Deep Brain Stimulation to Treat Drug-Resistant Epilepsy in 7-year-old
Epilepsy is a common neurological problem in India. However, with advancements in investigations and medicines, the disease is manageable in majority of the cases. About two-thirds of all epilepsy patients exhibit good control over symptoms and disease progression with medication. However, the remaining one-third continue to experience seizures despite medication, and come under the category of patients with drug-resistant epilepsy.
Management of drug-resistant epilepsy requires a comprehensive workup, including a special epilepsy protocol involving use of magnetic resonance imaging (MRI) and video electroencephalography (EEG) of the brain to identify the root cause. If a clear focal point is found in the brain, which is responsible for these seizures, an epilepsy surgery can be done offering excellent outcome at centres with experienced surgeons. But, in some patients, no such foci are found despite extensive workup, including MRI, video EEG or positron emission tomography (PET) scan, etc. However, satisfactory improvement can be achieved in such patients with the use of stimulation techniques including Deep Brain Stimulation (DBS) and Vagal Nerve Stimulation (VNS). Here, we discuss the case of a young girl with recurrent seizures since childhood.
Case Study
A 7-year-old girl presented at Medanta - Gurugram with a history of recurrent seizures since 10 months of age. All her seizures were grand mal seizures – involving loss of consciousness and violent muscle contractions lasting for 2-3 minutes followed by prolonged confusion in the recovery phase. Her seizures were frequent, with one to two episodes being reported in a week. The patient was born after a full-term, normal delivery with age-appropriate developmental milestones. She did not have a history of head injury or any family history of epilepsy. The patient was on multiple anti-epileptic drugs without significant improvement in her condition.
The patient was worked up in detail for drug-resistant epilepsy using clinical assessment followed by MR imaging and video EEG. Using video EEG, her seizures were recorded and correlated with EEG changes at the time. This helped in diagnosing the type of epilepsy she suffered from. However, we could not establish a single focal point of origin, and multiple areas showed abnormal firing or spikes.
Her MRI brain epilepsy protocol was done, and it only showed diffused brain atrophy in view of non-localization of epilepsy. PET-CT brain was also done which showed diffused hypometabolism in bilateral temporal, parietal and left occipital lobes. Overall, the MRI and PET scan indicated that the brain was significantly abnormal at multiple points.
No clear seizure foci could be found indicating diffused brain changes and hence epilepsy surgery to remove such foci was not feasible. Such cases of diffused brain damage with drug-resistant epilepsy pose significant challenge for the treating neurologists. They remain a major cause of morbidity for majority of the population suffering from epilepsy.
Earlier done for managing movement disorders, DBS is now being done for intractable drug-resistant epilepsy targeting various cortical and subcortical structures. For the procedure, very thin electrodes are placed deep in the brain to stimulate certain parts. But electrode placement in cases of childhood epilepsy can be challenging as the targeted area is ventral thalamus – a crucial area of the brain surrounded by numerous critical nuclei and white matter tracts in addition to ventricles. Even the smallest error in the trajectory can cause significant morbidity, besides leading to sub-optimal outcomes.
Our patient underwent DBS targeting bilateral thalami. To control the seizure frequency, two trajectories were planned - tranventricular and subcaudate paraventricular. Target was the anterior nucleus of the thalamus (ANT). The anterior nucleus of the thalamus is used as target for limbic seizure disruption. It is around 4x10x5.5 mm in size and located at the floor of the lateral ventricles surrounded by the choroid plexus, thalamostriate vein and the internal cerebral veins. In our case, we used the right side tranventricular trajectory to hit the sweet spot, and for the left side we used paraventricular trajectories as shown in the images.
After careful planning and submillimeter checks, the electrodes were placed in the brain by tranventricular and subcaudate trajectories under neuro-navigation guidance. The surgery was uneventful with good clinical outcome. In the post-operative period, the patient regained consciousness on the same day. She was shifted to room on Day 1 of surgery and was discharged on Day 3 in stable condition. During her post-operative hospital stay, she did not have any seizures. On her one-month post-operative follow up as well, the child was doing well and did not report having any major seizures. Initial results for DBS in epilepsy treatment were promising in this case and we expect it to offer good control of seizures in the long run.
DBS has emerged as a safe and effective treatment modality for the management of drug-resistant epilepsy non-amenable by surgery showing excellent results.
Medanta-Gurugram is pioneer in DBS surgery for epilepsy in India and has done four such procedures after extensive patient evaluation for optimal outcome.
