title: A transcranial doppler ultrasonography study of cerebrovascular CO2 reactivity in mitochondrial encephalomyopathy.
abstract: OBJECTIVE
  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 = a x e(K < PETCO2), 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.
authors.affiliation: Department of Pediatrics, Osaka University Medical School, Japan.
authors.forename: R
authors.initials: R
authors.lastname: Kodaka
authors.forename: Y
authors.initials: Y
authors.lastname: Itagaki
authors.forename: M
authors.initials: M
authors.lastname: Matsumoto
authors.forename: T
authors.initials: T
authors.lastname: Nagai
authors.forename: S
authors.initials: S
authors.lastname: Okada
mesh_terms: D000293:Adolescent; D000328:Adult; D002245:Carbon Dioxide / Q000032:analysis* / Q000378:metabolism; D002560:Cerebrovascular Circulation / Q000502:physiology; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D017241:MELAS Syndrome / Q000000981:diagnostic imaging* / Q000378:metabolism; D008279:Magnetic Resonance Imaging; D008297:Male; D015899:Tomography, Emission-Computed, Single-Photon; D014057:Tomography, X-Ray Computed; D017585:Ultrasonography, Doppler, Transcranial
chemical_list: D002245:Carbon Dioxide