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(Stroke. 1996;27:1350-1353.)
© 1996 American Heart Association, Inc.

Articles

A Transcranial Doppler Ultrasonography Study of Cerebrovascular CO₂ Reactivity in Mitochondrial Encephalomyopathy

Ryuhei Kodaka, MD; Yusuke Itagaki, MD; Masayasu Matsumoto, MD; Toshisaburo Nagai, MD Shintaro Okada, MD

the Department of Pediatrics (R.K., Y.I., T.N., S.O.) and the First Department of Internal Medicine (M.M.), Osaka University Medical School (Japan).

Correspondence to Ryuhei Kodaka, MD, Department of Pediatrics, Osaka University Medical School, 2-2 Yamadaoka, Suita-shi, Osaka 565, Japan.

Background and Purpose To elucidate the pathogenic role of vascular involvement such as mitochondrial angiopathy in patients with mitochondrial encephalomyopathy (MEM), we used the transcranial Doppler sonography (TCD) method to detect impairment of cerebrovascular CO₂ reactivity.

Methods The cerebral perfusion reserve in 13 MEM patients, including 6 with MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes) was studied by TCD for different CO₂ partial pressures. For the parameter of mean flow velocity, the mean spatial Doppler frequency (fm) was obtained from the right and left middle cerebral arteries and basilar artery under conditions of normocapnia, hypercapnia, and hypocapnia in cases in which hyperventilation was possible. By fitting the obtained fm and the end-tidal CO₂ partial pressure (PETCO₂) to the exponential formula fm=axe^(KxPETCO₂), where a is the theoretical fm at a PETCO₂ of 0 mm Hg, the parameter K, an index of CO₂ reactivity, was calculated.

Results The K value was lower than control values at at least one site of the middle cerebral arteries and basilar artery of all patients with MELAS as well as the other MEM patients except for one patient with myoclonic epilepsy with ragged-red fiber and one with Kearns-Sayer syndrome.

Conclusions Our results suggest that there is a high incidence of impairment of cerebrovascular CO₂ reactivity in MEM patients. Moreover, the noninvasive TCD method was found useful for evaluation of cerebral hemodynamics in MEM patients.

Key Words: carbon dioxide • hemodynamics • mitochondrial encephalomyopathy • transcranial Doppler • vasomotor reactivity

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