Abstracts

Rationale: Lennox-Gastaut syndrome (LGS) is a severe and disabling epileptic syndrome characterized by drug-resistant generalized seizures, generalized spike-and-wave discharges, and cognitive impairment. The age of seizure onset in the majority of patients with LGS is < 8 years old. The clinical features and outcome in patients with onset in later childhood and adulthood (“late-onset LGS”) are not well characterized. Methods: Patients evaluated at the Mayo Clinic in Rochester, MN between January 1, 2000-March 1, 2017 who presented with onset of LGS > 10 years old were identified. Data abstracted included age of onset, seizure-types, etiology, treatments, EEG and neuroimaging results, cerebrospinal fluid findings, and autoimmune evaluation. Results: Eleven patients (9 females) were identified. Mean age in which patients had intractable seizures with features of LGS: 16.2 (range 10-32), the mean age of seizure onset: 11 (range 2-19). All had tonic, atonic, tonic-clonic seizures, and 4 had myoclonic and 8 had atypical absence seizures. Five had normal intellectual function at onset. The median number of previously ineffective AEDs was 12 (range 4-16). Treatments tried included the following: clobazam (n=9), felbamate (n=8), divalproex sodium (n=10), rufinamide (n=10), medical marijuana (n=2), dietary therapy (ketogenic and/or Modified Atkins’s diet) (n=5), VNS (n=7) (1 found effective with absence), and DBS (n=1). Etiology was likely prior intrathecal methotrexate for ALL in two, and remained unknown for the other nine. CSF was obtained in 5 patients: mean CSF protein: 54 (range 43-68, normal value: 0-35); mean nucleated cell count: 1.6 (range 1-4, normal value: 0-5); mean oligoclonal bands (n=4): 0 (normal value: < 4); mean IgG index (n=4): 0.54 (range 0.48-0.6, normal value: < 0.85). CSF and/or serum paraneoplastic antibodies were tested in 5 patients. One patient had positive antibodies (potassium channel antibody and neuronal ganglionic acetylcholine receptor antibody on serum testing); this was not confirmed with repeat testing. At last follow-up, only one patient worked and none were able to drive. One died of probable SUDEP. Conclusions: The clinical course of late-onset LGS has not been well described previously. Late onset LGS in this case series was refractory to medications that are often reported to be efficacious in early onset LGS in addition to being physically and socially disabling. Those undergoing CSF examination had mild protein elevation suggesting the presence of CNS inflammation. However, there was no specific serologic evidence of neural antibody autoimmunity in those cases tested. Funding: None