Epileptogenesis in tuberous sclerosis complex-related developmental and epileptic encephalopathy.

Epileptogenesis in infants with tuberous sclerosis complex (TSC) is a gradual and dynamic process leading to early onset and difficult-to-treat seizures. Several cellular, molecular, and pathophysiologic mechanisms, including mammalian target of rapamycin (mTOR) dysregulation, GABAergic dysfunction, and abnormal connectivity, may play a role in this epileptogenic process, and may also contribute to the associated developmental encephalopathy. Disease specific antiseizure medications or drugs targeting the mTOR pathway have proved to be effective in TSC-associated epilepsy. Pre-symptomatic administration of vigabatrin, a GABAergic drug, delays seizure onset and reduces the risk of a subsequent epileptic encephalopathy, such as infantile spasms syndrome or Lennox-Gastaut syndrome. Everolimus, a rapamycin-derived mTOR inhibitor, reduces seizures frequency especially in younger patients. This evidence suggests that everolimus should be considered early in the course of epilepsy. Future trials are needed to optimize the use of everolimus and to determine whether earlier correction of the mTOR dysregulation can prevent the progression to developmental and epileptic encephalopathies or mitigate their severity in infants with TSC. Clinical trials of several other potential antiseizure drugs (cannabidiol and ganaxolone) that target contributing mechanisms are also underway. This review provides an overview of the different biological mechanisms occurring in parallel and interacting throughout the life course, even beyond the epileptogenic process, in individuals with TSC. These complexities highlight the facing challenges in the prevention and treatment of TSC-related developmental and epileptic encephalopathy.