Symmetrical lesions in the basal ganglia.

Bilateral and symmetrical non-space occupying lesions in the basal ganglia of 27 cases were studied. Nine cases had low attenuation lesions while the remaining 18 had high attenuation lesions due to bleeding or calcifications. The clinical presentations and final diagnosis were collated and related to these changes. In the low-attentuation cases, definite hypoxic-ischaemic insults were the aetiological basis for low attenuation lesions in 3 cases; and hypothesised to be the basis in the remaining six. Amongst the high attenuation group, bleeding was noted in 4 cases with trauma or cardiac arrest. The remainder had calcifications. It is suggested that a hypoxic-ischaemic pathophysiological phenomenon might have also accounted for some of these calcifications. The co-existence of both low and high attenuation lesions in the same patients in some of our cases tends to lend credence to this hypothesis.