technetium-tc-99m-exametazime and MELAS-Syndrome

Hypoperfusion on single-photon emission computed tomography (SPECT) of the stroke-like lesion (SLL) at the hyperacute stage of mitochondrial encephalopathy with lactic acidosis and stroke-like episodes (MELAS) is considered to be a supportive evidence of the mitochondrial angiopathy theory. Our objectives were to examine whether other neuroimages, especially transcranial color-coded sonography (TCCS), done at the hyperacute stage of stroke-like episode (SLE) is consistent with hypoperfusion of the SLL. We reviewed the magnetic resonance imaging (MRI), SPECT, cerebral angiography, and TCCS of a patient with MELAS syndrome, all of which were performed at the hyperacute stage of one SLE. MRI on the 1st day post SLE showed right temporoparietal lesion with vasogenic edema. SPECT on the 2nd day showed focal decreased uptake of technetium-99m hexamethylpropyleneamine oxime ((99m)Tc-HMPAO) in the same region, but cerebral angiography and TCCS on the 3rd day showed increased regional cerebral blood flow (rCBF) and distal arteriole dilation in the same region. TCCS can delineate increased rCBF of the SLL at the hyperacute stage of SLE. We propose that the discrepancy between the decreased (99m)Tc-HMPAO uptake and increased rCBF might be caused by mitochondrial dysfunction. The phenomenon of "hypoperfusion" on SPECT might be caused by cell dysfunction but not decreased rCBF. We suggest that SPECT can be complemented by angiography and TCCS in future studies to delineate the perfusion status of SLLs.

Topics: Adult; Brain Edema; Cerebral Angiography; Cerebrovascular Circulation; Humans; Hyperemia; Image Processing, Computer-Assisted; Magnetic Resonance Imaging; Male; MELAS Syndrome; Middle Cerebral Artery; Perfusion; Radiopharmaceuticals; Stroke; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon; Tomography, X-Ray Computed; Ultrasonography, Doppler, Transcranial

A 55-year-old woman was diagnosed with the syndrome of mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS). She was referred for Tc-HMPAO brain SPECT because of visual hallucinations, which were suspected to be related to epileptic seizures. Ictal SPECT images showed remarkable hyperperfusion in the left occipital cortex, which returned to near-normal status on the interictal SPECT images after treatment with anticonvulsants. It is very rare to see such an ictal SPECT image of epileptic or epilepsy-like disorders, especially in the setting of MELAS syndrome with visual hallucination.

Topics: Brain; Epilepsy; Female; Hallucinations; Humans; MELAS Syndrome; Middle Aged; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon

The abnormalities of intracranial hemodynamics associated with strokelike episodes in MELAS are variable depend on the time phase from the onset of strokelike episodes and on the progression of the dementia state. To clarify the regional cerebral blood flows (rCBF) in the natural course of MELAS is very important to understand the pathogenic mechanism of this disorder, either cytopathy, angiopathy or both. We analyzed the serial studies of brain statistical parametric mapping (SPM) 99 single photon emission computed tomography (SPECT) in 5 MELAS patients in maximum 10 years interval, who fulfilled the clinical, pathological and genetic criteria of MELAS, and have an A3243G mutation in the mitochondrial tRNA(Leu(UUR)) gene. SPM is a proven and effective method for the voxel-by-voxel analysis of functional images which show the advantage in its promise of fully automated neurophysiological imaging analysis throughout the whole brain using various statistical analyses. SPECT acquisition was initiated and was reconstructed by iterative algorithm and were processed and analyzed with SPM 99 for Windows software. Statistics were displayed as Z scores (threshold: P < 0.01). The inappropriate intracranial hemodynamics was found not only at the acute but at the interictal phase, and was getting worse as the disease progress. Hypoperfusion in the posterior cingulate cortex was always observed (corrected P < 0.01) in MELAS patients, which is the typical finding reported in Alzheimer's disease. The inappropriate intracranial hemodynamics is a common feature and may be related with mitochondrial angiopathy in the natural course of MELAS.

