Predicting hand function after hemispherotomy: TMS versus fMRI in hemispheric polymicrogyria

Patients with hemispheric malformations of cortical development (such as polymicrogyria) often develop medically intractable epilepsies for which hemispherotomy can be an excellent treatment option. Transcranial magnetic stimulation (TMS) and functional magnetic resonance imaging (fMRI) are noninvasive methods used to evaluate the sensorimotor system in adults and children before surgery. Preoperative results of both methods and their predictive values regarding hand function after hemispherotomy are described in four boys with hemispheric polymicrogyria, pharmacoresistent epilepsy, and hemiparesis with preserved grasp function of the paretic hand. TMS showing ipsilateral projections from the contralesional hemisphere but no evidence of crossed corticospinal projections from the lesioned hemisphere correctly predicted preserved postoperative grasp function in all four patients. In contrast, the interpretation of sensorimotor fMRI in patients with congenital hemiparesis is more difficult, as ipsilesional activation can occur as it was the case in three of four patients in the current study. This activation might represent contralaterally preserved primary somatosensory (S1) and not primary motor (M1) representation and is apparently not necessary for the paretic hand to still perform grasp movements.

Long-term use of zonisamide in refractory childhood-onset epilepsy

This open label study examined the long-term efficacy and safety of zonisamide as adjunctive therapy in mentally retarded and multiple-handicapped patients with severe childhood-onset epilepsy. The study included 24 patients (mean age 12.5 years, range 2-40 years) which had different severe epilepsy syndromes (75% focal, 12.5% generalized, 12.5% refractory status epilepticus) refractory to at least 6 (median 10) anti-epileptic drugs. All patients were followed for at least 18 months after beginning of zonisamide treatment. Mean duration of zonisamide therapy was 55 weeks (range 5-168 weeks) and mean maintenance dosage was 7.7 mg/kg/day (range: 4-16 mg/kg/day). The patients received an average of 1.9 (range 1-3) concomitant antiepileptic drugs. The initial response rate defined as a > or =50% reduction of seizure frequency after 8 weeks was 58.3% (14 of 24 patients). Four of 14 initial responders developed loss of efficacy during long-term treatment. The retention rate after 18 months was 41.7% (10 of 24 patients). One patient (4.2%) became completely seizure-free after initiation of zonisamide treatment and remained seizure-free for the entire observation period of 18 months. Overall, zonisamide was well tolerated. Side effects were observed in 46% of patients and were mild to moderate. They mostly occurred during titration and subsided in maintenance dosing. Only in two patients (8.3%) zonisamide therapy was discontinued due to side effects (loss of appetite). No serious side effects were observed. These results are similar to the findings of Japanese studies suggesting that long-term use of adjunctive zonisamide therapy may be beneficial for treating mentally retarded, multiple handicapped patients with highly refractory childhood-onset epilepsy.

Identification of successful clinical fMRI sessions in children: an objective approach

PURPOSE

The term clinical functional magnetic resonance imaging (fMRI) describes an examination with direct clinical impact on the patient. Interpretation of clinical fMRI especially in children, however, is often difficult due to suboptimal data quality. The current gold standard is standardized visual evaluation. To evaluate such data in an automated and objective way, we developed an approach to identify successful sessions.

METHODS

Average activation inside a predefined, task-specific region of interest (ROI) is compared with average activation in the rest of the brain, and their ratio (classification factor [Fc]) is determined for different statistical thresholds (T). The approach was tested and validated using 239 clinical pediatric fMRI sessions (sensorimotor, perceptive /productive language). Performance was assessed in terms of sensitivity, specificity, and positive likelihood ratio.

RESULTS

Best performance was found for Fc ≥ 2 and T ≥ 2.5, achieving a sensitivity of 0.87 and specificity of 0.94. Comparing the different domains, sensitivity was lowest for language production tasks, mainly due to atypical activation foci.

CONCLUSION

We demonstrate that an objective, automated framework for the classification of clinical pediatric fMRI sessions may provide important additional information, supporting visual evaluation, especially from sensorimotor and language perception domains. In the current form, atypical or strong network activation is not easily captured.

Epileptiform discharges in the context of self-limited pediatric focal epilepsy (EDSelFEC) in pediatric hemispherotomy patients: Role of white matter abnormalities

OBJECTIVE

To investigate the frequency of epileptiform discharges associated with self-limited focal epilepsy (EDSelFEC) in children who have undergone a hemispherotomy and to evaluate whether patients with coexistence of EDSelFEC and structural hemispheric epilepsies differ from patients without coexistence of EDSelFEC and whether there are differences between the two groups with regard to preoperative management and postoperative outcome.

METHODS

Data on 131 children who underwent a hemispherotomy between January 1999 and January 2015 were retrieved from the Epilepsy center's epilepsy surgery database. Children with EDSelFEC were compared with children without EDSelFEC with respect to epileptogenic hemispheric pathology, family history, age at epilepsy onset, timing of surgery, lesion laterality, preoperative cognitive function, response to sodium channel blocker antiepileptic medication, and surgical outcome. Parental consent was obtained.

RESULTS

EDSelFECs were present in the EEG in 27 (21%) of the 131 cases. None of the patients had seizures associated with EDSelFECs. The percentages of EDSelFECs varied between pathology groups: vascular lesions: 38%, focal cortical dysplasia: 16%, polymicrogyria: 5%, Rasmussen encephalitis: 10%, hemimegalencephaly: 8%, mild malformation of cortical development with oligodendroglial hyperplasia:20%, other pathologies: 22%. EDSelFEC in the vascular group were significantly correlated with MRI changes showing white matter damage in addition to cortical damage (p =.02). 82.1% of EDSelFEC were located multifocal versus 4.8% multifocality in EDs other than EDSelFEC. EDSelFEC were significantly more often exacerbated by sodium channel blockers than EDs caused by structural (cortical) lesions. No differences were found between EDSelFEC+ and EDSelFEC- patients with respect to other variables studied.

SIGNIFICANCE

A significant number of children with hemispheric epileptogenic lesions, particularly children with pre-/perinatal vascular lesions, hemiplegia, and white matter lesions in addition to cortical lesions, presented with coexisting EDSelFEC.