Clinical commentary Epileptic Disord 2010; 12 (2): 160-6
Epilepsy surgery for refractory epilepsy due to encephalocele: a case report and review of the literature Howard J. Faulkner1, David R. Sandeman2,4, Seth Love3, Marcus J. Likeman6, Desnomd A. Nunez7, Samden D. Lhatoo1,4,5 1
Department of Neurology Department of Neurosurgery 3 Department of Neuropathology 4 Bristol Complex Epilepsy Surgery Service 5 Department of Neurophysiology 6 Department of Radiology 7 Department of Otolaryngology, Frenchay Hospital, North Bristol NHS Trust, Bristol, United Kingdom 2
Received October 27, 2009; Accepted February 22, 2010
ABSTRACT – The management of medically intractable epilepsy is frequently assisted by the identification of structural abnormalities made possible by modern imaging techniques. The association between meningoencephaloceles and epileptic seizures is well reported in the literature. We report a patient with refractory right frontal lobe epilepsy caused by a right nasal meningoencephalocele who was rendered seizure free by endoscopic nasal excision and skull base repair, obviating the need for resective epilepsy surgery. Epilepsy patterns associated with encephalocele and their management are reviewed. Key words: epilepsy, epilepsy surgery, encephalocele, cortical dysplasia,
gyrus rectus
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infectious damage to the skull base (Mandl et al., 2007; Nager, 1987). Patients usually present with direct neurological complications due to traction or herniation of involved cortex resulting in weakness, sensory disturbance (Fountas et al., 2005) or with seizures (Ruiz García, 1971). They may also present with CSF otorrhoea or rhinorrhoea, recurrent meningitis and symptoms related to encroachment on adjacent regions such as nasal obstruction (Kohrmann et al., 2007; Magliulo et al., 1998). An encephalocele can be visualised on CT or MR imaging. The presence of a bony defect is best shown on
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doi: 10.1684/epd.2010.0308
Correspondence: S.D. Lhatoo, FRCP Departments of Neurology and Neurophysiology, Frenchay Hospital, Bristol BS16 1LE, United Kingdom
Encephaloceles are characterised by defects of the bony skull through which herniation of the intracranial contents can occur. Encephaloceles are classified according to their location and contents. Those containing only cerebrospinal fluid (CSF) and meninges are termed craniomeningoceles; if the lesion also contains neural tissue then it is termed a meningoencephalocele. Encephaloceles may be congenital, due to failure of neural tube closure, resulting in a bony defect through which herniation of neural tissue may occur from birth or at a later date (Naidich et al., 1992) They may also be acquired lesions following traumatic, neoplastic, metabolic, or
Epilepsy and encephaloceles
skull base CT with MRI enabling differentiation of the contents and showing any connection with brain tissue (Schuknecht et al., 2008). The imperative for surgical treatment is usually strong, given the potential for recurrent meningitis, brain damage from herniation and refractory seizures. The surgical approach and technique is dependent upon the position and size of both the defect and the encephalocele (Woodworth et al., 2004).
Case study A 32-year-old female patient was referred with medically refractory seizures. These began at 19 years of age and were characterised by nocturnal generalised convulsive seizures, 30-60 minutes after sleep onset. There was a single daytime seizure at age 24 with no obvious preceding partial onset. Initial brain MR imaging was reported as normal (although with subsequent review, a nasal meningoencephalocele was visible). The seizures were well controlled with sodium valproate. At age 27 there was a change in seizure type to one of complex partial seizures, without preceding aura, occurring twice per week. The episodes were typified by behavioural arrest and confused speech, lasting up to two minutes, followed by a two-hour period of amnesia during which she could perform complex tasks. Physical examination remained normal throughout. There was no response to carbamazepine, topiramate, levetiracetam, lamotrigine, phenytoin, tiagabine or zonisamide. MRI scans 1.5T and subsequently 3T were performed as part of a pre-surgical workup with a view to resective surgery. These showed a 3 cm right nasal meningoencephalocele with a prolapsed right gyrus rectus through a defect in the cribriform plate (figure 1). Skull base CT confirmed a defect in the cribriform plate. A 18-FDG PET-scan showed no distinct areas of hypometabolism. Prolonged video-EEG monitoring was carried out, using the 10-20 electrode system supplemented by bilateral sphenoidal electrodes, with partial drug withdrawal. Inter-ictal EEG showed regional right-sided slowing and bilateral synchronous as well as asynchronous sharp waves with an electrical maximum in the sphenoidal electrodes (figure 2A). During monitoring, we documented two of her habitual partial seizures, characterised by a right frontal ictal EEG onset, maximum at F8, Fp2, and F4 respectively, which spread within seconds to the whole of the right hemisphere and subsequently the left hemisphere (figure 2B). Nasal endoscopy demonstrated a right intra-nasal mass consistent with an encephalocele. After discussion with the otorhinolaryngologist, we decided to address the treatment for the meningoencephalocele and refractory epilepsy in a two-staged approach. Firstly we planned to
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Figure 1. Pre-operative 3T MRI scans with coronal T2 sequences identfied a 3 cm right nasal meningoencephalocele with a prolapsed right gyrus rectus through a defect in the cribriform plate.
