The mirror focus phenomenon and secondary epileptogenesis in human epilepsy

McCarthy, Richard J.; O’Connor, Michael J.; Sperling, Michael R.

doi:10.1016/s0896-6974(96)00077-1

Cited by 16 publications

(10 citation statements)

References 18 publications

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“…The demographic properties of our sample also offer important clues related to the epileptiform processes we have isolated. First, the prevalence of patients with bilateral spikes in our sample (35%) is similar to other reports of patients with potential mirror epileptogenesis . It is likely that not all of the patients in our sample will develop a secondary epileptogenic focus, but it is reassuring that the ratio of such patients is similar to other reports.…”

Section: Discussionsupporting

confidence: 88%

“…A key characteristic of focal TLE is the eventual presence of subclinical epileptiform activity in both the ictal and contralateral “healthy” hemisphere. Such contralateral interictal activity is clinically important, as it may represent a form of pathology spread that leads to the birth of independent seizure foci . Once the secondary focus is fully capable of generating independent seizures, the clinical value of surgical treatment drops from 78% to 58% .…”

mentioning

confidence: 99%

“…Such contralateral interictal activity is clinically important, as it may represent a form of pathology spread that leads to the birth of independent seizure foci. 2,3 Once the secondary focus is fully capable of generating independent seizures, the clinical value of surgical treatment drops from 78% to 58%. 4 Even when a secondary ictal focus is not demonstrated, the simple presence of contralateral interictal spikes presurgery and their persistence after surgery, is an indicator of poor surgery outcome.…”

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confidence: 99%

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Contralateral interictal spikes are related to tapetum damage in left temporal lobe epilepsy

et al. 2014

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Summary Objective In temporal lobe epilepsy (TLE) the epileptogenic focus is focal and unilateral in the majority of patients. A key characteristic of focal TLE is the presence of sub-clinical epileptiform activity in both the ictal and contralateral "healthy" hemisphere. Such interictal activity is clinically important as it may reflect the spread of pathology, potentially leading to secondary epileptogenesis. The role played by white matter pathways in this process are unknown. Methods We compared three interhemispheric white matter tracts (anterior commissure, fornix, and tapetum) to determine the pathway most associated with the presence of contralateral interictal spikes. Forty patients with unilateral left or right TLE were categorized based on the presence or absence of contralateral interictal spikes. ANOVAs were run on diffusion properties from each tract (fractional anisotropy, FA; and mean diffusivity, MD). Results The analyses revealed that left TLE patients with bilateral interictal spikes had lower FA and higher MD in the tapetum. RTLE patients did not show this effect. No significant associations with bilateral activity was observed for the other tracts. BOLD functional connectivity data revealed that homotopic lateral, not mesial, temporal areas were reliably correlated in bilateral patients, independent of ictal side. Significance Our results indicate that, among the tracts investigated, only the tapetum was associated with contralateral epileptiform activity, implicating this structure in seizures and possible secondary epileptogenesis. We describe two mechanisms that might explain this association (the interruption of inhibitory signals or the toxic effect of carrying epileptiform signals toward the healthy hemisphere), but also acknowledge other rival factors that may be at work. We also report that TLE patients with bilateral spikes had increased lateral bi-temporal lobe connectivity. Our current results can be seen as bringing together important functional and structural data to elucidate the basis of contralateral interictal activity in focal, unilateral epilepsy.

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Section: Discussionsupporting

confidence: 88%

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confidence: 99%

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confidence: 99%

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Contralateral interictal spikes are related to tapetum damage in left temporal lobe epilepsy

et al. 2014

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“…Diaschisis is frequently observed by electrophysiological and scanning techniques or metabolic changes in humans and several animal models of stroke, traumatic brain injury, or epilepsy. [47][48][49][50][51] Histochemically identified associative and transhemispheric diaschisis has been observed in all known animal models of cerebral stroke by the use of different markers. Therefore, it is not clear to what extent certain effects are model dependent, and it seems more likely that the detection of diaschisis depends on the markers or tracers and their concentrations studied (optimal concentrations may be different for the penumbra and the remote regions) as well as on the time after injury, because diaschisis is a transient phenomenon.…”

