It remains controversial whether FBDS is an epileptic seizure or not. Advances in digital EEG techniques enabled to assess ictal direct-current shifts (icDCs), which define core ictal focus. A few studies have addressed icDCs in FBDS. Faciobrachio-cervical dystonic seizures (FBCDS) beginning with FBDS followed by cervical dystonic movements quickly evolving into the contralateral shoulder, has not been described.

We reviewed clinical features, brain MRIs, and EEG recorded during seizures in 3 patients with anti-LGI1 encephalitis (all male, median age 72 years). LGI1 antibodies were identified at Dalmau’s laboratory (Barcelona). The seizures were classified into FBDS, FBCDS, or others, and their association with brain MRI and EEG findings were evaluated.

Brain MRI revealed acute unilateral basal ganglia (BG) lesion with gadolinium enhancement in 2 patients (67%). 168 events including 32 typical FBDS and 6 FBCDS were recorded. The icDCs preceded the onset of dystonic seizures in 27/32 (84%) of typical FBDS and 6/6 (100%) of FBCDS. FBDS/FBCDS were seen more frequently in the 2 patients with BG lesions than in the other one (30/74 vs. 8/94, p<0.001). Typical FBDS was preceded by icDCs maximized at the contralateral centro-parieto-temporal area in 22/32 (69%) while FBCDS at the contralateral frontal area in 6/6. The duration was longer in frontal icDCs than in non-frontal ones (8.0 sec vs. 0.82 sec, p<0.01).

FBDS can occur without BG lesion, but acute BG lesions may increase susceptibility to dystonic seizures by altering the cortico-BG-thalamo-cortical network in the presence of LGI1 antibodies. Dystonic seizures are often preceded by icDCs, suggesting involvement of the cortex (probably epileptic origin), but frontal dominant icDCs of having a relatively long duration may characterize “FBCDS”, which is phenotypically different from typical FBDS preceded by centro-parieto-temporal icDCs with a short duration.