Cerebral blood flow, vascular response and metabolism in patients with MELAS syndrome--xenon CT and PET study.
Two patients with MELAS syndrome underwent serial measurement of cerebral blood flow (CBF) with xenon CT while they were presenting stroke like episodes accompanying cerebral lesion detectable with CT. One of them underwent PET measurement of regional cerebral metabolic rate of oxygen (CMRO2) and glucose (CMRGlu) after his symptoms and lesion disappeared.


METHODS
The xenon CT CBF study was performed by 4 min wash-in and 3 min wash-out protocol with serial measurement of endexpiratory concentration of xenon gas. The CBF after acetazolamide loading was also quantified in one of them. The PET study was performed to quantify CBF, CMRO2, oxygen extraction fraction (OEF) and cerebral blood volume (CBV) by continuous inhalation of O-15 labeled gases and arterial blood sampling. The PET measurement of CMRGlu was performed by i.v. injection of F-18 FDG and arterial blood sampling.


RESULTS
1) During the symptomatic period, Xe-CBF was normal or slightly increased both in and outside the low density lesion. 2) The CBF response to acetazolamide loading was well preserved both in and outside the low density lesions. 3) After the neurological symptoms and low density lesions disappeared, Xe-CBF pattern and vascular response was the same as during the symptomatic period. 4) In the PET study, normal or slightly increased PET-CBF, increased CMRGlu and markedly decreased CMRO2 in comparison to normal control was noted resulting in a marked decrease in OEF and CMRO2/CMRGlu ratio, a characteristic metabolic pattern for MELAS.


CONCLUSIONS
In the present cases, resting CBF and vasomotor reactivity was well preserved both in symptomatic and remission period. On the contrary, abnormal metabolic pattern was noted. The stroke like episode of the present patients is more likely attributed to metabolic failure than vascular accident.
Nariai
T
T
Department of Brain Medical Science, Tokyo Medical and Dental University, Japan.
Ohno
K
K
Akimoto
H
H
Ohta
Y
Y
Nagaoka
T
T
Hirakawa
K
K
Ishii
K
K
Senda
M
M
D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D002560:Cerebrovascular Circulation; D006801:Humans; D017241:MELAS Syndrome / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008297:Male; D010100:Oxygen / Q000097:blood; D014055:Tomography, Emission-Computed; D014057:Tomography, X-Ray Computed / Q000379:methods; D014978:Xenon
D001786:Blood Glucose; D014978:Xenon; D010100:Oxygen