Abstracts

Rationale: Understanding the trajectory of normal somatosensory development has important clinical implications, particularly in the evaluation and treatment of patients with epilepsy or lesions near eloquent cortex. Whole-head magnetoencephalography (MEG) provides a non-invasive approach to assessing the integrity of eloquent cortices and is of particular utility for mapping the representation of the somatosensory cortex relative to the irritative zone. In the current retrospective analysis of over 400 epilepsy patients, we explored somatosensory conduction velocity (CV) development from infancy to adulthood in patients who underwent MEG functional mapping. Specifically, we sought to assess the yield of MEG upper extremity somatosensory mapping across the age spectrum, in both the awake and sedated sleep states, and enhance our understanding of somatosensory pathway development.


Methods: All patients included in this analysis were referred for MEG testing as part of their epilepsy evaluation, between January 2019 and December 2023 at Le Bonheur Children’s Hospital. Of 472 sessions, 269 were performed awake (mean age 17.00 years; range 5.44-64.27 years) and 203 under sedation (mean age 7.04 years; range 0.70-26.19 years). Whole-head MEG was used to perform upper extremity somatosensory mapping following electrical stimulation of the median nerve. Success was determined by fitting a single dipole representing the peak of the N20m (early) or P35m (middle) evoked field, that localized to the hand region of the contralateral postcentral gyrus. Conduction velocity (CV) was calculated using ((H/2)/t), where H and t represent patient’s height (m) and the hand somatosensory evoked field latency (s), respectively.


Results: In the awake-MEG group, the success rate for MEG in at least one hemisphere was 89.78%, compared to 58.87% in the sedated group. The average somatosensory CV was 35.08 m/s (range 19.71-45.50 m/s) for the left hand and 35.00 m/s (range 20.00-48.30 m/s) for the right hand in the awake-MEG group. In the sedated group, the average CV was 25.96 m/s (range 12.41-40.72 m/s) for the left hand and 26.56 m/s (range 13.17-41.67 m/s) for the right hand. No significant differences in CV were found between the left and right hands. Figure 1 shows age-related changes in hand somatosensory CV, which increases with age and then plateaus. Age accounted for 52.57% of the variability in left-hand CV (R² = 0.5257, adj R² = 0.5203, p < 0.001) and 47.42% for the right-hand CV (R² = 0.4742, adj R² = 0.4681, p < 0.001).


Conclusions: This study demonstrates that somatosensory conduction velocity (CV) increases with age and then plateaus, reflecting the maturation of somatosensory pathways from infancy to adulthood, in patients with epilepsy. These findings provide valuable insights into the trajectory of sensorimotor development in epilepsy as a function of age and may enhance the clinical utility of MEG functional mapping in the evaluating these patients.


Funding: NA