Regional cerebral blood flow and cerebrovascular reactivity during chronic stage of stroke-like episodes in MELAS -- implication of neurovascular cellular mechanism.
BACKGROUND
Ischemic vascular hypothesis as a causative role in the pathogenesis of stroke-like episodes in MELAS remains to be debated.


METHODS
This study consisted of two parts. Part 1 is a clinicoradiological study during acute stage of 18 consecutive stroke-like episodes in six patients with MELAS. Part 2 is a SPECT study to assess the regional cerebrovascular reactivity (rCVR) to acetazolamide during chronic stage in five patients with MELAS.


RESULTS
Headache and epileptic seizure were the most common presenting symptoms. Unique features of acute stroke-like lesions included progressive spread of cortical lesions with vasogenic edema, focal periodic epileptiform discharges, focal hyperperfusion, and cortical laminar necrosis during subacute stage. During chronic stage, SPECT showed hypoperfusion in non-affected occipital cortex in three patients as well as in previously affected regions in four. The rCVR was preserved in three patients, focally impaired in one, and extensively impaired in one, but relatively preserved in the occipital cortex in all patients.


CONCLUSIONS
Stroke-like episodes could be non-ischemic neurovascular events initiated by neuronal hyperexcitability. Once neuronal hyperexcitability develops in a focal brain region, epileptic activities depolarize adjacent neurons, leading to a propagation of epileptic activities into the surrounding cortex, and resulting in energy imbalance. The mechanisms for neuronal hyperexcitability remain to be elucidated.
Iizuka
Takahiro
T
Department of Neurology, School of Medicine, Kitasato University, 1-15-1 Kitasato, Sagamihara, Kanagawa, 228-8555, Japan. takahiro@med.kitasato-u.ac.jp
Sakai
Fumihiko
F
Ide
Toshimitsu
T
Miyakawa
Saori
S
Sato
Mayumi
M
Yoshii
Shintaro
S
D000086:Acetazolamide; D000328:Adult; D000368:Aged; D001921:Brain / Q000098:blood supply / Q000000981:diagnostic imaging* / Q000503:physiopathology; D002256:Carbonic Anhydrases; D002536:Cerebral Arteries / Q000000981:diagnostic imaging* / Q000503:physiopathology; D002560:Cerebrovascular Circulation; D002908:Chronic Disease; D004734:Energy Metabolism; D004827:Epilepsy / Q000000981:diagnostic imaging / Q000378:metabolism / Q000503:physiopathology; D005260:Female; D006801:Humans; D017241:MELAS Syndrome / Q000000981:diagnostic imaging* / Q000503:physiopathology; D008297:Male; D008564:Membrane Potentials; D008875:Middle Aged; D009474:Neurons / Q000378:metabolism; D020521:Stroke / Q000000981:diagnostic imaging* / Q000209:etiology / Q000503:physiopathology; D009435:Synaptic Transmission; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*; D014661:Vasoconstriction; D014666:Vasomotor System / Q000000981:diagnostic imaging / Q000503:physiopathology
D002256:Carbonic Anhydrases; D000086:Acetazolamide