Temporal Lobe Encephaloceles: A Potentially Curable Cause of Seizures

Exploration of epileptic networks in temporal lobe encephaloceles with stereotactic EEG: Electroclinical characteristics and surgical outcomes

OBJECTIVE

Temporal lobe encephaloceles (TLEN) have been implicated as a cause of temporal lobe epilepsy (TLE), the treatment which is primarily surgical; however, there is no clear consensus on the optimal surgical approach, because it is unclear whether TLE related to TLEN can be addressed by a restricted encephalocele resection or if a more extensive resection is required. The aim of the current article is to report the clinical and electrophysiological profile of patients with TLE secondary to TLEN who underwent stereotactic electroencephalography (SEEG) implantation to identify the epileptogenic network.

METHODS

A retrospective review was performed of patients with TLE related to TLEN who underwent SEEG implantation. Medical charts were reviewed for demographic data, the results of noninvasive and invasive investigations, and operative details. Surgical outcomes were based on Engel classification with at least 6 months follow-up.

RESULTS

Nine patients were identified. The mean age at epilepsy onset was 28 years (range, 15-41 years), and 7/9 patients were female. Scalp EEG revealed interictal epileptiform activity most often maximum in the frontotemporal and/or temporal regions. A discrete TLEN was often not identified on initial imaging, but was identified during re-review or at the time of surgery. Seizure onset zones during SEEG were localized to the mesial temporal structures, the temporal pole, or both. One patient became seizure-free following SEEG and another refused further surgery. Of the 7 patients who underwent epilepsy surgery, 5/7 underwent an anterior temporal lobectomy-surgical outcomes were favorable, with 5/7 achieving Engel I outcomes.

SIGNIFICANCE

Invasive SEEG monitoring demonstrated ictal onsets may not be restricted to the TLEN, and often the temporal pole and mesial structures are involved at seizure onset. Ictal propagation patterns vary significantly, which may be related to the underlying pathology and explain the variability in semiology. These findings may inform surgical treatment options.

PLAIN LANGUAGE SUMMARY

Temporal lobe encephaloceles can cause intractable epilepsy, although their presence may be missed on routine imaging. The management of encephaloceles is primarily surgical; however, the optimal surgical approach can be unclear. Invasive monitoring with SEEG may help characterize the epileptogenic network and result in more optimal surgical outcomes.

Clinical characteristics and surgical outcomes of epilepsy associated with temporal encephalocele: A systematic review

Temporal encephaloceles (TE) are an under-identified, potentially intervenable cause of epilepsy. This systematic review consolidates the current data to identify the major clinical, neuroimaging, and EEG features and surgical outcomes of epilepsy associated with TE. Literature searches were carried out using MEDLINE, Embase, PsycINFO, Scopus, and Cochrane Library databases from inception to December 7, 2023. Studies were included if they described clinical, neuroimaging, EEG, or surgical data in ≥5 patients with TE and epilepsy. Of 562 studies identified in the search, 24 met the eligibility criteria, reporting 423 unique patients with both epilepsy and TE. Compared to epilepsy patients without TE, those with TE had a higher mean age of seizure onset and were less likely to have a history of febrile seizures. Seizure semiologies were variable, but primarily mirrored temporal lobe onset patterns. Epilepsy patients with TE had a higher likelihood of having clinical or radiographic features of idiopathic intracranial hypertension (IIH) than those without. Brain MRI may show ipsilateral mesial temporal sclerosis (16 %). CT scans of the skull base usually revealed bony defects near the TE (90 %). Brain PET scans primarily showed ipsilateral temporal lobe hypometabolism (80 %), mostly in the anterior temporal lobe (67 %). Scalp EEG mostly lateralized ipsilateral to the implicated TE (92 % seizure onset) and localized to the temporal lobe (96 %). Intracranial EEG revealed seizure onset near the TE (11 of 12 cases including TE-adjacent electrodes) with variable timing of spread to the ipsilateral hippocampus. After surgical treatment of the TE, the rate of Engel I or ILAE 1 outcomes at one year was 75 % for lesionectomy, 85 % for anterior temporal lobectomy (ATL), and 80 % for ATL with amygdalohippocampectomy. Further studies are needed to better elucidate the relationship between IIH, TE, and epilepsy, improve the identification of TE, and optimize surgical interventions.

[Surgical treatment of focal drug-resistant epilepsy associated with temporal lobe encephalocele]

BACKGROUND

In recent years, temporal lobe encephalocele has become more common in patients with focal drug-resistant epilepsy. Despite available experience, there are still no clear recommendations for choosing the extent of surgery in these patients.

OBJECTIVE

To evaluate the effectiveness of diagnosis and surgical treatment of focal drug-resistant epilepsy associated with temporal lobe encephalocele.

MATERIAL AND METHODS

The study included 21 patients with focal temporal lobe epilepsy and temporal lobe encephalocele. All patients underwent continuous video-EEG monitoring and MRI of the brain. There were 12 (57.4%) selective encephalocele resections and 9 (42.6%) anterior temporal lobectomies. The median follow-up period was 31 months.