excise the meningoencephalocele and second, to carry out resective frontal cortex surgery through craniotomy. At surgery, the meningoencephalocele was dissected off the walls of the right nasal cavity, decompressed and the dura and herniated brain tissue excised. An intracranial-free abdominal fat graft was placed through the skull base defect and attached to its edge, then sealed from below with harvested nasal septal cartilage. Histology of the excised meningoencephalocele confirmed meningeal structures and the presence of brain tissue (figure 3). Neurons within the tissue appeared haphazardly arranged, without consistent orientation or discernable lamination but the individual cells did not show significant dysmorphism. No ballooned cells were present. Post-operative MRI scans showed complete excision of the meningoencephalocele and satisfactory repair to the right frontal skull base (figure 4). Following the procedure, there was dramatic seizure remission; no seizures were reported, compared to twice weekly before surgery, completely obviating the need for potentially hazardous further resective brain surgery. The patient has remained seizure free for more than 2 years, having elected to remain on medical treatment (200 mg lamotrigine and 100 mg zonisamide, twice daily).
Discussion Detailed epilepsy protocol imaging in our case left little doubt about the presence of the gyrus rectus section of the
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A
B
Figure 2. A) Inter-ictal EEG revealed right-sided slowing and bilateral synchronous as well as asynchronous sharp waves with an electrical maximum in the sphenoidal electrodes. B) Ictal EEG revealed right frontal onset, maximum at F8, Fp2, and F4 respectively, with spread to the right and subsequently the left hemisphere.
right orbito-frontal lobe within the meningoencephalocoele; this was confirmed through subsequent histology. Prolonged video-EEG monitoring, which captured habitual seizures, suggested a right frontal ictal onset zone concordant with the imaging findings. We postulate that the mechanism of epileptogenicity in this patient lay in an irritative, traction effect on orbitofrontal cortical tissue as it prolapsed through the bony defect into the upper nasal cavity. Additionally the neurons within the resected tissue appeared haphazardly arranged, without consistent orientation or discernable lamination. Although individual cells did not show significant dysmorphism and no ballooned cells were
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present, an element of dysplasia either secondary to the encephalocele or as part of the congenital abnormality, cannot be ruled out. What is remarkable about this case is the prolonged, terminal seizure freedom that occurred following trans-nasal endoscopic excision of the prolapsed cortex with the rest of the meningoencephalocoele. It is likely that the patient would otherwise have required craniotomy and possibly prolonged intracranial EEG monitoring in order to delineate the epileptogenic zone and guide resection. Having been seizure free for over two years, it is unlikely that this outcome is simply chance or part of the variability within the natural history of an individual’s epilepsy.
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A
B
c
D
Figure 3. A) Histology of the resected specimen revealed central nervous tissue (which appears beige in this haematoxylin/van Gieson-stained section). The specimen was partly covered by respiratory epithelium (arrow). Towards the epithelial surface, the central nervous tissue was partly subdivided by fibrocollagenous septa, which are stained magenta. B) High magnification showed many neurons (arrows) within the central nervous tissue. C) Immunohistochemistry for glial fibrillary acidic protein highlighted a meshwork of astrocytic processes (brown reaction product). The neurons (arrows) were not labelled. D) Immunohistochemistry for MHC class II antigen revealed scattered activated microglia (brown reaction product) between the unlabelled neurons (arrows), astrocytes and oligodendrocytes.
