Nonconvulsive seizure (finding)

I've had a request to add a new concept "Nonconvulsive seizure (finding)" as a subtype of "91175000 |Seizure (finding)|"

• Definition: "Seizure detected only via continuous EEG with no external manifestation."
• Use case: Nonconvulsive seizures can occur in critically ill patients who do not have status epilepticus or generalized epilepsy. [Available SNOMED concepts are "Nonconvulsive status epilepticus" (442512002) and "Generalized non-convulsive epilepsy" (1929790090).]
• References:
  • https://www.ncbi.nlm.nih.gov/pubmed/29733464 
  • https://link.springer.com/chapter/10.1007/978-3-319-31230-9_7 
  • https://www.epilepsybehavior.com/article/S1525-5050(11)00357-X/abstract

The request seemed reasonable but I wanted to check with the group to see if the is current terminology, and what your thoughts are about adding this concept.

The terminology 'Non-convulsive seizure' does not figure in the current ILAE seizure classification. The ILAE terminology equivalent to the suggested label would be called a ’non-motor seizure’.  However, this is not what the suggested definition appear to intend. Seizures require both qualifying electrographic (EEG) changes AND a clinical correlate (symptom or sign). I do not think that the ILAE recommends the use of the word 'seizure’ to refer to electrographic-only events, even where it is suspected that the patient would seizure were neuromuscular blocking agents or anaesthesia withdrawn. The exception to this may be in neonates where it is proposed that electrographic-only seizures may be a valid concept, but the neonatal classification has not yet been published and is under internal review, and is not what these papers are referring to.

Nonconvulsive status epilepticus is a valid form of status epilepticus (see Trinka et al. ILAE definition and classification of status epilepticus, Epilepsy 2015) but this may have external manifestations (that are simply subtle, or at least not prominent). I suspect that the authors of these papers are either referring to non-convulsive status epilepticus or electrographic epileptiform changes in a comatose patient.

I would recommend not adding the term (it is certainly erroneous in its current form) until the group can discuss it. However, this may be delayed by Covid-19.

Hi All, could you please advise, has this request for "Nonconvulsive seizure (finding)" as a subtype of "91175000 |Seizure (finding)|" been discussed any further by the group?  Best wishes, Maria