Rationale: Type 2 Focal cortical Dysplasia’s (FCD) are a common cause of focal epilepsy.The lesions of this pathology are epileptogenic, restricted,and commonly visible on MRI. FCDs have a preponderance to the frontal lobes (57%),and are seldom reported in the parietal lobe.The intraparietal sulcus is either a continuous or interrupted sulcus in the posterior lateral parietal lobe that runs parallel to the interhemispheric fissure and connects to the post central sulcus anteriorly and parietooccipital sulcus posteriorly.
This study aims to describe the semiology, clinical characteristics, electrographic (both scalp and stereo EEG), and imaging of Type 2 FCD in the IPS.
Methods:
We reviewed the database of all patients at Cleveland Clinic Epilepsy surgery center (N=4388, age range: 1-73yo) from 2000-2023. There were 177 parietal resections, and 5 cases of biopsy/imaging features of Type 2 Focal cortical dysplasia in the intraparietal sulcus (n=5, age range 19-27yo).
Results: There were four cases of biopsy proven Type 2 FCD and one case of imaging (MRI post processing technique-MAP) positive Type 2 FCD. 2 cases were right and 3 were left sided.Epilepsy originating from the IPS had varying semiology despite uniform pathology. Two cases had complex visual/sensory auras of feeling dizzy/blurry/palinopsia,1 case had an aura of psychiatric origin-anxiety,1 had somatosensory auras, and 1 had multiple auras that varied in nature from somatosensory, gustatory, and olfactory(in table 1). Despite this, the initial hypothesis included parietal lobe epilepsy(PLE) in all these cases. Most patients (4/5) underwent 2 surgeries; the second surgery was to increase the excision margins of the previous resection. Three out of 5 patients had Engel 1 outcomes after their second surgery. The white matter tracts connecting the IPS include super laterally, the Superior Longitudinal Fasciculus II(SLF) and Middle Longitudinal Fasciculus (MLF-inferior to SLF), posteriorly, the Optic radiation and infero-medially, the Inferior frontal occipital fasciculus (IFOF).The first and second patient had initial involvement of networks caudal to the IPS, the optic radiation or IFOF causing complex visual aura followed by elementary motor features due to rostral spread of the seizure.The third and fourth patients describe how parietal lobe epilepsies can mimic temporal or prefrontal/orbitofrontal epilepsies with psychic, gustatory and
olfactory auras followed by complex motor followed by elementary motor seizures. This is due to the temporo-limbic spread and involvement of SLF and MLF. Notably, the fourth and fifth patients had contralateral somatosensory auras- commonly seen in patients with PLE. Most of these patients had a correlation between imaging and electroclinical data, which is known to lead to better outcomes.
Conclusions:
Identification & surgical management of PLE is challenging.The IPS is functionally diverse serving as a hub for visuospatial, cognitive & sensorimotor processes. We demonstrate that electroclinical presentation of restricted epilepsies involving IPS is variable even in the presence of uniform pathology and localization concordance at the lobar level.
Funding: None