R E Hogan

Saint Louis University, Saint Louis, MI, United States

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Publications (14)50.72 Total impact

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    ABSTRACT: We compared manual and automated segmentations of the hippocampus in patients with mesial temporal sclerosis. This comparison showed good precision of the deformation-based automated segmentations.
    Journal of Digital Imaging 04/2012; 13:217-218. · 1.10 Impact Factor
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    ABSTRACT: Controlled-release formulations of Valproate (VPA) reduce side effects by minimizing peak plasma VPA concentrations in patients with epilepsy. However, the impact of this on anti-seizure efficacy has not been thoroughly explored. Here the pharmacokinetics and pharmacodynamics of chronic intermittent (consequently, peak VPA concentrations) and continuous VPA administration were directly compared in two rat models of epilepsy. Genetic Absence Epilepsy Rats from Strasbourg (GAERS) received a single acute bolus of VPA (100 mg/kg intravenously) combined with electroencephalography (EEG) and/or blood sampling for 180 min post-injection. GAERS and epileptic rats post-kainic acid-induced status epilepticus were chronically infused intravenously (3-5 days, respectively) with (i) saline followed by in random order (ii) intermittent and (iii) continuous VPA (42 mg/kg/h), separated by two days of wash-out. Seizures were quantified using video-EEG monitoring and VPA levels measured in brain, cerebrospinal fluid and plasma. Following acute VPA administration seizure suppression in GAERS persisted after plasma VPA levels became very low. Chronic intermittent and continuous VPA significantly suppressed seizures in both models (p<0.01) with no difference between administration regimens. In GAERS, the pattern of seizure suppression during intermittent treatment was constant, in contrast to the fluctuating VPA plasma and brain levels. There was discordance between the temporal pattern of plasma, brain VPA levels and seizure suppression efficacy in GAERS. Administration regimes that result in fluctuating VPA blood levels achieve equivalent sustained seizure suppression as those that maintain steady mid-range concentrations.
    Seizure 01/2011; 20(1):72-9. · 2.00 Impact Factor
  • Injury-international Journal of The Care of The Injured - INJURY-INT J CARE INJURED. 01/2010; 41.
  • Journal of Clinical Neuroscience. 03/2009; 16(3):464–465.
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    ABSTRACT: To compare hippocampal surface structure, using large deformation high dimensional mapping (HDM-LD), in subjects with temporal lobe epilepsy (TLE) with (HS+ve) and without (HS-ve) hippocampal sclerosis. The study included 30 HS-ve subjects matched with 30 HS+ve subjects from the previously reported epilepsy patient cohort. To control for normal right-left asymmetries of hippocampal surface structure, subjects were regrouped based on laterality of onset of epileptic seizures and presence of HS. Gender ratio, age, duration of epilepsy and seizure frequency were calculated for each of the four groups. Final HDM-LD surface maps of the right and left TLE groups were compared to define differences in subregional hippocampal involvement within the groups. There were no significant differences in comparisons of the left TLE (left HS-ve compared with HS+ve) or right TLE (right HS-ve compared with HS+ve) groups with respect to age, duration of epilepsy or seizure severity scores. HDM-LD maps showed accentuated surface changes over the lateral hippocampal surface, in the region of the Sommer sector, in the hippocampi affected by HS. However, HS-ve hippocampi showed maximal surface changes in a different pattern, and did not involve the region of Sommer sector. We conclude that differences in segmental volume loss between the HS-ve and HS+ve groups are suggestive that the underlying pathophysiology of hippocampal changes in the two groups is different, and not related to chronic seizure duration or severity.
    Journal of neurology, neurosurgery, and psychiatry 07/2008; 79(6):636-40. · 4.87 Impact Factor
  • R E Hogan
    JAMA Neurology 10/2001; 58(9):1484-6. · 7.58 Impact Factor
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    ABSTRACT: Changes in body weight were evaluated in 349 patients from a study comparing efficacy of add-on therapy with tiagabine (TGB), carbamazepine (CBZ) or phenytoin (PHT). TGB add-on therapy showed no significant weight changes when added to either PHT or CBZ. CBZ add-on therapy showed a significant percentage weight gain of a mean body increase of 1.5% (P = 0.002). Adjunctive TGB therapy had no significant effect on total body weight, while adjunctive CBZ therapy was associated with weight gain.
    Epilepsy Research 09/2000; 41(1):23-8. · 2.24 Impact Factor
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    ABSTRACT: In five patients with mesial temporal sclerosis, the authors verified the precision and reproducibility of hippocampal segmentations with deformation-based magnetic resonance (MR) imaging. The overall percentage overlap between automated segmentations was 92.8% (SD, 3.5%), between manual segmentations was 73.1% (SD, 9.5%), and between automated and manual segmentations was 74.8% (SD, 10.3%). Deformation-based hippocampal segmentations provided a precise method of hippocampal volume measurement in this patient population.
    Radiology 08/2000; 216(1):291-7. · 6.34 Impact Factor
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    R E Hogan, V J Lowe, R D Bucholz
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    ABSTRACT: Ictal and interictal single-photon emission CT (SPECT) play an increasingly important role in the surgical evaluation of patients with epilepsy. We present a method of coregistration of MR, SPECT, and CT images to correlate structural data (MR imaging), blood flow changes (SPECT), and location of subdural electrodes (CT) for patients undergoing image-guided surgical treatment of epilepsy. MR-SPECT root mean square (rms) mismatch distances were 2.1 to 2.5 mm, and MR-CT rms mismatch distances were 1.0 to 4.5 mm. Coregistration assisted in image-guided placement of subdural electrodes and in surgical resection of the suspected epileptogenic focus.
