of 55 patients (7.3%) had strokes later than 30 days, 1 of which was in the only patient not stented.

CONCLUSIONS

The NEUROLINK System is associated with a high rate of successful stent deployment. Strokes occurred in 6.6% of patients within 30 days and in 7.3% between 30 days and 1 year. Although restenoses occurred in 35% of patients, 61% were asymptomatic. Further trials involving the NEUROLINK System are warranted.

Simultaneous ischemic and neurotoxic brain damage after coronary angiography

Transient cortical blindness following intra-arterial catheter angiography is a known rare complication. We report the case of a 56-year-old man who suffered from transient cortical blindness and neuropsychological deficits after coronary angiography. Serial CT scans revealed reversible pathologic parenchymal contrast enhancement of the right occipital lobe as well as left middle cerebral artery infarction at the same time. CT changes and time course of clinical symptoms are presented and discussed for both lesions of presumably different etiology.

[Early manifestation and dynamics of the development of vertebrobasilar circulation disorder associated with cervicovertebral dysfunction, directions of the prophylaxis and treatment]

206 children and young patients have been observed to diagnose the origin and dynamics of the development of vertebrobasilar circulation disturbances. The great importance was given to detail data collection by questionnairing and studying outpatient medical records of the patients since early childhood. The obtained data were compared with those of healthy people of similar age. Risk factors and the development of symptoms of the disease with age were analyzed in the article. Genetical and constitutional factors are of great importance in the development of vascular and musculoskeletal systems pathologies. The intensity of the pathologic process and dynamics of its development connected directly with the number and pathologic factors duration. Early manifestation of vertebrobasilar disturbances is considered in practice as vegetovascular dystonia. Taking into account a reflex factor in the development of the pathology, reflex therapeutic methods will be pathogenetically justified.

Neuroradiological features of vertigo

The diagnostic pathway in a patient with vertigo starts with the accurate evaluation of medical history followed by a general physical and neurological examination. This step can often lead to the identification of the correct cause of the disease or, at least, to a distinction between peripheral and central vertigo. Neuroradiological investigations have to be considered as elective diagnostic procedures and include: computed tomography (CT), magnetic resonance (MR), MR angiography (MRA), angiography. For the diagnosis of peripheral vertigo, benign paroxysmal positional vertigo, labyrinthitis, Meniere disease, perilymphatic fistula, local trauma, toxic labyrinthitis, acute otitis media and chronic middle ear effusion,the role of imaging techniques is controversial. CT and MR are performed to rule out other pathologies and to confirm the diagnosis. Increased resolution and application of special MR sequences enhancing the intralabyrinthine fluids have enabled more detailed analysis of labyrinthine structures and pathology. Both T2 and T1 contrast sequences are necessary. A high resolution CT study is required when otitis media is suspected and in the follow-up of post-traumatic vertigo. The causes of central vertigo are numerous and include: vertebro-basilar circulation vascular events, multiple sclerosis (MS), migraine-associated vertigo, cerebellar and brainstem tumors, CNS infections. Among them cerebrovascular ischemia and multiple sclerosis are the most frequent. In these situations imaging studies become mandatory. CT can diagnose most cerebellar hemorrhages and some cerebellar and brainstem acute ischemia, enhanced MR has proved to be the most sensitive tool to detect posterior fossa lesion. Diffusion-weighted MR can reveal acute ischemic changes before routine MR. There has been evidence that MR angiography, providing angiogram-like images of the intracranial vessels may sometimes avoid invasive angiography. MRA resolution is not as good as traditional angiography and may also be compromised by movements and other artifacts. Selective angiography of the posterior circulation is often indicated for therapeutic decisions.

Moyamoya angiopathy with dolichoectatic internal carotid arteries, patent ductus arteriosus and pupillary dysfunction: a new genetic syndrome?

We report on 2 children with moyamoya angiopathy and bilateral dolichoectatic internal carotid arteries in combination with iris hypoplasia with bilateral fixed dilated pupils and a history of patent ductus arteriosus. Both were symptomatic with moyamoya angiopathy and underwent bilateral extracranial-intracranial (EC-IC) bypass operations for cerebral revascularization. This is the first report on moyamoya angiopathy and bilateral dolichoectatic internal carotid arteries with simultaneous occurrence of ocular and cardiovascular malformations. There have been descriptions of cerebral vascular abnormalities in combination with either congenital heart disease or ocular abnormalities but not with both presenting together. The combination of these separate congenital developmental defects may not be purely coincidental: we propose that the 2 probands are affected with a not yet recognized clinical syndrome of probably genetic etiology.