RESULTS

The overall effectiveness of surgical treatment with postoperative Engel class I was 76% (16 cases). Selective encephalocele resection was followed by postoperative Engel class I in 10 patients (83%). There were 6 (67%) patients with similar outcomes after temporal lobectomy. Mean volume of resected tissue adjacent to encephalocele was 8.3 cm3.

CONCLUSION

Surgery is a highly effective treatment for patients with epileptic seizures following temporal lobe encephalocele. In our sample, favorable postoperative outcomes were achieved in 76% of patients (Engel class I). There were no significant differences in effectiveness between selective resection and temporal lobectomy. Further research is necessary for a clear protocol of surgical treatment of focal drug-resistant epilepsy associated with encephalocele.

Distinctive electro-clinical, neuroimaging and histopathological features of temporal encephaloceles associated to epilepsy

OBJECTIVE

Encephaloceles (ENCs) may cause clinical complications, including drug-resistant epilepsy that can be cured with epilepsy surgery.

METHODS

We describe clinical, diagnostic, and neuropathological findings of 12 patients with temporal ENC and epilepsy evaluated for surgery and compare them with a control group of 26 temporal lobe epilepsy (TLE) patients.

RESULTS

Six patients had unilateral and 6 bilateral temporal ENCs. Compared to TLEs, ENCs showed i) later epilepsy onset, ii) higher prevalence of psychiatric comorbidities, iii) no history of febrile convulsions, and iv) ictal semiology differences. Seven patients had MRI signs of gliosis, and 9 of intracranial hypertension. Interictal EEG analysis in ENCs demonstrated significant differences with controls: prominent activity in the beta/gamma frequency bands in frontal regions, interictal short sequences of low-voltage fast activity, and less frequent and more localized interictal epileptiform discharges. Ictal EEG patterns analyzed in 9 ENCs showed delayed and slower contralateral spread compared to TLEs. All ENCs that underwent surgery (7 lobectomies and 1 lesionectomy) are in Engel class I. Neuropathological examination revealed 4 patterns: herniated brain fragments, focal layer I distortion, white matter septa extending into the cortex, and altered gyral profile.

CONCLUSIONS AND SIGNIFICANCE

The described peculiarities might help clinicians to suspect the presence of largely underdiagnosed ENCs.

Drug-resistant temporal lobe epilepsy with temporal encephaloceles: How far to resect

PURPOSE

This study sought to evaluate the impact of surgical extent on seizure outcome in drug-resistant temporal lobe epilepsy (DR-TLE) with temporal encephaloceles (TE).

METHODS

This was a single-institution retrospective study of patients who underwent surgery for DR-TLE with TE between January 2008 and December 2020. The impact of surgical extent on seizure outcome was evaluated. In a subset with dominant DR-TLE, the impact of surgical extent on neuropsychometric outcome was evaluated.

RESULTS

Thirty-four patients were identified (female, 56%; median age at surgery, 43 years). TE were frequently overlooked on initial magnetic resonance imaging (MRI), with encephaloceles only detected after repeat or expert re-review of MRI, additional multi-modal imaging, or intra-operatively in 31 (91%). Sixteen (47%) underwent limited resections, including encephalocele resection only (n = 5) and encephalocele resection with more extensive temporal corticectomy sparing the amygdala and hippocampus (n = 11). The remainder (n = 18, 53%) underwent standard anterior temporal lobectomy and amygdalohippocampectomy (ATLAH). Limited resection was performed more frequently on the left (12/17 vs. 4/17, p = 0.015). Twenty-seven patients (79%) had a favourable outcome (Engel I/II), and 17 (50%) were seizure-free at the last follow-up (median seizure-free survival of 27.3 months). There was no statistically significant difference in seizure-free outcomes between limited resection and ATLAH. In dominant DR-TLE, verbal memory decline was more likely after ATLAH than limited resection (3/4 vs. 0/9, p = 0.014).

CONCLUSION

Expert re-review of imaging and multi-modal advanced imaging improved TE identification. There was no statistical difference in seizure-free outcomes based on surgical extent. Preservation of verbal memory supports limited resection in dominant temporal cases.

MRI features to aid the identification of lateral temporal bone cephaloceles

OBJECTIVES

To evaluate ancillary MRI features which may aid the identification of lateral temporal bone cephaloceles (LTBCs).

METHODS

A retrospective cohort study analysed patients with MRI evidence of surgically confirmed spontaneous LTBCs as defined by intracranial contents traversing the tegmen tympani or mastoideum. Cases were identified from radiology and surgical databases. Two observers analysed three-dimensional T 2W temporal bone and whole brain imaging according to a priori criteria by consensus, with emphasis on the relationship of any adjacent cerebrospinal fluid (CSF) cleft to the defect. The contents, location, and clinical features of the LTBCs were recorded.

RESULTS

Eighteen patients (11 female, 7 male; mean age 59.3 years, age range 42-86 years) with 20 surgically confirmed spontaneous LTBCs (2 bilateral;16 unilateral) were evaluated. A temporal lobe sulcus or other CSF cleft extending to or traversing the defect was identified in 19/20 (95%) cases. Isointense CSF tympanomastoid signal was present in 41.2% cases, whilst superior semi-circular canal dehiscence was found in 40% of cephaloceles. At least two MRI features of idiopathic intracranial hypertension were seen in 38.9% patients. Cephaloceles were most commonly centred on the tegmen tympani (55%). Meningoencephaloceles were present in 95% cases.