This case is illustrative of the fact that a multi-disciplinary approach involving the epileptologist, the epilepsy surgeon and the ENT surgeon can result in an effective solution for a refractory problem which minimises treatment morbidity. Although rare, meningoencephaloceles are described in 33 previously reported cases in the literature (table 1). Of those cases where the data was reported: 82% were congenital, presentation was typically in middle age (mean age 34) and 78% were female. The female preponderance is seen with encephalocele of all types and may be genetic in origin. The remaining 18% were due to trauma, post-operative complications, neoplasms and osteopetrosis. The location of encephaloceles associated with seizures is variable; 45% temporal, 23% occipital, 29% frontal (including 13% nasal) and 3% parietal. Associated cranial abnormalities are reported in only 15% of cases. These
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include band heterotopia, nodular heterotopia, diffuse cortical dysplasia and schizencephaly. The fact that the majority of cases show no other pathology strongly suggests that the encephalocele alone can act as an epileptic focus. Further evidence for the encephalocele as the epileptic focus comes from the high levels of concordance with EEG localisation; 81% of cases showed EEG localisation to the site of the encephalocele. Of the remaining cases, one had a normal EEG and three had non-specific diffuse EEG abnormalities associated with other developmental structural pathology including cortical dysplasia and heterotopia. In 18 cases surgical treatment strategies were reported. In total, 56% underwent local excision of the encephalocele contents and 44% underwent a wider excision with a lobectomy. Of the surgically managed encephaloceles,
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33% were extra-temporal, of which 100% were managed with local excision of the encephalocele contents, and 67% were temporal. In contrast to other locations however, 67% of the temporal lobe encephaloceles were treated with lobectomy versus only 33% with local excision of the encephalocele contents. This may reflect a familiarity with temporal lobe resection. Post-operatively, there was no difference in the seizure freedom rates between those patients who underwent a lobectomy and those who underwent a local excision of encephalocele contents. Of the 17 cases with post-operative data on seizure frequency and outcome, 100% were seizure free. Those who underwent a local excision thus had equal rates of seizure freedom to those who underwent more extensive resections, irrespective of the location of the encephalocele. The similar rate of seizure freedom suggests that wide resections may not be required in this situation. The current case, with a minimally invasive local excision via a nasal endoscopic approach, furthers this argument. Figure 4. Post-operative 1.5T MRI scans with coronal STIR sequences showed resection of the meningoencephalocele.
Table 1. Reported cases of meningoencephalocele associated with epileptic seizures. Authors
Age, sex Location of encephalocele
Additional Congenital cranial or acquired abnormalities
Type of epilepsy
EEG
Treatment
Histology
Outcome
Ruiz García, 1971
30, female
Left temporal
n/a
Congenital
Complex partial left temporal
Left temporal
Temporal lobe resection
Seizure free
Hyson et al., 1984
40, female
n/a
Acquired post ENT procedure
Complex Bitemporal partial interictal foci temporal lobe
Temporal lobe resection
Seizure free
Andermann et al., 1985
34, female
n/a
Congenital
Bilateral temporal
Bilateral temporal
n/a
38, female
n/a
Congenital
Complex partial right temporal
Normal neuronal tissue
Seizure free
Elster and Branch, 1989 Scully et al., 1989
27, female 63, female
n/a
Congenital
n/a
n/a
n/a
Left frontal
n/a
Congenital
Complex partial GTCS
Right temporal at depth recordings n/a
Resection of encephaloceles Anterior temporal lobe resection
n/a
Rosenbaum et al., 1985
Right temporal lobe into external auditory canal Bilateral temporal and frontal Right temporal multiple (30) small Temporal
Encephalocele with gliosis and fibrosis n/a
Gliosis
Seizure free (4 months)
Whiting et al., 1990
18, female
Right temporal lobe encephalocele Right temporal
n/a
Congenital
Complex Right frontopartial right temporal temporal lobe
