Enlarged perivascular spaces in the basal ganglia across epilepsy subtypes

The glymphatic system is thought to be the brain's primary waste clearance system, responsible for eliminating soluble metabolites and proteins from the central nervous system. It consists of the cerebrospinal fluid, the interstitial fluid, and a conduit between the two, perivascular spaces (PVS). PVS and glymphatics may impact the pathophysiology of epilepsy and its associated neuropsychiatric comorbidities, potentially via reduced clearance of excitotoxic substances. This study investigates enlarged PVS burden in a large patient group with various types of epilepsy.

A total of 467 people with various types of epilepsy were recruited from the Hospital das Clínicas, University of Campinas, Brazil; 267 had temporal lobe epilepsy with hippocampal sclerosis (TLE-HS), 71 had TLE with no magnetic resonance imaging (MRI)-visible lesions, 65 had focal extratemporal epilepsy, and 64 had idiopathic generalized epilepsy. They were matched for age and sex with 473 healthy volunteers as controls. All participants were scanned with T1-weighted MRI, and a deep-learning algorithm, PINGU (Perivascular-Space Identification Nnunet for Generalized Usage), was applied to segment PVS. The volumes of PVS in the white matter (WM) and basal ganglia (BG) were calculated, and PVS volume fraction (PVS-VF) was used as a dependent variables in a general linear model, with the diagnostic group as the independent variable of interest.

The epilepsy group, across all subtypes, had higher PVS-VF in the BG compared to controls (101%-140%, effect size = .95-1.37, p < 3.77 × 10^-15). There was no difference in PVS-VF in the WM between the epilepsy groups and healthy controls, or between different epilepsy subtypes. Only the TLE-HS group had a PVS-VF asymmetry in the WM, with more PVS on the contralateral side, particularly in the temporal lobes. There was no association between PVS-VF and duration of illness.

There is an increase in PVS volume in the BG across broad subtypes of epilepsy, suggesting either a common mechanism of seizure generation or a common consequence of seizures.