A meta-analysis was conducted to explore the effectiveness of DBS in patients with refractory epilepsy. The analysis included studies that examined the use of DBS for treating these patients. In this analysis, a successful outcome was defined as a reduction of 50% or more in the frequency of seizures.
In the initial analyses of all the studies, we observed moderate heterogeneity, indicating significant differences among the included studies. These variations could be attributed to differences in study design, study populations, and intervention protocols. The studies mainly focused on three regions: the anterior nucleus thalamic, centromedial, and hypothalamus. There was a high degree of variability in the stimulation parameters utilized across the studies, highlighting the need for further investigation into the optimal parameters for stimulation. The analyses on stimulation parameters indicate that both the voltage and frequency of stimulation, as well as the type of stimulation (intermittent vs. continuous), significantly impact the success rates of the interventions. This suggests that carefully selecting the voltage, frequency, and type of stimulation can play a crucial role in the effectiveness of interventions.
The results emphasize the need to customize stimulation parameters to improve the effectiveness of interventions. A deeper understanding of predictors of seizure outcomes can assist neurosurgeons in identifying which surgery candidates are more likely to experience improvement, enabling them to provide appropriate guidance to patients and their families (56).
Despite the higher number of studies on ANT, our analysis shows that HP and CM result in a reduction in more patients. The hippocampus is an essential part of the Papez circuit, which begins with the hippocampus sending signals through the fornix to the mammillary bodies. These bodies then send signals through the mammillothalamic tract to ATN, which in turn project to the anterior cingulate cortex. Finally, the anterior cingulate cortex sends signals back to the hippocampus, completing the circuit (57, 58).
The potential antiepileptic effects of DBS may stem from the long-term modulation of important neural circuits (59). Modulating DBS could lead to significant changes within the neural networks, disrupting seizure propagation or modifying the seizure threshold (60).
In summary, this meta-analysis highlights the effectiveness of DBS in treating patients with refractory epilepsy. It shows significant success rates with a 50% or greater reduction in seizure frequency. The observed moderate heterogeneity suggests variations across studies due to differences in design, populations, and intervention protocols. Notably, the effectiveness of DBS is significantly influenced by stimulation parameters such as voltage, frequency, and type. These findings emphasize the need to customize these parameters to optimize patient outcomes and underscore the potential of DBS to modulate neural circuits, thereby improving seizure control. Understanding predictors of seizure outcomes can help neurosurgeons in selecting suitable candidates for DBS and ultimately improve patient care. While there is a greater focus on the ANT region, analyses reveal that the HP and CM regions are more effective in reducing seizures, indicating a need for further exploration of the mechanisms and optimal stimulation protocols within these regions.
Limitations
The systematic review on the characterization of clinical presentation and etiology of seizures reported several limitations that should be taken into consideration. Firstly, the review only included studies published in English, which might have led to the exclusion of relevant non-English studies, potentially introducing language bias. Additionally, the review highlighted the influence of large relative sample sizes of pivotal trials compared to other included studies, which could have skewed the overall findings and conclusions. Furthermore, the inclusion of observational, nonrandomized, and retrospective studies in the review may have reduced the reliability of the results, as these types of studies are prone to various biases and confounding factors. Another limitation was the clinical heterogeneity of the patients both between and within the groups, as factors such as patient age, baseline seizure frequency, duration of epilepsy, antiseizure medication (ASM) usage, and medical history were not consistently controlled for across the included studies. This lack of control for inter-study heterogeneity may have affected the generalizability and reliability of the review's findings. Overall, while the systematic review provides valuable insights, it is important to interpret its results with caution due to these identified limitations.