Are invasive cortical stimulations effective in brain atrophy?

Electrical brain stimulation is a treatment method for brain disorder patients. The majority of patients with a severe brain disorder have brain atrophy. However, it is not clearly understood if electrical brain stimulation is effective even to brain atrophy. In this work, we developed anatomical head models with varying degrees of brain atrophy, so that we could investigate the effects of subdural/epidural cortical stimulations. The correlation between brain atrophy and cortical stimulation was quantified by calculating the effective volume that cortical stimulation influenced in this brain atrophy simulation study. The results showed that the effective volumes in both cortical stimulations decreased significantly with brain atrophy. There was also a strong correlation (0.9989) between the cerebrospinal fluid (CSF) and brain atrophy. The increase in CSF volume following brain atrophy reinforced the shunting effect between the brain and CSF and appeared to be the cause of a decrease in the stimulation effect on the brain. Overall, the epidural cortical stimulation was more sensitive (up to 57%) to the severity of the brain atrophy than the subdural cortical stimulation.