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BRIEF COMMUNICATIONS: Gian Paolo Anzola, Eva Morandi, Francesco Casilli, and Eustaquio Onorato Different degrees of right-to-left shunting predict migraine and stroke: Data from 420 patients Neurology 2006; 66: 765-767 [Abstract] [Full text] [PDF]

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Different degrees of right-to-left shunting predict migraine and stroke: Data from 420 patients

Gordon J. Gilbert   (1 June 2006)

Reply from the Authors

Gian Paolo Anzola, Eustaquio Onorato, Eva Morandi, Francesco Casilli   (1 June 2006)

Different degrees of right-to-left shunting predict migraine and stroke: Data from 420 patients 1 June 2006
Gordon J. Gilbert, Dept. of Physiology and Biophysics, University of South Florida School of Medicine 500 Pasadena Avenue South, St. Petersburg, FL 33710 Send Correspondence to journal: Re: Different degrees of right-to-left shunting predict migraine and stroke: Data from 420 patients drgg22{at}tampabay.rr.com Gordon J. Gilbert	The authors of this article [1] suggest only embolism as a possible explanation of their findings that the size of right-to-left shunt predicts the occurrence of migraine and of stroke. It has recently been proposed [2] that migraine may be a physiological response to hypoxia, as evidenced by its high incidence in a wide variety of hypoxia-provoking circumstances. This hypothesis would predict that increasing degrees of right-to-left shunting would, by increasing the levels of hypoxia, inflate the frequency and intensity of migraine attacks. It is possible that the authors' data includes pO2 levels on each of the 420 patients reported and that a strong inverse correlation might be found between pO2 levels and migraine frequency and intensity. If so, it is possible that oxygen inhalation by these patients could reduce the incidence and severity of migraine attacks yet not alter the occurrence of putative embolism. References 1. Anzola GP, Morandi E, Casilli F, Onorato, E. Different degrees of right-to-left shunting predict migraine and stroke: Data from 420 patients. Neurology 2006;66:765-767. 2. Gilbert, GJ. The Purpose of Migraine. Florida Med Assn Quart J 2005; Oct:26-27. Disclosure: The author reports no conflicts of interest.
Reply from the Authors 1 June 2006
Gian Paolo Anzola, S. Orsola Hospital FBF Via Vittorio Emanuele II, 27 25100 Brescia - Italy, Eustaquio Onorato, Eva Morandi, Francesco Casilli Send Correspondence to journal: Re: Reply from the Authors gpanzola{at}numerica.it Gian Paolo Anzola, et al.	We appreciate Dr Gilbert’s suggestion that right-to-left shunts may facilitate migraine through the mechanism of increasing hypoxia. [1,2] It is not our policy to routinely measure pO2 saturation in patients undergoing transcranial Doppler (TCD) testing for right-to-left shunt unless desaturation is clinically suspected, which was not the case in the patients included in the study. Comparing TCD with arterial blood gas measurement in patients without obvious pulmonary disease has yielded disappointing results in terms of the correlation between blood oxygen content and degree of the shunt [3], which means that the amount of the shunted blood is many times too small to induce a clinically significant hypoxia. However, both Devuyst et al and our patients were examined in the recumbent position [1,3], whereas right-to-left shunt may increase to a significant extent on standing, not only in patients with the platypnoea- orthodeoxya syndrome [4] but also in normal individuals. [5] We believe that Gilbert’s hypothesis needs to be properly tested in prospective studies aimed at assessing the variation of both pO2 and right-to-left shunt from the recumbent to the upright position. References 3. Devuyst G, Piechowski-Józwiak B, Karapanayiotides T et al. Controlled Contrast Transcranial Doppler and Arterial Blood Gas Analysis to Quantify Shunt Through Patent Foramen Ovale. Stroke 2004;35:859-863. 4. Cheng TO. Platypnea-orthodeoxya syndrome: Etiology, differential diagnosis, and management. Cathet Cardiovasc Interv 1999;47:64–66. 5. Telman G, Kouperberg E, Sprecher E, Yarnitsky D. The positions of the patients in the diagnosis of patent foramen ovale by Transcranial Doppler. J Neuroimaging. 2003;13:356–358. Author Disclosure: The authors report no conflicts of interest.