Conflict of intentions due to callosal disconnection

Three patients with callosal syndrome manifested a peculiar symptom in that they were unable to perform intended whole body actions because another intention emerged in competition with the original one. Attempts were made to clarify the symptomatology of this manifestation and its possible mechanism is discussed.

The three patients are described and previous reports on patients with callosal damage were reviewed. Four additional patients with similar symptoms were found and the clinical features common to all seven patients were examined.

This symptom could not be attributed to unilateral movement disorders such as unilateral apraxia, intermanual conflict, or compulsive manipulation of tools. The manifestations included marked hesitation in initiating actions, interruption of actions, repetitive actions, and performance of unintended actions with difficulty in correcting them. All patients, except one, had a lesion in the posterior half of the body of the corpus callosum, and there was no significant involvement of the cerebral cortex. The symptom became manifest later than 4 weeks after callosal damage. It occurred during spontaneous actions, but not during well automated actions nor when following instructions.

This symptom, tentatively named "conflict of intentions", can be regarded as a fragment of diagonistic dyspraxia originally described by Akelaitis, although it can occur independently of intermanual conflict. Normally, the right and left cerebral hemispheres may be complementarily modifying automated whole body actions in order to adapt behaviour to changes of the environment as well as to the intention. Partial callosal disconnection without significant cortical involvement would exaggerate the disparity between the role of each hemisphere through the reorganisation of neural systems after callosal damage. Such double, often contrary, behavioural tendencies may sometimes simultaneously enter the patient's awareness.