CONCLUSION

A temporal lobe sulcus or CSF cleft extending to or traversing the defect may aid the identification of LTBCs. Isointense CSF tympanomastoid signal, superior semi-circular canal dehiscence and MRI features of idiopathic intracranial hypertension are only present in under half of LTBCs.

ADVANCES IN KNOWLEDGE

The study details novel ancillary MRI features of LTBCs which may aid their identification.

The Predictors of Seizures in Patients with Encephalocele: An 11-Year Experience from a Tertiary Hospital

INTRODUCTION

The aim of the study was to investigate and identify the predictors associated with the incidence of seizures in patients with encephalocele (EC).

METHODS

A retrospective analysis was undertaken of patients treated for EC at a tertiary medical center in Tehran between 2010 and 2021. Data including age at presentation, gender, location, size, and content of EC, ventriculomegaly, hydrocephalus, associated anomalies, and neurodevelopmental delay (NDD) were evaluated for their prognostic value. In addition, univariate and multivariate analyses were performed to identify the correlation between independent predictors and seizure incidence.

RESULTS

One hundred and two cases of EC were identified. Seventy-one ECs (69.6%) were posterior ECs, while 31 (30.4%) were anterior. Neural tissue was found in 43 (42.2%) of the ECs. Thirty-three patients (32.4%) had ventriculomegaly, of which 90.9% underwent shunt placement for progressive or symptomatic hydrocephalus. Seizure was found in 26 (25.5%) patients. On univariate analysis, presence of other anomalies, postoperative infections, and NDD were associated with seizures (p < 0.05). When the anomalies were categorized into intracranial and extracranial groups in univariate analysis, none was associated with statistically significant increase in seizure (p values of 0.09 and 0.61, respectively). Although according to multivariate analysis, only the association between other associated anomalies and seizure was near significant (OR: 2.0, 95% CI: 0.95-4.2, p = 0.049). Children with NDD and postoperative infection were, respectively, 3.04 and 1.3 times more at risk to experience seizures compared to other patients.

CONCLUSION

We found a rate of 25.5% risk of seizure in patients with EC. This study could not find any significant predictors of seizure in children with EC. However, pediatric patients with postoperative infections including sepsis, wound infection, and NDD require more consideration to reduce the risk of seizure.

Temporal encephaloceles and coexisting epileptogenic lesions

OBJECTIVE

This study was performed to identify coexisting structural lesions in patients with epilepsy and known temporal encephaloceles (TEs).

METHODS

Forty-seven structural magnetic resonance imaging (MRI) scans of patients with epilepsy and radiologically diagnosed TEs were retrospectively reviewed visually and using an automated postprocessing software, the Morphometric Analysis Program v2018 (MAP18), to depict additional subtle, potentially epileptogenic lesions in the 3D T1-weighted MRI data. All imaging findings were evaluated in the context of clinical and electroencephalographical findings.

RESULTS

The study population consisted of 47 epilepsy patients (38.3% female, n = 18). The median age at the time of the scan was 40 years (range 12-81 years). Twenty-one out of 47 MRI scans (44.7%) showed coexisting lesions in the initial MRI evaluation; in 38.3% (n = 18) of patients, those lesions were considered probably epileptogenic. After postprocessing, probable epileptogenic lesions were identified in 53.2% (n = 25) of patients. Malformations of cortical development had initially been reported in 17.0% (n = 8) of patients with TEs, which increased to 38.3% (n = 18) after postprocessing. TEs and other epileptogenic lesions were considered equally epileptogenic in 21.3% (n = 10) of the cases in the initial MR reports and 25.5% (n = 12) of the cases after postprocessing.

SIGNIFICANCE

Temporal encephaloceles are a potential cause of MRI-negative temporal lobe epilepsy. According to our data, TEs can occur with other lesions, suggesting that increased awareness is also required in patients with lesional epilepsy. TEs may not always be epileptogenic; hence, their occurrence with other structural pathologies may influence the presurgical evaluation and surgical approach. Finally, TEs can be associated with malformations of cortical development, which may indicate a common developmental etiology of those lesions.

Introducing the "Temporal Thumb Sign" in Pediatric Patients With New-Onset Idiopathic Seizures With and Without Elevated Cerebrospinal Fluid Opening Pressure

BACKGROUND

Temporal lobe changes, such as anterior temporal lobe meningoceles or encephaloceles, have been documented as possible epileptogenic foci in a subset of pediatric patients with seizures. In our study, we aim to analyze a different structural change in the temporal lobe, remodeling of the posterior temporal skull base by the inferior temporal gyrus called the "temporal thumb sign" (TTS), in pediatric patients presenting with new-onset seizures with or without elevated opening pressure (OP), patients presenting with confirmed diagnosis of idiopathic intracranial hypertension (IIH) without seizure presentation, and healthy controls.

METHODS

Magnetic resonance imaging scans of 163 pediatric patients were studied retrospectively for the presence of TTS. We analyzed the scans of 43 patients with elevated OP and confirmed IIH, 40 patients with elevated OP and new-onset idiopathic seizures, 40 patients with normal OP and new-onset idiopathic seizures, and 40 age- and sex-matched healthy controls.

