From search for "neurology handedness"
It is generally accepted that most people have left-hemispheric language dominance, though the actual incidence of atypical language distribution in non–right-handed subjects has not been extensively studied. The authors examined language distribution in these subjects and evaluated the relationships between personal handedness, family history of sinistrality, and a language laterality index (LI) measured with fMRI.

Methods: The authors used whole-brain fMRI to examine 50 healthy, non–right-handed subjects (Edinburgh Handedness Inventory quotient between -100 and 52)