Functional disorganization of the left limbs in a tumour of the corpus callosum infiltrating the hemispheres.
A disorganization in the responses of the left limbs is described in a 61-year-old right-handed female patient, who had a tumour of the C.c. which infiltrated both hemispheres. The patient was unable to use the left limbs in an appropriate and purposeful way, to differentiate their parts and locate them, to identify objects by tactile means, to write or construct with her left hand, and she was also unaware of her left limbs.

The conventional terms such as dyspraxia, agraphia, imperception and so forth, which denote these disorders, are in this case only of descriptive value; there was no loss of corresponding faculties as implied by these terms since the patient responded in most respects adequately with the right limbs. Nor, for the same reason, is the disorganization due to a lowering of general cortical functions. The nature of the disorganization is regarded as operational; the patient is unable to apply her intelligence when the left limbs are employed as the agents of cortical activity. We may consider intelligence as a potential which can normally be directed to any field of operation. In the case described, this shift failed to take place when the patient operated the left limbs.

In the light of the massive disorganization of the left limbs, the problem of left-sided dyspraxia and left-sided unawareness has been reviewed. There is evidence that the left-sided dyspraxia is, in the cases described, not the only disturbance at the conceptual level of the left limbs. As to unawareness of the left limbs, this is as a rule associated with motor and sensory loss on this side which greatly restricts investigation; disorders such as found in our case may therefore remain undisclosed. To approach these phenomena without considering this particular setting is likely to lead to false conclusions.

There was in our case, distinct from the imperception of the left limbs, which formed part of the left-sided syndrome, a lowered and fluctuating awareness of illness and of particular defects. This is part of an amnesic syndrome present at the same time.

Anatomically the damage which can be related to the left-sided syndrome was in our case the lesion of the right parietal region, and that of the C.c.; these are the areas which are involved in cases of left-sided imperception and left-sided dyspraxia respectively. It is suggested that the right parietal region may be a focal point in a circuit which maintains activities of the left limbs at a conceptual level, and that the C.c. may have a subsidiary role in that function.