Neurocysticercosis and related seizures

  • Author / Creator
    Dametto, Ericson
  • Neurocysticercosis, the major global cause of acquired epilepsy, is a parasitic disease caused by Taenia solium larvae. Patients may have seizures whether larvae in brain are alive or degenerated (calcified). We assessed whether parasitic lesions produce changes in structural brain scans that are associated differentially with the presence of seizures. Using magnetic resonance imaging (MRI) of brain, including diffusion tensor imaging (DTI), with the metrics of fractional anisotropy (FA), axial diffusivity (AD or L1), and mean diffusivity (MD) we examined relationships of clinical findings with white matter pathologic features (ischemia, myelination, axonal damage, inflammation, and edema). We also focused on susceptibility weight imaging (SWI). In the first study, we examined DTI results from 51 patients, with (n=38) or without (n=13) seizures in the fifteen days before scanning, under treatment for a single lesion. We measured FA, AD, and MD, over regions of interest (ROIs), defined within the lesion area, and in part of the brain hemisphere (i.e., half brain minus ventricle and infratentorial region), respectively. Metrics of DTI over the ROIs were compared between hemispheres to calculate an index of asymmetry. Patients exhibiting seizures and single lesion had higher brain asymmetry for AD and MD. DTI did not differ between groups, comparing lesion implantation site and the surrounding nervous tissue with the symmetrical contralateral area. These findings support the idea that inflammatory processes related to neurocysticercosis lesions can affect large areas of brain hemispheres, in the context of recent seizures. In the second study, we examined 92 brain lesions in 64 patients under treatment for neurocysticercosis: comprising 71 lesions with seizures and 21 lesions without. With seizures, peak lesion frequencies were observed in precentral gyrus, hippocampus and areas proximal to these structures. Lesions in this group were closer to the brain cortex than non-seizure group lesions. Brain volume affected by the disease was also bigger in the seizure group. Characteristics of lesions included: contours that can be smooth or rough; the presence of parasite’s head; the peri-lesion gradient; the intra-lesion double gradient, and the enhancement of the nourishing vessel (vasa nutricia). Odds of having seizures were higher in the absence of peri-lesion gradient, resembling a shadow between the image of the lesion and the nervous tissue. Finally, sites of lesion implantations follow anatomical patterns of the brain diseases caused by emboli. This innovative finding (related to the deployment of lesions similarly to other emboli) is consistent with the transit paths of larvae from intestine through blood to the brain. These results indicate that in vivo MRI analysis of brain lesions in neurocysticercosis is a useful approach for increasing our understanding of determinants of seizures in this disease. Further examination of lesion–symptom relationships with MRI and using parallel electroencephalographic (EEG) studies may yield clinically useful information about seizures in this patient population that may be identifiable through more widely available EEG technology. Such clinical translational advances would be extremely helpful in attempts to combat and treat this disease in areas where MRI analysis may be neither accessible nor affordable.

  • Subjects / Keywords
  • Graduation date
    Spring 2017
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.