    American Journal of Neuroradiology 01/1999; 20(6):1054-8. · 3.17 Impact Factor
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    ABSTRACT: To assess patterns of postictal cerebral blood flow in the mesial temporal lobe by coregistration of postictal 99mTc-HMPAO SPECT with MRI in patients with confirmed mesial temporal lobe epilepsy. Ten postictal and interictal 99mTc-HMPAO SPECT scans were coregistered with MRI in 10 patients with confirmed mesial temporal lobe epilepsy. Volumetric tracings of the hippocampus and amygdala from the MRI were superimposed on the postictal and interictal SPECT. Asymmetries in hippocampal and amygdala SPECT signal were then calculated using the equation: % Asymmetry =100 x (right - left) / (right + left)/2. In the postictal studies, quantitative measurements of amygdala SPECT intensities were greatest on the side of seizure onset in all cases, with an average % asymmetry of 11.1, range 5.2-21.9. Hippocampal intensities were greatest on the side of seizure onset in six studies, with an average % asymmetry of 9.6, range 4.7-12.0. In four scans the hippocampal intensities were less on the side of seizure onset, with an average % asymmetry of 10.2, range 5.7-15.5. There was no localising quantitative pattern in interictal studies. Postictal SPECT shows distinctive perfusion patterns when coregistered with MRI, which assist in lateralisation of temporal lobe seizures. Hyperperfusion in the region of the amygdala is more consistently lateralising than hyperperfusion in the region of the hippocampus in postictal studies.
    Journal of Neurology Neurosurgery &amp Psychiatry 09/1997; 63(2):235-9. · 4.92 Impact Factor
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    ABSTRACT: Patients with reflex epilepsies may provide insights into cerebral pathophysiology. We report a patient with an unusual form of reflex epilepsy in whom seizures are induced by tooth brushing. Magnetic resonance imaging (MRI) demonstrated a right posterior frontal low-grade tumor predominantly involving the precentral gyrus. Video-telemetry demonstrated right-sided epileptiform activity during a typical induced complex partial seizure. An ictal single photon emission computed tomography (SPECT) scan showed an area of hyperfusion that corresponded to the MRI lesion on coregistration with a surface-matching technique. A subsequent coregistered interictal SPECT scan demonstrated hypoperfusion in the same region. Ours is the first report to demonstrate a structural focus in this unusual form of reflex epilepsy. Possible mechanisms to explain the induction of the seizures are discussed.
    Epilepsia 08/1996; 37(7):694-7. · 3.91 Impact Factor
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    ABSTRACT: We describe a technique of brain surface matching of single-photon emission CT and MR images in human subjects and document the accuracy of this technique with the use of fiduciary markers. This mismatch averaged 4.3 mm as measured by the fiduciary markers and 2.1 mm as measured by the root mean square distance.
    American Journal of Neuroradiology 05/1996; 17(4):793-7. · 3.17 Impact Factor
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    ABSTRACT: We present a case of uncontrolled temporal lobe epilepsy due to a focal left temporal neuronal heterotopia associated with the nevoid-basal-cell carcinoma syndrome. This is the first pathologically described lesion associated with temporal lobe epilepsy in this syndrome. Because the patient's seizures resolved after a modified left anterior temporal lobectomy, this case illustrates that epilepsy in patients with the nevoid basal-cell carcinoma syndrome is potentially curable and should be investigated appropriately.
    Neurology 03/1996; 46(2):574-6. · 8.25 Impact Factor
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    ABSTRACT: We objectively assessed surface structural changes of the hippocampus in mesial temporal sclerosis (MTS) and assessed the ability of large-deformation high-dimensional mapping (HDM-LD) to demonstrate hippocampal surface symmetry and predict group classification of MTS in right and left MTS groups compared with control subjects. Using eigenvector field analysis of HDM-LD segmentations of the hippocampus, we compared the symmetry of changes in the right and left MTS groups with a group of 15 matched controls. To assess the ability of HDM-LD to predict group classification, eigenvectors were selected by a logistic regression procedure when comparing the MTS group with control subjects. Multivariate analysis of variance on the coefficients from the first 9 eigenvectors accounted for 75% of the total variance between groups. The first 3 eigenvectors showed the largest differences between the control group and each of the MTS groups, but with eigenvector 2 showing the greatest difference in the MTS groups. Reconstruction of the hippocampal deformation vector fields due solely to eigenvector 2 shows symmetrical patterns in the right and left MTS groups. A "leave-one-out" (jackknife) procedure correctly predicted group classification in 14 of 15 (93.3%) left MTS subjects and all 15 right MTS subjects. Analysis of principal dimensions of hippocampal shape change suggests that MTS, after accounting for normal right-left asymmetries, affects the right and left hippocampal surface structure very symmetrically. Preliminary analysis using HDM-LD shows it can predict group classification of MTS and control hippocampi in this well-defined population of patients with MTS and mesial temporal lobe epilepsy (MTLE).
    American Journal of Neuroradiology 27(10):2149-54. · 3.17 Impact Factor

Publication Stats

179 Citations
50.72 Total Impact Points

Institutions

  • 1999–2012
    • Saint Louis University
      • Division of Nephrology
      Saint Louis, MI, United States
  • 2008–2011
    • Washington University in St. Louis
      • Department of Neurology
      San Luis, Missouri, United States
  • 1996–1997
    • Royal Melbourne Hospital
      Melbourne, Victoria, Australia