Robert R Hammond

London Health Sciences Centre, London, Ontario, Canada

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Publications (65)219.84 Total impact

  • The Canadian journal of neurological sciences. Le journal canadien des sciences neurologiques 01/2015; · 1.60 Impact Factor
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    ABSTRACT: Advances in MRI have the potential to improve surgical treatment of epilepsy through improved identification and delineation of lesions. However, validation is currently needed to investigate histopathological correlates of these new imaging techniques. The purpose of this work is to develop and evaluate a protocol for deformable image registration of in-vivo to ex-vivo resected brain specimen MRI. This protocol, in conjunction with our previous work on ex-vivo to histology registration, completes a registration pipeline for histology to in-vivo MRI, enabling voxel-based validation of novel and existing MRI techniques with histopathology. A combination of image-based and landmark-based 3D registration was used to register in-vivo MRI and the ex-vivo MRI from patients (N=10) undergoing epilepsy surgery. Target registration error (TRE) was used to assess accuracy and the added benefit of deformable registration. A mean TRE of 1.35±0.11 and 1.41±0.33mm was found for neocortical and hippocampal specimens respectively. Statistical analysis confirmed that the deformable registration significantly improved the registration accuracy for both specimens. Image registration of surgically resected brain specimens is a unique application which presents numerous technical challenges and that have not been fully addressed in previous literature. Our computed TRE are comparable to previous attempts tackling similar applications, as registering in-vivo MRI to whole brain or serial histology. The presented registration pipeline finds dense and accurate spatial correspondence between in-vivo MRI and histology and allows for the spatially-local and quantitative assessment of pathological correlates in MRI. Copyright © 2014. Published by Elsevier B.V.
    Journal of Neuroscience Methods 12/2014; 241. · 1.96 Impact Factor
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    ABSTRACT: Objective To investigate the histopathological correlates of quantitative relaxometry and DTI and determine their efficacy in epileptogenic lesion detection for pre-operative evaluation of focal epilepsy. Methods We correlated quantitative relaxometry and DTI with histological features of neuronal density and morphology in 55 regions of the temporal lobe neocortex, selected from 13 patients who underwent epilepsy surgery. We made use of a validated non-rigid image registration protocol to obtain accurate correspondences between in-vivo MRI and histology images. Results We found T1 to be a predictor of neuronal density in the neocortical GM using linear mixed effects models with random effects for subjects. FA was a predictor of neuronal density of large-caliber neurons only (pyramidal cells, layers 3/5). Comparing multivariate to univariate mixed effects models with nested univariate demonstrated that employing T1 and FA together provided a significantly better fit than T1 or FA alone in predicting density of large-caliber neurons. Correlations with clinical variables revealed significant positive correlations between neuronal density with age (rs = 0.726, pfwe = 0.021). This study is the first to relate in-vivo T1 and FA values to the proportion of neurons in GM. Interpretation Our results suggest that quantitative T1 mapping and DTI may have a role in pre-operative evaluation of focal epilepsy and can be extended to identify gray matter pathology in a variety of neurological disorders. This article is protected by copyright. All rights reserved. Copyright © 2014 American Neurological Association.
    Annals of neurology. 11/2014;
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    ABSTRACT: Gout is a rheumatological disorder found exclusively in human species. It is caused by deposition of crystals of monosodium urate in joints, cartilages, tendons, and soft tissues. Involvement of the spine, however, is rare. In this report, we describe two patients presented to King Abdulaziz Medical City in Jeddah with clinical features of cervical myelopathy, including neck pain, L'hermitte phenomena, quadriparesis and sensory deficit (shoulder level). Magnetic resonance imaging confirmed the presence of cervical cord compression with intrinsic cord signal abnormalities. Both patients had laminectomy and intraoperatively; severe canal stenosis was identified. A whitish cheesy material was noticed causing significant root compression. The pathology was diagnostic of gout. In this article, we present two difficult cases with interesting clinical, radiological and pathological findings. We emphasize on the importance of early diagnosis to prevent morbidity.
