Abstracts

Rationale: Cavum septum pellucidum (CSP) refers to the potential cavity between the laminae of the septum pellucidum (SP). CSP exists as a normal phenomenon in utero, with closure occuring between 6 months gestation to 2 months post-term. Non-closure of SP has been considered a normal variant, with prevalence of 0.79-5.5% in varying population studies. Acquisition of CSP secondary to head trauma is well recognised, but only identified as a novel consequence of injury if serial imaging is available. CSP no longer represents an epiphenomenon of contact sport, but has a direct relationship to loss of cerebral volume, poorer memory performance and cognitive outcomes (Lee et al 2020;77(1):35-42). There is very little published on potential links between CSP and epilepsy, although scarce literature is available, such as case reports and small centre studies. We reviewed the incidence of CSP in patients admitted to our Epilepsy Monitoring Unit (EMU) over a two-year period, relative to epilepsy classification and history of convulsive seizure (ILAE 2017).

Methods: We reviewed MRI neuroimaging on 217 consecutive patients admitted to the EMU at Beaumont Hospital, Ireland between July 2018 – July 2020. Epilepsy classification at discharge, alternate diagnoses (Non-epileptic attack disorder [NEAD], syncope or other pathology [parasomnia or stereotyped behavioural events]), and inconclusive studies were recorded. Only patients with available MRI studies were included. Patients were then stratified into those with CSP on MRI. Risk factors for epilepsy, such as head injury or peri-natal injury were also recorded.

Results: Of the 217 patients, 191 had MRI imaging available and were included in the study. Patients studied had an age range of 17-78 years (mean 39 years), with 63% being female. A diagnosis of epilepsy was established in 108 patients. NEAD was diagnosed in 59 patients, seven had other pathology and 17 had inconclusive studies.

When a diagnosis of epilepsy was established, 36.1% of patients had CSP vs. 19% in those with NEAD or diagnosis of other pathology.

CSP was present in 55 patients, of whom 70.9% had epilepsy and 21.8% had NEAD, with only 1 patient diagnosed with syncope and 3 with inconclusive studies. Of those with both epilepsy and CSP, 74.3% had a documented history of generalised tonic-clonic seizures.

Conclusions: In our study, individuals with epilepsy had higher rates of CSP compared to the general population (36.1% vs. 0.7-5.5%). Convulsive seizures were documented in the majority of patients with both epilepsy and CSP (74.3%). This suggests that CSP is an anatomic marker of cerebral volume change or injury resulting from uncontrolled convulsive epilepsy. Additionally, the presence of CSP on initial MRI may assist the diagnosis and seizure classification of epilepsy in patients where there is diagnostic uncertainty.

Our study highlights a correlation between convulsive epilepsy and CSP, suggesting that CSP is a marker of convulsive seizures. This should prompt greater awareness of CSP during initial patient evaluation and epilepsy classification.

Funding: Please list any funding that was received in support of this abstract.: There was no funding received in support of this abstract.