Functional Neurosonology Reveals Impaired Cerebrovascular Reactivity in Multiple Sclerosis.

BACKGROUND AND PURPOSE: Vascular aspects like global cerebral hypoperfusion are frequently reported in patients with multiple sclerosis (MS). Although mechanistic question remains unanswered, this hemodynamic impairment may be caused by a widespread endothelial dysfunction. Furthermore, impaired cerebrovascular reactivity (CVR) has been described in patients with MS by means of hypercapnic perfusion magnetic resonance imaging (MRI). We sought to further evaluate potential hemodynamic restriction in patients with MS using functional sonographic methods. METHODS: We evaluated consecutive patients with MS and healthy controls with adequate bilateral transtemporal window. CVR was assessed by bilateral transcranial Doppler monitoring of proximal middle cerebral arteries. Mean flow velocities were recorded before and after 30 seconds of breath holding. Vasomotor response was quantified by breath holding index (BHI). RESULTS: A total of 42 patients with MS (mean age 39 ± 12 years; 69% women) were compared to 31 healthy controls (mean age 35 ± 11 years; 71% women). BHI was lower in patients with MS compared to healthy controls (.70 ± .43 vs. .93 ± .55; P = .006), documenting a lower cerebrovascular response to hypercapnia. There was no correlation between patient age (r = .1254; P = .277), expanded disability status scale (r = .1838; P = .109), and disease duration (r = .1882; P = .101) with BHI in patients with MS. CONCLUSIONS: These preliminary sonographic findings appear to independently corroborate the previously reported observation of impaired CVR on brain MRI in patients with MS. However, the underlying pathophysiological mechanisms as well as the clinical impact of this observation remain elusive.

Coordination of cluster ensembles via exact methods.

We present a novel optimization-based method for the combination of cluster ensembles for the class of problems with intracluster criteria, such as Minimum-Sum-of-Squares-Clustering (MSSC). We propose a simple and efficient algorithm-called EXAMCE-for this class of problems that is inspired from a Set-Partitioning formulation of the original clustering problem. We prove some theoretical properties of the solutions produced by our algorithm, and in particular that, under general assumptions, though the algorithm recombines solution fragments so as to find the solution of a Set-Covering relaxation of the original formulation, it is guaranteed to find better solutions than the ones in the ensemble. For the MSSC problem in particular, a prototype implementation of our algorithm found a new better solution than the previously best known for 21 of the test instances of the 40-instance TSPLIB benchmark data sets used in [1], [2], and [3], and found a worse-quality solution than the best known only five times. For other published benchmark data sets where the optimal MSSC solution is known, we match them. The algorithm is particularly effective when the number of clusters is large, in which case it is able to escape the local minima found by K-means type algorithms by recombining the solutions in a Set-Covering context. We also establish the stability of the algorithm with extensive computational experiments, by showing that multiple runs of EXAMCE for the same clustering problem instance produce high-quality solutions whose Adjusted Rand Index is consistently above 0.95. Finally, in experiments utilizing external criteria to compute the validity of clustering, EXAMCE is capable of producing high-quality results that are comparable in quality to those of the best known clustering algorithms.

Multiple lung abscesses due to acinetobacter infection: a case report.

Acinetobacter species are well-known causes of nosocomial infections. Recent increasing evidence emphasize on the role of these pathogens in community-acquired infections.We report a case of a 16-yr-old female with fever, sore throat, productive cough, malaise and the presence of lung consolidation with multiple abscesses on radiographic examination. The patient had no significant medical history. After a detailed diagnostic work-up the diagnosis of community acquired Acinetobacter pneumonia with multiple lung abscesses was made. The Acinetobacter stain was susceptible to a variety of antimicrobial agents and the patient's condition improved rapidly. A new computed tomography chest scan, three months later, confirmed full recovery.The presence of lung abscesses due to Acinetobacter infection is an extremely uncommon manifestation of the disease. This case underlines the emergent role which these, often multi-drug resistant, bacteria may play in the future, perhaps in community infections as well.

Intravenous tissue plasminogen activator and flow improvement in acute ischemic stroke patients with internal carotid artery occlusion.

BACKGROUND AND PURPOSE: It has been suggested that intravenous tissue plasminogen activator (TPA) would not lyse the large thrombus associated with internal carotid artery (ICA) occlusion and, therefore, would be ineffective in this setting. Vascular imaging, safety, and outcome of TPA therapy for ICA occlusion is not well described. Our goal was to determine the site of occlusion, early recanalization after TPA infusion, and its relationship to outcome. METHODS: We reviewed our database of all stroke patients treated with i.v. TPA between July 1997 and July 1999. We identified all cases with carotid occlusion suggested by transcranial Doppler (TCD) and angiography. Occlusion and recanalization were assessed by site including proximal ICA (prICA), terminal ICA (tICA), and middle cerebral artery (MCA). Baseline National Institutes of Health Stroke Scale (NIHSS) scores and follow-up Rankin scores were obtained. RESULTS: We treated 20 patients with carotid occlusion (age 63.9 +/- 10.8 years, 11 males, 9 females). Time to TPA infusion after stroke onset was 128 +/- 66 minutes. Baseline NIHSS scores were 16.4 +/- 5.4. Time to follow-up was 3.5 +/- 4.9 months (2 patients were lost to follow-up). Occlusion sites were prICA 40%, tICA 70%, and concurrent MCA 45%. Multiple sites were involved in 10/20 patients (50%). Among patients with pretreatment and posttreatment vascular imaging studies (n = 18), recanalization in the prICA and tICA was complete in 10%, partial in 16%, and none in 74%. MCA recanalization was complete in 35%, partial in 24%, and none in 41%. At follow-up, Rankin 0-1 was found in 8 patients (44%), Rankin 2-3 in 3 (17%), and Rankin 4-5 in 3 (17%). Mortality was 22% (n = 4) including 1 fatal intracerebral hemorrhage. Improvement was closely related to resumption of MCA flow (P < .01). CONCLUSIONS: Most patients did not recanalize their ICA occlusion after intravenous TPA therapy. However, recanalization of associated proximal MCA clot, found in 45% of our patients, or improved MCA collateral flow was strongly associated with good outcome.