    Journal of Taibah University Medical Sciences. 09/2014;
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    ABSTRACT: The purpose of this study was to describe a series of patients with pathologically proven chronic encephalitis who had a nonprogressive course during a long follow-up, suggestive of a "benign" variant of Rasmussen's encephalitis (RE). Four patients who were referred to our Comprehensive Epilepsy Program at London Health Science Centre in London, Ontario, were diagnosed with chronic encephalitis on a pathological basis after epilepsy surgery to treat their partial-onset seizures. None of our four cases followed the typical course of RE despite their childhood-onset seizures between ages 2 and 12years. One was preceded by a mild head trauma and fever at onset. None had epilepsia partialis continua (EPC). Their long-term follow-up revealed a nonprogressive form of the syndrome with respect to the neurological examination, EEG, MRI, and neuropsychological findings. These cases extend the spectrum of childhood-onset intractable epilepsy with chronic encephalitis to include nonprogressive variants of RE. The absence of EPC may be a prognostic indicator of a nonprogressive course.
    Epilepsy & Behavior 12/2013; 31C:85-90. · 2.06 Impact Factor
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    ABSTRACT: Adult-onset leukodystrophies are clinically and pathologically heterogeneous diseases, and the overlapping morphologic features among these disorders can lead to confusion in pathologic classification. We report 3 recent autopsy cases that illustrate the clinicopathologic distinction between the 3 entities. The first, autosomal dominant leukodystrophy, is characterized clinically by early autonomic dysfunction and genetically by LMNB1 (lamin B1 gene) duplication. Recently, another clinical subtype emerged without the early autonomic dysfunction but with a similar genetic abnormality documented in 1 family. We reviewed the reported autopsy cases and show that both clinical subtypes share distinctive pathologic features. Other forms of adult-onset leukodystrophy can be classified based on the histologic evidence of the primary pathologic processes. A case of axonopathy with secondary demyelination serves as a prototype for adult-onset leukoencephalopathy/leukodystrophy with axonal spheroids; the genetic mutation of CSF1R (colony stimulating factor 1R) was recently discovered in patients with this disorder. A case of a primary demyelinating disease with no other distinctive pathologic features is designated as orthochromatic leukodystrophy. Pigmented glia can be present in both of the latter two categories and should not be used as a differentiating diagnostic feature. Based on the observations of our cases and literature review, we propose an algorithm for a practical diagnostic approach to adult-onset leukodystrophies.
    Journal of neuropathology and experimental neurology. 10/2013;
  • The Canadian journal of neurological sciences. Le journal canadien des sciences neurologiques 09/2013; 40(5):728-33. · 1.60 Impact Factor
  • The Canadian journal of neurological sciences. Le journal canadien des sciences neurologiques 01/2013; 40(1):85-8. · 1.60 Impact Factor
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    ABSTRACT: We developed novel methodology for investigating the use of quantitative relaxometry (T1, T2) and diffusion tensor imaging (DTI) for lateralization in temporal lobe epilepsy. Patients with mesial temporal sclerosis confirmed by pathology (N = 8) and non-MTS unilateral temporal lobe epilepsy (N = 6) were compared against healthy controls (N = 19) using voxel-based analysis restricted to the anterior temporal lobes, and laterality indices for each MRI metric (T1, T2, fractional anisotropy (FA), mean diffusivity, axial and radial diffusivity) were computed based on the proportion of significant voxels on each side. The diffusivity metrics were the most lateralizing MRI metrics in MTS and non-MTS subsets, with significant differences also seen with FA, T1 and T2. Patient-specific multi-modal laterality indices were also computed and were shown to clearly separate the left-onset and right-onset patients. Marked differences between left-onset and right-onset patients were also observed, with left-onset patients exhibiting stronger laterality indices. Finally, neocortical abnormalities were found to be more common in the non-MTS patients. These preliminary results on a small sample size support the further investigation of quantitative MRI and multi-modal image analysis in clinical determination of seizure onset. The presence of more neocortical abnormalities in the non-MTS group suggests a role in seizure onset or propagation and motivates the investigation of more sensitive histopathological analysis to detect and delineate potentially subtle neocortical pathology.
