Cases reported "Brain Ischemia"

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1/7. Outcome of acute ischemic lesions evaluated by diffusion and perfusion MR imaging.

    BACKGROUND AND PURPOSE: diffusion and perfusion MR imaging have been reported to be valuable in the diagnosis of acute ischemia. Our purpose was to ascertain the value of these techniques in the prediction of ischemic injury and estimation of infarction size, as determined on follow-up examinations. methods: We studied 18 patients with acute ischemic stroke who underwent echo-planar perfusion and diffusion imaging within 72 hours of symptom onset. Quantitative volume measurements of ischemic lesions were derived from relative mean transit time (rMTT) maps, relative cerebral blood volume (rCBV) maps, and/or apparent diffusion coefficient (ADC) maps. Follow-up examinations were performed to verify clinical suspicion of infarction and to calculate the true infarction size. RESULTS: Twenty-five ischemic lesions were detected during the acute phase, and 14 of these were confirmed as infarcts on follow-up images. Both ADC and rMTT maps had a higher sensitivity (86%) than the rCBV map (79%), and the rCBV map had the highest specificity (91%) for detection of infarction as judged on follow-up images. The rMTT and ADC maps tended to overestimate infarction size (by 282% and 182%, respectively), whereas the rCBV map appeared to be more precise (117%). Significant differences were found between ADC and rMTT maps, and between rCBV and rMTT maps. CONCLUSION: Our data indicate that all three techniques are sensitive in detecting early ischemic injury within 72 hours of symptom onset but tend to overestimate the true infarction size. The best methods for detecting ischemic injury and for estimating infarction size appear to be the ADC map and the rCBV map, respectively, and the diffusion abnormality may indicate early changes of both reversible and irreversible ischemia.
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2/7. diffusion MRI in ischemic stroke compared to pathologically verified infarction.

    BACKGROUND: diffusion MRI abnormality correlates with pathology in animal ischemic stroke models. A combined retrospective and prospective analysis of consecutive patients over a 3-year period who had a clinical diagnosis of probable new ischemic stroke, underwent diffusion MRI, and were later studied at autopsy was performed. methods: Inclusion criteria for the retrospective analysis were 1) symptom onset within 14 days of presentation, 2) diffusion MRI within 28 days of symptom onset, and 3) autopsy within 16 weeks of symptom onset. patients with suspected further infarcts between MRI and autopsy were excluded. The locations of all areas of MRI abnormality were identified by a blinded neuroradiologist, and recent infarcts were identified by review of pathologic records and microscopic slides. RESULTS: Eleven patients were identified who fulfilled inclusion criteria, with 25 discrete pathologic infarcts. diffusion MRI abnormality corresponded to pathologically verified infarction in 23 cases, was present in two locations where no pathologic infarct was identified, and was absent in two locations where an infarct was present at autopsy. In two cases, despite clinical suspicion of acute ischemic stroke, no MRI abnormality or pathologic infarct was found. The sensitivity and specificity of diffusion MRI were 88.5% (95% CI, 69.9% to 97.6%) and 96.6% (95% CI, 91.5% to 99.1%). Accuracy was 95.1% (95% CI, 90.2% to 98%). Three further patients who died during the course of the retrospective analysis were studied prospectively, and are described separately. CONCLUSIONS: These findings suggest high accuracy of diffusion MRI for detection of ischemic infarction compared with pathologic examination.
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3/7. Prognostic significance of SSEP, BAEP and serum S-100B monitoring after aneurysm surgery.

