*Tuan Dang anh, *Thang Le nam
*Neurology Department, National Hospital of Pediatrics, Hanoi, Vietnam
ABSTRACT
Purpose: To describe some clinical manifestations and some characteristics of the epileptogenic lesion in twelve children suffering from drug-resistant localization-related epilepsy. To retrospectively analyze the post-operative seizure outcome among these twelve patients, based upon Engel classification system.
Methods: Twelve patients (6 male, 6 female), younger than 18 years, operated on from 2010 to 2012 and followed-up for at least 6 months were identified at National Hospital of Pediatrics. Individualized microsurgical resections, aimed at removal of the epileptogenic lesion, were performed as indicated by the results of presurgical evaluations, which included video-electroencephalographic monitoring, specialized MR Imaging and PETCT scan when needed.
Results: Twelve children with drug-resistant localization-related epilepsy have been treated surgically at National Hospital of Pediatrics over a two-year period (2010-2012). Sex ratio: 1/1. Mean age at surgery: 6.875 years. Mean duration before surgery: 3.79 years. Mean age at seizure onset: 3.03 years. Seizure semeiology: simple partial seizure: 33.3% (4/12), partial seizure with 2nd generalization: 33.3% (4/12), generalized seizure: 25% (3/12) and complex partial seizure: 8.3% (1/12). EEG abnormalities were ipsilateral to the epileptogenic lesion in 58.3% of cases (7/12), contralateral in 8.3% (1/12) and bilateral in 33. 3% (4/12). Anatomically, temporal lobe involvement accounted for 58.3% of cases (7/12), extra-temporal lobe and multi-lobar involvements accounted for the remaining 41.6% (5/12). Histopathologically, FCD: 41.6% (5/12), low-grade tumors: 25% (3/12), hippocampal sclerosis: 8.3% (1/12), Rasmussen syndrome 16.6% (2/12) and unremarkable: 8.3% (1/12).
At post-operative follow-up, 8 patients (66.67%) were in Engel’s class I. Temporal lobe group had the best post-operative seizure outcome (with 71.4% of cases had Engel class IA and 28.6% had Engel class IID). Hemimegalencephaly had the worst post-operative seizure outcome (with 100% of cases had Engel class IVB and class IVC).
Conclusion: Drug-resistant localization-related epilepsy in children could be cured successfully by resective surgery in the majority of cases.
Keywords: Drug-resistant localization-related epilepsy in children, epileptogenic lesion, epilepsy surgery, post-operative seizure outcome.
INTRODUCTION
National hospital of Pediatrics (NHP), a central hospital located in Hanoi, Vietnam, is a busy referral centre for children with all kind of diseases, including epilepsy.
Epilepsy surgery at NHP began in 2010 with the first patient being a 16-year-old girl suffering from left-sided hippocampal sclerosis. For this patient, a left-sided anterior temporal lobectomy was done, which resulted in complete seizure-freedom, without any complication. Since then, under the condition of limited resources, there have been a total of 12 children who received surgical treatment till November 2012. Post-operatively, cessation or reduction of seizures was achieved in 83.3% of these patients. In term of epilepsy surgery for pediatric population, our series is the largest one throughout the country.
The preliminary result of this surgical treatment is reported herein.
PATIENTS AND METHOD
By retrospectively reviewing medical records of 12 patients with drug-resistant localization-related epilepsy, younger than 18 years, operated on at Neurology Department, National Hospital of Pediatrics, from 2010 to 2012 with a post-operative follow-up of at least 6 months.
Presurgical investigations
A comprehensive presurgical work-up included: (1) history to find out the age at seizure onset, type and frequency of seizures; (2) neurological examination and, when feasible, neuropsychological testing; (3) interictal scalp electroencephalography (EEG) and, when needed, prolonged video-EEG monitoring; (4) 1.5-tesla magnetic resonance imaging (MRI) of brain with appropriate protocols; (5) digital substraction angiography of brain (Philips DICOM Viewer) and finally (6) positron emission tomography (PET) in few selected patients.
Surgery
All the patients received tailored microsurgical resections aimed at removal of the epileptogenic lesion (EL), as defined by anatomo-electro-clinical data. MRI-based Stryker Neuronavigation system was used in all operations.
