Sudden Unexpected Death in Epilepsy (SUDEP) is defined as the sudden, unexpected, and unexplained
death of a person with epilepsy. SUDEP accounts for between 8 and 17% of all epilepsy-related deaths, rising
to 50% in patients for which current therapies are ineffective. Amongst all neurological conditions, it is second
only to stroke for number of life-years lost. Increasing evidence supports apnea (breathing cessation) as the
primary cause of death following a seizure. Apnea and oxygen desaturation have been reported in a large
percentage of patients during and after convulsive seizures, and of the 9 SUDEP cases that were monitored by
video-EEG in epilepsy monitoring units (EMUs) at the time of death, all involved respiratory arrest occurring
before terminal asystole (MORTEMUS study). A better understanding of the key processes involved in
respiratory dysfunction and subsequent SUDEP would allow for the development of novel rescue therapies.
SUDEP occurs across numerous epilepsy populations. One such vulnerable population are patients with
SCN8A epileptic encephalopathy (EE), who have a gain of function mutation in the NaV1.6 sodium channel.
Our mice models harbor Scn8a mutations identified in patients that suffered SUDEP, and produce many of the
clinical symptoms of the patients, including spontaneous generalized tonic-clonic seizures, apnea, and
SUDEP. Using these clinically relevant mice models we will test our CENTRAL HYPOTHESIS that SUDEP
occurs when breathing ceases after a seizure, as a result of constant tonic inspiratory activity, and
failure of breathing recovery is due to impaired cardiorespiratory homeostasis. AIM 1: We will determine
the role of the Bötzinger complex (BötC) and retrotrapezoid nucleus (RTN) brainstem neurons on coordinating
inspiratory activity during seizure-induced apnea using optogenetic techniques. AIM 2: Epilepsy patients at risk
for SUDEP have impaired central chemosensitivity. We show that our SCN8A EE mice also have impaired
central chemosensitivity. We propose to assess in vivo CO2-sensitivity at developmental time points leading up
to SUDEP and determine if inhibition of sodium channel (INa) currents can rescue CO2-sensitivity. We will
determine changes in RTN neurons to determine their CO2/H+-sensitivity, intrinsic excitability, and INa currents.
Finally, we will use shRNA to knockdown NaV1.6 in the RTN and assess its contribution to in vivo CO2-
sensitivity and SUDEP. AIM 3: Impaired cardiac control is a contributor of SUDEP, and we find that
bradycardia occurs immediately prior to SUDEP. We will determine in vivo parasympathetic cardiac drive
leading up to SUDEP and determine effects of INa inhibition. We will make recordings from parasympathetic
cardiovagal neurons and determine the effects of NaV1.6 knockdown on bradycardia and SUDEP. These
studies will significantly impact our current understanding of the cardiorespiratory alterations that lead to
SUDEP and could provide important insight into novel therapeutic targets to prevent SUDEP.