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 »  Abstract
 »  Introduction
 »  Material and methods
 »  Results
 »  Discussion
 »  Conclusion
 »  References

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Year : 2000  |  Volume : 48  |  Issue : 2  |  Page : 112-5

Transcranial Doppler evaluation of blood flow velocity changes in basal cerebral arteries in cerebral AVMs following embolisation and surgery.


Departments of Neurosurgery and Neuroradiology, Neurosciences Centre, All India Institute of Medical Sciences, New Delhi, 110029, India.

Correspondence Address:
Departments of Neurosurgery and Neuroradiology, Neurosciences Centre, All India Institute of Medical Sciences, New Delhi, 110029, India.

  »  Abstract

Blood flow velocities in the basal cerebral arteries were evaluated in 41 patients with supratentorial arteriovenous malformation (AVM), using a transcranial doppler 64-B instrument. The AVM was surgically excised in 20 patients and embolised in 21 patients. Blood flow velocities in feeding basal cerebral arteries were found markedly decreased in both the groups, at 24 hours after intervention. On follow up study at 3 months, blood flow velocity in feeding cerebral artery was found to be increased in 47 percent of patients who were embolised, but remained normal in all the patients who underwent surgery.

How to cite this article:
Tyagi S K, Mahapatra A K, Mishra N K. Transcranial Doppler evaluation of blood flow velocity changes in basal cerebral arteries in cerebral AVMs following embolisation and surgery. Neurol India 2000;48:112


How to cite this URL:
Tyagi S K, Mahapatra A K, Mishra N K. Transcranial Doppler evaluation of blood flow velocity changes in basal cerebral arteries in cerebral AVMs following embolisation and surgery. Neurol India [serial online] 2000 [cited 2020 Dec 1];48:112. Available from: https://www.neurologyindia.com/text.asp?2000/48/2/112/1564




   »   Introduction Top

Arteriovenous malformation (AVM) accounts for approximately one percent of all strokes i.e. the annual incidence rate is of the magnitude of 1 to 3 per 1,00,000 persons. AVM are located supratentorially in about 90% of the patients.[1],[2],[3] Traditionally, surgery is the treatment of choice in non-eloquent and approachable areas.[2],[3],[4],[5],[6] Embolisation is being increasingly considered as a modality of treatment not only for the arteriovenous malformation in eloquent and surgically inaccessible areas, but also as a preoperative procedure to reduce the arterial supply.
Transcanial doppler (TCD) is a good, non invasive bedside method to assess the blood flow velocity in major cerebral vessels.[1],[7],[8],[9] Surprisingly, transcranial doppler has not been used very often in cerebral arteriovenous malformation to study the blood flow velocity changes, while they are intervened either by surgical excision or by embolisation,[10] in basal cerebral arteries. In this study, we evaluated blood flow velocity changes in basal cerebral artery, after open surgery and embolisation, in the patient with cerebral AVM.


   »   Material and methods Top

A prospective study was carried out in 41 patients with supratentorial cerebral AVMs who were admitted for embolisation (21) or surgical excision (20). The study was carried out over a period of 3 years between 1993 through 1996. Flow velocities in basal cerebral arteries were recorded at the time of admission, 24 hours and 3 months after intervention. Flow velocities in basal cerebral arteries, especially middle cerebral artery and internal carotid artery of both sides, were evaluated in all these cases. Blood flow velocity was measured using transcranial doppler instrument. 2 MHz ultrasonic transducer was used to evaluate the flow velocities in basal cerebral arteries. The values were compared with the normal values (30-80 cm/sec) already standardized on the machine. Pre-intervention CT scan and 4 vessel DSA were performed in all these cases of supratentoial AVM. Angiography was repeated immediately after embolisation, and in cases of surgical excision, when the patients were haemodynamically as well as clinically stable. Embolisation was carried out through transfemoral route, using NBCA and Lipoidol mixture.