Histology
Surgical specimens were routinely processed for histological determinations. For histopathological categorization, the revised WHO classification for tumors of the central nervous system and a recent classification of focal cortical dysplasias (FCD) were employed (8), (9), (12).
Post-operative seizure outcome
Post-operative seizure outcome was assessed by using the Engel classification system (10), (11), (13).
RESULTS
Table 1. Patient summary
Pt. | Age at surgery/Sex | Age at seizure onset | Duration before surgery | Clinical Semeiology | EEG AbN. |
1 | 16 years/ female | 4 years | 12 years | Complex partial seizure | Ipsilateral |
2 | 12 years/male | 8 years | 4 years | Partial seizures with 2nd generalization | Ipsilateral |
3 | 2 1/2 years/male | 6 months | 2 years | Partial seizures with 2nd generalization | Ipsilateral |
4 | 4 years/female | 2 years 6 months | 18 months | Partial seizures | Contralateral |
5 | 16 years/ female | 13 years | 3 years | Partial seizures with 2nd generalization | Ipsilateral |
6 | 7 years/male | 4 years | 3 years | Partial seizures with 2nd generalization | Bilateral |
7 | 1 year/male | 3 months | 10 months | Partial seizures | Ipsilateral |
8 | 1 1/2/years female | 6 months | 12 months | Partial seizures | Bilateral |
9 | 9 years/female | 1 month | 9 years | Tonic seizures with head nods | Ipsilateral |
10 | 7 years/male | 1 years | 6 years | West Sd. then generalized seizures with head nods | Bilateral |
11 | 4 years/male | 2 years | 2 years | Partial seizures with 2nd generalization | Ipsilateral |
12 | 3 years/female | 8 months | 2 years | West Sd. then atonic seizures with head nods | Bilateral |
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Abbreviation: 2nd: secondary, AbN.: Abnormalities, Pt.: patient, Sd.: syndrome
Table 2. Patient summary (con’t)
Pt. | Location of epileptogenic lesion | Surgical procedures | Histopath. | Post.Op Sz. outcome (Engel class) | Post.Op Compl. | F/u duration |
1 | L. hippocampus | ATL-AH | Hippocampal sclerosis | IA | (-) | 31 months |
2 | L. anterior mesial temporal * | ATL-AH | DNET | IA | (-) | 27 months |
3 | L. enlarged hemisphere (HME) | Partial frontal lobectomy | FCD II B | IVB | (-) | 19 months |
4 | L. atrophied multilobar | Anatomical hemispherectomy | Rasmussen Sd. | IA | (-) | 18 months |
5 | L. mesial temporal | ATL-AH | Low-grade astrocytoma | IID | (-) | 17 months |
6 | R. lateral temporal | Partial temporal lobectomy | Ganglioglioma | IA | (-) | 17 months |
7 | R. mesial temporal | ATL-AH | Unidentified | IID | (-) | 16 months |
8 | R. enlarged hemisphere (HME) * | Anatomical hemispherectomy | FCD II B | IVC | Massive ICH | Deep coma |
9 | R. upper mesial frontal * | Partial frontal lobectomy | FCD IIA | IA | (-) | 14 months |
10 | R. lower mesial temporal | ATL-AH | FCD IIA | IA | PCA infarction | 9 months |
11 | R. atrophied multilobar | Anatomical hemispherectomy | Rasmussen Sd. | IA | (-) | 6 months |
12 | L. lower mesial temporal | ATL-AH | FCD IIA | IA | (-) | 6 months |
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Abbreviation:*: patients who had both MRIAnd PET done, ATL-AH: Anterior temporal lobectomy and amygdalohippocampectomy, Compl. complication, DNET dysembryoplastic neuroepithelial tumor, EL epileptogenic lesion, FCD focal cortical dysplasia, F/u: follow-up, ME: hemimegalencephaly, Histopath. Histopathology, ICH: intracranial hemorrhage, L. left, Post.Op: post-operative, PCA: posterior cerebral artery, R.: right, Sz.: seizure
During a 26-month period, from October 2010 to November 2012, there were 6 boys and 6 girls with the range of ages from 13 months to 16 years (mean age at surgery: 6.875 years) received surgical treatment. Table 1 and table 2 list some basic data of each patient. All of these patients had drug-resistant localization-related epilepsy. The mean duration from age at seizure onset to age at surgery (i.e. mean duration before surgery) was 3.79 years, ranging from 10 months to 12 years.
