Rotational compression of the vertebral artery at the point of dural penetration. Case report

Vertebral artery segment at the suboccipital dural penetration site: an anatomical study using magnetic resonance imaging

PURPOSE

The morphology of the vertebral artery (VA) segment at the suboccipital dural penetration site has little been explored with magnetic resonance imaging (MRI). Therefore, the aim of this study was to examine the structure using MRI.

METHODS

In total, 94 patients underwent thin-sliced, contrast MRI in the axial, coronal, and sagittal planes involving the atlas, axis, occipital bone, and V3 and V4 segments of the VA.

RESULTS

The VA segment at the suboccipital dural penetration site was well-delineated in 93% on the axial images and in 95% on the coronal images. The axial images showed that 82% of the VA penetration sites were located in the middle third of the dural sac. Meanwhile, the coronal images revealed that the heights of both VA penetration sites were located at the same level in 87%. The axial VA penetration angle, which is formed by the VA and tangential line of the dural sac, was 66 ± 11.9° on the right side and 61 ± 14.1° on the left side. The coronal VA penetration angle, which is formed by the tangential line of the VA and dural sac, was 111 ± 24.6° on the right side and 112 ± 19.9° on the left side.

CONCLUSIONS

The morphology of the VA segment is considerably variable at the suboccipital dural penetration site, while most penetration sites are located in the middle third of the dural sac on axial MRI. These should be assumed during surgeries around the suboccipital VA penetration site.

Advances in the Pathogenesis, Diagnosis and Treatment of Bow Hunter's Syndrome: A Comprehensive Review of the Literature

Bow hunter's syndrome (BHS), also known as rotational vertebral artery (VA) occlusion syndrome, is a rare yet treatable type of symptomatic vertebrobasilar insufficiency resulting from mechanical occlusion or stenosis of the VA during head and neck rotation or extension. The symptoms of BHS range from transient vertigo to posterior circulation stroke. The underlying pathology is dynamic stenosis or compression of the VA by abnormal bony structures with neck rotation or extension in many cases, such as osteophyte, disc herniation, cervical spondylosis, tendinous bands or tumors. Imaging approaches, such as Doppler sonography, computed tomography and angiography, as well as magnetic resonance imaging and angiography, are widely used in the diagnosis and evaluation of this syndrome. Digital subtraction angiography with head rotation remains the gold standard diagnostic method. Conservative management, surgery and endovascular procedures are the three major treatment methods for BHS, whereas some symptomatic patients may need operative treatment including surgery and endovascular procedures when conservative management is not adequate.

Increased risk of posterior circulation infarcts among ischemic stroke patients with cervical spondylosis

BACKGROUND

Cervical spondylosis is one of the extrinsic factors causing vertebral artery stenosis. Several case studies have reported compression of the vertebral artery induced by cervical osteophytes that has resulted in posterior circulation infarcts (POCI). However, to the best of our knowledge, no studies have yet analyzed differences in the risk factors and stroke subtypes between ischemic stroke patients with cervical spondylosis and those without.

PURPOSE

In the case-controlled study reported here, we analyzed the risk factors and stroke subtypes in ischemic stroke patients with and without cervical spondylosis. Characteristics in all the recruited patients with POCI and non-POCI were further compared to extract other risk factors that could predict the occurrence of POCI.

METHODS AND PATIENTS

We filtered out ischemic stroke patients with cervical spondylosis ("Stroke+C" group) by International Classification of Diseases, Ninth Revision codes. We analyzed the data of 38 subjects in the Stroke+C group and 152 sex- and age-comparable ischemic stroke patients without cervical spondylosis ("Stroke-C" group). We recorded the demographic characteristics including sex and age, and stroke risk factors, including diabetes mellitus, hypertension, heart disease, hyperlipidemia, and smoking habits. The stroke classifications were defined by the Oxford Community Stroke Project classification. All subjects were further categorized into POCI or non-POCI groups. The ultrasound findings of the vertebral arteries (extracranial and intracranial) in the Stroke+C group were also recorded.

RESULTS

More patients in the Stroke+C group tended to have POCI (34.2%) than patients in the Stroke-C group (17.5%) (odds ratio [OR] =2.41, P<0.05). Furthermore, hypertension (OR=3.41, P<0.01) and cervical spondylosis (OR=2.41, P<0.05) were two independent risk factors for POCI in ischemic stroke patients.

CONCLUSION

Ischemic stroke patients with cervical spondylosis are more prone to POCI than those without cervical spondylosis. Hypertension is another identified risk factor for POCI in ischemic stroke patients. The occurrence of POCI should be highlighted for patients with cervical spondylosis.

Simultaneous bilateral stenosis of the vertebral arteries treated by unilateral decompression: a case report

A 56-year-old man presented with a 3-month history of progressive dizziness. His dizziness was aggravated when his head was rotated to the right side. Diagnostic angiography showed that a normal right-sided vertebral artery in the neutral position became an abnormal vertebral artery with two stenotic lesions at the C3-4 and C5-6 levels when the patient's head was turned to the right. A normal left-sided vertebral artery also showed a stenotic lesion at the C2 level when the patient's head was turned right. The axial dimensions of the bilateral vertebral arteries were similar. The patient was successfully treated with decompression of only one level (C5-6). We conclude that if a bilateral stenosis is found upon one directional head rotation and the bilateral vertebral arteries are similarly sized, a one-sided treatment may suffice.

Bow-hunter's syndrome caused by dynamic vertebral artery stenosis at the cranio-cervical junction--a management algorithm based on a systematic review and a clinical series

Bow hunter's syndrome (BHS) is defined as symptomatic, vertebro-basilar insufficiency caused by mechanical occlusion of the vertebral artery (VA) at the atlanto-axial level during head rotation. In the literature, about 40 cases have been reported. However, due to the rarity of this pathology, there are no guidelines for diagnosis and treatment. Conservative, surgical, and endovascular concepts have been proposed. In order to work out an algorithm, we performed a systematic review of the literature and a retrospective analysis of patients, which have been treated in our institutions over the last decade. The clinical series was comprised of five patients. The symptoms ranged from transient vertigo to posterior circulation stroke. Diagnosis was established by dynamic angiography. In all patients, the VA was decompressed; one patient required additional fusion. The clinical and radiological results were good, and the treatment-related morbidity was low. The literature review demonstrated that Bow hunter's syndrome is a rare pathology but associated with a pathognomonic and serious clinical presentation. The gold standard of diagnosis is dynamic angiography, and patients were well managed with tailored vertebral artery decompression. By this management, clinical and radiological results were excellent and the treatment-related morbidity was low.

Transient rotational compression of the vertebral artery caused by herniated cervical disc. Case report

Of the many causes of vertebrobasilar insufficiency (VBI), extrinsic compression of the vertebral artery (VA) is relatively uncommon. A syndrome of VBI caused by extrinsic compression of the VA secondary to head rotation has been termed positional vertebrobasilar ischemia. The authors present a case of transient VBI caused by herniation of a cervical disc. Transcranial Doppler ultrasonography was used preoperatively to confirm the diagnosis and intraoperatively to monitor cerebral perfusion and to confirm that adequate decompression of the VA had been achieved.