   »   Results Top

Doppler recording of middle cerebral artery and internal carotid artery blood flow velocities, were obtained in all 41 subjects on both the sides. In 16 (9.7%) vessels doppler signals were not of sufficient intensity to allow velocity determination.
Blood flow velocity in basal cerebral artery feeding AVM was found to be pathologically increased in 38 patients (92.5%), while it was normal in 3(7.5%) cases. All the feeding vessels were on the ipsilateral side of arteriovenous malformation. In 31 cases, feeding basal cerebral arteries were MCA in which blood flow velocity was found to be pathologically increased, with an average flow velocity of 109 cm/sec. Maximum values were in the range of 168 cm/sec i.e. about three fold increased blood flow velocity as compared to average velocity in normal middle cerebral artery [Figure 1a]. In 20 of these 31 cases, blood flow velocity was found to be raised in ipsilateral internal carotid artery as well. Internal carotid artery (ICA) of ipsilateral side was found as the main feeding vessel in 7 cases, on the basis of increased blood flow velocity. The average blood flow velocity in ICA feeding AVMs was found to be 90 cm/sec., which is about twice as high as blood flow velocity in the contralateral ICA.
In 21 cases, who underwent embolisation, more than 80% ablation was achieved in 18 cases angiographically. In 20 operative cases, complete excision of AVM was achieved. In all 41 (21+20)
cases, repeat TCD evaluation of blood flow velocity was undertaken after 24 hours of intervention (either embolisation or surgery). Post interventional TCD evaluation of basal cerebral arteries blood flow velocity revealed marked decrease in blood flow velocity in 34 cases [Figure 1b]. In 2 post operative cases, we could not insinuate the basal cerebral arteries on the side of surgery because of scalp swelling. After intervention, blood flow velocity decreased markedly and came down to normal range. In one case of partially embolised supratentorial AVM, the velocity in feeding basal cerebral artery did not decrease to the normal value. Drop in flow velocity was more in patients who were operated as compared to those who were embolised.
Blood flow study was repeated 3 months after surgery in 14 patients out of 20 patients operated. In all these patients, blood flow velocity in basal cerebral artery of ipsilateral side of AVM remained with in normal range. In all patients of embolisation, repeat TCD was done after 12 weeks. Eight out of 17 patients showed increase in blood flow velocity in feeding basal cerebral artery as compared to the study done after 24 hours of embolisation. In rest of the 9 cases, there was no increase in blood flow velocity [Table I].


   »   Discussion Top

The diagnosis of AVM is usually made by angiography. Angiography is mandatory in the management of a case of AVM, since all arteries that contribute to the malformation, as well as the draining veins must be delineated in detail.
A transducer of frequency of 2 MHz provides a satisfactory intracranial recording of velocities in the middle cerebral artery (MCA) and internal carotid artery (ICA). Cerebral AVMs can be considered in two parts. One part is arterio-venous shunt itself and the other part consists of arteries and veins involved in conveying blood to and from the AVM.[11] In an AVM the vascular resistance is comparatively lower than normal cerebrovascular resistance at normal perfusion pressure. This accounts for increased blood flow, which is well known to increase the diameter of feeding arteries of AVM. Futhermore, these channels have a characteristically high blood flow velocities.
Increased blood flow velocity in feeding vessels of AVM has been shown on transcranial doppler evaluation.[9],[12] Keller followed up 20 cases of cerebral AVMs using transcranial doppler before and after intervention. Of these 20 cases, 2 patients had catheter embolisation, 1 patient had irradiation and 17 were operated. Before treatment, 19 of these patients had abnormally high blood flow velocity. After treatment, normal findings were present in all the 20 patients, indicating that major part of AVM was removed or major feeding artery had been obliterated. Takesetta et al studied cerebral blood flow with SPECT in 15 cases of cerebral AVMs and showed decreased profusion in all cases following surgery.[13]
The present study showed an increased flow velocity in feeding cerebral arteries in 38 out of 41(92.5%) cases. Increased blood flow velocity was also found in the internal carotid artery in 20 of 41 patients. In one case of AVM, fed by a foetal type origin of posterior cerebral artery, blood flow velocity was found increased in internal carotid artery as well. In 3 patients with supratentorial AVM, blood flow velocity was found with in normal range even in the feeding basal cerebral artery, though it was far above the contralateral arteries.
In 85.8% of embolised cases, velocity dropped to normal range (30-80cm/sec.) in immediate post embolisation period, whereas in 3 patients velocity remained high. Angiographic evaluation of these 3 cases revealed catheter induced spasm in 1 case and in the other two cases AVM was embolised only upto 50%. After 3 months, TCD evaluation was done in 17 embolized patients, which revealed increased blood flow velocity in 8 patients (47%) as compared to immediate post embolisation values. Hence repeat embolisation was found mandatory. High blood flow velocity in arterial feeders also helps hyperselective catheterization with flow guided catheters. All AVMs subjected to endovascular therapy were large AVMs with multiple feeders.
Following surgery, ipsilateral basal cerebral artery could not be insinuated in 2 patients because of scalp swelling. In 16 cases, blood flow velocity dropped to the normal range post operatively and remained normal in 14 cases even after 3 months. All operated AVMs were comparatively smaller in size with few feeders in superficial locations. Difference between the number of patients having normal velocity at 3 months after embolisation and surgery was found to be statistically significant (chi square with Yate's correction factor X2=6.59, p=<0.01).


