Neurology -- Correspondence for Shechter et al., 58 (3) 422-427

Correspondence published:

Migraine and autonomic nervous system function: A population-based, case-control study: Milena De Marinis (25 February 2003)

Migraine and autonomic nervous system function: A population-based, case-control study 25 February 2003

Milena De Marinis
La Sapienza University Rome Italy
Send Correspondence to journal:
Re: Migraine and autonomic nervous system function: A population-based, case-control study

m.de.marinis{at}mclink.it Milena De Marinis

In the article by Shechter et al. [1], the authors do not seem to know that systolic and diastolic blood pressure values in the sitting position are the result of the interaction of different systems and do not provide information on the sympathetic nervous system which may be used for autonomic nervous system assessment. Although a "marginally" (with no statistical significance) increase in diastolic blood pressure was found in patients with disabling migraine, the authors dwell extensively with this point in the discussion. They state that "increased diastolic blood pressure in migraine cases could be secondary to sympathetic hyperfunction or reflex response to sympathetic hypofunction" and conclude that this finding is indicative of autonomic nervous system dysfunction.
Among the tests that can provide information on sympathetic function [2, 3, 4, 5], the authors used only one mental stressor test, the "mirror star-tracing test" which did not reveal any significant abnormality in migraine patients. However, as this test may have individual variability and low reproducibility, it should have been associated with at least one other test such as the cold pressor test or handgrip.
The authors performed Valsalva maneuver, but state that 40% of patients and 39% of controls not a negligible number of subjects, were unable to complete a valid test. Since both patients and controls were young and did not suffer from any disease that might have impaired their physical performance, I wonder why the test was not repeated to obtain "the power to detect differences" as the author claim at the end of the discussion.
In this paper, the only significant finding indicative of autonomic nervous system involvement is the decrease in deep breathing response found in migraine patients with disabling migraine.
Heart rate is controlled by the inhibitory tonus of the vagus. In deep breathing, the activity of the cardiohinibitory center is directly inhibited by the respiratory center neurons during the inspiration phase (tachycardia), before returning to its basal tonus during the expiration phase (bradycardia). A decrease in deep breathing ratio is, therefore, indicative of parasympathetic hypofunction. [2, 3, 4, 5]
In the discussion, the authors claim that "sympathetic stimulation increases heart rate and parasympathetic stimulation decreases heart rate during deep breathing". This statement is incorrect, because the sympathetic system has inotropic and a cronotropic effect on the heart and the tachycardia that occurs during deep breathing is the result of the inhibition of vagal cardioinhibitory activity on the heart. [2, 3, 4, 5]
References
1) Shechter A, Stewart WF, Silberstein SD, Lipton RB. Migraine and autonomic nervous system function. A population-based, case-control study. Neurology 2002;58:422-427.
2) Ewing DJ. Analysis of heart rate variability and other non- invasive tests with special reference to diabetes mellitus. In: Bannister R, Mathias CJ, eds. Autonomic failure. A textbook of clinical disorders of the autonomic nervous system. Oxford: Oxford University Press, 1992:312- 333.
3) Mathias CJ, Bannister R. Investigation of autonomic disorders. In: Bannister R, Mathias CJ, eds. Autonomic failure. A textbook of clinical disorders of the autonomic nervous system. Oxford: Oxford University Press, 1992:255-290.
4) Gilbey MP, Spyer KM. Physiological aspects of autonomic nervous system function. Curr Opinion Neurol Neurosurg 1993;6:518-523.
5) Appenzeller O, Oribe E. Testing autonomic reflexes. In: Appenzeller O and Oribe E eds. The autonomic nervous system. An introduction to basic and clinical concepts. Amsterdam: Elsevier, 1997:671 -710.