Inclusion Criteria:

• 1. An Institutional Review Board (IRB) approved informed consent is signed and dated before any study-related activities.
• 2. Male and female subjects ages 18 to 75, inclusive.
• 3. Documented history of at least two (2) seizures per week. Seizures can be generalized and/or focal.
• 4. Diagnosed with intractable or refractory epilepsy.
• 5. Have a caregiver/family member who stays with the subject, has the ability to detect seizures, and is willing to provide the information needed for the study.
• 6. Have implanted vagus nerve stimulation (VNS).
• 7. Have the ability to understand the requirements of the study and are willing to comply with all study requirements.
• 8. Must have a working Apple iPhone.

Exclusion Criteria:

• 1. Women who are either pregnant or breastfeeding.
• 2. Subjects unable/unwilling to wear the Apple Watch and EEG Wearable for extended periods.
• 3. Requires the use of a ventilator.
• 4. Requires the use of supplemental oxygen.
• 5. Uses a pacemaker or other electronic neurostimulator, except the VNS.
• 6. Any medical or surgical condition that in the opinion of the investigator may interfere with participation in the study.