In term of clinical semeiology: the most common seizure types were simple partial seizures (4/12 patients or 33.3%) and partial seizure with 2nd generalization (4/12 or 33.3%), followed by generalized seizure (3/12 or 25%) and complex partial seizure (1/12 or 8.3%).
EEG abnormalities were ipsilateral to the epileptogenic lesion in 58.3% of cases (7/12), bilateral in 33.3% (4/12) and even contralateral (false lateralisation) in 8.3% (1/12).
Laterality of epileptogenic lesion: 6 were on the left hemisphere and remaining 6 were on the right hemisphere.
Anatomically, temporal lobe involvement accounted for 58.3% of cases (7/12), extra-temporal lobe and multi-lobar involvements accounted for the remaining 41.6% (5/12).
At time of pre-surgical work-up, 10/12 (83.3%) patients were taking combination therapy with at least 2 antiepileptic drugs together.
The surgical procedures are shown in table 2 with anterior temporal lobectomy and amygdalohippocampectomy (ATL-AH) being the most common procedure performed (6/12 or 50%).
Histopathological findings consisted of FCD in 5/12 patients (41.6%), low-grade tumors in 3/12 (25%), Rasmussen syndrome in 2/12 (16.6%), hippocampal sclerosis in 1/12 (8.3%), and unremarkable in 1/12 (8.3%).
Duration of post-operative follow-up ranged from 6 months to 27 months. And post-operative seizure outcome is presented in table 2.
DISCUSSION
Diagnostic issue
All of our patients had drug-resistant localization-related epilepsy with epileptogenic lesion localized in one hemisphere.
Remarkably, among our series, there were 3 patients who were labeled as generalized epilepsy longtime before being identified as eligible surgical candidates. Particularly, 2 of these patients was diagnosed as having West syndrome at first, then their seizures evolved into “generalized” seizures with head nods. After the epileptogenic lesion was removed from right-sided temporal lobe (patient 10) and from left-sided temporal lobe (patient 12), these patients became seizure-free, completely (Engel class IA). Indeed, this reflected the nature of these patients’ seizures as localization-related, instead of “generalized” epilepsy. West syndrome, although formally classified as generalized epilepsy, could be due to a focal epileptogenic lesion (mostly FCD). This finding has been well documented by various authors (1), (4), (5).
The third patient (patient 9), a 9-year-old girl, whose “generalized” seizures consisted of head nods with two arms raising & then stiffening of body. After her epileptogenic lesion (FCD IIA) was removed from upper mesial part of the right-sided frontal lobe, there were no more seizures (Engel class IA).
Post-operative seizure outcome
Cessation or reduction of seizures was achieved in 83.3% of our patients as the whole group. Nevertheless, the figure varied greatly depending on the extent of epileptogenic lesion.
The most common subgroup in our series, temporal lobe epilepsy, had the best outcome (71.4% of patients had Engel class IA and 28.6% had Engel class IID). This excellent outcome is in line with many authors reporting temporal lobe epilepsy surgery in medical literature (2), (3), (7), (10), (11), (12), (13).
Meanwhile, subgroup with hemimegalencephaly (HME), the most severe form of FCD (6), had the worst post-operative seizure outcome (1 patient had Engel class IVB and the other had Engel class IVC), although there were only 2 patients with HME in our series. The poor seizure outcome there could be explained by the underlying widespread epileptogenic lesion in HME patients, and also partly by our limited experience in doing surgery for this complex condition.
Although our series is small in number, this demonstrates that surgery is really a very valuable treatment option for patients suffering from drug-resistant localization-related epilepsy, especially temporal lobe epilepsy.
However, to improving substantially the epilepsy surgery, there are much work to do, i.e., the development of presurgical invasive EEG and also intraoperative electrocorticography, since these highly specialized explorations are still not available at our hospital.
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