Abstracts

Trisomy 15 has long been associated with mental retardation and seizures. It is well known that single gene defects can produce partial epilepsy. One of the best studied examples is autosomal dominant nocturnal frontal lobe epilepsy in which mutations affecting the neuronal nicotinic acetylcholine receptor (ACHR) produce a focal epilepsy syndrome. Interestingly, one of the candidate ACHR subunits is located on chromosome 15. Similarly, benign epilespy with centrotemporal spikes may also be linked to chromosome 15. Abnormal function of GABA receptors has also been hypothesized to contribute to partial seizures. Of note, two GABA receptor subunits are encoded on chromosome 15. Abnormal expression of any of these genes may result in an underlying substrate that is more prone to the development of seizures. More recently, partial trisomy 15 had been associated with temporal lobe abnormalities in one kindred suggesting that focal developmental structural abnormalities are another mechanism by which genetic abnormalities can lead to partial seizures. Either of these mechanisms may contribute to the epilepsy associated with Trisomy 15. Patients with chromosomal abnormalities are typically presumed to have diffuse abnormalities which would make them poor candidates for epilepsy surgery. The purpose of this report is to present a case of epilepsy in a patient with Trisomy 15 successfully treated with epilepsy surgery. At the end of this event, particpants should be able to discuss the potential role of resective surgery in epilepsy related to a chromosomal abnormalities.
The patient is a 21 year old female with a history of Trisomy 15 diagnosed at age 10, mental retardation and medically refractory seizures diagnosed at age 14 which, in retrospect, started in early childhood. She was having daily seizures including 30 episodes of status epilepticus in the three months prior to her initial evaluation at our center. MRI and 18FDG PET were negative. Scalp video/EEG monitoring suggested left neocortical temporal onset of seizures with left frontotemporal interictal abnormalities. SPECT suggested lateral temporal onset. Intracranial monitoring confirmed left neocortical temporal seizure onset and she subsequently underwent an extensive left temporal resection.
At the one year follow-up after surgery, she has had only a single seizure consisting of 30 seconds of staring and decreased responsiveness in association with a febrile illness. Her family feels that her speech, language, responsivenss and mood have all improved following surgery.
This case demonstrates that focal resection may be beneficial even in patients in which the presumed etiology involves a diffuse abnormality. Further study is suggested to better define the role of epilepsy surgery in patients with chromosomal abnormalities. This case also illustrates the complexities of epileptogenesis in which the diffuse pathology of a chromosomal abnormalitiy results in a focal epilepsy.