Sudden unexpected death in epilepsy (SUDEP) is a category of death in people 
with epilepsy occurring in the absence of a known structural cause of death and 
is most likely heterogeneous with regard to mechanisms and circumstances. SUDEP 
is particularly difficult to investigate in research studies for several 
reasons, including its relatively low incidence, its unpredictable occurrence 
often in unwitnessed settings, and its low rate of complete autopsy 
examinations. Over the past two decades, two complementary definitions have been 
used in most SUDEP studies, but often with variations. We propose here a unified 
SUDEP definition and classification to resolve current ambiguities and to 
retrieve cases that would not have been further studied if the previous 
definitions were used. The proposed Unified SUDEP Definition and Classification 
contains, in addition to concepts inherent in the previous definitions, nine 
main recommendations. (1) The word "unexpected," and not the word "unexplained," 
should be uniformly used in the term SUDEP. (2) The SUDEP category should be 
applied when appropriate, whether or not a terminal seizure is known to have 
occurred. (3) The "Possible SUDEP" category should be used only for cases with 
competing causes of death, with cases left unclassified when data are 
insufficient to reasonably permit their classification. (4) Cases that would 
otherwise fulfill the definition of SUDEP should be designated as "SUDEP Plus" 
when evidence indicates that a preexisting condition, known before or after 
autopsy, could have contributed to the death, which otherwise is classified as 
SUDEP (e.g., coronary insufficiency with no evidence of myocardial infarction or 
long-QT syndrome with no documented primary ventricular arrhythmia leading to 
death). (5) To be considered SUDEP, the death should have occurred within 1 h 
from the onset of a known terminal event. (6) For status epilepticus as an 
exclusion criterion for SUDEP, the duration of seizure activity should be 30 min 
or more. (7) A specific category of SUDEP due to asphyxia should not be 
designated, the distinction being largely impractical on circumstantial or 
autopsy evidence, with more than one mechanism likely to be contributory in many 
cases. (8) Death occurring in water but without circumstantial or autopsy 
evidence of submersion should be classified as "Possible SUDEP." If any evidence 
of submersion is present, the death should not be classified as SUDEP. (9) A 
category of "Near-SUDEP" should be agreed to include cases in which 
cardiorespiratory arrest was reversed by resuscitation efforts with subsequent 
survival for more than 1 h. Scenarios that demonstrate the basis for each SUDEP 
category are described. If disagreement exists about which category fits a 
particular case, we suggest the use of consensus decision by a panel of informed 
reviewers to adjudicate the classification of the case.