Effects of temporary occlusion of a vertebral artery on the human vestibular system

Intraoperative Hemodynamic Measurements of the Vertebral Artery and Common Carotid Artery

The hemodynamics in the vertebrobasilar artery (VBA) system were investigated in patients with vertebrobasilar insufficiency (VBI). Vertebral artery (VA) stump pressure and blood flows in the VA and common carotid artery (CCA) were intraoperatively measured in 45 patients who underwent surgical correction of the first segment of the VA (V1) for angiographic tortuosity, kinking, and/or stenosis manifesting as symptomatic VBI. The effects of changes in the systemic arterial blood pressure (SABP) induced by trimethaphan, phenylephrine, and cervical epidural anesthesia were also investigated. The VA stump pressure was 79.3 +/- 13.6 (mean +/- SD) mmHg and the ratio of the VA stump pressure to the SABP was 0.87 +/- 0.08. The baseline values were SABP 90.5 +/- 10.1 mmHg, VA blood flow 53.4 +/- 33.0 ml/min, and CCA blood flow 204.3 +/- 50.3 ml/min. During changes in the SABP, autoregulation of the blood flow in the VA appeared tighter than in the CCA. During cervical epidural anesthesia, blood flows in both the VA and CCA were significantly reduced in response to SABP reduction. This study demonstrated that the VBA system maintains excellent autoregulation with good collateral flows and cervical sympathetic nerve function. However, this autoregulatory capacity may be overwhelmed by unexpected occlusion of the VA due to postural changes associated with tortuosity, kinking, and/or stenosis of the V1 segment.

Vertebral artery-posterior inferior cerebellar artery bypass with a superficial temporal artery graft to treat aneurysms involving the posterior inferior cerebellar artery

OBJECT

In patients with aneurysms that require occlusion of the posterior inferior cerebellar artery (PICA), revascularization of this artery should be performed. A novel surgical method for revascularization of the PICA is presented.

METHODS

After a segment of the superficial temporal artery (STA) was harvested, the aneurysm was treated by trapping, followed by placement of a vertebral artery (VA)-PICA bypass in which the STA segment was used as a graft. When the length of the proximal PICA was inadequate, the distal end of the STA was anastomosed to the proximal PICA in an end-to-side fashion. When the length of the proximal PICA was adequate, the STA was anastomosed to the proximal PICA in an end-to-end fashion. In either case, the proximal end of the STA was anastomosed to the VA in an end-to-side fashion. This procedure was used in nine patients whose aneurysms involved the PICA. Although partial lateral medullary syndrome developed in one of them, follow-up evaluation revealed graft patency in all patients. There were no instances of recurrent hemorrhage or ischemia.

CONCLUSIONS

Although this procedure requires harvesting of an STA graft and two anastomoses, it facilitates anterograde flow to the PICA territory. It also involves minimal mobilization of brainstem perforating vessels and the proximal PICA.

Transcutaneous angioplasty of vertebral artery atheromatous ostial stricture

The authors report experience of intravascular angioplasty of atheromatous ostial strictures of the vertebral artery in 24 patients. After reviewing the technique, they outline the indications provided through Doppler velocimetric data. The results seem to be encouraging as symptoms disappeared completely in 21 patients.

Revascularization of the extracranial vertebral artery at any level without cross-clamping

Hemodynamic insufficiency resulting from extracranial vertebral artery stenosis or occlusion is believed to be the major cause of vertebrobasilar transient ischemic attacks. The major difficulties in treating this disorder have been exposure of the vertebral artery distal to the stenosis and the risk of vertebral artery cross-clamping for vein grafting or carotid artery transposition. The authors describe a new technique for vertebral artery reconstruction at any level by the use of an intraluminal shunt, thus avoiding the necessity to cross-clamp the artery. This procedure was successfully performed at all three levels of the extracranial vertebral artery: C7-4, C3-1, and C-1 to the foramen magnum. The technique of exposure of the vertebral artery at these three levels and the method of vein grafting without cross-clamping are described. The initial results of the procedure are presented.

Distribution of the blood flow supplied by the vertebral artery in humans as assessed by emission CT

Though unilateral blood distribution of the vertebral artery has not been studied in humans, it is significant when considering the ischemic events especially embolic occlusion in vertebrobasilar system. To clarify the blood distribution, Krypton-81m was continuously infused into the vertebral arteries of 10 patients. Radioactivity was recorded by a rotating gamma camera. The perfusion images, reconstructed by computer in the transaxial plane, were classified according to whether the distribution was equal, or predominantly unilateral. Overlapping of blood supply from each vertebral artery was studied. In addition, the perfusion from one of the vertebral arteries revealed four distribution patterns with respect to laterality. A) ipsilateral; B) contralateral; C) bilateral; D) mosaic. Images obtained following perfusion of the vertebral artery show less uniformity compared to that of the internal carotid artery, suggesting a complicated vascular supply of the vertebral basilar territory. This complex distribution can be classified by the use of continuous infusion of Krypton-81m.

Carotid to distal vertebral artery bypass for vertebrobasilar ischemia. Case report

A simple technique is described for a venous graft between the common carotid artery and the extracranial vertebral artery. In the case described, the vertebral artery was shown angiographically to be occluded and reconstituted by collateral vessels. This patient had symptoms of vertebrobasilar insufficiency which resolved postoperatively.

Subclavian to distal vertebral artery bypass. Case report

✓ A simple technique is described for extracranial vertebral artery vein bypass grafting, utilizing an internal shunt that avoids prohibitively dangerous vertebral artery cross-clamping. This procedure was carred out successfully in a patient with vertebrobasilar insufficiency.

[The blood vessels of the posterior cranial fossa. anatomy, pathophysiology, clinic--a survey (author's transl)]

Pathophysiology and tomography of the blood vessels of the posterior cranial fossa gain clinical interest in treatment of diseases of the inner ear, complications of middle ear inflammations, tumors of the pyramid and cerebello-pontine angle. Numerous variations in the arterial venous system restrict neuroradiological procedures. Techniques to treat a thrombosis of the sinuses were developed 50 years ago. Surgical procedures to remove glomus tumors of the pyramid could be improved by new anatomical and surgical experiences. Unilateral neck dissection occasionally alters the blood flow in the sinuses of the posterior cranial fossa causing serious complications.

Electrical stimulation of the stellate ganglion and the vertebral nerve

✓ Vestibular responses elicited by electrical stimulation of the stellate ganglion and of the periarterial nerve around the proximal vertebral artery were observed in 15 cases of intermittent vertebral artery compression (Powers' syndrome) during surgical treatment under local anesthesia. Stimulation of the periarterial nerve produced many varieties of pupillary change with or without ocular movements, nystagmus, posterior headache, and dizziness. The ocular changes included mydriasis or miosis of the ipsilateral or contralateral pupil, inconsistent hippus, conjugate or disconjugate eye movements, and horizontal or vertical nystagmus. Stimulation of the stellate ganglion, however, produced prompt and full mydriasis of the ipsilateral pupil without other eye changes, headache, or dizziness. From the data available it seems likely that the periarterial neural structure including the vertebral nerve and plexus (“deep or posterior cervical sympathetic system”) is functionally different from the cervical sympathetic system including the stellate ganglion (“anterior cervical sympathetic system”).