Andrew Charles, MD, Professor, Director of Headache Research and Treatment Program, UCLA David Geffen School of Medicine, discusses migraine diagnosis and diagnostic criteria that focus on associated symptoms such as light and sound sensitivity, nausea and vomiting and fatigue and interference with daily functioning.
Pain does not have to be a diagnostic criteria.

Reading:

Devor WN, Napoli R, Saccà L. Vascular smooth muscle cell dysfunction in patients with migraine.
Neurology. 2010 Jan 5;74(1):94;

Hagen K, Zwart JA, Aamodt AH, Nilsen KB, Bråthen G, Helde G, Stjern M, Tronvik EA, Stovner LJ.
The validity of questionnaire-based diagnoses: the third Nord-Trøndelag Health Study 2006-2008.
J Headache Pain. 2010 Feb;11(1):67-73

Polensek SH, Tusa RJ. Nystagmus during Attacks of Vestibular Migraine: An Aid in Diagnosis.
Audiol Neurootol. 2009 Nov 5;15(4):241-246