This is a post-market, open observational long-term effectiveness follow-up study of participants with drug-resistant epilepsy with partial-onset seizures previously enrolled in a randomized controlled trial (PuLsE) comparing Best Medical Practice with or without adjunctive Vagus Nerve Stimulation Therapy.

In 2005 Cyberonics, Inc. initiated PuLsE: an open, prospective, randomized, parallel group study directly comparing Best Medical Practice with and without adjunctive VNS Therapy.

In July 2008, the decision was made to discontinue this study due to lower than expected enrolment, impairing the possibility to meet the primary objective with appropriate statistical power. However, the relatively large number of participants (n=121) randomized in the original PuLsE study offers the possibility to generate scientifically valuable and original findings if additional follow-up data can be gathered. After consultation with the PuLsE Investigators, Cyberonics decided to implement an observational long-term follow-up of the participants enrolled in the original PuLsE study.

Inclusion Criteria:

To be eligible for the study, the participant must meet all the following criteria:

1. Participant must have been randomized in the original PuLsE study.
2. Participant must have baseline data from the original PuLsE study.
3. Participant is able to give accurate seizure counts, health outcomes information, and complete study instruments with minimal assistance.
4. Participant or legal guardian understands study procedures and has voluntarily signed an informed consent for PuLsE 2 in accordance with institutional and local regulatory policies.

Exclusion Criteria:

The presence of any of the following will exclude a participant from the study:

1. Participant has a history of non-compliance with the completion of a seizure diary.
2. Participant currently uses, or is expected to use during the study, short-wave diathermy, microwave diathermy, or therapeutic ultrasound diathermy.
3. Participant is expected to require full body magnetic resonance imaging during the clinical study.

The study population will consist of participants previously enrolled in the original PuLsE study diagnosed with drug-resistant epilepsy with partial-onset seizures. All patients will be analyzed according to the treatment that they have actually received and followed in this new study regardless of what treatment groups they were randomized in the previous study.