Apraxia, Handedness and Language Laterality

Apraxia is a disorder that is characterized by an impairment in the ability to perform new or previously learned movements that cannot be explained by sensory or motor abnormalities. It is often not recognized by the patient and family members, and the prevalence of apraxia may therefore be somewhat underestimated. The prognosis for recovery is very good, and the presence of apraxia during the acute period after a stroke is not associated with an overall worse prognosis for recovery. Although apraxia most often coexists with aphasia, the two phenomena can also be dissociated. Studies of right- and left-handed patients with apraxia have revealed that apraxia always results from a lesion of the hemisphere contralateral to the dominant hand. The theoretical importance of apraxia, therefore, is that it demonstrates a very close relationship between hemispheric dominance for programming of motor acts and handedness. Whereas the relationship between cerebral language dominance for language and handedness is highly variable, particularly in left-handers, the relationship between cerebral dominance for motor programming and handedness appears to be much more robust.