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(Stroke. 1999;30:2238-2248.)
© 1999 American Heart Association, Inc.

Letters to the Editor

Usefulness of Transcranial Color-Coded Sonography in the Diagnosis of Cerebral Vasospasm

Jaroslaw Krejza, MD, PhD

Department of Radiology

Zenon Mariak, MD, PhD

Department of Neurosurgery

Jerzy Walecki, MD, PhD

Department of Radiology, Bialystok Medical Academy, Bialystok, Poland

Key Words: blood flow velocity • ultrasonography, Doppler,transcranial

	Introduction

Top Introduction References

 
To the Editor:

We read with great interest the article by Proust et al¹ on the sonographic diagnosis of cerebral vasospasm that was recently published in Stroke. Although we do agree with their conclusions, two important methodological aspects of their article deserve further comment and clarification to make their results reproducible.

First, the authors state that they measured the diameter of the middle cerebral artery (MCA) as well as the velocity at a distance of 2 cm from the internal carotid artery (ICA) bifurcation. Even ignoring the fact that the site of measurement of the MCA diameter, demonstrated in their article in Figure 1, appears to be at a distance of 8 mm from the ICA bifurcation, the average length of the M1 segment is, according to most data from the literature,^{2 3} only 15 mm. This strongly suggests that velocity measurements must have been sampled at a main branch of the MCA instead of its main trunk. The authors point out that they adopted "a standard technique to identify the basal cerebral arteries." However, the sources they cite, Bogdahn et al⁴ and Tsushiya et al,⁵ do not specify the site of MCA insonation, whereas Schöning et al,⁶ to whose results the authors relate their own findings, preferred to obtain the sample volume close to the ICA bifurcation. Taking into account that highly disturbed flow tends to be the rule at this location,⁷ the optimal site for MCA insonation still has to be pinpointed, even more so because a distant lateral placement of the sample volume results in less favorable angle of insonation of the vessel.^{5 6 8}

This latter point leads us to another methodological remark, this concerning the angle of insonation of the MCA. The authors maintain that their mean angle of the MCA insonation is 21±14.6°. They claim the angle obtained was so favorable that its necessary correction was only slight and TCCS velocities obtained were the same as those measured with TCD sonography. The authors claim the results to be similar to those of Schöning et al.⁶ Nevertheless, that source and others^{5 8 9 10} clearly state that angle-corrected velocities in the MCA are significantly higher than those obtained by conventional TCD. Moreover, Schöning's mean angle of MCA insonation was 26.6±14.4°, with the velocity predominantly taken close to the bifurcation. We also found a similar angle of insonation (29±14°) at a distance of 10 mm lateral to the bifurcation.¹⁰ At the MCA insonation site reported by Proust et al,¹ ie, at 2 cm from the ICA bifurcation, the angle of insonation was reported elsewhere^{5 6} to be mainly between 30° and 50°, a value evidently different from that of the authors. For the critical velocity of 120 cm/s, obtained with TCD at the angle of insonation 30°, velocity would have become 139 cm/s.

These methodological inconsistencies imply that the velocity threshold proposed for diagnosis of vasospasm of the MCA may be imprecise and may need recalculation. This conclusion is strengthened by the fact that blood flow velocity declines steeply within the age span into which fall most of the patients examined by Proust et al.¹ Our results,¹⁰ similar to those obtained by Martin et al,⁹ indicate that the average value of mean velocity in the MCA decreases from 81 cm/s in the people aged 40 to 59 cm/s in those above 60 years. Therefore, the age factor should not be ignored in the attempt to establish velocity thresholds for the diagnosis of cerebral vasospasm.^{9 10} Velocities of 120 cm/s are encountered as an upper limit of normal values in the TCCS technique in healthy subjects up to the age of 40 years.¹⁰

	References

Top Introduction References

 

1. Proust F, Callonec F, Clavier E, Lestrat JP, Hannequin D, Thiébot J, Fréger P. Usefulness of transcranial color-coded sonography in the diagnosis of cerebral vasospasm. Stroke. 1999;30:1091–1098.[Abstract/Free Full Text]
2. Ring BA. The middle cerebral artery. In: Newton TH, Potts GD, eds. Radiology of the Skull and Brain. Great Neck, NY: CV Mosby Co; 1974:1442–1526.
3. Weir B. Anatomy. In: Weir B, ed. Aneurysms Affecting the Nervous System. Baltimore, MD: Williams & Wilkins; 1987:308–343.
4. Bogdahn U, Becker G, Winkler J, Greiner K, Perez J, Meurers B. Transcranial color-coded real-time sonography in adults. Stroke. 1990;21:1680–1688.[Abstract/Free Full Text]
5. Tsuchiya T, Yasaka M, Yamaguchi T, Kimura K, Omae T. Imaging of the basal cerebral arteries and measurement of blood velocity in adults by using transcranial real-time color flow Doppler sonography. AJNR Am J Neuroradiol. 1991;12:497–502.[Abstract]
6. Schöning M, Bucholz RD, Walter J. Comparative study of transcranial color duplex sonography and transcranial Doppler sonography in adults. J Neurosurg. 1993;78:776–784.[Medline] [Order article via Infotrieve]
7. Kerber CW, Liepsch D. Flow dynamics for radiologists, II: practical considerations in the live human. AJNR Am J Neuroradiol. 1994;15:1076–1086.[Abstract]
8. Baumgartner RW, Mattle PH, Aaslid R. Transcranial color-coded duplex sonography, magnetic resonance angiography, and computed tomography angiography: methods, applications, advantages, and limitations. J Clin Ultrasound. 1995;23:89–111.[Medline] [Order article via Infotrieve]
9. Martin PJ, Evans DH, Naylor AR. Transcranial color-coded sonography of the basal cerebral circulation: reference data from 115 volunteers. Stroke. 1994;25:390–396.[Abstract]
10. Krejza J, Mariak Z, Walecki J, Szydlik P, Lewko J, Ustymowicz A. Transcranial color Doppler sonography of basal cerebral arteries in 182 healthy subjects: age and sex variability and normal reference values for blood flow parameters. AJR Am J Roentgenol. 1999;172:213–218.[Abstract/Free Full Text]

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