Cerebellar stroke: more than meets the eye

Patients with a cerebellar stroke are difficult to diagnose and a challenge for neurologists and emergency room physicians. The clinical presentation may be ambiguous, and initial computed tomography scan can be normal. In order to recognize a cerebellar stroke, a full examination of the cerebellar function is indicated, but this part of the neurologic examination is often omitted. We present a patient in whom the diagnosis of occlusive basilar artery disease was delayed. Current treatment options in the intensive care unit are additionally discussed.

Vertebrobasilar dolichoectasia diagnosed by magnetic resonance angiography and risk of stroke and death: a cohort study

OBJECTIVE

There are only limited epidemiological studies evaluating the association between vertebrobasilar dolichoectasia (VBD) and outcomes. This study was designed to elucidate the outcome and prognosis of adults diagnosed with VBD by magnetic resonance angiography (MRA) and to ascertain if these outcomes were independent of known vascular risk factors.

METHODS

A cohort study was designed to compare VBD cases identified retrospectively from a computerised database of MRA reports with age and sex matched controls evaluated after a 4-7 year period, and 1440 MRA reports were reviewed. The inclusion criteria were age > or =18 years and a radiological diagnosis of VBD. Patients were excluded if there was haemodynamically significant stenosis or occlusion of the posterior circulation. Data were obtained by medical record review and telephone questionnaires. The primary outcome measure was transient or fixed posterior circulation dysfunction (PCD), with a secondary outcome measure of all cause mortality.

RESULTS

Sixty four VBD cases were obtained, and 19 cases (30%) were excluded due to refusal and/or insufficient follow up data. From the same computerised database, 45 controls were selected by consecutive sampling. The mean age at follow up was 73.4 years for VBD cases and 73.1 years for controls, with a median follow up period of 64 months. VBD was associated with fixed/transient PCD (p = 0.0001; estimated adjusted odds ratio (OR) of 20.6 and confidence interval (CI) of 4.4 to 95.3), and with all cause mortality (OR = 3.6 CI 1.3 to 10.3); (p = 0.018). VBD cases had 36% mortality, with 50% occurring within 34 months of the initial diagnosis. The VBD cumulative survival curve was statistically different from the controls (p = 0.012 by Mantel-Cox log rank test).

CONCLUSIONS

This study suggests that VBD may be an independent risk factor for stroke. VBD cases had an increased likelihood for PCD, all cause mortality, and reduced cumulative survival independent of other vascular risk factors in this cohort. Larger population based prospective studies are required to verify these results.

‘Ecstasy’-induced subarachnoid haemorrhage: an under-reported neurological complication?

In the face of escalating recreational use of 'Ecstasy' (3,4-methylenedioxymethamphetamine, MDMA), physicians need to be aware of its possible adverse effects. We report two young patients who suffered subarachnoid haemorrhage following ingestion of 'Ecstasy' tablets. Angiographic studies demonstrated features consistent with vasculitis in both cases. Recognition of this association is important and highlights the significance of eliciting a careful drug history, particularly in cases of 'angiogram negative' subarachnoid haemorrhage.

[Radiologic investigation of vertebrobasilar insufficiency and quantification of vertebrobasilar flow with magnetic resonance imaging]

PURPOSE

To evaluate the contribution of cervical spine radiograms, Doppler US, cervical and cranial MRI, MRA and two dimensional quantification flow in the diagnosis of vertebrobasilar insufficiency.

MATERIALS AND METHODS

We prospectively examined 25 patients having signs of vertebrobasilar insufficiency (16 females and 9 males, aged 34 to 74 years) and 25 controls of the same age and sex with MRI, MRA, Doppler US and cervical radiograms. Cervical spine radiograms were evaluated for the presence of degenerative changes, osteophytes and loss of height. The flow velocities of the basilar artery and vertebral arteries were measured with two dimensional quantification flow, using time-velocity graphics achieved by means of a region of interest drawn on transverse sections of the vessels. Posterior circulation in farcts and slow flow in vertebrobasilar system arteries were investigated on brain MR images and the presence of cervical osteophytes, spinal cord compression and the effect of the presence of degenerative changes on vertebral arteries were evaluated on cervical MR images. Paired samples T-test, independent samples T-test, Wilcoxon W, Mann-Whitney U and chi-square tests were used for statistical analysis. The significance level was taken at p below 0.05.

