Keith A Siller, M.D.

Perfusion CT improves diagnostic accuracy for hyperacute ischemic stroke in the 3-hour window: study of 100 patients with diffusion MRI confirmation
Lin, Ke; Do, Kinh G; Ong, Phat; Shapiro, Maksim; Babb, James S; Siller, Keith A; Pramanik, Bidyut K
2009 ;28(1):72-79, Cerebrovascular diseases
PURPOSE: Conventional noncontrast CT (NCCT) is insensitive to hyperacute cerebral infarction in the first 3 h. Our aim was to determine if CT perfusion (CTP) can improve diagnostic accuracy over NCCT for patients presenting with stroke symptoms in the 3-hour window. METHODS: Consecutive patients presenting to our emergency department with symptoms of ischemic stroke <3 h old and receiving NCCT and CTP as part of their triage evaluation were retrospectively reviewed. Patients with follow-up diffusion-weighted MRI (DWI) <7 days from ictus were included. Two readers rated the NCCT and CTP for evidence of acute infarct and its vascular territory. CTP selectively covered 24 mm of brain centered at the basal ganglia with low relative cerebral blood volume in a region of low cerebral blood flow or elevated time to peak as the operational definition for infarction. A third reader rated all follow-up DWI for acute infarct and its vascular territory as the reference standard. Sensitivity, specificity, and predictive values were calculated. An exact McNemar test and generalized estimating equations from a binary logistic regression model were used to assess the difference in detection rates between modalities. A two-sided p value <0.05 was considered significant. RESULTS: 100 patients were included. Sixty-five (65%) patients had follow-up DWI confirmation of acute infarct. NCCT revealed 17 (26.2%) acute infarcts without false positives. CTP revealed 42 (64.6%) acute infarcts with one false positive. Of the 23 infarcts missed on CTP, 10 (43.5%) were outside the volume of coverage while the remaining 13 (56.5%) were small cortical or lacunar type infarcts (<or=15 mm in size). CTP was significantly more sensitive (64.6 vs. 26.2%, p < 0.0001) and accurate (76.0 vs. 52%, p < 0.0001) and had a better negative predictive value (59.6 vs. 42.2%, p = 0.032) than NCCT. CONCLUSION: In a retrospective cohort of 100 patients with symptoms of hyperacute stroke in the 3-hour window, CTP provided improved sensitivity and accuracy over NCCT
— id: 100480, year: 2009, vol: 28, page: 72, stat: Journal Article,

Accuracy of the Alberta Stroke Program Early CT Score during the first 3 hours of middle cerebral artery stroke: comparison of noncontrast CT, CT angiography source images, and CT perfusion
Lin, K; Rapalino, O; Law, M; Babb, J S; Siller, K A; Pramanik, B K
2008 May;29(5):931-936, AJNR. American journal of neuroradiology
BACKGROUND AND PURPOSE: The Alberta Stroke Program Early CT Score (ASPECTS) is a reliable method of delineating the extent of middle cerebral artery (MCA) stroke. Our aim was to retrospectively compare the accuracy of ASPECTS on noncontrast CT, CT angiography (CTA) source images, and CT perfusion maps of cerebral blood volume (CBV) during the first 3 hours of middle cerebral artery (MCA) stroke. MATERIALS AND METHODS: First-time patients with MCA stroke who presented <3 hours from symptom onset and were evaluated by noncontrast CT/CTA/CT perfusion, had confirmed acute nonlacunar MCA infarct on diffusion-weighted MR imaging (DWI) within 7 days, and had follow-up angiography were included. Patients were excluded for persistent MCA occlusion or stenosis. Two raters through consensus assigned an ASPECTS on the noncontrast CT, CTA source images, and the section-selective (2 x 12 mm coverage) CT perfusion CBV maps. ASPECTS on follow-up DWI served as the reference standard. For each CT technique, the detection rates of regional infarction, the mean ASPECTS, and the linear correlation to final ASPECTS were determined and compared. P values <.05 were considered significant. RESULTS: Twenty-eight patients satisfied the criteria with DWI performed at a mean of 50.3 hours (range, 22-125 hours) post-CT imaging. Of 280 ASPECTS regions, 100 were infarcted on DWI. The accuracy of noncontrast CT, CTA source images, and CT perfusion CBV for detecting regional infarct was 80.0%, 84.3%, and 96.8%, respectively (P < .0001). The mean ASPECTSs of noncontrast CT, CTA source images, CT perfusion CBV, and DWI were 8.4 +/- 1.8, 8.0 +/- 1.8, 6.8 +/- 1.9, and 6.5 +/- 1.8, respectively. The mean noncontrast CT and CTA source image ASPECTS was different from that of DWI (P < .05). Correlation of noncontrast CT, CTA source images, and CT perfusion CBV ASPECTS with final ASPECTS was r(2) = 0.34, r(2) = 0.42, and r(2) = 0.91, respectively. CONCLUSION: In a retrospective cohort of MCA infarcts imaged <3 hours from stroke onset, ASPECTS was most accurately determined on CT perfusion CBV maps
— id: 79102, year: 2008, vol: 29, page: 931, stat: Journal Article,