Screening for intracranial stenosis with transcranial Doppler: the accuracy of mean flow velocity thresholds.

BACKGROUND: Patients with 50% intracranial arterial stenosis may require more intensive therapies for stroke prevention. Transcranial Doppler (TCD) is a convenient noninvasive screen for intracranial stenosis. The accuracy of different mean flow velocity (MFV) thresholds for determining the degree of stenosis remains uncertain. METHODS: The authors prospectively compared the accuracy of TCD criteria and MFV thresholds to magnetic resonance, computed tomography, and digital subtraction angiography in patients with symptoms of recent or remote stroke or transient ischemic attack. Stenosis on angiography was measured as 0%, < 50%, or > or = 50% diameter reduction. RESULTS: Of 136 consecutive patients, 33 (24%) had distal internal carotid artery (ICA), middle cerebral artery (MCA), posterior cerebral artery, or basilar artery stenosis on angiography (14 patients [10%] were excluded due to incomplete TCD examinations, mainly from a lack of temporal windows). TCD showed 31 true-positive, 9 false-positive, 2 false-negative, and 94 true-negative studies. For all vessels, TCD had a sensitivity of 93.9% (confidence interval [CI] = 89%-98%), a specificity of 91.2% (CI = 87%-96%), a positive predictive value (PPV) of 77.5%, and a negative predictive value (NPV) of 97.9%. The trade-off in sensitivity and specificity for MCA MFV thresholds was as follows: MFV > or = 80 cm/s had a sensitivity of 100%, a specificity of 96.9% (CI = 94%-99%), a PPV of 84%, and an NPV of 100%. MFV > or = 100 cm/s had a sensitivity of 100%, a specificity of 97.9% (CI = 96%-99%), a PPV of 88.8%, and an NPV of 94.9%. MFV > or = 120 cm/s had a sensitivity of 68.7% (CI = 61%-78%), a specificity of 100%, a PPV of 100%, and an NPV of 94.9%. Reasons for false-positive findings include collateralization of flow in the presence of proximal ICA stenosis and prestenotic to stenotic MCA velocity ratios of 1: < or = 2. CONCLUSION: TCD is both sensitive and specific in identifying > or = 50% intracranial arterial stenosis. A MFV threshold cutoff of 100 cm/s has an optimal sensitivity and specificity trade-off for > or = 50% MCA stenosis. To help avoid false-positive results, a prestenotic to stenotic MCA velocity ratio of 1: > or = 2 should be used in addition to the MFV threshold.

Clinical and sonographic patterns of tandem internal carotid artery/middle cerebral artery occlusion in tissue plasminogen activator-treated patients.

BACKGROUND AND PURPOSE: The National Institutes of Health Stroke Scale (NIHSS) is predictive of thrombus presence but has limited ability to identify occlusion location in the anterior circulation. We describe clinical and sonographic patterns that are associated with tandem internal carotid artery (ICA) and middle cerebral artery (MCA) occlusions. METHODS: Consecutive acute ischemic stroke patients receiving intravenous tissue plasminogen activator (TPA) were studied. Pretreatment NIHSS scores and bedside transcranial Doppler (TCD) were obtained for all patients. RESULTS: A total of 95 patients treated with intravenous TPA at 132+/-60 minutes from stroke onset were studied. On TCD, 48 had isolated MCA occlusion (mean NIHSS 16.8+/-5.8, median 17, range 5 to 28); and 16 had tandem ICA/MCA occlusion (mean NIHSS 18.8+/-5.8, median 22, range 8 to 29; P=NS). In the MCA occlusion and tandem ICA/MCA occlusion groups, 19% and 11%, respectively, had NIHSS scores <12 points. Compared with the NIHSS scores in patients with hemiplegia, forced gaze deviation, and complete neglect, the lower NIHSS scores were attributable to partial arm and/or leg paresis, gaze preference, and partial neglect. In those patients, TCD showed > or =2 major collateral channels and low-resistance flow at the M1 origin, suggesting perfusion of perforating arteries. Although TCD cannot differentiate between high-grade ICA stenosis or occlusion, collateral flow patterns and stenotic signals at the terminal ICA differentiated tandem lesions from isolated MCA occlusion (P<0.01). CONCLUSIONS: Tandem ICA/MCA occlusion was found on TCD in 17% of TPA-treated patients. NIHSS scores were similar in patients with isolated MCA and tandem occlusions. Lower NIHSS scores were seen in patients with a higher number of major collateral flow channels and higher Thrombolysis in Brain Ischemia (TIBI) flow grades at the MCA origin.