Abstract
Some surgical failures after temporal lobe epilepsy surgery may be due to the presence of an extratemporal epileptogenic zone. Of particular interest is the medial parietal lobe due to its robust connectivity with mesial temporal structures. Seizures in that area may be clinically silent before propagating to the symptomatogenic temporal lobe. In this paper, we present an overview of the anatomical connectivity, semiology, radiology, electroencephalography, neuropsychology, and outcomes in medial parietal lobe epilepsy. We also present two illustrative cases of seizures originating from the precuneus and the posterior cingulate cortex. We conclude that the medial parietal lobe should be strongly considered for sampling by intracranial electrodes in individuals with nonlesional temporal lobe epilepsy, especially if scrutinizing the presurgical data produces discordant findings.
Highlights
Presurgical evaluation of patients with pharmacoresistant temporal lobe epilepsy (TLE) integrates multimodal diagnostic tools with the aim of identifying the seizure onset zone. These often include a careful assessment of the seizure semiology, electroencephalography, neuropsychology, and radiology (MRI, PET, SPECT)
We present two lesional cases of seizures originating in the precuneus [8] and the posterior cingulate cortex (PCC) [9], manifesting as TLE
An active area of research currently is using machine learning methods to predict laterality in patients with MRI negative focal epilepsy [48, 49]. While none of these studies is specific to the medial parietal lobe, they may be applied to any focal epilepsy, whether mesial temporal or neocortical
Summary
Presurgical evaluation of patients with pharmacoresistant temporal lobe epilepsy (TLE) integrates multimodal diagnostic tools with the aim of identifying the seizure onset zone. These often include a careful assessment of the seizure semiology, electroencephalography (scalp video-EEG), neuropsychology, and radiology (MRI, PET, SPECT). About 30–40% of patients do not achieve seizure freedom after TLE surgery [5–7] In some cases, this may be due to a cortically silent extratemporal seizure-onset zone from which seizures rapidly propagate to the temporal lobe, where they become clinically and electrographically manifest. This may be due to a cortically silent extratemporal seizure-onset zone from which seizures rapidly propagate to the temporal lobe, where they become clinically and electrographically manifest These zones may be frontal, occipital, parietal, opercular, or insular. Parietal Lobe Epilepsy integrated evaluation of the implicated anatomical connectivity, semiology, neuroimaging, neuropsychological testing, and electroencephalography to optimize surgical outcomes
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