Evaluating middle cerebral artery collateral blood flow reserve using acetazolamide transcranial Doppler ultrasound in patients with carotid occlusive disease
Russell, Stephen M; Woo, Henry H; Siller, Keith; Panasci, David; Leroux, Peter D
2008 Nov;70(5):466-470, Surgical neurology
BACKGROUND: The objective of this study is to examine the utility of acetazolamide TCD ultrasound in the evaluation of MCA collateral blood flow reserve in patients with carotid occlusive disease. METHODS: Acetazolamide TCD and cerebral angiography were performed for 28 carotid territories in 14 patients with carotid occlusive disease. The percentage change in mean blood flow velocity and PI in the MCA was measured before and after 1 g of acetazolamide was administered. The carotid territories were divided into groups according their angiographic findings: (1) mild/moderate (<70%) vs severe (> or =70%) extracranial carotid artery stenosis, and (2) active collateral blood flow to the MCA territory vs no collateral blood flow to the MCA. RESULTS: After acetazolamide injection, the percentage increase in mean MCA velocity for mild/moderate vs severe carotid artery stenosis was 43% +/- 10% and 19% +/- 6%, respectively, indicating less collateral blood flow reserve in patients with severe stenosis (P = .04). The percentage decrease in the PI for MCA territories with vs without angiographic evidence of collateral blood flow was 4.6% +/- 4% and 16% +/- 3%, respectively (P = .04), indicating an exhausted vascular reserve in patients with evidence of active collateral blood flow on angiography. CONCLUSIONS: A decrease in the PI after acetazolamide administration represents a safe and noninvasive indicator of limited collateral blood flow reserve to the MCA territory ipsilateral to an extracranial carotid stenosis. Further study into the role acetazolamide TCD has in the preoperative evaluation of these patients, including threshold values, is warranted
— id: 91701, year: 2008, vol: 70, page: 466, stat: Journal Article,

Cholesterol in neurologic disorders of the elderly: stroke and Alzheimer's disease
Reiss, Allison B; Siller, Keith A; Rahman, Mohammad M; Chan, Edwin S L; Ghiso, Jorge; de Leon, Mony J
2004 Oct;25(8):977-989, Neurobiology of aging
Mechanisms for the regulation of intracellular cholesterol levels in various types of brain and vascular cells are of considerable importance in our understanding of the pathogenesis of a variety of diseases, particularly atherosclerosis and Alzheimer's disease (AD). It is increasingly clear that conversion of brain cholesterol into 24-hydroxycholesterol and its subsequent release into the periphery is important for the maintenance of brain cholesterol homeostasis. Recent studies have shown elevated plasma concentrations of 24-hydroxycholesterol in patients with AD and vascular dementia, suggesting increased brain cholesterol turnover during neurodegeneration. The oxygenases involved in the degradation and excretion of cholesterol, including the cholesterol 24-hydroxylase and the 27-hydroxylase, are enzymes of the cytochrome P-450 family. This review focuses on the newly recognized importance of cholesterol and its oxygenated metabolites in the pathogenesis of ischemic stroke and AD. The reduction in stroke and AD risk in patients treated with cholesterol-lowering statins is also discussed
— id: 45967, year: 2004, vol: 25, page: 977, stat: Journal Article,

The role of diamox transcranial dopplers in extracranial carotid disease
Woo H; Russell S; Panasci D; Siller K; Leroux P
1999 ;90:392-392, Journal of neurosurgery
— id: 63777, year: 1999, vol: 90, page: 392, stat: Journal Article,

Neuropsychological sequelae of cardiopulmonary bypass versus other major surgery: a prospective comparison
Jonas S; D'Hollosy M; Siller K; Grieco G
1998 ;5(Suppl 1):S14-S14, European journal of neurology
— id: 63776, year: 1998, vol: 5, page: S14, stat: Journal Article,

CATASTROPHIC CENTRAL-NERVOUS-SYSTEM DYSFUNCTION DURING METHYLPREDNISOLONE INJECTION FOR REFRACTORY PAIN SYNDROMES - REPORT OF 2 CASES
SILLER, KA; PANASCI, D; GEOCADIN, R; NELSON, J; GRIESZ, M; VARLOTTA, G
1995 AUG ;38(2):297-298, Annals of neurology
— id: 63774, year: 1995, vol: 38, page: 297, stat: Journal Article,

THE TREATABLE DEMENTIA OF CONCURRENT KLINEFELTERS AND PRIMARY SJOGRENS SYNDROMES
SILLER, KA; WEINREB, HJ; KIMMEL, SC
1995 AUG ;38(2):292-292, Annals of neurology
— id: 63773, year: 1995, vol: 38, page: 292, stat: Journal Article,

Intraarterial urokinase for acute ischemic stroke during interventional neuroradiological procedures
Berenstein A; Siller KA; Setton A; Nelson PK; Levine DN; Kupersmith M
1994 ;44:A356-A356 Suppl 2, Neurology
— id: 20610, year: 1994, vol: 44, page: A356, stat: Journal Article,

INTERNAL CAROTID-ARTERY DISSECTION CAUSED BY EXERCISE - 3 CASE-REPORTS
SILLER, KA; RILES, TS; GOPINATHAN, G
1993 AUG ;34(2):318-319, Annals of neurology
— id: 63775, year: 1993, vol: 34, page: 318, stat: Journal Article,