    Epilepsy research 01/2013; · 2.48 Impact Factor
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    ABSTRACT: Prodigious efforts and landmark discoveries have led toward significant advances in our understanding of atherosclerosis. Despite significant efforts, atherosclerosis continues globally to be a leading cause of mortality and reduced quality of life. With surges in the prevalence of obesity and diabetes, atherosclerosis is expected to have an even more pronounced impact upon the global burden of disease. It is imperative to develop strategies for the early detection of disease. Positron emission tomography (PET) imaging utilizing [(18)F]fluorodeoxyglucose (FDG) may provide a non-invasive means of characterizing inflammatory activity within atherosclerotic plaque, thus serving as a surrogate biomarker for detecting vulnerable plaque. The aim of this review is to explore the rationale for performing FDG imaging, provide an overview into the mechanism of action, and summarize findings from the early application of FDG PET imaging in the clinical setting to evaluate vascular disease. Alternative imaging biomarkers and approaches are briefly discussed.
    Journal of Nuclear Cardiology 10/2012; 19(6). · 2.65 Impact Factor
    This article is viewable in ResearchGate's enriched format
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    The Canadian journal of cardiology 09/2012; 28(5):S162. · 3.94 Impact Factor
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    Society of Nuclear Medicine (SNM) 2012; 06/2012
  • Circulation 01/2012; 126(21 Supplement):A17612. · 14.95 Impact Factor
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    Canadian cardiovascular society (CCS) Congress 2011; 10/2011
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    ABSTRACT: This article can be accessed at: http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=9340764&fulltextType=MR&fileId=S031716710001194X
    The Canadian journal of neurological sciences. Le journal canadien des sciences neurologiques 05/2011; 38(3):507-11. · 1.60 Impact Factor
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    ABSTRACT: Many patients with an oligodendroglioma (OD) experience seizures, some of which become refractory to anti-epileptic drugs (AEDs). This study aims (1) to quantify the rate of seizures and medically refractory epilepsy in patients with ODs; and (2) to determine if there is any association between short-term and long-term survival, and the presence and drug-responsiveness of seizures. A retrospective review was conducted of the medical records of patients who had been pathologically identified as having an OD at the London Health Sciences Centre or the London Regional Cancer Program in London, Ontario from January 1996 to July 2008. Deaths were ascertained by reviewing all hospital records. Survival analysis was performed. One-hundred sixty-six patients met inclusion criteria. Epileptic seizures were the presenting feature or occurred as part of the initial manifestation of the OD in 75.3% of patients, with 90.4% (n=150) experiencing at least one seizure and 76.5% developing epilepsy over the course of observation. Of the 150 patients with seizures, 23 experienced a single seizure (13.9% of the 166), whereas 127 patients experienced multiple seizures (76.5%). In those with multiple seizures, the epilepsy was refractory to drug treatment slightly more than half the time (54.3%). Survival analysis demonstrated consistently superior survival among those with a single seizure. Those without seizures had the worst survival rates over the first few years post-diagnosis; but then no further deaths occurred. Survival among those with refractory seizures tended to be better than among those whose seizures were drug responsive, over the first 10 years post-diagnosis. Seizures are common and may influence survival in patients with oligodendogliomas. Those who experience just one seizure appear to do best.
    Epilepsy research 02/2011; 94(1-2):39-44. · 2.48 Impact Factor
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    ABSTRACT: Patients can become weak in ICU from various etiologies and mechanisms. Establishing the diagnosis is invaluable for prognostic determination and specific management. We evaluated the relative contributions of clinical, laboratory, electomyographic studies (EMG), and percutaneous muscle biopsy (MB) in determining the cause of muscular weakness that developed in a series of patients while in ICU. The principal objective is to determine the concordance between results of the EMG and MB studies in patients with ICU-acquired weakness. We retrospectively reviewed hospital charts for clinical features, and results of laboratory investigations, EMG studies, and MB results in 11 consecutive patients who underwent both EMG and MB while in ICU. We excluded patients with previously diagnosed muscular weakness or neurological