CASPR2-related epilepsy: A distinctive and unrecognized form of epilepsy in adult and elderly males.

Objective: The aim of this study was to describe the clinical features of contactin-associated protein-like 2 (CASPR2)-IgG-associated seizures.

Methods: Nine patients were retrospectively collected from two epilepsy centers. For each patient we obtained a full clinical, neurophysiological, and MRI study along with detection of antineuronal autoantibodies from serum and CSF. The patients were followed up for 1-6 years.

Results: The patients were nine male subjects aged 56-85 years (mean: 66) with a 1- to 14-year (mean: 6,3 median: 6) history of seizures. The seizures were classified as focal onset seizures with impaired awareness, usually preceded by epigastric aura (two), piloerection (two), olfactory hallucinations (two), nausea and dizziness (one). Tonic-clonic seizures were present in five patients. Seizure frequency was high in six cases and sporadic in three. Most patients reported memory impairment (eight) or behavioral/mood changes (four). Interictal EEGs usually showed bilateral or unilateral temporal epileptiform abnormalities. A number of seizures arising from the temporal lobes, with bilateral asynchronous onset, were recorded on long-term video-EEG monitoring in two patients. MRI disclosed nonspecific white matter T2 hyperintensities suggestive of chronic vascular changes in four patients and bilateral T2-FLAIR amygdalo-hippocampal hyperintensity in three cases. Neuropsychological study demonstrated various degrees of cognitive impairment in the majority of cases. Increased titers of CASPR2 autoantibodies were detected in the serum and CSF, which persisted over time in four cases. Drug resistance to common anti-seizure medications was present in seven cases who benefited from immunotherapy.

Significance: CASPR2-IgG testing should be performed among old male patients with a recent or even not recent onset of focal seizures with impaired awareness particularly when these seizures are accompanied by cognitive impairment or behavioral disturbances. In these cases, anti-seizure medications may be ineffective while immunotherapy may lead to a prompt improvement of seizures and cognitive deficits.