Geminate consonant grapheme-colour synaesthesia (ideaesthesia).

Background: Synaesthesia is a neurological condition which manifests clinically as an involuntary experience of a sensory or cognitive pathway upon stimulation of a second unrelated sensory or cognitive pathway

Case Presentation: We report a 55 year old male who presented with a life-long history of grapheme-colour synaesthesia in which the triggering grapheme was the double letter 'll' (a geminate consonant), but not 'l' as a single letter. This patient's synaesthesia was also font specific (becoming more evident with serif fonts) and influenced by migraine headache (being suppressed during the prodrome and aura of a migraine headache)

Conclusion: These results suggest that geminate consonants are uniquely processed rather than treated as two individual consonants. Also, the existence of a mechanistic relationship between synesthetic and migrainous events sequence was verified.