Global and intertuberal epileptic networks in tuberous sclerosis based on stereoelectroencephalographic (sEEG) findings: a quantitative EEG analysis in pediatric subjects and surgical implications.

OBJECTIVE: Recent evidence favors a network concept in tuberous sclerosis (TSC) with seizure generation and propagation related to changes in global and regional connectivity between multiple, anatomically distant tubers. Direct exploration of network dynamics in TSC has been made possible through intracranial sampling with stereoelectroencephalography (sEEG). The objective of this study is to define epileptic networks in TSC using quantitative analysis of sEEG recordings. We also discuss the impact of the definition of these epileptic networks on surgical decision-making. METHODS: Intracranial sEEG recordings were obtained from four pediatric patients who presented with medically refractory epilepsy secondary to TSC and subjected to quantitative signal analysis methods. Cortical connectivity was quantified by calculating pairwise coherence between all contacts and constructing an association matrix. The global coherence, defined as the ratio of the largest eigenvalue to the sum of all the eigenvalues, was calculated for each frequency band (delta, theta, alpha, beta, gamma). Spatial distribution of the connectivity was identified by plotting the leading principal component (product of the largest eigenvalue and its corresponding eigenvector). RESULTS: Four pediatric subjects with TSC underwent invasive intracranial monitoring with sEEG, comprising 31 depth electrodes and 250 contacts, for localization of the epileptogenic focus and guidance of subsequent surgical intervention. Quantitative connectivity analysis revealed a change in global coherence during the ictal period in the beta/low gamma (14-30 Hz) and high gamma (31-80 Hz) bands. Our results corroborate findings from existing literature, which implicate higher frequencies as a driver of synchrony and desynchrony. CONCLUSIONS: Coordinated high-frequency activity in the beta/low gamma and high gamma bands among spatially distant sEEG define the ictal period in TSC. This time-dependent change in global coherence demonstrates evidence for intra-tuberal and inter-tuberal connectivity in TSC. This observation has surgical implications. It suggests that targeting multiple tubers has a higher chance of seizure control as there is a higher chance of disrupting the epileptic network. The use of laser interstitial thermal therapy (LITT) allowed us to target multiple disparately located tubers in a minimally invasive manner with good seizure control outcomes.

Pattern, management and outcome of cervical spine injuries associated with head injuries in paediatric patients.

INTRODUCTION: This study examines the management and outcome of cervical spine injuries in children with head injuries, to assess the need for surgical treatment. MATERIAL AND METHODS: We performed a retrospective analysis (1995-2005) of 445 children admitted intubated and ventilated to the intensive care unit with head injuries. OUTCOME MEASURES: Frankel grade for spinal injuries and Glasgow Outcome Scale (GOS) for head injuries. RESULTS: Cervical spine injuries were detected in 11 patients (incidence 2.5%, mean age: 6.3 years, range: 21 months-15 years). The injuries were: C1/2 distraction: 2; C1/2 subluxation: 2; odontoid peg fracture with C1/2 dislocation and cord transection: 1; disruption of posterior longitudinal ligament at C2: 1; odontoid peg fracture with C2/3 distraction: 1; C2/3 subluxation: 1; C3 lamina fracture: 1; C3/4 facet fracture: 1; C6/7 fracture dislocation with cord transection: 1. One patient was managed operatively, ten patients nonoperatively, two with halo vests and eight with hard collars. There were three deaths (mortality 27%) associated with severe head injuries. At 6 months follow-up, two patients remained quadriplegic (Frankel Grade A), one of them ventilator dependent, one had residual motor function but of no practical use (Frankel Grade C), five had good spinal outcome (Frankel Grade E). Seven patients had good head injury outcomes (GOS 5), one remained disabled (GOS 3). CONCLUSION: Most children with cervical injury can be managed nonoperatively with good outcomes. Surgical management may be necessary in severe unstable injuries.

Lumbar canal stenosis presenting with acute bilateral foot drop.

We present a case of bilateral foot drop of acute onset related to lumbar canal stenosis in the absence of an acute disc prolapse, either on imaging or at surgery. The clinical and radiological findings in this case are discussed. Possible mechanisms for this occurrence are discussed and the relevant literature is reviewed.

Meningioma presenting with transient ischaemic attacks.

A case of sphenoid wing meningioma mimicking the presentation of a transient ischaemic attack (TIA) is described. Based on findings from neuroimaging in this case, possible explanations of the mechanism of this uncommon presentation of meningiomas are discussed and the literature is reviewed.