Resection of encephalocele Anterior temporal lobe resection
Meningioangiomatosis
Seizure free
n/a
Congenital
Complex partial right temporal Complex partial
Right temporal
Normal neuronal tissue Gliosis
Seizure free
Complex partial
Right temporal
Anterior temporal lobe resection Resection of encephalocele Anterior temporal lobectomy
Gliosis
Seizure free
30, female Leblanc et al., 37, 1991 female
Left temporal
n/a
Congenital
Wilkins et al., 36, 1993 female
Right temporal
n/a
Congenital
n/a
Left temporal
Seizure free
(continued)
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Table 1. Reported cases of meningoencephalocele associated with epileptic (continued). Authors
Age, sex Location of encephalocele
Mulcahy et al., 1997
25, female
Additional Congenital cranial or acquired abnormalities
Type of epilepsy
EEG
Treatment
Histology
Outcome
Left anterior n/a temporal pole encephalocele
Congenital
Simple partial Left temporal Left temporal lobe focus seizures
Resection n/a of encephalocele
Symptom free
Guettat et al., 32, 1998 female
Right frontoethmoidal
Acquired post ENT operation
Complex partial
Right frontotemporal
n/a
n/a
n/a
Morioka et al., 2000
Occipital encephalocele with Congenital left frontal Schizencephaly and Subcortical heterotopia
Complex partial
Bifrontal slow wave
n/a
n/a
n/a
32, male Occipital encephalocele with Congenital diffuse cortical dysplasia
GTCS
Diffuse slow wave
n/a
n/a
n/a
46, male Bitemporal
Congenital
Complex partial temporal
n/a
Resection Inflamed of encephalo- neuroglia cele
Seizure free
Normal
Medical
Seizure free
Yang et al., 2004
26, female
n/a
n/a
Eichler et al., 55, 2005 female
Right frontal n/a nasal encephalocele
Acquired traumatic RTA
GTCS
Fountas et al., 2005
Right Parietal encepalocele
Congenital
Simple motor n/a seizures and GTCS
12, male Right n/a temporal lobe into external auditory canal
Acquired due to neoplasm
Complex partial temporal and GTCS
Right Temporal temporal lobe lobe on depth resection electrodes
Astrocytoma and oligodendrocytoma
Seizure free
37, female
Left temporal n/a lobe into external auditory canal
Congenital
Complex partial temporal
Left temporal Temporal lobe on depth lobe electrodes resection
Gliosis
Seizure free
Rojas et al., 2006
1 week old, female
Left fronto-ethmoidal encephalocele with nodular heterotopia
Congenital
Complex partial left frontaltemporal
Left temporal focus
Repair at day 10
n/a
Unclear
Bui et al., 2007
n/a
1 x frontal
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
5 x occipital
n/a
n/a
n/a
n/a
n/a
n/a
n/a
36, male Left temporal
n/a
Congenital
GTCS
Left posterior frontotemporal
Resection of encephalocele
Gliosis
Seizure free
26, male Left temporal
n/a
Congenital
Complex partial
Left temporal
Resection of encephalocele
Gliosis
Seizure free
Mandl et al., 2007
43, female
Bilateral frontal nasal
n/a
Acquired osteopetrosis
Complex partial
Right temporal
Resection of Brain tissue encephalocele
Seizure free
Melbournechambers et al., 2007
1 week old, female
Left nasoethmoidal encephalocele with band heterotopia
Congenital
Complex partial left frontal
n/a
Medication
n/a
RIP
GTCS
Diffuse slow wave
n/a
n/a
n/a
61, female
n/a
32, male Occipital encephalocele with Congenital cortical dysplasia
Normal brain tissue
Resection Gliotic/ 2 yrs of encephalo- oedematous Seizure free cele cerebral cortex
Morley and 48, Kolson, 2008 female
Right frontal nasal
n/a
Congenital
Complex partial
Bifrontal
n/a
n/a
n/a
Vargas et al., 45, 2008 female
Right temporal
n/a
Congenital
Complex partial
Right temporal
n/a
n/a
n/a
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Conclusion The association between meningoencephaloceles and epileptic seizures is well reported in the literature. Surgical management of such encephaloceles has also been widely reported to result in seizure freedom. The optimum surgical technique will depend upon the specific circumstances. However, our data suggest that limited resection of the encephalocele contents alone may be sufficient for the management of the associated seizures. The present case, utilising minimally invasive endoscopic surgical techniques, provides a novel technique for epilepsy surgery.
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Disclosure. None of the authors has any conflict of interest to disclose.
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