RESULTS

The TTS was detected most frequently in patients with elevated OP and seizures at 72.5% compared with patients with IIH with no seizures and patients with normal OP and seizures (32.6% and 27.5%, respectively). The TTS had a frequency of 12.5% in the control group. The TTS had the highest combination of specificity and sensitivity (72.5% and 72.5%) in patients with seizures and elevated OP compared with patients with seizures and normal OP (P value < 0.001).

CONCLUSIONS

Our results suggest the Kamali "temporal thumb sign" is a novel imaging feature that may be used as a sensitive and specific imaging finding associated with seizures and elevated OP in the pediatric population.

The neurodevelopmental outcomes of children with encephalocele: a series of 102 patients

OBJECTIVE

The overall prognosis of encephalocele (EC) is not well described. However, the presence of some risk factors may result in neurodevelopmental delay (NDD) and negatively affect the prognosis of affected patients. The goal of this study was to evaluate neurodevelopmental outcome, as well as the impact of a number of factors on the outcome in patients with ECs.

METHODS

This was an observational, retrospective study including 102 children with EC who were followed at the pediatric neurosurgery department of a tertiary medical center between the years 2010 and 2021. The authors evaluated NDD status according to the Centers for Disease Control and Prevention classification via clinical evaluation and parent interviews in the outpatient setting.

RESULTS

There were 52 boys and 50 girls. The median age at the time of surgery was 4 months (range 1 day-7.5 years). Seventy-one patients (69.6%) had posterior ECs, whereas 31 (30.4%) had anterior ECs. Forty-three (42.2%) of the ECs contained neural tissue. Of the 102 patients, 33 (32.4%) had ventriculomegaly. In terms of NDD, 14 (14.9%) had mild/moderate delay, whereas 17 patients (18.1%) had severe NDD. On univariate analysis, posterior location, size of sac, presence of neural tissue, ventriculomegaly, symptomatic hydrocephalus, and postoperative infection were correlated with NDD. On a multivariate logistic regression model, only neural tissue presence had a statistically significant association with NDD (OR 7.04, 95% CI 1.33-37.2, p = 0.022). Although not statistically significant, children with ventriculomegaly were 2.6 times as likely to have NDD (95% CI 0.59-11.19, p = 0.362).

CONCLUSIONS

This is a single-center study with a large sample size in which the neurodevelopmental status of patients with EC was assessed, and the authors tried to find the risk factors of NDD in these patients. The results showed that the presence of neural tissue within the EC sac was the only risk factor that had independent statistically significant association with NDD.

Imaging in medically refractory epilepsy at 3 Tesla: a 13-year tertiary adult epilepsy center experience

Objectives

MRI negative epilepsy has evolved through increased usage of 3 T and insights from surgically correlated studies. The goal of this study is to describe dedicated 3 T epilepsy MRI findings in medically refractory epilepsy (MRE) patients at a tertiary epilepsy center to familiarize radiologists with an updated spectrum and frequency of potential imaging findings in the adult MRE population.

Methods

Included were all patients with MRE admitted to the epilepsy monitoring unit who were discussed at weekly interdisciplinary imaging conferences at Toronto Western Hospital with MRI studies (3 T with dedicated epilepsy protocol) performed between January 2008 and January 2021. Lesion characterization was performed by two readers based on most likely imaging diagnosis in consensus. Lobes involved per case were recorded.

Results

A total of 738 patients (386 female; mean age 35 years, range 15–77) were included. A total of 262 patients (35.5%) were MRI negative. The most common imaging finding was mesial temporal sclerosis, seen in 132 patients (17.9%), followed by encephalomalacia and gliosis, either posttraumatic, postoperative, postischemic, or postinfectious in nature, in 79 patients (10.7%). The most common lobar involvement (either partially or uniquely) was temporal (341 cases, 58.6%). MRE patients not candidates for surgical resection were included in the study, as were newly described pathologies from surgically correlated studies revealing findings seen retrospectively on reported MRI negative exams (isolated enlargement of the amygdala, temporal pole white matter abnormality, temporal encephalocele).

Conclusion

This study provides an updated description of the spectrum of 3 T MRI findings in adult MRE patients from a tertiary epilepsy center.

Seizure as the presenting sign of idiopathic intracranial hypertension

A 38-year-old man presented to the emergency room with a new generalised tonic-clonic seizure. He also complained of headaches, and brain MRI/magnetic resonance venography (MRV) showed an anterior left temporal encephalocoele with gliosis and brain parenchyma herniating into the left foramen ovale. Ophthalmic examination revealed bilateral optic disc oedema and his lumbar puncture confirmed an elevated opening pressure of 48 cm of water. He was diagnosed with idiopathic intracranial hypertension (IIH) and his papilloedema resolved with weight loss and acetazolamide. Raised intracranial pressure (ICP) can be associated with encephalocoeles and lead to seizures. It is important to screen for papilloedema in these patients as they are at risk for permanent vision loss. This was a unique case in which IIH was diagnosed only after a seizure due to an encephalocoele, which was likely related to chronically undetected raised ICP.

