title: Clinical correlates of phosphene perception in migraine without aura: an Asian study.
abstract: BACKGROUND
  Although controversy exists with regard to the presence of hypoexcitability versus hyperexcitability of the visual cortex in migraine patients, there remain a group who do not perceive phosphenes (P-). However, its clinical implications have not been systematically addressed. In this study, we hypothesize that P- patients classified as migraine without aura (MO) have distinct clinical features.
  
  
  METHODS
  Twenty-nine Asian MO patients (7 men; mean age: 44; median: 45; range: 25 to 65) were consecutively entered into the study. Visual cortex transcranial magnetic stimulation (TMS) was performed in the migraine interictum.
  
  
  RESULTS
  Of the 19 patients, 19 (66%) were able to perceive phosphenes (P+), while 10 (34%) were not able to after repeated TMS (P-). P- patients had significantly higher headache frequency (p=0.008) and pain score (p=0.002) compared with P+ patients. In addition, there was significant positive correlation of phosphene threshold with pain score (r=0.52, p=0.02) in P+ patients. There was no significant difference between P+ and P- patients in terms of age (t-test, p=0.6).
  
  
  CONCLUSIONS
  Our study is inkeeping with the hypothesis that interictal visual cortex excitability is reduced in relation to the severity of migraine in Asian MO patients, and lack of phosphene perception may be related to significantly elevated thresholds beyond the output of TMS stimulators.
authors.affiliation: Department of Neurology, National Neuroscience Institute, Singapore General Hospital, Outram Road, Singapore 169608, Singapore. lo.yew.long@sgh.com.sg
authors.forename: Y L
authors.initials: YL
authors.lastname: Lo
authors.forename: S Y
authors.initials: SY
authors.lastname: Lum
authors.forename: S
authors.initials: S
authors.lastname: Fook-Chong
authors.forename: S L
authors.initials: SL
authors.lastname: Cui
authors.forename: H C
authors.initials: HC
authors.lastname: Siow
mesh_terms: D000328:Adult; D000368:Aged; D001208:Asia; D044466:Asian People; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D020326:Migraine without Aura / Q000175:diagnosis / Q000208:ethnology / Q000503:physiopathology*; D009460:Neurologic Examination; D010147:Pain Measurement; D017288:Pain Threshold / Q000502:physiology; D010719:Phosphenes / Q000502:physiology*; D011237:Predictive Value of Tests; D011379:Prognosis; D012684:Sensory Thresholds / Q000502:physiology; D012720:Severity of Illness Index; D012846:Singapore; D050781:Transcranial Magnetic Stimulation; D014793:Visual Cortex / Q000503:physiopathology*; D014795:Visual Pathways / Q000503:physiopathology; D014796:Visual Perception / Q000502:physiology*