RESULTS

From the statistical analysis, we found that there were more pathologic findings on MRA within the patient group compared with the controls (p = 0.002). The velocities measured by MRI were significantly affected by the presence of unknown bright objects on brain MR images, osteophytes on cervical MR images, loss of height and the presence of osteophytes on radiograms in patients having VBI signs, when compared to the controls. In both groups, the measurements of flow velocity in vertebral arteries by Doppler US did not correlate with the measurements by two dimensional quantification flow.

CONCLUSION

Among the methods we used in our study, MRA was the most specific in the diagnosis of patients with vertebrobasilar insufficiency. However, two dimensional quantification flow can be used as a noninvasive but indirect method to investigate the influence of several factors on the hemodynamics.

Basilar artery occlusion in children: misleading presentations, "locked-in" state, and diagnostic importance of accompanying vertebral artery occlusion

Basilar artery occlusion in children is rare. The clinical diagnosis of basilar artery occlusion is often difficult because the initial neurologic findings, most frequently hemiparesis, involuntary movements, or headache, are often transient and can suggest complicated migraine, seizures, or both. We have reviewed 37 previously reported pediatric cases of basilar artery occlusion and present 3 additional ones. In the 40 cases, basilar artery occlusion alone occurred in 22; in the other 18, there was accompanying vertebral artery occlusion. In the cases of pure basilar artery occlusion, the most common causes were trauma and arteritis, but in most such cases, the etiology could not be determined. The cause was found much more often in cases of basilar artery occlusion with accompanying vertebral artery occlusion, with trauma being the most frequent etiology, especially in boys between 6 and 14 years. Of the 37 previously reported pediatric cases of basilar artery occlusion, 7 were "locked in" early in the course (mute, quadriparetic, aware, and communicative with eye movements), as were our 3 cases. In most cases of basilar artery occlusion that are locked in, the basilar artery occlusion involves its midportion, sparing the anterior inferior cerebellar and superior cerebellar arteries.

Unusual vertebral artery origins: examples and related pathology

Anomalies of the vertebral arteries are uncommon, but important to recognize in the diagnosis and catheter based evaluation and treatment of patients suffering cerebrovascular disease. This article illustrates our experience with such anomalies. These include the vertebral artery arising as the fourth and most distal branch of the aortic arch, as a right subclavian artery branch arising distal to the right thyrocervical trunk, as a right common carotid artery branch in a patient with an aberrant right subclavian artery, and a case of left vertebral artery proximal duplication, with both aortic and left subclavian vertebral arteries present in the same patient; the latter join to form a single distal cervical vertebral artery.

Cooperative study of ruptured vertebrobasilar artery aneurysms in the Tohoku district in Japan

A multicenter study investigated the clinical characteristics and overall outcome of 342 cases of ruptured vertebrobasilar artery aneurysms among 6783 ruptured intracranial berry aneurysms in 73 hospitals across the Tohoku district in Japan between 1992 and 1996. The incidence of ruptured vertebrobasilar artery aneurysms was less frequent than previously reported. The incidence was 5% among all intracranial berry aneurysms. One hundred eleven patients had aneurysms of the basilar artery bifurcation, 98 had vertebral-posterior inferior cerebellar artery aneurysms, 44 had basilar-superior cerebellar artery aneurysms, and 28 had distal posterior inferior cerebellar artery aneurysms. Aneurysm clipping was performed in 238 cases (70%), intravascular treatment in 22 (6%), drainage in 22 (6%), and conservative treatment in 60 (18%). Approximately 50% of patients were in good condition at admission. At 3-month follow up, 46% had good recovery, 14% had moderate disability, 10% had severe disability, 4% were vegetative state, and 27% died. Vertebral artery aneurysms showed favorable outcomes compared to basilar artery bifurcation aneurysms. Surgical results in the 238 operated cases were good recovery in 60%, moderate disability in 18%, severe disability in 10%, vegetative state in 2%, and death in 11% of cases. Worse postoperative outcomes were observed in patients with high preoperative Hunt and Kosnik grades or aneurysms larger than 10 mm, and in patients over 70 years of age.