   »   Conclusion Top

This study reveals that the transcranial doppler is a useful measure for monitoring the blood flow velocities in feeders of AVMs. Further more, it is a simple bed side non invasive method to evaluate the blood flow velocity in feeding basal cerebral arteries. On the basis of blood flow findings, one can detect whether or not the AVM is completely ablated after embolisation. Regular follow up transcranial doppler evaluation could be used as a guide in timing the next stage of endovascular procedure.

 

  »   References Top

1.Giller AC, Mathews D, Walker B et al: Prediction of tolerance to carotid artery occlusion using transcranial doppler ultrasound. J Neurosurg 1994; 81: 15-19.  Back to cited text no. 1    
2.Mohr JP: Neurological manifestations and factors related to therapeutic decisions. In Wilson CB, BM Stein, Intracranial Arteriovenous Malformations. Williams and Wilkins, Baltimore 1984; 1-11.   Back to cited text no. 2    
3.Mohr JP, Caplan LR, Melsky JW et al: The harvard cooperative stroke registry: A prospective registry. Neurology ( Nfinneap.) 1978; 28: 754-762.   Back to cited text no. 3    
4.George ED, Pevsner PH: Combined neurosurgical neuroradiological therapy for cerebral arteriovenous malformation: The Walter Reed protocol, In Smith RR, Haerer AF, Russell WF. Vascular malformation and fistulas of the brain. Raven Press, New York 1982; 169-191.   Back to cited text no. 4    
5.Nornes H, Grip A: Hemodynamic aspects of cerebral arteriovenous malformations. J Neurosurg 53: 456-464.   Back to cited text no. 5    
6.Wilson CB, U Hs, Domingue J: Microsurgical treatment to intracranial vascular malformations. J Neurosurg 1979; 51: 446 -454.   Back to cited text no. 6    
7.Aaslid R, Huber P, Nornes H: Evaluation of cerebrovascular spasm with transcranial doppler ultrasound. J Neurosurg 1984; 60: 37-41.   Back to cited text no. 7    
8.Aaslid R, Markwalder TM, Nornes H: Noninvasive transcranial doppler ultrasound recording of flow velocity in basal cerebral arteries. J Neurosurg 1982; 57: 769-774.   Back to cited text no. 8    
9.Lindegard KF , Bakke SJ, Grobmund P et al: Assessment of intracranial hemodynamics in carotid artery disease by transcranial Doppler ultrasound. J Neurosurg 1985; 63: 890-898.   Back to cited text no. 9    
10.Keller HM: Diagnosis and follow up of patients with cerebral AVM using Doppler ultrasound: In Microneurosurgery III A-M.G. Yegsargil (eds) - Theme medial publishers INC New York 1987; 240-249. Kaplan HA, Aronson SM, Browder DJ: Vascular malformations of the brain. An anatoniical study. J Neurosurg 1961; 18: 630-635. Nornes H, Lundar T, Wikeby P: Cerebral arteriovenous malformation, results of microsurgical management. Acta Neurochir 1979; 50: 243-257.   Back to cited text no. 10    
11.Takesetta G, Toyanuna H, Nakane K et al: Evaluation of regional cerebral blood flow changes in perifocal brain tissue on SPECT before and after removal of arteriovenous malformations. Nuclear Med communications 1994; 15: 461-468.   Back to cited text no. 11    

 

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