conditions prior to ICU admission. Electomyographic studies suggested axonal neuropathy in three cases; MB confirmed this in one case, but showed myopathic features in two. EMG showed myopathic features in two cases; MB confirmed this in both cases. EMG suggested neuromyopathy in four cases, confirmed by MB in one case only. One patient, subsequently diagnosed with myasthenia gravis with decrement on repetitive nerve stimulation and positive anti-acetylcholine receptor antibodies, had non-specific findings on MB. EMG and MB are complementary investigations. They agreed completely in four cases but in the rest of the cases there was uncertainty as to the primary process based on the results of electrophysiological studies. In only one case was there a clear discordance between electrophysiological studies and muscle biopsy. We suggest that muscle biopsy should be performed more frequently as it establishes the diagnosis and thus the prognosis with more certainty than EMG in some patients. EMG is much more difficult in the ICU and more susceptible to confounding technical factors, but remains indispensable for the diagnosis of neuromuscular transmission defects.
    Neurocritical Care 12/2010; 13(3):326-30. · 3.04 Impact Factor
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    ABSTRACT: We present a case of an atypical clival meningeal melanoma treated with a multidisciplinary staged transcrusal and transsphenoidal endoscopic surgical approach. A 45-year-old woman presented with a 15-month history of visual symptoms, neck pain, and unsteadiness. Magnetic resonance imaging of the head revealed a clival mass with both intracranial and extracranial involvement. Endoscopic clival biopsy suggested a melanocytic tumor. Extensive imaging and dermatological workup did not demonstrate a primary source. A multidisciplinary staged surgical resection included a transcrusal approach to resect the intracranial component, followed by transsphenoidal endoscopic resection of the extracranial component. Postoperatively, she received adjuvant radiation. At 1 year following surgery, the patient retains full preservation of hearing, facial nerve function, and extraocular movements. To our knowledge, this is the first case report of a combined surgical approach for a primary clival meningitic melanoma.
    Skull Base 09/2010; 20(5):349-55. · 0.66 Impact Factor
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    ABSTRACT: The goal of this study was to optimize intraoperative neuropathology consultations by studying trends and sources of diagnostic error. We hypothesized that errors in intraoperative diagnoses would have sampling, technical, and interpretive sources. The study also audited diagnostic strengths, weaknesses and trends associated with increasing experience. We hypothesized that errors would decline and that the accuracy of "qualified" diagnoses would improve with experience. The pathologist's first 100 cases (P1), second 100 (P2), and most recent 100 (P3, after ten years in practice) formed the data set. Intraoperative diagnoses were scored as correct, minor error or major error using the final diagnosis as the gold-standard. Incorrect diagnoses were re-examined by two reviewers to identify sources of error. Among the 300 cases there were 22 errors with 11 in P1, 9 in P2 and 2 in P3. Sampling contributed to 17 errors (77%), technical factors to 7 (32%) and interpretive factors to 16 (73%). Improvement in diagnostic accuracy between P1 and P2 (p = 0.8143), or P2 and P3 (p = 0.0582) did not reach significance. However, significant improvement was found between P1 and P3 (p = 0.0184). The present study was a practical and informative audit for the pathologist and trainees. It reaffirmed the accuracy of intraoperative neuropathology diagnoses and informed our understanding of sources of error. Most errors were due to a combination of sampling, technical and interpretive factors. A significant improvement in diagnostic proficiency was observed with increasing experience.
    The Canadian journal of neurological sciences. Le journal canadien des sciences neurologiques 09/2010; 37(5):620-4. · 1.60 Impact Factor
  • Skull Base Surgery 10/2009; 19(03). · 0.60 Impact Factor

Publication Stats

567 Citations
219.84 Total Impact Points

Institutions

  • 2001–2014
    • London Health Sciences Centre
      • • Department of Pathology
      • • Department of Clinical Neurological Sciences
      London, Ontario, Canada
  • 1998–2014
    • The University of Western Ontario
      • • Department of Clinical Neurological Sciences
      • • Department of Pathology
      London, Ontario, Canada
  • 2013
    • Western University
      London, Ontario, Canada
  • 2008
    • Università Telematica "E-Campus"
      Campobasso, Molise, Italy
  • 1995
    • University of Pittsburgh
      • Division of Neuropathology
      Pittsburgh, Pennsylvania, United States