Semiology, EEG, and neuroimaging findings in temporal lobe epilepsies

Temporal lobe epilepsy (TLE) is the most common type of focal epilepsy. First descriptions of TLE date back in time and detailed portraits of epileptic seizures of temporal origin can be found in early medical reports as well as in the works of various artists and dramatists. Depending on the seizure onset zone, several subtypes of TLE have been identified, each one associated with peculiar ictal semiology. TLE can result from multiple etiological causes, ranging from genetic to lesional ones. While the diagnosis of TLE relies on detailed analysis of clinical as well as electroencephalographic (EEG) features, the lesions responsible for seizure generation can be highlighted by multiple brain imaging modalities or, in selected cases, by genetic investigations. TLE is the most common cause of refractory epilepsy and despite the great advances in diagnostic tools, no lesion is found in around one-third of patients. Surgical treatment is a safe and effective option, requiring presurgical investigations to accurately identify the seizure onset zone (SOZ). In selected cases, presurgical investigations need intracerebral investigations (such as stereoelectroencephalography) or dedicated metabolic imaging techniques (interictal PET and ictal SPECT) to correctly identify the brain structures to be removed.

A case report of congenital temporal bone encephalocele presenting as a tumor in a child

An encephalocele may be congenital or acquired and is characterized by the herniation of cranial contents through a skull bone defect. Most congenital encephaloceles occur in the occipital area, and temporal bone encephaloceles in children are rare. Congenital encephaloceles can be diagnosed either prenatally or after birth. We describe the case of a congenital temporal bone encephalocele in a 2-month-old boy that was diagnosed after birth. The patient presented with seizures and a bulging mass in the right neck that was detected by his mother during the second month after birth. The combined results from brain magnetic resonance imaging, computed tomography, and histological analysis confirmed the diagnosis of encephalocele. Although the surgical repair was offered, the family declined.

Middle Fossa Encephaloceles Treated via the Transmastoid Approach: A Case Series and Review of the Literature

BACKGROUND

Middle fossa (MF) encephaloceles are rare lesions resulting from herniation through defects in the tegmen tympani or mastoideum. Underlying etiologies and clinical presentations are variable. Surgical goals include fistula obliteration, resection of nonfunctioning parenchyma, and dehiscence repair. The middle cranial fossa approach (MCFA), transmastoid approach (TMA), and combined (MCFA + TMA) approaches have been described. The minimally invasive TMA provides excellent exposure of the pathology and allows for ample working room to repair the defect.

OBJECTIVE

We present short-term follow-up results in patients treated via the TM repair at our institution.

METHODS

A retrospective review of patients with symptomatic encephaloceles treated via the TMA by our multidisciplinary team. Patient demographics, clinical presentations, intraoperative findings, repair technique, and outcomes were highlighted.

RESULTS

A total of 16 encephaloceles in 13 patients were treated. Defect etiologies included spontaneous (50.0%), secondary to chronic infection (25.0%), or cholesteatoma (18.8%). Defects were most often within the tegmen mastoideum (68.8%). Average length of surgery was 3.3 h (95% CI: 2.86-3.67) and length of stay 3.9 d (95% CI: 3.09-4.79). On short-term follow-up (average 11.5 mo), no patients experienced postoperative cerebrospinal fluid leak or recurrence. The majority of patients (83.3%) experienced confirmed improvement or stabilization of hearing.

CONCLUSION

MF encephaloceles present with various clinical manifestations and result from multiple underlying etiologies. The TMA is an alternative to craniotomy and our short-term results suggest that this approach may be utilized effectively in appropriately selected cases.

Endoscopic endonasal repair of a temporal lobe meningoencephalocele in the pterygoid fossa: A case report and literature review

Introduction

Meningoceles are defined as herniation of the meninges through a skull base defect. If brain tissue is herniated as well, then it is called meningoencephalocele. The most common locations of meningoceles are the cribriform plate and the lateral recess of the sphenoid sinus, with the most common presentation being CSF leakage. We present a case of temporal lobe meningocele that herniated through a defect in the greater wing of the sphenoid bone to the pterygoid fossa and that was diagnosed incidentally while evaluating the patient for seizures.

Methodology

Case report and literature review.

Conclusion

The endonasal endoscopic approach is a suitable minimally invasive approach for the management of pterygoid fossa lesions, including meningoceles. In this case, the patient had epilepsy with the surgery resulting in the resolution of the seizures.

•

Endonasal approach can be considered as a minimally invasive approach for lesions in the pterygoid fossa.

•

Meningocele are to be considered as a possible etiology for pterygoid fossa masses connected with the middle cranial fossa.

•

Surgical resection of encephalomeningocele should be considered for the management of intractable seizures.

