Evaluating E2007 (Perampanel) in Patients With Painful Diabetic Neuropathy (PDN) or Post-Herpetic Neuralgia (PHN)

• Mean Change From Baseline in Short Form-McGill Pain Questionnaire (SF-MPQ): Sensory and Affective Scores, From Baseline to Week 48. [ Time Frame: Baseline and Week 48 ] [ Designated as safety issue: No ]
  Mean change from baseline to open-label study endpoint and other study visits in SF-MPQ scores sensory and affective). SF-MPQ was completed to assess intensity of pain over the past 48 days for all 15 descriptors: throbbing, shooting, stabbing, sharp, cramping, gnawing, hot-burning, aching, heavy, tender, splitting,tiring-exhausting, sickening, fear-causing, punishing-cruel. Each descriptor was scored by participant on a 4-point intensity scale (0=none to 3=severe) and totaled in each subclass (sensory range 0-45); higher scores indicated higher intensity of pain.
• Mean Change From Baseline in SF-MPQ Visual Analog Scale (VAS): From Baseline to Week 48. [ Time Frame: Baseline and Week 48 ] [ Designated as safety issue: No ]
  SF-MPQ VAS consists of a line 0 to 100 millimeters (mm) in length; range is 0 (no pain) to 100 mm (worst possible pain). Subjects placed a mark indicating the intensity of their pain. Distance from left-hand end of line was measured and entered on Case Report Form (CRF) as score in mm. Higher score indicates greater level of pain.
• Mean Change From Baseline in SF-MPQ Current Pain Intensity (CPI): From Baseline to Week 48 [ Time Frame: Baseline and Week 48 ] [ Designated as safety issue: No ]
  Mean change from baseline in SF-MPQ (CPI) at study endpoint. Affective score ranges from 0-5. Higher scores indicate more severe pain (0=no pain, 1=mild, 2=discomforting, 3=distressing, 4=horrible, 5=excrutiating).

• Analysis of Patient Global Impression of Change (PGIC) at Week 48/End of Treatment (EOT) [ Time Frame: Baseline and Week 48 ] [ Designated as safety issue: No ]
  The PGIC asked subjects to evaluate the change in their overall status compared with the start of open-label treatment on a scale ranging from 1 (very much improved) to 7 (very much worse). [Please note high withdrawl rate during study].
• Mean Change From Baseline in Short Form 36 Item (SF-36) Health Survey: Physical and Mental Component Scores From Baseline to Week 48/EOT [ Time Frame: Baseline and Week 48 ] [ Designated as safety issue: No ]
  Mean change from baseline in SF-36 Item Health Survey Scores at study endpoint. Each component on the SF-36 Item Health Survey is scored from 0-100 with higher scores reflecting better subject status.

The purpose of this study is to evaluate the safety, tolerability and continued efficacy of perampanel in patients previously enrolled in double-blind, placebo-controlled studies for Painful Diabetic Neuropathy (PDN) or Post-Herpetic Neuralgia (PHN).

Inclusion Criteria:

Each patient must meet all of the following criteria to be enrolled in this study:

1. Met and continues to meet all inclusion and none of the exclusion criteria for the preceding PDN or PHN study and received study drug or placebo under double-blind conditions.
2. Completed the preceding double-blind study End of Treatment (EOT) Visit no more than 12 weeks prior to Baseline (Visit 1) for the open-label study. The eligibility status of patients who do not enroll during this 12 week period will be evaluated on a case by case basis via discussion between the Investigator and the Sponsor.
3. Males and females ≥18 years of age. Female patients should be either of nonchildbearing potential as a result of surgery or menopause (1 year after onset), or of childbearing potential and practicing a medically acceptable method of contraception (e.g., abstinence, a barrier method plus spermicide, or intrauterine device [IUD]) for at least 1 month before the Baseline Visit (Visit 1) and for 1 month after the end of the study (Visit 16). They must also have a negative pregnancy test at Baseline (Visit 1). Female patients using hormonal contraceptives must also be using an additional approved method of contraception (e.g., a barrier method plus spermicide or IUD) throughout the study.
4. Provide written informed consent prior to entering the study and prior to undergoing any study-related procedures.
5. Is reliable, willing, and able to cooperate with the study procedures.

Exclusion Criteria:

Patients who meet the following criterion will be excluded from this study:

1. Patients who discontinued early for any reason from the preceding double-blind study.
2. Patients who have a clinically significant finding(s) that would make them unsuitable for the study in the opinion of the investigator or Sponsor.