Basilar artery stenosis mimicking the lacunar syndrome of pure motor hemiparesis

BACKGROUND

Stereotyped, repeated transient ischemic attacks manifesting as pure motor hemiparesis are most often attributed to ischemia of the internal capsule or ventral pons resulting from in situ disease of the small penetrating arteries.

CASE DESCRIPTION

We report a 61-year-old man presenting with recurrent episodes of left-sided weakness consistent with the lacunar syndrome of pure motor hemiparesis. Subsequent neuroimaging revealed infarction of the right ventral pons and a critical basilar artery stenosis as the inciting lesion. Despite maximal antithrombotic therapy, he continued to have repeated symptoms. Angioplasty and stenting were attempted but both failed due to plaque recoil and technical difficulties. After the procedure, the patient had no further ischemic episodes and remained symptom-free at two months.

CONCLUSIONS

This case illustrates the imprecise and discordant relationship between the mode of presentation of a stroke syndrome and its presumed pathophysiology. The lacunar syndrome of pure motor hemiparesis should be recognized by clinicians as a mode of stroke presentation due not only to small vessel disease, but also to large artery atherosclerotic disease such as basilar artery stenosis. Prompt institution of treatment can lead to a good clinical outcome.

Sudden bilateral simultaneous deafness with vertigo as a sole manifestation of vertebrobasilar insufficiency

A 68 year old woman presented with bilateral sudden simultaneous hearing loss and transient spontaneous vertigo as a sole manifestation of vertebrobasilar insufficiency. Extensive investigation to exclude other causes was unremarkable. Magnetic resonance imaging of the brain, including diffusion images, showed no abnormalities. A magnetic resonance angiogram showed severe stenosis of the middle third of the basilar artery. A pure tone audiogram showed moderate sensorineural-type hearing loss bilaterally. The localisation and mechanism of an isolated cochleovestibular dysfunction are discussed.

Apraxia of tool use: an autopsy case of biparietal infarction

Although disorders in the use of single objects have been reported, there have been few detailed analyses. We describe the autopsy case of a 65-year-old, right-handed male patient with severe impairment of actual tool use which was caused by biparietal infarctions. He persistently and stably showed a severely defective use of actual objects, single or multiple, and relatively well-preserved pantomimes of object use and intransitive gestures. He did not have aphasia or dementia, and his ability for tool naming and function description was completely preserved. The author identified similar patterns of errors about a tool-action(-target) relationship both in single-object use and multiple-object use. Lesion analysis showed cortical infarcts mainly located in the bilateral inferior parietal lobules, extending into the temporal lobe on the right side.

Experimental subarachnoid haemorrhage models in rats

There is no comprehensive and reliable model available in small animals that are suitable for the study of subarachnoid haemorrhage (SAH). In the study we reviewed the advantages and disadvantages of available SAH models in rats and presented our model. Experimental SAH was induced in a group of 350-450 g Sprague-Dawley rats. A 2 mm-diameter burr hole was drilled and, working under a microscope, haemorrhage was produced by transclival puncture of the basilar artery with a 20 microns thick piece of glass. The rats were assigned to either the experimental group (n: 7) or the control group (n: 7). Local cerebral blood flow (LCBF), intracranial pressure (ICP), and cerebral perfusion pressure (CPP) were measured for 60 min after SAH, after which the rats were decapitated. Microscopic examinations were done on three different segments of the basilar artery. There was a significant and sharp drop in LCBF just after SAH was induced (56.17 +/- 12.80 mlLD/min/100 g and 13.57 +/- 5.85 mlLD/min/100 g for baseline and post-SAH, respectively; p < 0.001), the flow slowly increased by the end of the experiment but never recovered to pre-SAH values (43.63 +/- 7.6 mlLD/min/100 g, p < 0.05). ICP (baseline 7.33 +/- 0.8 mmHg) increased acutely to 70.6 +/- 9.2 mmHg, and also returned to normal levels by 60 min after SAH. CPP (baseline 75.1 +/- 4.9 mmHg) dropped accordingly (to 21.0 +/- 6.3 mmHg) and then increased, reaching 70.1 +/- 4.9 mmHg at 60 min after SAH. Examinations of the arteries revealed decreased inner luminal diameter and distortion of the elastica layer. We present an inexpensive and reliable model of SAH in the rat that allows single and multiple haemorrhages and to study the early and late course of pathological changes.