Encephalocele-Associated Drug-Resistant Epilepsy of Adult Onset: Diagnosis, Management, and Outcomes

Epileptogenic encephaloceles, most frequently located in the temporal lobe, are a known lesional cause of focal epilepsy. Data are limited regarding diagnosis, management, and outcomes of patients with epilepsy in the setting of an encephalocele, because the literature mostly comprises case reports, case series, and retrospective studies. We conducted a broad literature review for articles related to encephaloceles and epilepsy regardless of level of evidence. Hence, this review provides a summary of all available literature related to the topic. Thirty-six scientific reports that fulfilled our inclusion criteria were reviewed. Most reported patients presented with focal impaired awareness seizures and/or generalized tonic-clonic seizures. Although most of the encephaloceles were located in the temporal lobe, we found 5 cases of extratemporal encephaloceles causing epilepsy. More patients who underwent either lesionectomy or lobectomy were seizure free at time of follow-up. In the temporal lobe, there is no clear consensus on the appropriate management for epileptic encephaloceles and further studies are warranted to understand the associated factors and long-term outcomes associated with epilepsy secondary to encephaloceles. Reported data suggest that these patients could be manageable with surgical procedures including lesionectomy or lobectomy. In addition, because of data suggesting similar results between procedures, a more conservative surgery with lesionectomy and defect repair rather than a lobectomy may have lower surgical risks and similar seizure freedom.

Temporal encephaloceles in epilepsy patients and asymptomatic cases: Size may indicate epileptogenicity

OBJECTIVE

This study was undertaken to identify temporal encephaloceles (TEs) and examine their characteristics in patients with temporal lobe epilepsy (TLE) and extratemporal lobe epilepsy (ETLE), as well as in asymptomatic cases.

METHODS

Four hundred fifty-eight magnetic resonance imaging scans were examined retrospectively to identify TE in 157 patients with TLE, 150 patients with ETLE, and 151 healthy controls (HCs).

RESULTS

At least one TE was identified in 9.6% of the TLE patients (n = 15, 95% confidence interval [CI] = 5.3%-15.3%), in 3.3% of patients with ETLE (n = 5, 95% CI = 1.1%-7.6%), and in 2.0% of the HCs (n = 3, 95% CI = .4%-5.7%), indicating a significantly higher frequency in patients with TLE compared to ETLE and HC subjects (p = .027, p = .005). Examining the characteristics of TEs in both asymptomatic and epilepsy patients, we found that TEs with a diameter of less than 6.25 mm were more likely to be asymptomatic, with a sensitivity of 91.7% and a specificity of 73.3% (area under the curve = .867, 95% CI = .723-1.00, p = .001).

SIGNIFICANCE

Temporal encephaloceles may occur without presenting any clinical symptoms. Patients with TLE show a higher frequency of TEs compared to the ETLE and HC groups. According to our study, TE size could be used to suggest potential epileptogenicity.

Anatomical Variations, Mimics, and Pitfalls in Imaging of Patients with Epilepsy

Epilepsy is among one of the most common neurologic disorders. The role of magnetic resonance imaging (MRI) in the diagnosis and management of patients with epilepsy is well established, and most patients with epilepsy are likely to undergo at least one or more MRI examinations in the course of their disease. Recent advances in high-field MRI have enabled high resolution in vivo visualization of small and intricate anatomic structures that are of great importance in the assessment of seizure disorders. Familiarity with normal anatomic variations is essential in the accurate diagnosis and image interpretation, as these variations may be mistaken for epileptogenic foci, leading to unnecessary follow-up imaging, or worse, unnecessary treatment. After a brief overview of normal imaging anatomy of the mesial temporal lobe, this article will review a few important common and uncommon anatomic variations, mimics, and pitfalls that may be encountered in the imaging evaluation of patients with epilepsy.

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

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.

MR Imaging Features of Middle Cranial Fossa Encephaloceles and Their Associations with Epilepsy

BACKGROUND AND PURPOSE

Middle cranial fossa encephaloceles are an increasingly recognized cause of epilepsy; however, they are also often encountered on neuroimaging in patients with no history of seizure. We characterized the MR imaging features of middle cranial fossa encephaloceles in seizure and nonseizure groups with the hope of uncovering features predictive of epileptogenicity.

MATERIALS AND METHODS

Seventy-seven patients with middle cranial fossa encephaloceles were prospectively identified during routine clinical practice of neuroradiology at a tertiary care hospital during an 18-month period. Thirty-five of 77 (45%) had a history of seizure, 20/77 (26%) had temporal lobe epilepsy, and 42/77 (55%) had no history of seizures. Middle cranial fossa encephalocele features on MR imaging were characterized, including depth, area, number, location, presence of adjacent encephalomalacia, and degree of associated parenchymal morphologic distortion. MR imaging features were compared between the seizure and nonseizure groups.

RESULTS

No significant difference in MR imaging features of middle cranial fossa encephaloceles was seen when comparing the seizure and nonseizure groups. Comparison of just those patients with temporal lobe epilepsy (n = 20) with those with no history of seizure (n = 42) also found no significant difference in MR imaging features.

CONCLUSIONS

Anatomic MR imaging features of middle cranial fossa encephaloceles such as size, number, adjacent encephalomalacia, and the degree of adjacent parenchymal morphologic distortion may not be useful in predicting likelihood of epileptogenicity.

