Long-Term Safety, Tolerability and Efficacy in Perampanel Treated Parkinson's Disease Patients With Motor Fluctuations

Inclusion Criteria: * Patients enrolled in Study E2007-E044-204 and who either completed 12 weeks of study drug treatment or who withdrew from the study due to lack of efficacy. Exclusion Criteria: * Pregnant or lactating women. * Women of child bearing potential unless infertile (including surgically sterile) or practicing effective contraception (e.g. abstinence, IUD-intrauterine device, or barrier method plus hormonal method). These patients must also be willing to remain on their current form of contraception for the duration of the study. Postmenopausal women may be recruited but must be amenorrhoeic for at least 1 year to be considered of non-child bearing potential. * Fertile men not willing to use reliable contraception and fertile men with partners not willing to use reliable contraception. These patients and their partners must also be willing to remain using reliable contraception for the duration of the study. * Patients with a past or present history of drug or alcohol abuse. * Patients with a past (within one year) or present history of psychotic symptoms requiring antipsychotic treatment. Patients may be taking anti-depressant medication, however the dose must have been kept stable for at least 8 weeks prior to baseline visit. * Patients with unstable abnormalities of the hepatic, renal, cardiovascular, respiratory, gastro-intestinal, haematological, endocrine or metabolic systems which might complicate assessment of the tolerability of the study medication. * Patients with significantly elevated liver enzymes (abnormal bilirubin or serum transaminase levels of more than 1.5 times the upper normal limit). * Patients with current or prior treatment (within 4 weeks prior to the Baseline visit) with medication known to induce the enzyme cytochrome P450 3A4 including but not limited to; carbamazepine; dexamethasone; ethosuximide; phenobarbital; phenytoin; primidone; rifabutin; rifampicin; and St John's Wort. * Current or prior treatment (within 4 weeks prior to baseline visit) with methyldopa, budipine, reserpine or intermittent use of liquid forms of levodopa or as needed (prn) apo-morphine. * Patients with previous stereotactic surgery (e.g. pallidotomy) for Parkinson's disease or who are likely to undergo surgery for Parkinson's disease while participating in this study. * Patients receiving deep brain stimulation (DBS) or who are likely to undergo DBS for Parkinson's disease while participating in the extension study. * Patients with clinically significant cognitive impairment (mini-mental state examination (MMSE) \<24 and /or fulfilling diagnostic and statistical manual of mental disorders (DSM IV) criteria for dementia due to Parkinson's disease). * Patients with conditions affecting the peripheral or central sensory system.