Bilateral vertebral artery occlusion resulting from giant cell arteritis: report of 3 cases and review of the literature

Giant cell arteritis (GCA) is known to affect the extracranial part of the vertebral arteries. Bilateral vertebral artery occlusion (BVAO) is a rare but serious neurologic condition. We report 3 patients with autopsy-proven (2 patients) or clinically diagnosed (1 patient) GCA causing BVAO. A review of the literature concerning BVAO revealed 5 other cases of BVAO resulting from GCA and 110 cases with underlying arteriosclerotic disease. Our 3 patients (mean age, 66 yr; range, 60-78 yr) with BVAO resulting from GCA all had initial severe headache followed by the onset of stepwise progressive, partly side-alternating neurologic deficits due to bilateral infarctions in the vertebrobasilar circulation territory. This course, more accelerated in BVAO due to GCA than in BVAO of arteriosclerotic origin, seems to be a typical, if not particular, clinical syndrome. BVAO was the first clinical manifestation of GCA in 1 of our patients and in 1 published case. From a clinical view, BVAO resulting from GCA differs from BVAO of arteriosclerotic origin by the much higher mortality rate (75% versus 19%, respectively), the presence of headache (100% versus 22%), fever (50% versus 0%), and elevated erythrocyte sedimentation rate (ESR in all GCA cases >45 mm/h; no data in the arteriosclerotic patient group), but not by the neurologic signs themselves. Therapy of BVAO resulting from GCA is purely empiric. In view of the serious prognosis, we propose treatment with intravenous high-dose glucocorticoids and additional immunosuppression with cyclophosphamide; the use of anticoagulation depends on the individual patient's estimated risk-benefit profile. Although BVAO due to GCA is rare, physicians and especially rheumatologists or neurologists should be aware of this entity because of its high mortality in patients without immediate introduction of a high-dose immunosuppressive therapy. Suspicion of GCA should arise in a patient aged over 50 years with no other vascular risk factors suffering from bilateral symptoms of ischemia in the vertebrobasilar territory, with a quickly progressing stepwise course and with headache, fever, or history of myalgia. ESR and temporal artery biopsy should be performed without delay. Early diagnosis of GCA is necessary for immediate initiation of intensive antiinflammatory and immunosuppressive treatment, without which progressive deterioration and systemic involvement are likely to be fatal.

[Blood flow insufficiency in vertebrobasilar system]

Ethiopathological and clinical factors of vertebral blood flow insufficiency development are discussed in the article. Distinct connection between pathogenesis and stages of clinical manifestation is proved and nosological independence of vertebrobasilar disease is validated. Used in combined therapy of patients with the disease, cavinton is shown to exert a positive effect on the main clinical symptoms.

Evaluation of cerebral blood flow reserve in patients with cerebrovascular disease by SPECT using technetium-99m-L, L-ethyl cysteinate dimer

A technique for measuring the resting and acetazolamide (Acz)-activated cerebral blood flow without blood sampling by consecutive single-photon emission computed tomography (SPECT) using technetium-99m-L, L-ethyl cysteinate dimer (99mTc-ECD), called the 99mTc-ECD-RVR method, was recently developed by Matsuda et al. and Takeuchi et al. We evaluated the cerebral blood flow reserve in 77 patients with cerebrovascular diseases and 24 controls using this method. Baseline mean CBF (mCBF) was calculated from the application of Patlak plot graphical analysis with radionuclide angiography, and quantitative regional CBF (rCBF) images were obtained from qualitative axial SPECT images by the mCBF and Lassen's linearization correction. The activated SPECT images were obtained by subtraction of the first image from the second image. The mean increment ratio (IR) by calculating the mean CBF for the pre- and post-Acz in the controls was 1.26+/-0.12 (mean+/-SD). In patients with cerebrovascular disease, the reduction of the mean IR and regional IR was parallel with the degree of stenosis. This noninvasive method was also considered to be useful in evaluating the change in the hemodynamic reserve in cerebrovascular disease.

