Evaluation of a new-onset seizure
What exactly is a seizure? It is defined as a “transient occurrence of signs and/or symptoms due to abnormal, excessive or synchronous neural activity in the brain”. Here's a case scenario:
A 45 y/o M presents to the ER with the first ever witnessed Generalized Tonic-Clonic seizure or GTC.
Let’s get down to work!
First things first, take a history
If someone presents with a new onset seizure, the first step is to take a history. It's crucial to get information from the witness, even if that means asking the patient to call them. Find out how the seizure started and ask close-ended questions about the different types of auras. This information can help in the diagnosis and management of the seizure.
Differential diagnosis
Differential diagnoses for new-onset seizures include TIA, migraine, convulsive syncope, FND, and amyloid spells.
*If there are repeated transient neurological episodes in an older adult, it's important to consider seizure over TIA.
Provoked vs. unprovoked seizures
Once a seizure is confirmed, the next step is to differentiate between provoked and unprovoked seizures. Provoked seizures can be caused by underlying pathology, such as CNS infection, stroke, TBI, drug-induced, or metabolic factors. The timeframe for these seizures can differ from 24 hours to 7 days.
To differentiate between the two, a comprehensive metabolic panel (CMP), urine and serum toxicology screen, and neuroimaging should be done. If within normal limits, it’s an unprovoked seizure.
* Multiple unprovoked seizures in 24 hours are considered a single seizure for diagnostic and therapeutic purposes.
Investigations
EEG and neuroimaging are essential tests to be done for a first-onset seizure. The highest yield of EEG is in the first 24 hours. Ambulatory EEG is preferred over a routine EEG.
Imaging studies, such as CT or MRI, can help identify any abnormalities in the brain.
Risk of a second unprovoked seizure
The risk of a second unprovoked seizure after the first one is 21% to 45% within the first two years. Factors that increase the risk include EEG epileptiform activity, nocturnal occurrence, previous history of stroke or TBI, and abnormal MRI.
Management plan
The decision to start medication or consider watchful waiting should be individualized. The choice of medication depends on factors such as the type of seizure, adverse effects, comorbidities, metabolism of the drug, and gender of the patient. Find more on the choice of medication here.