Degree to which bifid median nerves and persistent median arteries cosegregate. At the top of the figure are the numbers of study participants with each specific abnormality. Below, the bar graph illustrates the frequency of co-occurrence of this abnormality with the other abnormalities listed. For example, there are 16 participants who have a right persistent median artery (PMA). Of these, 7 also have a bifid right median nerve (7 of 16, or 44%). There are 502 participants without a right persistent median artery, and in this group 39 subjects have a right bifid median nerve (39 of 502, or 7.8%). PMA, persistent median artery; bifid, bifid median nerve.