Delayed Cerebrospinal Fluid Rhinorrhea Associated With Ethmoidal Encephalocele After Resection of Remote Meningioma

Diagnosis and treatment of neurosurgical pathology present unique challenges in underserved areas, and many conditions may go undiagnosed, misdiagnosed, or untreated for prolonged periods. The development of an unusual complication, seemingly unrelated to an area of neurosurgical intervention, may be particularly perplexing to non-neurosurgical providers, particularly in areas where neurosurgical procedures have not historically been available. A 44-year-old male presented with a giant meningioma which was successfully resected. A nasal encephalocele was noted preoperatively but was not addressed due to lack of associated symptoms and distance from the tumor. The patient lived on a remote island and was lost to follow-up. He developed delayed cerebral spinal fluid (CSF) rhinorrhea three months after surgery, which was diagnosed and treated by local providers as allergic rhinitis for 11 months until he presented with new-onset seizure. Imaging demonstrated descent of the lateral ventricle into the encephalocele. The encephalocele was amputated and the skull base defect was repaired successfully. The alteration of ventricular anatomy and CSF fluid dynamics following tumor resection appears to have created an environment where a non-traumatic CSF leak could develop where it had previously shown no signs of developing. It may be prudent to treat skull base defects prophylactically to prevent this type of complication, particularly in patients of remote regions where regular follow-up is difficult.

Diagnosis and management of spontaneous cerebrospinal fluid fistula and encephaloceles

PURPOSE OF REVIEW

To describe the current state in the diagnosis and management of spontaneous cerebrospinal fluid (sCSF) fistula and encephaloceles.

RECENT FINDINGS

The increased incidence of obesity has resulted in more cases of sCSF fistula and encephaloceles. Obesity results in increased intracranial pressure and a greater chance of developing a sCSF fistula or encephalocele. Obstructive sleep apnea can also result in transient increase in intracranial pressure and has been shown to be common in patients with sCSF fistula. Treatment of CSF fistula is usually necessary because of the increased risk of meningitis. The use of hydroxyapatite bone cements to repair the temporal bone defects has been described with a high success rate of closing the fistula and a low complication rate. Concurrent superior semicircular canal dehiscent can be seen in up to 15% of cases and should be suspected during the surgical approach to avoid potential sensorineural hearing loss and chronic imbalance.

SUMMARY

sCSF fistula and encephaloceles are an uncommon cause of hearing loss, middle ear effusion, and otorrhea, but should be recognized and repaired because of the risk of meningitis.

Repair of a large primary subtemporal encephalocele in a 3-year-old child: case report

Primary encephaloceles (PEs) present only rarely in the temporal region; in the rare instance that they project through the floor of the middle fossa they are secondary. In this case report the authors report on the management of a giant PE extending through the floor of the middle fossa.An 8-month-old boy presented to the authors' service with a large PE projecting into his neck through a missing left middle fossa floor; the lesion was causing significant meta-, dys-, and hypoplasia of the structures of the anterolateral neck on that side. Surgical goals for this patient included the following: 1) removal of potentially epileptogenic and dysfunctional tissue; 2) preservation of cranial nerves; 3) prevention of cognitive decline or iatrogenic deficit; 4) prevention of CSF leak; 5) reconstruction of skull base; 6) prevention of airway and swallowing compromise; and 7) cosmesis. After a multidisciplinary evaluation with ENT, plastic surgery, and neurology, an operation was performed using a preauricular infratemporal approach when the patient was 3 years old. Gliotic tissue was resected and amygdala, hippocampus, and middle cerebral artery were preserved.The immediate results of the operation showed good immediate outcome. Seizure freedom and neurodevelopment outcomes remain to be seen at follow-up.

Prevalence of Asymptomatic Middle Cranial Fossa Floor Pits and Encephaloceles on MR Imaging

BACKGROUND AND PURPOSE

Temporal lobe encephaloceles are increasingly identified and treated as epileptogenic foci. However, there is relatively scant research on the prevalence of asymptomatic encephaloceles. This study set out to describe the frequency of incidental temporal lobe encephaloceles and middle cranial fossa pits.

MATERIALS AND METHODS

A retrospective review was completed of high-resolution (≤0.5-mm section thickness) axial T2WI for internal auditory canal protocol imaging. The presence and laterality of middle cranial fossa pits (small bony defects containing CSF) and encephaloceles (brain parenchyma protrusion through osseous defects with or without bony remodeling) were recorded. Electronic medical records of patients with encephaloceles were searched for a history of seizure.

RESULTS

A total of 203 patients were included in the final cohort; 106 (52.2%) women. Forty-five (22.2%) patients had middle cranial fossa pits: 14 (31.1%) unilateral on the right, 17 (37.8%) unilateral on the left, and 14 (31.1%) bilateral. Ten (5.0%) patients had ≥1 encephalocele, none of whom had a documented history of seizure in the electronic medical record. No significant difference was noted in the frequency of pits or encephaloceles based on sex (P = .332 and P = .383, respectively) or age (P = .497 and P = .914, respectively).

CONCLUSIONS

Incidental middle cranial fossa pits are common findings, and their prevalence is not related to age or sex. Temporal lobe encephaloceles, though rarer, also exist occasionally among asymptomatic patients. Such findings have diagnostic implications for encephaloceles identified during imaging work-up for epilepsy.

Medial Temporal Encephalocele and Medically Intractable Epilepsy: A Tailored Inferior Temporal Lobectomy and Case Report

BACKGROUND AND IMPORTANCE

Temporal lobe encephaloceles are increasingly recognized as a potential cause of medically refractory epilepsy and surgical treatment has proven effective. Resection of the encephalocele and associated cortex is often sufficient to provide seizure control. However, it is difficult to determine the extent of adjacent temporal lobe that should be resected. We present a case report and our technique of a tailored inferior temporal pole resection.

