Thalamic Recordings in Children Undergoing SEEG (TRICS)

Stereoelectroencephalography (SEEG) forms a key part of the pre-surgical evaluation in children who may be candidates for epilepsy surgery. It can help delineate the location of the putative epileptogenic zone, guiding further treatments including resective, disconnective and ablative epilepsy surgery techniques. However, less than 35% of children undergoing SEEG end up becoming seizure free following further treatment.

Open and closed loop stimulation of thalamic nuclei via deep brain stimulation (DBS) and responsive neurostimulation (RNS) are emerging treatment options for epilepsy. Thalamic target nuclei vary between studies and there are currently no gold standard personalised methods for choosing a target. This stems from the limited systematic neurophysiological recordings from thalamic nuclei; investigators currently do not understand the ictal and interictal thalamic signatures of involvement in epilepsy and do not understand how functional connectivity can be altered within and between patients.

In this prospective study, the investigators aim to recruit 30 patients undergoing SEEG as part of their pre-surgical evaluation for drug resistant epilepsy at Great Ormond Street Hospital over a period of 3 years. Once recruited, the investigators will target 3 nuclei bilaterally in each patient - the anterior, centromedian and pulvinar nuclei - using additional SEEG electrodes. Following clinical recording, the investigators will conduct two stimulation experiments, the first using single pulse electrical stimulation to measure effective connectivity between the thalamus and cortical regions and the second to study the effects of simulated DBS currents on cortical local field potential signatures.

This study will lay the foundation for a personalised approach to thalamic neuromodulation for drug-resistant epilepsy by identifying neurophysiological biomarkers of thalamic involvement in epilepsy, paving the way for closed loop neuromodulation strategies that aim to optimise response using these biomarkers.

Study Overview

• Status: Recruiting
• Conditions: Focal Epilepsy
• Intervention / Treatment: Procedure: Additional electrodes into bilateral anterior, centromedian and pulvinar thalamic nuclei

• Study Type: Interventional
• Enrollment (Estimated): 30
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Aswin Chari, PhD; Phone Number: 07726780817; Email: aswin.chari.18@ucl.ac.uk
• Study Contact Backup: Name: Martin Tisdall, MD; Email: martin.tisdall@gosh.nhs.uk

Study Locations

• United Kingdom
  • London, United Kingdom, WC1N 3JH
    • Recruiting
    • Great Ormond Street Hospital for Children
    • Contact: Aswin Chari, PhD; Phone Number: 07726780817; Email: aswin.chari.18@ucl.ac.uk

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child; Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

1. All children undergoing SEEG as part of their pre-surgical evaluation at GOSH
2. Participants/parents/legal guardian provide informed consent for inclusion

Exclusion Criteria:

1) Lack of informed consent

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm

Intervention / Treatment

Experimental: Thalamic SEEG; The centromedian, anterior and pulvinar nuclei on each side will be chosen as target for new electrodes.

Procedure: Additional electrodes into bilateral anterior, centromedian and pulvinar thalamic nuclei; The centromedian, anterior and pulvinar nuclei on each side will be chosen as target for new electrodes; up to 6 additional electrodes may be added but, where possible, existing electrode trajectories will be extended to facilitate recording. At the beginning of the recording process, usually within the first 24-48 hours of implantation, we will conduct 2 study-specific stimulation experiments: Single pulse electrical stimulation (SPES):; N-of-1 trials of simulated DBS: We will simulate high (130Hz) and low (6Hz) frequency DBS currents from each pair of thalamic nuclei (always bilateral) and record spontaneous interictal neuronal activity in all other cortical contacts for 15 minutes. We will also record SPES from each of the cortical contacts.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Ictal thalamic involvement	Experienced neurophysiologists will assess, during ictal activity, whether each of the nuclei are involved in the seizure and, if so, the latency between first cortical contact onset and thalamic nucleus onset.	Hospital discharge (maximum one month from SEEG implantation)
Epileptogenicity index	We will quantify ictal involvement by measuring the epileptogenicity index in each nucleus.	Hospital discharge (maximum one month from SEEG implantation)
Interictal power distribution	To assess interictal signatures, we will assess power at different frequencies in the nuclei using the 'fitting oscillations & one over f' (FOOOF) method.	Hospital discharge (maximum one month from SEEG implantation)
Single pulse electrical stimulation (SPES):	We will systematically conduct SPES from all cortical and thalamic contacts and record responses in all other contacts. This measures the effective connectivity.	Hospital discharge (maximum one month from SEEG implantation)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Incidence of bleeding	Radiological evidence of bleeding or clinically new neurological symptoms during SEEG implantation	Hospital discharge (maximum one month from SEEG implantation)

Collaborators and Investigators

• Sponsor: Great Ormond Street Hospital for Children NHS Foundation Trust

Study record dates

Study Major Dates

• Study Start (Actual): September 1, 2025
• Primary Completion (Estimated): August 1, 2028
• Study Completion (Estimated): December 1, 2028

Study Registration Dates

• First Submitted: May 24, 2024
• First Submitted That Met QC Criteria: June 5, 2024
• First Posted (Actual): June 12, 2024

Study Record Updates

• Last Update Posted (Actual): February 2, 2026
• Last Update Submitted That Met QC Criteria: January 29, 2026
• Last Verified: January 1, 2026

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Brain Diseases; Central Nervous System Diseases; Nervous System Diseases; Epilepsy; Epilepsies, Partial
• Other Study ID Numbers: 23BI31

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED
• IPD Plan Description: IPD may not be allowed to be shared by our ethical approvals. We may make anonymised data available based on restrictions of ethical approvals.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No