Inclusion Criteria:
1. Ages 18 years to 89 years.
2. Adult males or females, non-pregnant, on reliable contraceptive regimen as appropriate.
3. Patient and legal representative as appropriate capable of signing written informed consent, completing electronic seizure diary, participating in questionnaires.
4. EEG features of generalized epilepsy performed within two years of enrollment with EEG anomalies not explained by contributory medical history; CT and/or MRI within the last ten years demonstrating no anatomic etiology of epilepsy.
5. MRGE, defined as persistent generalized tonic-clonic seizures, with or without concomitant absence, myoclonic, or focal seizures, despite compliance with at least two anti-seizure medications at therapeutic doses, with at least two generalized tonic-clonic seizures per month in the three months prior to HIFU procedure; must be willing to continue medication regimen during the duration of participation in the study.
6. Patient has not already undergone surgical implantation of RNS, VNS, DBS, or any other device used for management of MRGE that is not compatible with 3 Tesla MRI.
Exclusion Criteria:
1. 1\. Pregnancy.
2. Unable or unwilling to comply with inclusion criteria as described.
3. Prior disqualifying medical or surgical history:
1. Patients with advanced kidney disease or on dialysis
2. Patients with unstable cardiac status:
I. Unstable angina pectoris on medication II. Subjects with documented myocardial infarction within six months of protocol entry III. Significant congestive heart failure defined with ejection fraction \< 40 IV. Subjects with unstable ventricular arrhythmias V. Subjects with atrial arrhythmias that are not rate-controlled c. Patients with severe hypertension (diastolic BP\>100 on medication) d. Patients exhibiting any behavior consistent with ethanol or substance abuse e. Patients with history of abnormal bleeding, hemorrhage, and/or coagulopathy f. Patients receiving anticoagulant or drugs known to increase risk of hemorrhage within one month of focused ultrasound procedure g. Patients with cerebrovascular disease h. Patients with brain tumors i. Patients who are not able or unwilling to tolerate the required prolonged stationary position during treatment. The average treatment time (the time from the first scan to allocate transducer position and ending with the last energy delivery) is 1:56 ± 0.41 hrs (Min: 0.48 hrs, Max: 5:54 hrs) j. Patients with unstable psychiatric disease, uncontrolled depressive symptoms, psychosis, delusions, hallucinations, or suicidal ideation
4. Patients who are not candidates for HIFU.
a. Patients who have an Overall Skull Density Ratio of 0.40 (±0.05) or less as calculated from the screening CT
5. Patients with standard contraindications for MRI such as non-MRI compatible implanted devices including cardiac pacemakers, size limitations, etc.
6. Inability to tolerate MRI without premedication, sedation, or anesthesia.
7. Known intolerance or allergies to MRI contrast agent (e.g. Gadolinium or Magnevist)
8. History of craniotomy or other prior cranial procedure that would render phase correction with CT inaccurate.
9. Subjects with risk factors for intraoperative or postoperative bleeding:
1. Platelet count less than 100,00 per cubic millimeter
2. INR coagulation studies exceeding local institution laboratory standards
3. Documented coagulopathy
10. Subject with life-threatening systemic disease that include and not limited to the following: HIV, liver failure, blood dyscrasias, etc.