CLINICAL PRESENTATION

A 32-yr-old man with an 11-yr history of medically refractory epilepsy. Prolonged electroencephalography (EEG) revealed frequent left and rare right frontotemporal sharp waves. Numerous seizures were captured with EEG, all of which originated from the left temporal region. Statistical parametric mapping (SPM) subtraction ictal–interictal SPECT coregistered with magnetic resonance imaging (MRI) (SISCOM) demonstrated ictal hyperperfusion in the anterior left temporal lobe. MRI showed 2 encephaloceles in the left anterior temporal lobe with the accompanying bony defects in the floor of the middle cranial fossa apparent on the computed tomography scan. The patient underwent left temporal craniotomy with intraoperative electrocorticography, resection of the encephaloceles, and a tailored inferior temporal lobectomy (IFTL) and repair of the middle fossa defects. At 7 mo follow up he reported seizure-freedom since surgery.

CONCLUSION

Resection of temporal encephalocele and adjacent cortex is safe and effective procedure for select patients with medically refractory epilepsy. This video demonstrates our technique which provides a more standardized approach to the resection.

Detection and Characteristics of Temporal Encephaloceles in Patients with Refractory Epilepsy

BACKGROUND AND PURPOSE

Temporal encephaloceles are increasingly visualized during neuroimaging assessment of individuals with refractory temporal lobe epilepsy, and their identification could indicate an intracranial abnormality that may be related to a potential seizure focus. Careful review by an experienced neuroradiologist may yield improved detection of TEs, and other clinical, neurophysiologic, and radiologic findings may predict their presence.

MATERIALS AND METHODS

Data were reviewed retrospectively in patients at our institution who were presented at a multidisciplinary conference for refractory epilepsy between January 1, 2010, and December 31, 2016. Clinical, neurophysiologic, and imaging data were collected. An expert neuroradiologist reviewed the latest MR imaging of the brain in patients for whom one was available, noting the presence or absence of temporal encephaloceles as well as other associated imaging characteristics.

RESULTS

A total of 434 patients were reviewed, 16 of whom were excluded due to unavailable or poor-quality MR imaging. Seven patients had temporal encephaloceles reported on initial imaging, while 52 patients had temporal encephaloceles identified on expert review. MR imaging findings were more often initially normal in patients with temporal encephaloceles (P < .001), and detection of temporal encephaloceles was increased in patients in whom 3T MR imaging was performed (P < .001), the T2 sampling perfection with application-optimized contrasts by using different flip angle evolutions sequence was used (P < .001), or the presence of radiologic findings suggestive of idiopathic intracranial hypertension was noted. Seizure onset by scalp electroencephalogram among patients with temporal encephaloceles was significantly more likely to be temporal compared with patients without temporal encephaloceles (P < .001). A significant correlation between intracranial electroencephalogram seizure onset and patients with temporal encephaloceles compared with patients without temporal encephaloceles was not observed, though there was a trend toward temporal-onset seizures in patients with temporal encephaloceles (P = .06).

CONCLUSIONS

Careful review of MR imaging in patients with refractory temporal lobe epilepsy by a board-certified neuroradiologist with special attention paid to a high-resolution T2 sequence can increase the detection of subtle temporal encephaloceles, and certain clinical and neurophysiologic findings should raise the suspicion for their presence.

Epilepsy Surgery for Skull-Base Temporal Lobe Encephaloceles: Should We Spare the Hippocampus from Resection?

The neurosurgical treatment of skull base temporal encephalocele for patients with epilepsy is variable. We describe two adult cases of temporal lobe epilepsy (TLE) with spheno-temporal encephalocele, currently seizure-free for more than two years after anterior temporal lobectomy (ATL) and lesionectomy sparing the hippocampus without long-term intracranial electroencephalogram (EEG) monitoring. Encephaloceles were detected by magnetic resonance imaging (MRI) and confirmed by maxillofacial head computed tomography (CT) scans. Seizures were captured by scalp video-EEG recording. One case underwent intraoperative electrocorticography (ECoG) with pathology demonstrating neuronal heterotopia. We propose that in some patients with skull base temporal encephaloceles, minimal surgical resection of herniated and adjacent temporal cortex (lesionectomy) is sufficient to render seizure freedom. In future cases, where an associated malformation of cortical development is suspected, newer techniques such as minimally invasive EEG monitoring with stereotactic-depth EEG electrodes should be considered to tailor the surrounding margins of the resected epileptogenic zone.

[Surgery for intractable epilepsy in a patient with encephalocele of the temporal lobe: a case report]

We describe a case of surgical treatment of intractable temporal epilepsy in a female patient with congenital middle cranial fossa encephalocele. We present clinical-anamnestic and neuroimaging data as well as the microscopic and macroscopic pictures of encephalocele. We analyze outcomes of surgery for this pathology, which have been reported in the literature. To date, there have been a few articles on this subject in the domestic literature. The development of neuroimaging techniques and a growing number of verified encephalocele cases promote the widespread use of surgery for treatment of intractable epilepsy. Congenital encephalocele should be considered in the differential diagnosis of intractable temporal epilepsy, and, if verified, surgical treatment is the method of choice in most cases.