(Plural noun used to denote a singular) A period of melancholy or low spirits; a whim or brief surge of enthusiasm about something; vertigo, dizziness or migraine - in these medical senses also used as a singular noun.
While making Mutiny on the Bounty in Tahiti, the megrims of working with Marlon Brando drove him to drink more than usual.
We know that achilleas were cultivated in gardens long before 1440 and that Gerard (writing in 1597) recorded that the leaves, when put up the nose, would relieve migraine - or "megrim" as he called it
Unattributed, Telegraph, 16 August 2003. Telegraph
Schubert's song cycle is not a quick fix for anything, least of all adolescent megrims.