Research & Development

Epilepsy Surgery

1. Cost Effectiveness

 Dr. Samuel Wiebe is conducting the world's first randomised control trial for the assessment of the impact of epilepsy surgery on health care costs. The components of this study have received praise from several international epileptologists.

2. Psychological Studies

 Dr. Paul Derry and co-workers found that patients with significant neuroticism cope less well with the process of in-patient evaluation for intractable epilepsy.

3. Mesial Occipital Epilepsy

 Dr. Samuel Wiebe and co-workers are describing the Epilepsy Unit's group of patients with mesial occipital epilepsy as a syndrome within the larger context of all occipital epilepsies.

4. Subdural Electroencephalography

 Dr. Warren Blume and co-workers are studying the findings and value of subdural electroencephalography as part of the presurgical investigation in intractable patients.

5. Neuroradiology

 Dr. Donald Lee has correlated neuroradiological appearances in the temporal lobe with neuropathological results supporting a strictly visual analysis of MRI in temporal lobe epilepsy patients.

 Dr. Ravi Menon and co-workers are commencing studies of the fMRI in temporal lobe and occipital lobe epilepsies.

Basic Mechanisms

1. Hippocampal Pathophysiology

 Dr. Stan Leung has found a paradoxical preservation of presynaptic GABA release in the kindling model. This is due to the down regulation of GABAB presynaptic receptors in this model. This resultant preservation of inhibition in the kindling model has been viewed as an attempt by the CA1 region at self preservation. (Others have found this effect in the granule cells).

2. Electrical Stimulation And Lesional Epileptogenesis

 Dr. Parbeen Pathak is exploring the relationship of epileptogenesis to epileptogenic lesions. Part of this involves examining after-discharge thresholds surrounding the epileptogenic lesion (Epilepsia (1997) 38 (abstract)).

3. Neuroscience Epilepsy Group

 This has been established with Drs. J.P. Cain, S. Leung, C. Naus, J. Parrent, and S. Brudzynski.

Clinical Research

1. Surgical Outcome In Patients With Normal Pathology

 Other projects at early stages include: analysis of surgical outcome in patients with normal pathology by Drs. G.R. Ganapathy and W.T. Blume.

2. Usefulness of Decadron in Reducing Peri-Operative Morbidity Following Subdural Electrode Insertion.

 Dr. Ramesh Sahjpaul is conducting a double blind placebo controlled randomized trial in patients with medically intractable epilepsy. If Decadron is found to reduce peri-operative morbidity an identical study will be conducted with patients undergoing craniotomy.

3. Intraoperative Speech Testing Paradigm

 Drs. C. Kubu and R. Sahjpaul have developed an extensive intraoperative speech testing paradigm to assist in dominant hemisphere resections and to further their understanding of cortical language localization to be implemented in January 1998.

Western Electrode Cortical Array

Description

Features

• All parts are medical grade stainless steel except the frame which is made from durable delrin.
• Additional recording electrodes can be plugged directly into array frame.
• Adjustable tension joints and spring electrodes provide a flexible and stable surface contact.
• Specially constructed universal joints give a wide range of electrode placement.
• Minimal obstruction of neurosurgical site.
• Stainless steel cage and removable tray protects array and makes it easy to handle during surgery.

For more information:
• Kent McNeill, LHSC

339 Windermere Rd.
London, Ontario, N6A 5A5
Bus (519)6633300 ext 5945
Fax (519)6633753

Electrode Fabrication

Tubular

Our tubular subdural electrodes are made of 100% biocompatible materials except for parts that are not implanted. Medical grade Silastic tubing is injected and sealed with Xray opaque Silastic elastomer. Contacts are made of 316 stainless steel rings. The signal is taken away from the contacts by means of 316 teflon coated annealed stainless steel wires.A concentric polyethylene tubing within the silastic structure provide means to insert a removable stainless steel guide wire, achieving dual flexibility for patient comfort. The electrode can accommodate up to seven contacts.

Paddle

We also produce a double sided paddle electrode. The materials used are the same as the tubular electrodes but a completely different structural design.Seven flat contacts are incorporated into each side of the electrode. The two sides are completely insulated from each other. This electrode is commonly used in our department to record ECOG from homologous mesial surfaces of each hemispheres.The paddle electrodes come in two different shapes: a slightly curved or a straight design.

Grid

We also manufacture grids with varying contact numbers. We have three types of grids. A standard flat shaped grid, a 3-D cup shaped grid to eliminate buckling at the edges in case of large contact numbers. The third type of grid does not contain spot welded stainless steel contacts as the other ones, but only looped stainless steel wires which act as contacts. The distance between contacts is usually lomm in all types of grids. Stimulation through the contacts is also possible.

Depth

Our depth electrodes are very similar in structure and shape to the tubular subdural electrodes. However, the tip consist of a stainless steel hollow "bullet", which is internally connected to a stainless steel tubing, which terminates in a Luer-lock connector. The system gives high rigidity and ability to inject dyes for marking the tip of the electrode. The depth electrode usually contains 4 contacts spaced lomm apart. We have a new depth electrode under development which is much thinner in diameter, have dual rigidity due to a guide wire and can be left in for chronic recordings of ECOG. Contact numbers can be up to 12 with varying spacing between O.lmm to lomm.

All of our electrodes come with the appropriate cables. These custom made cables have very high flexibility for patient comfort and safety. Since we are a small operation, we can custom make electrodes to patient and surgeons needs within our means. In most cases of electrodes we can vary contact spacings, electrode shapes and if the need arises , the materials the electrode is made oL The flexibility of tubular electrodes can be changed to suit the surgeons needs. Our new depth electrode under development will be stereotaxically implantable, dye markable and since it contains a concentric tubing within, tissue fluids can be withdrawn though it.

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Automated EEG Analysis

All this digital normative and epileptic EEG data allows us a great opportunity to analise and study EEG automatically. We continue to develop new techniques to facilitate recording, recognition and analysis. Some of the areas of interest are

• Frequency analysis of the EEG utilising a variety of analysis techniques to study the changes of EEG frequencies before, during and after epileptic seizures.
• Topographical mapping is used to better depict EEG analysis results using our own colour contour or 3D web mapping techniques from standard 10-20 and specialised electrode mapping configurations.
• Work is being done using MRI and CT information for spatial localisation of subdural electrodes and eventually applied to functional MRI imaging.
• Seizure/Spike Recognition in online recording and offline analysis will help to identify seizure activity. Many approaches of decomposition and evaluation , data elimination techniques such as artefact recognition and filtering, and the utilisation of neural networks.
• Seizure Analysis is hoped to help determine validity , onset localisation and spread. Aid neurologist in classifying seizures and determining seizure activation methods and involved areas for clinical workups and drug studies.
• We develop recording techniques for stimulation studies, OR and ICU monitoring , and longterm monitoring. etc

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