Non-motor seizures are almost four times more common in patients with recurrent undiagnosed seizures than in patients with new onset seizures.

The finding, from a retrospective review of patients presenting to a Melbourne ED with a seizure but without a pre-existing diagnosis of epilepsy, is a clue for ED physicians and emphasises the need for rigorous history-taking to help identify any prior seizures.

The study, published in Emergency Medicine Australasia, reviewed the records of 367 consecutive patients who presented to the ED between 2008 and 2016.

Those with known epilepsy and non-seizure diagnoses such as psychogenic non-epileptic  seizures, vasovagal syncope, stroke or TIA were excluded from the study leaving 97 eligible patients.

More than three-quarters (77.3%) were found to be cases of new onset seizures (NOS) rather than recurrent and previously undiagnosed seizures (RUS).

However the researchers warned that extracting a medical history from patients in a postictal state was often not feasible. As well, patients did not always recognise non-motor events such as a sense of intense deja-vu or depersonalisation as seizures.

“In our study, RUS patients had experienced a median of two prior seizures, usually non-motor focal impaired awareness seizures,” the study authors said. 

“This is consistent with an Australian study of newly diagnosed seizures which identified non-motor, low-impact first events to be strongly associated with diagnostic delay; this may be because patients may not recognise these events as seizures.” 

“Even if medical attention is sought, seizures may be misdiagnosed for a wide range of differentials including syncope or transient cerebral ischaemia.”

The study found 95.5% of patients with RUS and 44% with NOS subsequently met the diagnostic criteria for epilepsy.

Among NOS patients, “epileptogenic abnormalities on neuroimaging, with rapid CT imaging in the ED” was a high yield diagnostic investigation.

Most patients with RUS (54.6%) and NOS (68%) received CT scanning within four hours, input from the neurology team (90.9% RUS, 68% NOS) and were admitted to a ward (86.4% RUS, 90.7% NOS)  rather than discharged home.

However only a minority of patients – 9.1% with RUS and 41.3% with NOS – received an anti-epileptic drug in the ED.   

“Emergency physicians play a crucial role in the evaluation of seizure patients; skilful management, including appropriate epilepsy diagnosis, AED initiation and timely involvement of Neurology services may substantially alter patient outcomes by reducing the probability of further seizures,” the study authors concluded.