As chromosomes occur in pairs, the affected individual usually has one normal chromosome and the other replaced by a ring chromosome. However, this is not usually the case for every cell in the patient. In most individuals with ring chromosome 20 syndrome, a certain percentage have two normal chromosome 20s and the remainder have one normal and one ring 20 chromosome. This mixture is called mosaicism. A higher degree (percentage) of mosaicism appears to be associated with earlier age of seizure onset and presence of malformations. Yet, the degree of mosaicism does not determine response to drug treatment. Since the range in age of onset of seizures and IQ for a given mosaic ratio is relatively wide, prediction of phenotype based on the mosaicism ratio is somewhat limited. Occasionally, there is a variation, where the ring chromosome 20 syndrome is characterized by an extra ring chromosome in addition to the two normal ones and hence gives rise to a partial trisomy or supernumerary ring 20. This supernumerary ring 20 can cause multiple anomalies but no epilepsy, and this resulting syndrome should be differentiated from ring chromosome 20 syndrome. This confusion has persisted even in the literature. The genes in the q13.33 region of chromosome 20 have yet to be fully delineated. However, this telomeric region includes two genes that are related to other distinct epilepsy syndromes, autosomal dominant nocturnal frontal lobe epilepsy and benign familial neonatal convulsions.
As not all cases of ring chromosome 20 syndrome are the same, different individuals may respond to treatment in different ways.Alternates to antiepileptic drug treatment include the ketogenic diet and vagus nerve stimulation but not epilepsy surgery. Ketogenic Diet
The ketogenic diet is a high fat, low carbohydrate diet reserved for intractable childhood epilepsies. There are no published reports on the use of the ketogenic diet in patients with ring chromosome 20 syndrome. However, its efficacy and safety are well established in other difficult to control epilepsy syndromes. Epilepsy Surgery
Epilepsy surgery investigations are performed to identify a discrete seizure focus. Extensive investigations in ring chromosome 20 syndrome  patients fails to identify a discrete seizure focus and published data supports that that epilepsy in ring chromosome 20 syndrome  is not amenable to resective surgery. The Cost ranges between £50,000 - £200,000. VNS Therapy
The vagal nerve stimulator is a battery-powered device similar to a pacemaker that is implanted under the skin. It delivers a mild electrical stimulation to the brain via the vagus nerve and has proven to be effective for the treatment of complex partial seizures. There are only a few published reports on the success of this therapy in ring chromosome 20 epilepsy syndrome, making it unclear if this is the optimal therapy. Prognosis
Limited data is available for the long-term prognosis of ring chromosome 20 syndrome since only over 60 patients with this syndrome have been reported in published literature.