Coronal sections of cerebral hemispheres . One is anterior and through the optic chiasm and the posterior section is through the thalami. The left hemisphere (on the left side of the photograph) is smaller than the right hemisphere. The small size of the left hemisphere is due to a large cystic lesion that includes the external portion of the putamen, internal capsule, inferior portion of the frontal lobe and parts of the temporal lobe. Diagnosis: Old cystic infarct in the distribution of the left MCA.