'Alice in Wonderland Syndrome' (AiWS) (a.k.a. Todd's syndrome or dysmetropsia) is a neuro-psychological disorder in which patients experience visual* distortions - so that surrounding objects can appear larger or smaller (or nearer of further away) than they actually are.

It's known to be associated with infections of the Epstein-Barr virus (the cause of Glandular Fever), and also with brain tumours andMigraineplugin-autotooltip__plain plugin-autotooltip_bigMigraine

"Chronic migraine has a great detrimental influence on a patient’s life, with a severe impact on socioeconomic functioning and quality of life. Chronic migraine affects 1–2% of the general population, and about 8% of patients with migraine; it usually develops from episodic migraine at an annual conversion rate of about 3%.". But the neuro-psychological mechanisms are unknown.

For many years it was assumed to be a very rare condition, but recent surveys have suggested that as much as 9% of the population may have experienced it at some stage.

Source : Journal of the Academy of Child and Adolescent Psychiatry,Volume 28, issue 4

*Note: It can also feature auditory and time-distortion illusions.

Further reading : BioMed Research International, article ID 8243145.