Topics: Adolescent; Adult; Brain Mapping; Child; Female; Hemodynamics; Humans; Image Processing, Computer-Assisted; Magnetic Resonance Imaging; Male; MELAS Syndrome; Mutation; RNA, Transfer, Leu; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon

We report cerebral SPECT studies on two siblings with the syndrome of mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS). Tc-99m HMPAO brain SPECT was performed 8, 19 and 30 days after a stroke-like episode in one case and 10 days after a stroke-like episode, 6 h after a partial seizure and as a follow-up study in the other. Increased blood flow was seen in both these patients with stroke-like episodes due to MELAS. The cause of the increased blood flow is uncertain, but it may be related to the decreased pH created by local increase in lactic acid.

Topics: Adult; Brain; Cerebral Cortex; Cerebrovascular Circulation; Female; Humans; Hydrogen-Ion Concentration; Male; MELAS Syndrome; Radiopharmaceuticals; Stroke; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon

Topics: Adult; DNA, Mitochondrial; Electroencephalography; Epilepsia Partialis Continua; Gadolinium DTPA; Humans; Magnetic Resonance Imaging; Male; MELAS Syndrome; Point Mutation; Radiopharmaceuticals; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon

Topics: Adult; Brain; Cerebrovascular Circulation; Cerebrovascular Disorders; Follow-Up Studies; Humans; Male; MELAS Syndrome; Organotechnetium Compounds; Oximes; Radiography; Technetium Tc 99m Exametazime; Time Factors; Tomography, Emission-Computed, Single-Photon

To evaluate imaging findings in MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, strokes) syndrome for the presence and location of infarctions and the presence of lactate.. Eight patients were studied with MR (n = 8) and CT (n = 2). One patient underwent single-photon emission CT with technetium 99m hexamethyl-propyleneamine oxime and one patient had conventional catheter angiography. One fixed brain was studied with MR imaging. Five patients underwent single volume proton MR spectroscopy. Imaging studies were evaluated for atrophy, edema, and infarctions. Proton MR spectroscopy was visually analyzed for presence or absence of lactate.. One patient showed a cerebral infarction, and later a second distant infarction developed. One patient showed a transient area of cortical edema. Two patients had small nonspecific periventricular white matter abnormalities and one patient had diffuse white matter hyperintensities. Two patients had nonspecific MR abnormalities (probably age-related changes), and two had normal MR findings. None had basal ganglia involvement. Proton MR spectroscopy showed presence of lactate in one case with transient cortical edema; in two cases with nonspecific (probably age-related) brain findings; and in two patients with normal MR findings.. Patients with MELAS have a variety of MR findings. The fact that proton MR spectroscopy showed lactate in all five cases studied, regardless of MR findings, indicates that proton MR spectroscopy may be more sensitive in the detection of MELAS-associated abnormalities than MR imaging.

Topics: Adolescent; Adult; Aged; Aged, 80 and over; Brain; Brain Chemistry; Child, Preschool; Female; Humans; Infant; Lactates; Lactic Acid; Magnetic Resonance Imaging; Magnetic Resonance Spectroscopy; Male; MELAS Syndrome; Middle Aged; Organotechnetium Compounds; Oximes; Radiography; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon

NeuroSPECT of regional cerebral blood flow (rCBF) with Tc-99m HMPAO demonstrated left temporoparietal hyperemia in two patients with acute receptive aphasia. This finding prompted further testing with electroencephalography that added to the impression of ictal dysphasia. The differential diagnosis in one case included complicated migraine. NeuroSPECT depicts blood flow abnormalities in acute aphasic disorders, either due to ischemia, which is most commonly the cause, or due to hyperemia secondary to migraine or epilepsy. The treatment and prognosis of these latter conditions differ from stroke, and thus SPECT plays a role in patient management.

Topics: Adult; Aphasia, Wernicke; Cerebrovascular Circulation; Diagnosis, Differential; Epilepsy; Female; Humans; Hyperemia; MELAS Syndrome; Middle Aged; Organotechnetium Compounds; Oximes; Parietal Lobe; Technetium Tc 99m Exametazime; Temporal Lobe; Tomography, Emission-Computed, Single-Photon