Section: 35mentioning

confidence: 99%

Transient Increase of Manganese–Superoxide Dismutase in Remote Brain Areas After Focal Photothrombotic Cortical Lesion

Bidmon

Kato

Schleicher

et al. 1998

Stroke

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Background and Purpose-Free radicals including superoxide are responsible for postlesional cytotoxicity. In contrast to the constitutive CuZn-superoxide dismutases (SODs), manganese-superoxide dismutase (Mn-SOD) is inducible and has the potential to protect neurons by its superoxide dismutating activity. Therefore, we studied the presence and the regional changes in Mn-SOD within the brain after focal cortical ischemia. Methods-Focal cortical photothrombotic lesions were produced in the hindlimb region of rat brains. Animals were anesthetized and transcardially perfused with Zamboni's fixative. Mn-SOD was immunohistochemically localized using an antiserum against rat-Mn-SOD. Changes in Mn-SOD immunoreactivity were quantified by image analysis. Results-Focal photothrombosis caused a perilesional increase in Mn-SOD after 24 hours, followed by a further significant increase at 48 hours in perilesional cortex, ipsilateral corpus callosum, hippocampus, and thalamus, as well as in a homotopic cortical area within the nonlesioned hemisphere. At day 2, Mn-SOD was present in neurons and astrocytes. Up to day 7, Mn-SOD increased in the entire ipsilateral and contralateral cortex but remained higher elevated in the ipsilateral hippocampus and thalamus. Thereafter, Mn-SOD decreased globally but remained elevated in some cortical neurons up to day 60. Conclusions-The early transient increase of Mn-SOD in distinct brain regions, which are functionally connected via afferents and efferents, suggests that these regions are affected by the injury. It suggests that Mn-SOD protects the cells in these regions from superoxide-induced damage and therefore may limit the retrograde and anterograde spread of neurotoxicity. (Stroke. 1998;29:203-211.)

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“…Nevertheless, there is evidence to support the notion that secondary epileptogenesis may occur in human epilepsy. For example, patients with unilateral brain lesions and epilepsy may have bilateral interictal foci (Gupta et al, 1973; Hughes, 1985; Morrell, 1985; Gilmore et al, 1994; McCarthy et al, 1997). In a long‐term follow‐up study on 60 patients who underwent standard anterior temporal lobe resection for lesions associated with chronic, medically intractable seizures, Eliashiv et al (1997) observed late seizure recurrence in three patients; two had been seizure‐free for 10 years and one for 15 years after surgery, before recurrence of seizures in the absence of tumor recurrence.…”

Section: Secondary Epileptic Focimentioning

confidence: 99%

Molecular and diffusion tensor imaging of epileptic networks

Luat

Chugani

2008

Epilepsia

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SUMMARYSeveral studies have shown that seizure-induced cellular and molecular changes associated with chronic epilepsy can lead to functional and structural alterations in the brain. Chronic epilepsy, when medically refractory, may be associated with an expansion of the epileptic circuitry to involve complex interactions between cortical and subcortical neuroanatomical substrates. Progress in neuroimaging has led not only to successful identification of epileptic foci for surgical resection, but also to an improved understanding of the functional and microstructural changes in long-standing epilepsy. Positron emission tomography (PET), functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) are all promising tools that can assist in elucidating the underlying pathophysiology in chronic epilepsy. Studies using PET scanning have demonstrated dynamic changes associated with the evolution from acute to chronic intractable epilepsy. Among these changes are data to support the existence of secondary epileptogenesis in humans. MRI with DTI is a powerful tool which has the ability to characterize microstructural abnormalities in epileptic foci, and to demonstrate the white matter fibers and tracts participating in the epileptic network. In this review, we illustrate how PET and DTI can be applied to depict the functional and microstructural alterations associated with chronic epilepsy.

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The mirror focus phenomenon and secondary epileptogenesis in human epilepsy

Cited by 16 publications

References 18 publications

Contralateral interictal spikes are related to tapetum damage in left temporal lobe epilepsy

Contralateral interictal spikes are related to tapetum damage in left temporal lobe epilepsy

Transient Increase of Manganese–Superoxide Dismutase in Remote Brain Areas After Focal Photothrombotic Cortical Lesion

Molecular and diffusion tensor imaging of epileptic networks

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