    OBJECTIVE: Changes in evoked potentials (EPs) and increased levels of S-100B protein were used to identify cerebral ischemia or glial damage and to predict neurological outcome in aneurysm patients. MATERIAL AND methods: Somatosensory evoked potentials and Brainstem auditory-evoked potentials, and serum S-100B protein were simultaneously investigated pre- and postoperatively over a period of 10 days in 43 patients with 47 aneurysms (six in the posterior fossa). RESULTS: The EP scores showed a strong correlation with the clinical outcome. Sensitivity was 73%, and specificity 81%. Pathological S-100B levels >0.5 mg/l were equal in predictive values (correct positive eight, false positive six, correct negative 26, false negative three). Initially increased S-100B levels, long-lasting S-100B elevation, and secondary increasing S-100B values correlated with an unfavorable outcome. High peak S-100B values correlated with bad EP scores at discharge. EP deterioration was the first indicator anticipating S-100B elevation and clinical deterioration in five patients. There was a good correlation between pathological S-100B values or EP findings and infarction on CT scan. CONCLUSIONS: Both EPs and S-100B protein showed a comparable high predictive value for outcome. S-100B reflects the extent of primary brain damage after subarachnoid hemorrhage and time course of ongoing secondary brain damage. evoked potentials assess the functional integrity and tended to react earlier than S-100B protein before definitive structural damage occurred.
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4/7. Intracranial lesions in the fullterm infant with hypoxic ischaemic encephalopathy: ultrasound and autopsy correlation.

    To test the hypothesis that cranial ultrasound correlated with post-mortem findings in neonates with hypoxic ischaemic encephalopathy (HIE), the brains of 20 infants who died after at least two real time ultrasound scans were examined. The ultrasound abnormalities detected in the periventricular/subcortical white matter, cortex or thalami were compared with the macroscopic and histological appearances. Comparing the last ultrasound scan which was performed no longer than 12 hours before the infant died, with histological data, the sensitivity and specificity for lesions in the thalamus was 100% and 83.3% respectively; for cortical lesions 76.9 and 100% respectively and for lesions in the periventricular white matter 80% and 75% respectively. The value of cranial ultrasound for detecting intracranial abnormalities in infants with HIE was considerably better than reported previously. This could mainly be attributed to the use of a 10 MHz transducer which was of critical importance to identify lesions in the superficial cortical layer.
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5/7. Multilevel somatosensory evoked potentials (SEPs) for spinal cord monitoring in descending thoracic and thoraco-abdominal aortic surgery.

    The usefulness of somatosensory evoked potential (SEP) monitoring as a means of preventing paraplegia in descending aorta surgery was evaluated in 47 consecutive cases operated on for isthmic (14 cases), thoracic (22 cases), or thoraco-abdominal (11 cases) repair. An aortic dissection was found in 11 cases (acute in 6). Somatosensory evoked potentials were obtained by unilateral left and right posterior tibial nerve (PTN) stimulation at the ankle and recordings were performed on four channels: peripheral nerve, lumbar spinal, brain-stem, and cortical recordings. Our experience led to the following current strategy: the establishment of atrio(aorto)-femoral(aortic) bypass (29 cases), proximal and distal aortic cross-clamping, aortic repair with reimplantation of the culprit artery(ies) as indicated by SEP alterations. Five types of SEP alterations were defined on the basis of the neural level involved: type I (27.7% of cases) = distal spinal ischemia due to proximal aortic cross-clamping in the absence of bypass; type II (21.3%) = PTN ischemia due to left common femoral artery cross-clamping; type III (12.8%) = segmental spinal ischemia due to the exclusion of critical feeding arteries; type IV (4.3%) = ischemia in the left carotid artery territory; type V (4.3%) = global brain hypoperfusion due to systemic hypotension. Forty-five patients survived the operation and could be tested for neurological dysfunction. Three patients presented a postoperative spinal cord deficit, but this deficit was already present preoperatively in one case, so that the actual incidence of a new paraplegia in our series was 2/45 cases (4.4%). One of the two cases was clearly a delayed paraplegia with SEP alterations appearing several hours after the operation. Somatosensory evoked potentials were evaluated on the basis of their sensitivity, specificity, and impact on the surgical strategy. Regarding SEP sensitivity, we did not encounter any unexpected immediate paraplegia, but the critical factor appeared to be the duration of SEP absence due to spinal cord ischemia, which, according to the literature, should never exceed 30 min; after a longer absence, SEP return does not guarantee neurological recovery. Somatosensory evoked potential specificity was also 100%, but only 58% of the abnormalities found were actually consequent to spinal cord ischemia, the rest of the abnormalities being consequent to peripheral nerve or brain ischemia. Finally, SEP monitoring had a significant impact on surgical strategy in 19% of the cases. It is concluded that distal aortic perfusion and multilevel SEP monitoring play a significant role in preventing paraplegia in descending aorta surgery.
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6/7. Cortical thermal clearance as a predictor of imminent neurological deterioration.

