Abstracts

Rationale: Functional reorganization of cerebral cortex occurs in subjects with malformations of cortical development (MCD). Some MCD are activated by functional MRI (fMRI) paradigms suggesting functional integrity of dysplastic cortex and raising concerns about post-surgical deficits in patients with MCD and medically refractory epilepsy. We aimed to assess functional integrity of MCD in motor neural network in patients with epilepsy and MCD by use of fMRI. Methods: Fifty-four patients (31w/23m) aged 13-76 years (mean 35.3 years) with MCD and epilepsy were selected at the Department of Neurology and Neurosurgery, Medical University Innsbruck, Austria. All subjects underwent clinical, EEG, MRI (1.5-T) and fMRI (single-shot echoplanar imaging sequence, EPI). Single-subject image analysis was performed with statistical parametric mapping (SPM2). MCD diagnosis was based on MRI and classified according to Barkovich et al., Neurology 2005; 65(12):1873-87. MCD were located either in vicinity of primary motor cortex (M1) or in subependymal area along lateral ventricles. Simple motor tasks: tongue side-to-side movement, lip pursing, finger-to-thumb opposition and toe flexing were used for testing motor neural network. Subjects were monitored for mirror movements and correct task performance. All subjects had been seizure free for at least 48 hours prior to fMRI study. Results: Seven had focal cortical dysplasia type II (FCD II); three- dysplastic tumours; one- hemimegalencephaly; seven- tuberous sclerosis (TS); sixteen- periventricular nodular heterotopias (PNH); three- subcortical laminar heterotopia (SLH); fifteen- polymicrogyria (PMG); one- PMG with PNH and one- TS with PMG. Twenty patients had mild motor deficit, affecting mainly fine finger movements (7- on right, 7- on left, 6- bilaterally). Seven patients were left-handed. Fourteen patients had mild learning disability which did not prevent them from performing fMRI tasks correctly. Majority of patients (52/54) had focal epilepsy; 2/54 had Lennox-Gastaut syndrome; 39/54 (72%) were pharmacoresistant. Mean age at seizure onset was 14.9 years (range 0-61); mean epilepsy duration for time of fMRI- 21.4 years (range 2-61). Shift of motor function from MCD affecting M1 was observed in patients with FCD II (4/7, 57%) and TS (4/7, 57%), p=0.005. Malformed cortices involving M1 were activated only in patients with PMG (15/17, 88%) and SLH (2/3, 67%), p<0.001. PNH situated along lateral ventricles were not activated. Neither shift of function from affected M1 nor its integration in function were influenced by age at seizure onset, epilepsy duration, seizure outcome or handedness. Conclusions: In patients with MCD affecting primary motor cortex, simple motor task fMRI suggests functional integration of MCD due to abnormal neuronal migration (SLH) or organization (PMG) and shift of function from MCD due to abnormal neuronal proliferation/apoptosis (FCD II, TS).