Neuronal antibodies in adult patients with new-onset seizures: A prospective study

Immunotherapy in addition to antiepileptic drugs can improve seizure freedom rates in autoimmune epilepsy, highlighting the importance of early diagnosis. A diagnosis of autoimmune epilepsy can be supported by presence of serum antibodies to neuronal antigens. We asked how often neuronal antibodies are found in the serum of unselected adult patients with new-onset seizures and whether such testing could improve detection of autoimmune epilepsy.

We included 44 patients over the age of 25 presenting after at least one unprovoked seizure to the Neurology Clinic at Sahlgrenska University Hospital, Gothenburg, Sweden. The median time between the first-ever seizure in life and the serum sampling was 50 days (range 22-11,000). Antibody testing in serum was performed according to the manufacturer's instructions. The patients were followed for at least 1 year.

Epilepsy could be diagnosed already at the first visit in 21/44 patients (47.7%). Two patients (4.5%) were positive for neuronal antibodies: one against contactin-associated protein 2 (CASPR-2) and one against glutamate acid decarboxylase (GAD). Three patients (6.7%) displayed very weak immunoreactivity that was deemed clinically insignificant. One of the antibody-positive patients had only a single seizure. The other had a focal cortical dysplasia and was seizure-free on levetiracetam. None of the five patients with antibodies or immunoreactivity displayed any feature of autoimmune epilepsy.

We conclude that indiscriminate testing in patients presenting to a first seizure clinic with new-onset seizures or epilepsy is unlikely to improve detection of autoimmune epilepsy.