    Cerebral blood flow (CBF) is vital for the perfusion of brain tissue. It is frequently deranged in acute neurosurgical disorders, particularly subarachnoid haemorrhage and head injury. Despite its importance, in clinical practice the routine measurement of CBF is uncommon, as changes in CBF can occur abruptly. However, a method of CBF monitoring may be potentially useful, particularly if warning could be obtained of impending ischaemia before neurological deterioration. Measurement of tissue thermal clearance has been used as an estimate of local tissue blood flow since 1933. Its history is full of controversy, mostly centred around quantification. The ability of perfused tissues to clear heat is, as a first approximation, the sum of two components: a fixed component related to the constituents of the tissue, primarily the water content, and a variable convective component, related to the local blood flow. The mathematical relationship between flow and the observed increment in thermal clearance is still debatable. Here, the history of thermal clearance is reviewed, and the results of our work with a relatively simple device are described. It consisted of an implantable probe, designed to measure the thermal clearance of the cortical surface in arbitrary clearance units (CU), ranging from 27 CU (cadaveric) to 69 CU (well perfused brain). Pre- and postoperative studies showed that the system was capable of following changes in blood flow rapidly. The cortical thermal clearance (CTC) was monitored postoperatively in 24 patients after aneurysm surgery. Most remained clinically stable and had thermal clearances over 50 CU. In others, however, it was seen that a low-or falling-thermal clearance was associated with development of a neurological deficit. Analysis using receiver operating characteristics curves established that the method had a sensitivity of 0.86 and a specificity of 0.82 in the detection of a contralateral ischaemic motor deficit. No patient in whom the CTC remained above 50 CU ever developed a new neurological deficit, whereas all patients with a CTC below 35 did. The evidence-historical, mathematical, practical, and theoretical-that CTC is closely related to local blood flow is discussed. Changes in thermal clearance have been observed prior to the development of ischaemic neurological deterioration. Detection of imminent ischaemia may become increasingly important as means of improving cortical blood flow become more widely available. Whether such early detection- and subsequent treatment-of ischaemia will result in better patient outcome remains to be established. I believe it will.
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7/7. Failure of the hypotensive provocative test during temporary balloon test occlusion of the internal carotid artery to predict delayed hemodynamic ischemia after therapeutic carotid occlusion.

    BACKGROUND: Extensive experience and critical evaluation of the efficacy of a pharmacologic hypotensive challenge during conventional balloon test occlusion (BTO) of the internal carotid artery (ICA) is lacking. This prompted us to review our institution's most recent experience with this adjunctive provocative test before planned therapeutic balloon occlusion of the ICA. methods: Twenty consecutive cases of endovascular therapeutic balloon occlusion of the ICA were retrospectively reviewed. Conventional BTO under normotension and with hypotensive challenge were performed within a standardized protocol. RESULTS: Sixteen patients underwent provocative testing, of which 13 had BTO with hypotensive challenge. All patients in this group tolerated these maneuvers without acute neurologic deficit. Two (15%) of these patients developed delayed permanent neurologic deficits, which seemed to be attributable to hemodynamic ischemia. One of seven patients not undergoing hypotensive challenge also developed transient neurologic deficits after carotid occlusion. CONCLUSIONS: Despite the conceptually attractive and early positive experience of the hypotensive challenge in attempting to increase sensitivity and specificity of risk for developing delayed hemodynamic ischemia, we have found two significant false-negative results. This experience is reviewed in the context of risks of permanent balloon occlusion of the carotid artery after balloon test occlusion.
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