Anterior temporal encephaloceles: Elusive, important, and rewarding to treat

Abstract

Objective: To investigate the etiology and longitudinal clinical, neuropsychological, psychosocial, and surgical outcome profile of patients with medication refractory epilepsy and temporal encephaloceles with a view to highlight diagnostic clues and management strategies. Methods: The comprehensive epilepsy program databases at two surgical epilepsy centers from January 2000 to October 2018 were reviewed for this observational study, to identify patients with encephaloceles causing temporal lobe epilepsy (TLE) and treated with surgical resection. Their clinical, radiological, neuropsychological, psychiatric, and surgical data were obtained. Body mass index (BMI) data were also reviewed due to possible correlation between idiopathic intracranial hypertension and encephaloceles. Results: Thirteen patients (eight female) were identified; only three were recognized on initial magnetic resonance imaging (MRI) report. Temporal encephaloceles were identified on the left in eight patients, on the right in three patients, and bilaterally in two patients. One patient had a strong family history of encephaloceles. The median BMI for patients with seizure onset ≤20 years of age was 22.4, whereas for patients with onset >20 years median BMI was 32.6 (P = .06). Five patients underwent a focal lesionectomy, three patients had limited temporal lobectomy, and five patients had standard anterior temporal lobectomy. Median postoperative follow-up was 5.5 years. All but one patient were free of disabling seizures. Nine of ten neuropsychologically tested patients had no discernable cognitive decline postoperatively. Postoperative psychosocial adjustment features were present in four patients. Significance: Genetic factors and a possible association with idiopathic intracranial hypertension (given female predominance and elevated BMI) may contribute to the causation of temporal lobe encephaloceles. It is notable that a targeted surgical approach in the management of patients with TLE associated with encephaloceles has an excellent long-term clinical and neuropsychological outcome. Subtle encephaloceles should be actively searched for in patients with drug-resistant TLE because they significantly change surgical strategy and prognostication.

Temporal Encephaloceles and Epileptogenicity: Does Size Matter?

“…Even though no standardized imaging protocol was used to evaluate TEs in the TLE and ETLE groups and no interrater agreement on the radiological interpretation was provided, the results suggest an increased frequency of TEs in the TLE population that is typically undiagnosed in the first pass. The referral bias notwithstanding, this is in line with prior literature 3 , 6 , 7 and delivers an important message to the epilepsy community. Additionally, this investigation commendably attempts to differentiate between asymptomatic versus epileptogenic encephaloceles, focusing mostly on the size as a potential discriminator.…”

“…In Neurology, they have been mostly discussed as an indirect sign of increased intracranial hypertension (IIH) in individuals with increased body mass index (BMI). 3 Their association with seizures has gained substantial visibility in the last decade. It is still controversial, however, when they constitute incidental radiological findings versus sources of epileptogenesis.…”

“…In a recent review, 8 Ramos-Fresnedo et al amalgamated 267 published cases. Their ascertainment was performed using variable diagnostic criteria (e.g., brain contour abnormality, surrounding CSF signal, and associated parenchymal gliosis) 3 , 6 and heterogeneous imaging protocols ranging from skull based computed tomography (CT) to combined higher resolution 3 Tesla Magnetic Resonance Imaging (MRI) with specialized sequences facilitating their identification. 6 While most papers provided details on location and number, most lacked important characteristics such as size, typical appearance (i.e., meninges and brain as opposed to just arachnoid pits) and additional radiological stigmata of IIH.…”

“…Their association with epilepsy was mostly identified in hindsight based on clinical semiology and geographic linkage with scalp EEG, with intracranial monitoring being the exception rather than the rule in the published series. Clinical information on related risk factors such as family history, history of trauma, prior surgery, tumor, infection or inflammation that could predispose to skull defects without or with seizures, frequently presenting earlier in life, as well as information on BMI or IIH symptoms that are frequently associated with TEs without or with (typically later onset) epilepsy 3 was frequently absent. When surgical data were available, the majority of patients still underwent generous temporal resections, with lesionectomies or more restricted temporal lobectomies being a less popular course of action.…”

Making the Invisible Visible: Advanced Neuroimaging Techniques in Focal Epilepsy

“…Particularly, the two common etiologies, i.e., hippocampal sclerosis and focal cortical dysplasia, may need careful and specific attention for detection, as only subtle abnormalities may sometimes be found ( Bernasconi et al, 2019 ). Additionally, meningoencephalocele has been recently recognized as another etiology in drug-resistant focal epilepsy, which may sometimes show only subtle abnormalities ( Saavalainen et al, 2015 ; Tse et al, 2020 ). In cases with encephalocele, constructive interference in steady-state (CISS) imaging may be helpful for detection by enhancing the contrast between brain parenchyma and cerebrospinal fluid ( Wang et al, 2017 ) ( Figure 2 ).…”