Anticonvulsant derivatives useful in treating chronic neurodegenerative disorders

A method for treating chronic neurodegeneration comprising administering to a mammal afflicted with such condition a therapeutically effective amount of a compound

• of the formula I:
• wherein
• X is CH2 or oxygen;
• R1 is hydrogen or alkyl;
• and
• R2, R3, R4 and R5 are independently hydrogen or alkyl and, when X is CH2, R4 and R5 may be alkene groups joined to form a benzene ring and, when X is oxygen, R2 and R3 and/or R4 and R5 together may be a methylenedioxy group of the following formula (II):
• wherein
• R6 and R7 are the same or different and are hydrogen, lower alkyl or are alkyl and are joined to form a cyclopentyl or cyclohexyl ring.