Vertebrobasilar dissection: a possible role of whiplash injury in its pathogenesis

We reviewed 29 patients with vertebrobasilar dissections (VBD) to investigate the correlation between minor trauma and VBD and the clinical features of this trauma-related condition. Mean age was 43 years, with a male predominance (male/female ratio was 25/4). Seventeen patients presented with subarachnoid hemorrhage (SAH), and 12 with ischemic symptoms. Two patients presenting with ischemia had extracranial VBD (V3 segment). Angiographically, aneurysmal dilatation was observed in most SAH patients (13 patients) in contrast to narrowing or occlusion in most ischemic patients (10 patients). Among the 12 SAH patients treated with coil embolization or conservatively, five died, whereas all ischemic patients recovered well with anticoagulation and/or antiplatelet therapy. Seven patients had received minor or trivial head/cervical trauma, due to whiplash injury, minor fall, or during exercise, which were identified to precede with the lapse of some time (a few minutes or days) the onset of symptoms. All of these patients presented with ischemic symptoms, and they were younger than the other ischemic or SAH patients. The site of vertebral artery dissection was intracranial in four cases, extracranial in one case, and combined in two cases at the level of the V3 segment and the origin of the posterior inferior cerebellar artery. However, no SAH occurred. These clinicopathological findings, i.e. ischemia and angiographic narrowing/occlusion, suggest that dissections were subintimal. Therefore, it is believed that this minor or trivial trauma may primarily cause subintimal dissection with luminal compromise, leading to ischemic symptoms, rather than subadventitial or transmural dissection with aneurysmal dilatation, leading to SAH. This lesion may also occur in younger patients with a favorable outcome. Careful note should be made of patient for the early recognition of this disorder.

Transcranial sonography and vertebrobasilar insufficiency

OBJECTIVE

The objective was to discuss a case illustrating the role of transcranial Doppler sonography in the screening and treatment of a patient with intermittent vertebral artery brainstem ischemia.

CLINICAL FEATURES

A 28-year-old woman had neck pain, arm pain, headaches, and dizziness. Her symptoms occurred intermittently over several years. Past care had provided little relief. De Kleyn's test, transcranial Doppler sonography, and magnetic resonance imaging/magnetic resonance angiography helped establish a diagnosis of vertebrobasilar syndrome.

INTERVENTION AND OUTCOME

The patient was referred for neurosurgical evaluation. She subsequently chose to be treated with spinal manipulative therapy. Her neck pain, headaches, and radicular symptoms resolved. The dizzy spells abated to a tolerable level. The neurosurgeon subsequently re-evaluated the patient and recommended that surgery not be performed.

CONCLUSIONS

This illustrates a case of extra-arterial mechanical compression of the vertebral arteries documented by transcranial Doppler sonography procedures. Brainstem symptoms were correlated with a documented perfusion deficit during cervical positional testing. This case also demonstrated that spinal manipulative therapy may be safely used on patients with vertebrobasilar insufficiency when the biomechanics and related flow studies are elucidated.

Causes of complications from cervical spine manipulation

Cervical manipulation occasionally causes serious vertebrobasilar complications. The usual cause is vertebral artery dissection, however in some cases there has been no obvious arterial injury. The present paper reviews the mechanisms by which complications occur, particularly when the applied force is trivial or there is no injury to the vertebral arteries, and the factors that increase risk of complications. In addition, implications are drawn for use of the recently revised Australian Physiotherapy Association (APA) guidelines. In the absence of vertebral artery rupture, complications are proposed to arise from vasospasm, haemostasis, endothelial injury or turbulent flow. These mechanisms have a sound scientific basis but have yet to be demonstrated as specifically causing vertebrobasilar complications. The most important risk factors for vertebrobasilar complications appear to be prior trauma to the vertebral arteries and symptoms of vertebrobasilar ischaemia from previous manipulation. There is weak evidence that hypoplasia of the vertebral arteries also increases the risk of complications. Neither general vascular factors nor pre-existing degenerative conditions of the cervical spine increase risk of vertebrobasilar complications. The procedures described in the APA guidelines test adequacy of total cerebral perfusion during cervical movements rather than patency of the vertebral arteries or their susceptibility to injury. The guidelines may therefore indicate potential for surviving a complication from manipulation. They may also identify patients at risk of complications from minor trauma. It is recommended that the procedures described in the APA guidelines be applied prior to every manipulation, and that manipulation be avoided in the presence of any signs of vertebrobasilar insufficiency.