Cerebral blood flow and glucose metabolism in mitochondrial disorders.
OBJECTIVE
To investigate cerebral metabolism by 2-[18F]fluorodeoxy-d-glucose (FDG) uptake using PET and cerebrovascular reverse capacity by transcranial Doppler sonography (TCD) in different mitochondrial diseases (mitochondrial myopathy; mitochondrial encephalopathy, lactacidosis, and stroke-like episodes [MELAS]; and chronic external ophthalmoplegia).


BACKGROUND
Previous studies on individual patients with mitochondriopathies revealed abnormal accumulations of mitochondria in endothelium, smooth muscle cells, and pericytes of blood vessels in different parts of the nervous system (cerebrum, cerebellum, sural nerve) and skeletal muscle. On this basis, some investigators suggested a pathogenic role of vascular involvement in the MELAS syndrome and other encephalopathies. smhd1


METHODS
The authors investigated neuronal metabolism and cerebrovascular involvement with PET in 5 cases and with TCD with acetazolamide stimulation in 15 cases. The patients were divided into three groups: 1) interictal MELAS (n = 4); 2) progressive external ophthalmoplegia (n = 6); and 3) pure mitochondrial myopathy and neuropathy (n = 5). The results were compared with those from matched normal control subjects. The diagnoses were based on clinical phenotype as well as histopathologic and molecular analysis.


RESULTS
Cerebral glucose uptake was impaired in all patients, both with and without CNS symptoms, particularly in the occipital and temporal lobes. The vasoreactivity of the small arterioles to acetazolamide did not differ significantly between the patients and healthy control subjects or between the different groups of mitochondrial disorders.


CONCLUSIONS
MELAS does not appear to be a functional disturbance of arterioles leading to an ischemic vascular event. The clinical symptoms in MELAS are not the result of a mitochondrial angiopathy but are the consequences of a mitochondrial cytopathy affecting neurons or glia. There is no correlation between the decreased glucose metabolism and the duration of the disease.
Molnár
M J
MJ
National Institute of Psychiatry and Neurology, Budapest, Hungary. molnarm@jaguar.dote.hu
Valikovics
A
A
Molnár
S
S
Trón
L
L
Diószeghy
P
P
Mechler
F
F
Gulyás
B
B
D000086:Acetazolamide; D000140:Acidosis, Lactic / Q000000981:diagnostic imaging / Q000378:metabolism; D000328:Adult; D000368:Aged; D001783:Blood Flow Velocity; D001921:Brain / Q000098:blood supply / Q000000981:diagnostic imaging / Q000378:metabolism; D002257:Carbonic Anhydrase Inhibitors; D002560:Cerebrovascular Circulation; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D017241:MELAS Syndrome / Q000000981:diagnostic imaging / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D020768:Middle Cerebral Artery / Q000502:physiology; D017237:Mitochondrial Encephalomyopathies / Q000000981:diagnostic imaging / Q000378:metabolism; D017240:Mitochondrial Myopathies / Q000000981:diagnostic imaging / Q000378:metabolism*; D017246:Ophthalmoplegia, Chronic Progressive External / Q000000981:diagnostic imaging / Q000378:metabolism; D014055:Tomography, Emission-Computed; D017585:Ultrasonography, Doppler, Transcranial
D002257:Carbonic Anhydrase Inhibitors; D019788:Fluorodeoxyglucose F18; D005947:Glucose; D000086:Acetazolamide