engleski

Functional Tcd Study - Visual Evoked Response In Patients With Severe Carotid Disease

Introduction: Estimation of impaired cerebral vascular reserve by means of TCD in patients with severe carotid disease can be achieved by the assessment of cerebral blood flow changes in response to various vasodilatatory stimuli. In patients with high-grade stenosis or occlusion of the ICA significantly reduced cerebral vasomotor reactivity (VMR) have been demonstrated. Yet, attention has been mainly focused upon evaluating the hemodynamic effect of ICA stenosis on the middle cerebral artery (MCA). The data on the hemodynamic features of the posterior part of the circle of Willis, which can play an important role as a collateral channel in patients with significant ICA stenosis, are still sparse. The goal of this study was to evaluate the visual evoked response in posterior cerebral artery (PCA) by means of functional transcranial doppler (fTCD) in patients with severe carotid disease and to determine the hemodynamic effect of severe carotid disease on posterior circulation. Methods: Measurements were performed successively in the dark and during the white light stimulation in 49 right-handed patients with high-grade (70-99%) ICA stenosis or occlusion and compared with 30 healthy age and sex matched subjects. Mean values of mean blood flow velocities (MBFV) (cm/s &#177; 2SD) and mean reaction time (MRT) (s &#177; 2SD) during a period of one minute were analyzed. Results: MBFV in PCA during the white light stimulation (affected side patients 32, 6&#177; 11, 49, ipsilateral side controls 30, 56&#177; 8, 34, p<0, 4, NS ; unaffected side patients 29, 88&#177; 8, 6, ipsilateral side controls 29, 99&#177; 9, 5, p<0, 96, NS) and in the dark (affected side patients 23, 44&#177; 10, 84, ipsilateral side 21, 40&#177; 7, 32 controls, p<0, 37, NS ; unaffected side patients 21, 32&#177; 7, 08, ipsilateral side controls 20, 12&#177; 8, 33, p<0, 5, NS) between the two groups were similar. MRT showed a significantly prolonged visual evoked response in PCA in both affected (light: patients 29, 36&#177; 14, 46, controls 19, 67&#177; 11, 25, respectivety, p<0, 046 ; dark: patients 35, 25&#177; 11, 9, controls 21, 89&#177; 10, 31, respectively, p<0, 002 and unaffected side (dark: patients 33, 13&#177; 11, 12, controls 23, 89&#177; 11, 23, respectively, p<0, 032) of ICA in patients group. During the repetitive testing MBFV didn&#8217; t differ significantly (1. 32, 65&#177; 1 1, 69cm/s ; 2. 32, 14&#177; 11, 81cm/s ; 3. 31, 14&#177; 10, 91cm/s) (p<0, 1, respectively) in the group of carotid disease patients as well as MRT during the white light stimulation (1. 25, 63&#177; 10, 31s ; 2. 27, 81 &#177; 14, 72s ; 3. 28, 13&#177; 13, 77s) (p<0, 1, respectively) while in the dark the difference was significant statistically (1. 29, 25&#177; 10, 31s ; 2. 34, 68&#177; 13, 35s ; 3. 33, 38&#177; 14, 72s) (p<0, 02, respectively), but not clinically. During the repetitive white light stimulation in the group of healthy subjects MRT showed prolonged visual evoked response (1. 13, 00&#177; 6, 49s ; 2. 20, 67&#177; 16, 24s ; 3. 25, 33&#177; 14, 93s) as well as in the dark (1. 16, 67&#177; 11, 44s ; 2. 21, 67&#177; 11, 29s ; 3. 27, 33&#177; 11, 32s) (p<0, 0005, respectively) and significant MBFV decrease (1. 31, 33&#177; 8, 24cm/s ; 2. 30, 47&#177; 8, 44cm/s ; 3. 29, 87&#177; 8, 66cm/s) (p<0, 004, respectively), showing the exhaustion of the cerebral vasoreactive mechanisms in healthy subjects. Conclusion: Vasomotor reactivity of the PCA remained similar regardless of carotid stenosis suggesting an independent cerebral vascular capacity of the posterior circulation. Our data showed that MRT is the principal restrictive factor in the case of carotid stenosis suggesting the independence of cerebral vascular reserve capacity of the posterior part of Willis circle that is necessary to be considered separately from the anterior part.

functional TCD; visual stimulation; severe ceritid artery disease

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