Various organic diseases may cause parosmias (distortion of the sense of smell). Also, since smell and taste are intimately linked senses, disorders of gustation (e.g. dysgeusia- taste dysfunction) can present as a complaint related to smell, and "vice versa". These conditions, collectively termed chemosensory dysfunctions, are many and varied, and they may trigger a person to complain of an odor than is not present, however the diagnostic criteria for ORS require the exclusion of any such causes. They include pathology of the right hemisphere of the brain, substance abuse, arteriovenous malformations in the brain, and temporal lobe epilepsy.