Noninvasive evaluation of vertebrobasilar insufficiency.

The diagnosis of vertebrobasilar insufficiency (VBI) is a clinical challenge because its manifestations are subjective and difficult to quantify. We evaluate 61 patients with the clinical diagnosis of VBI and 30 control patients with other medical problems. We used duplex scanning to study the extracranial carotid, vertebral, and subclavian arteries, and a 2-MHz transcranial Doppler (TCD) to examine the intracranial vertebral and basilar arteries. Extracranial lesions were more common in VBI patients than among controls, including stenosis of the subclavian artery with and without subclavian-vertebral steal and stenosis of the vertebral artery. Intracranial abnormalities identified in the vertebrobasilar circulation included stenosis and occlusion of the intracranial vertebral artery and basilar artery steal. Overall, significant lesions were detected in 32.8% of VBI patients and 3.0% of controls (P less than 0.05). Systolic artery velocity (cm/sec) in the extracranial vertebral artery was higher in controls (65.9 +/- 23.3) than in VBI patients who had no evidence of vertebrobasilar steal (43.0 +/- 17.4, P less than 0.05). Patients with a steal mechanism had an intracranial vertebral artery systolic velocity of 90.0 +/- 38.9, compared with 53.0 +/- 15.0 in controls (2P less than 0.050). Intracranial vertebral artery systolic velocity was higher among VBI patients with significant carotid artery disease (greater than 50%, 76.7 +/- 28.8) than in those with less severe disease (less than 50%, 47.3 +/- 13.8, P less than 0.05). Evaluation and quantitation of the vertebrobasilar circulation using both intra- and extracranial noninvasive studies may afford further insight as to the pathophysiology of vertebrobasilar insufficiency and provide a readily available, direct, and simple method of initial and serial assessment of VBI patients.

Noninvasive assessment of cerebral collateral blood supply through the ophthalmic artery.

We assessed the potential of 2-MHz pulsed-wave transorbital Doppler ultrasonography to delineate the role of the ophthalmic artery as a source of collateral cerebral blood supply by comparing oculopneumoplethysmography, transorbital Doppler ultrasonography, periorbital continuous-wave Doppler ultrasonography, and transcranial Doppler ultrasonography in 25 patients with unilateral internal carotid artery occlusion and five controls with 10 normal internal carotid arteries. Systolic ophthalmic artery blood velocity was reduced ipsilateral to an internal carotid artery occlusion (38.2 +/- 10.2 cm/sec) compared with the contralateral and control velocities (46.0 +/- 10.3 and 47.5 +/- 6.8 cm/sec, respectively; p less than 0.05). Ophthalmic systolic pressure measured by oculopneumoplethysmography was 94.7 +/- 13.2 mm Hg ipsilateral to an internal carotid artery occlusion compared with 108.4 +/- 15.3 mm Hg on the contralateral side (p less than 0.01). Transorbital and periorbital Doppler ultrasonography detected reversed ophthalmic artery blood flow ipsilateral to an internal carotid artery occlusion in 44.0% and 40.0% of the patients, respectively. Systolic middle cerebral artery blood velocity was 55.2 +/- 22.3 cm/sec ipsilateral to an internal carotid artery occlusion compared with 79.4 +/- 23.5 cm/sec on the contralateral side (p less than 0.05) and 101.2 +/- 18.9 cm/sec in the controls (p less than 0.05). Reversed ophthalmic artery blood flow was associated with a low middle cerebral artery blood velocity and lack of major intracerebral collaterals. Transorbital Doppler ultrasonography permits noninvasive evaluation of the ophthalmic artery.(ABSTRACT TRUNCATED AT 250 WORDS)

The natural history of amaurosis fugax with minor degrees of internal carotid artery stenosis.

The natural history of amaurosis fugax with hemodynamically insignificant degrees of internal carotid artery stenosis is uncertain. Seventy-three patients over age 40 who presented with amaurosis fugax without obvious cause and had ipsilateral stenoses of 50% or less with carotid duplex scanning were followed for a mean period of 35.5 months (range 3-110) without surgical intervention. At the initial vascular laboratory duplex evaluation, 35 patients had normal arteries (47.9%), 29 had minor (0-19%) stenoses of the ipsilateral internal carotid arteries (39.7%), and 11 had 20-50% stenosis (15.1%). Four patients with 0-19% stenosis and one patient with 20-50% stenosis experienced a subsequent stroke or permanent ipsilateral blindness. When analyzed by life-table format, stroke, blindness, and early death were more frequent in patients with minor degrees of stenosis than in those with normal arteries. Investigations in all patients with amaurosis fugax should be aimed at identifying whether the symptoms are explained by arteriosclerotic, systemic, collagen, cardiac, hematologic, or ophthalmologic disease. When no other etiology is found, and localized carotid bifurcation atherosclerosis of even modest degrees is identified, an atheroembolic etiology should be considered.

Relationship of cerebral blood flow regulation to acute mountain sickness.

Acute mountain sickness (AMS) is a prevalent illness seen in humans exposed to high altitudes. An increase in cerebral blood flow as a result of cerebrovasodilatation is felt by many to be responsible for its occurrence. Using the recently developed transcranial Doppler (TCD), it has become possible to detect and quantify flow velocity in the large cerebral vessels. By this method, intracranial arterial blood flow velocities and vasodilatation were measured at high altitude and correlated with clinical symptoms. Mean middle cerebral artery velocity (MCA-V) showed a significant increase from 55 +/- 7 cm/s at sea level to 71 +/- 13 cm/s at 13,500 feet. The pulsatility index (PI) and vasomotor reactivity (VMR) both decreased (.71 +/- .11 at sea level to .53 +/- .12 at 13,500 and 45 +/- 17% sea level to 23 +/- 15% at 8,000 feet, respectively). These preliminary studies indicated that TCD technique is a viable tool for measurement of cerebral blood flow velocities and cerebral arterial vasodilatation at altitude.

