Topographic congruence of calcified parenchymal neurocysticercosis and other structural brain lesions with epileptiform activity

Seizure Semiology, Location of Lesion on Neuroimaging, and Interictal Electroencephalographic (EEG) Abnormalities in Children With Single-Lesion Neurocysticercosis-Is There a Correlation?

BACKGROUND

Single-lesion neurocysticercosis provides a model of seizure genesis secondary to an acquired lesion. We aimed to study the correlation of seizure semiology with the location of the lesion and interictal electroencephalographic (EEG) abnormalities in children with single-lesion neurocysticercosis. Methods: Prospective, observational study in children with single-lesion neurocysticercosis and seizures. Seizure classification was done after an interview with the parent/onlooker and the child. Localization and lateralization of the lesion were done by neuroimaging. The EEG abnormalities were classified based on their morphology and location. Results: Ninety-two children (7.9 ± 2.4 years) were included. Focal-onset seizures were the commonest (n = 54; 58.6%) seizures. Majority of the lesions were located in the frontal (n = 43; 47%) and parietal cortex (n = 34; 37%). EEG showed focal slowing (n = 15; 53.6%) and epileptiform spikes/spike-wave complexes (n = 13; 46.4%). There was a perfect agreement of clinical semiology with imaging lateralization (K = 1.0) and moderate agreement with imaging localization (K = 0.4). There was no significant agreement of clinical localization with EEG slowing (K = 0.1) or sharps (K = 0). There was moderate agreement (K = 0.6) of EEG slowing and substantial agreement (K = 0.7) of EEG sharps with clinical lateralization. Focal EEG slowing had moderate (K = 0.5) agreement with imaging lateralization. Focal sharps/spikes had substantial (K = 0.7) agreement with imaging lateralization. The positive predictive value (PPV) of seizure semiology for lateralization and localization was 100% and 68%, respectively. PVV of focal sharps for lateralization and localization was 84% and 70%, respectively. PPV of focal slowing for lateralization and localization was 77% and 65%, respectively. Conclusion: Seizure semiology in single-lesion neurocysticercosis correlates very well with lateralization but not so well with localization of lesion on neuroimaging. Focal EEG abnormalities are seen in nearly one-third of children with single-lesion neurocysticercosis. EEG often predicts the side of the lesion but has poor localizing value.

Clinical topography relationship in patients with parenchymal neurocysticercosis and seizures

OBJECTIVE

Discordances between imaging findings of parenchymal neurocysticercosis and seizure expression have been reported, and as such the possibility that neurocysticercosis and seizures may frequently coexist by chance has been raised. In this study, we evaluate the topographic relationship between seizure foci based on semiology and electroencephalography with the location of parenchymal neurocysticercotic lesions.

METHODS

Seizure information, neuroimaging (computed tomography and magnetic resonance imaging [MRI]) and electroencephalographic data from three randomized clinical trials of individuals with parenchymal neurocysticercosis and focal seizures were analyzed. Blinded epileptologists defined a potential seizure onset zone and a symptomatogenic zone for each individual based on semiology. The topographic relationship between semiology, either lesion location or areas of perilesional edema on baseline MRI, and electroencephalographic abnormalities were assessed.

RESULTS

Fifty-eight patients with one or two parenchymal neurocysticercotic lesions were included in this study. From them, 50 patients (86%; 95% CI, 75%-93%) showed a clinical-topography relationship with the potential seizure onset zone, and 44 (76%) also with the symptomatogenic zone. From the eight patients with no topographic relationship, five had focal seizures 30 days before or after the baseline MRI and showed perilesional edema. All of these five patients showed a clinical-topography relationship between such seizures and an area of perilesional edema, making a total of 55 patients (95%; 95% CI, 85%-99%) with clinical-topography relationship when perilesional edema is considered. Most patients with focal epileptiform discharges (7/8, 88%) had a topographic association between electroencephalographic focality, the potential seizure onset zone and a cysticercotic lesion.

CONCLUSION

Seizure semiology and focal epileptiform discharges are topographically related to neurocysticercotic lesions in most patients. These data strongly support seizure origin in the cortex surrounding these lesions.

Clinical presentation of neurocysticercosis-related epilepsy

Neurocysticercosis (NCC) is the most common parasitic infection of the central nervous system and a major risk factor for seizures and epilepsy. Seizure types in NCC vary largely across studies and seizure semiology is poorly understood. We discuss here the studies regarding seizure types and seizure semiology in NCC, and examine the clinical presentation in patients with NCC and drug-resistant epilepsy. We also provide evidence of the role of MRI and EEG in the diagnosis of NCC-related epilepsy. Focal seizures are reported in 60-90% of patients with NCC-related epilepsy, and around 90% of all seizures registered prospectively are focal not evolving to bilateral tonic-clonic seizures. A great number of cases suggest that seizure semiology is topographically related to NCC lesions. Patients with hippocampal sclerosis and NCC have different clinical and neurophysiological characteristics than those with hippocampal sclerosis alone. Different MRI protocols have allowed to better differentiate NCC from other etiologies. Lesions' stages might account on the chances of finding an interictal epileptiform discharge. Studies pursuing the seizure onset in patients with NCC are lacking and they are specially needed to determine both whether the reported events of individual cases are seizures, and whether they are related to the NCC lesion or lesions. This article is part of a Special Issue entitled "Neurocysticercosis and Epilepsy".