TRANSCRANIAL DOPPLER ULTRASONOGRAPHY STUDY OF CEREBROVASCULAR CO2 REACTIVITY IN MITOCHONDRIAL ENCEPHALOMYOPATHY

Background and Purpose To elucidate the pathogenic role of vascular in volvement such as mitochondrial angiopathy in patients with mitochondr ial encephalomyopathy (MEM), we used the transcranial Doppler sonograp hy (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 partia l pressures. For the parameter of mean flow velocity, the mean spatial Doppler frequency (fm) was obtained from the right and left middle ce rebral arteries and basilar artery under conditions of normocapnia, hy percapnia, and hy pocapnia in cases in which hyperventilation was poss ible. By fitting the obtained fm and the end-tidal CO2 partial pressur e(PETCO(2)) to the exponential formula fm=axe( )((KxPETCO2)), where a is the theoretical fm at a PETCO(2) Of 0 mm Hg, the parameter K, an in dex of CO2 reactivity, was calculated. Results The K value was lower t han control values at at least one site of the middle cerebral arterie s and basilar artery of all patients with MELAS as well as the other M EM 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 cerebrovascul ar CO2 reactivity in MEM patients. Moreover, the noninvasive TCD metho d was found useful for evaluation of cerebral hemodynamics in MEM pati ents.