[Crossed apraxia secondary to a right parietal infarct]

Crossed apraxia is an unusual alteration in praxic function due to a cerebral lesion which is contralateral to that which would be expected. We report a case of crossed apraxia due to a right parietal lesion in a left handed patient who had been obliged to be right handed. We discuss the peculiar neuropsychological profile and possible relation of this to left handedness.

A 75 year old man, left handed but obliged to use the right hand, suffered an acute episode of alteration in the management of utensils (lids, taps, medicine containers), although he maintained his usual social behaviour and orientation. On neurosomatic examination no focal deficits were observed. On MMST he scored 29/30, on the Edinburgh questionnaire he scored 35 (left handed dominance). On a Barcelona PIENC battery his scores were in the pathological range for subtests on understanding orders, carrying out symbolic gestures and imitating gestures, in perceiving super imposed images and visual memory. MRI showed a right parietal laminar infarct.

The patient showed clear bilateral ideo motor apraxia, which could not be justified/explained by visuo spatial agnosia secondary to a right parietal ischaemic lesion. It is usually considered that ideatory and ideomotor apraxias are due to left hemisphere lesions, whilst contsructive apraxia and apraxia related to dress are due to right hemisphere lesions. In this case, there was ideomotor apraxia secondary to a right parietal lesion, that is to say a crossed ideomotor apraxia, without crossing of other neuropsychological functions. This supports the theory of independence of hemisphere dominance for different cognitive functions. The frustrated left handedness of the patient might be related to the greater probability of unusual hemisphere dominance for ideomotor praxis function in this particular case.