Importance of cerebral collateral pathways during carotid endarterectomy.

Before surgery, we evaluated major intracranial collateral pathways using transcranial Doppler ultrasonography (TCD) in 50 patients who then underwent carotid endarterectomy with concurrent multimodality cerebral monitoring. Patients were grouped with respect to collateral pathways demonstrated preoperatively by TCD: Group 1, good collateralization with an anterior and/or posterior communicating artery ipsilateral to the operative carotid lesion (29 patients, 58%); Group 2, collateral pathways present but impeded by other proximal stenoses (nine patients, 18%); and Group 3, no collateralization identified (nine patients, 18%). Three patients (6%) could not be classified. TCD identified major collateral pathways with a sensitivity of 89% and a specificity of 80% when compared with arteriography. During carotid endarterectomy mean middle cerebral artery velocity, pulsatility index, and stump pressure were higher and the decrease in middle cerebral artery velocity with extracranial carotid artery cross clamping was significantly less among Group 1 patients than among Group 2 and 3 patients (p less than 0.05 for both groups). Group 1 patients required fewer intraoperative carotid artery shunts and developed fewer ischemic electroencephalographic abnormalities than did patients in Groups 2 and 3 (p less than 0.05 for both groups). TCD assessment of cerebral collateralization helps predict hemodynamic consequences of cross clamping during carotid endarterectomy.

Vertebral artery compression as an adjunct to transcutaneous Doppler ultrasound examination.

Transcranial Doppler (TCD) evaluation is dependent on the accurate identification of intracranial vessels. Manual extracranial vertebral artery compression was used to modulate blood flow in vessels of the vertebrobasilar system in 118 patients examined by TCD. Two examples of its utility are presented in detail. Complete examination by TCD should include evaluation of the posterior cerebral circulation and its collaterals; vertebral artery compression is a new and important adjunct to the complete evaluation of intracranial vascular anatomy and cerebral collateralization.

Effect of internal carotid artery occlusion on intracranial hemodynamics. Transcranial Doppler evaluation and clinical correlation.

Neurologic deficits that occur simultaneously with or subsequent to internal carotid artery occlusion may be influenced by the adequacy of the intracerebral collateral circulation. Transcranial Doppler ultrasonography was used to evaluate mean middle cerebral artery blood velocity and blood flow in major collateral arteries in 78 patients, including 39 patients with 40 internal carotid artery occlusions and 39 control patients with less severe extracranial cerebrovascular disease, matched for age and sex distribution. Middle cerebral artery blood velocity was 38.9 +/- 17.9 cm/sec ipsilateral to an occlusion, 50.9 +/- 18.3 cm/sec contralateral to an occlusion (p less than 0.01), and 56.8 +/- 14.4 cm/sec in the controls (p less than 0.01). Pulsatility index ipsilateral to an occlusion (0.86 +/- 0.32) was reduced compared with contralateral and control pulsatility indexes (1.05 +/- 0.33 and 1.03 +/- 0.18) respectively; p less than 0.05). Major intracerebral collateral arteries were detectable in 94.9% of occlusion patients and in 53.8% of controls (p less than 0.01). A posterior communicating artery was demonstrated ipsilateral to an occlusion in 80.0% of the patients and contralateral to an occlusion in 39.5% (p less than 0.01). An ipsilateral posterior communicating artery was identified in all 10 asymptomatic occlusions and in 75.8% of the symptomatic ones. Pulsatility index was 1.02 +/- 0.34 for asymptomatic occlusions and 0.76 +/- 0.30 for symptomatic occlusions (p less than 0.01). Transcranial Doppler ultrasonography permits noninvasive quantification of the cerebral hemodynamic consequences of internal carotid artery occlusion and direct evaluation of the collateral blood supply, which can be correlated with symptomatology.

Transcranial Doppler in the management of extracranial cerebrovascular disease: implications in diagnosis and monitoring.

Transcranial Doppler (TCD) insonation permits quantitative noninvasive evaluation of intracerebral arterial velocity. With the use of a 2 MHz Doppler through a transtemporal approach, middle cerebral artery blood velocity (MCA-V, centimeters per second) and major collaterals were measured in 96 patients, including 15 normal control subjects, 66 patients with extracranial cerebrovascular disease (ECCVD), and 15 patients with other medical problems without ECCVD. MCA-V was higher in control subjects (62.7 +/- 15.1) than in patients with ECCVD (45.0 +/- 16.3, p less than 0.05). There was a significant inverse correlation between MCA-V and the degree of internal carotid artery stenosis present by duplex examination. Twenty-three patients monitored during carotid endarterectomy had a mean MCA-V under anesthesia of 37.0 +/- 16.9, which decreased to 22.4 +/- 14.8 during cross-clamping (p less than 0.01). MCA-V during cross-clamping correlated directly with stump pressure (R = 0.87) and was higher when major collaterals were identified before operation by TCD than when none were seen (31.7 +/- 9.5 vs. 8.8 +/- 8.5, p less than 0.01). Shunt function was verified in all 11 patients shunted. Electroencephalographic changes occurred in four patients with an MCA-V of 14.7 +/- 8.5 compared with an average of 24.1 +/- 15.5 for patients with normal electroencephalograms. MCA-V increased from 46.6 +/- 21.2 before operation to 61.0 +/- 22.4 after carotid endarterectomy (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)