Abstracts

Rationale: Characteristic feature of ring chromosome 20 syndrome (R20s) is known to be nonconvulsive status epilepticus (NCSE) in adult. However, especially in younger children, other seizure types may be more prominent than NCSE and diagnosis of R20s is far more challenging. There have been few reports about long-term course of seizures in R20s, which is essential for both proper diagnosis and prognosis prediction of the chromosomal disorder. Methods: We retrospectively investigated 29 patients (17 females and 12 males) with R20s based upon their medical records and video-EEG records. All patients suffered from ring 20 chromosomal mosaicism. Ages at last visit ranged between 8 and 49 years. Periods from onset of seizures to the last hospital visit were between 2 and 42 years (average 20 years). Evaluated were the distribution of age at seizure onset, characteristics and clinical course of seizures. Results: Seizures seen in patients with R20s were divided into three types; 1.CPS, 2.Motor seizures, 3.NCSE. Age at onset of each type was; 1. 1.7-12 years (average 6.6) (n=11), 2. 2.5-22 years (average 8.7) (n=18), 3. 4.8-15 years (average 9.7) (n=26). 1. CPS preceded other seizure types. Loss of contact with blank staring was common feature, often associated with speech implying visual hallucination and affective symptoms such as fearful expression. The outcome was; transition to NCSE, persistence, remission in about one thirds of the patients, respectively. 2. Motor seizures consisted of one or more of motor components such as tonic, clonic, tonic-clonic, myoclonic and gestural automatisms. 18 patients had habitual motor seizures. The lower the age at epilepsy onset was, the greater chance of motor seizures the patient had in his clinical course. Nearly 80% of patients had motor seizures in the first decade of life, but the percentage dropped to 30% in the third decade of life. Motor seizure remit in most patients over time. 3. NCSE persisted in all patients. NCSE became milder or less frequent in 12 patients but was still disabling. Conclusions: ​In contrast to persistence of NCSE, CPS and motor seizures are prone to occur in patients with early onset R20s and remit or disappear during the course.