[Cerebral small infarcts of the precentral and postcentral gyri presenting with unilateral monoataxia: a report of two cases].

Two cases of unilateral monoataxia, due to small infarcts in the precentral and postcentral gyri, were reported. A 76-year-old man (case 1), and a 90-year-old woman (case 2) suddenly developed clumsiness of the left upper extremity. Neurological examination revealed cerebellar ataxia in the left upper extremity in both cases. But, the other abnormal neurological findings, including the muscle weakness, abnormal muscle tone, and proprioceptive deficit, were not noted. In case 2, cerebellar ataxia disappeared about ten days after the onset of the disease. On the other hand, ataxia of case 1 remained about two months after the disease onset. Brain magnetic resonance imaging (MRI) of cases 1 and 2, showed small infarcts at the border between the right precentral gyrus and postcentral gyrus. In addition, brain MRI of case 1 disclosed another infarcts in the just medial portion of the precentral knob and the centrum semiovale of central region, respectively. It was suggested that the mechanism of cerebellar ataxia caused by infarct in the central region, was not only due to the interruption of two distinctive neuronal pathways, including the corticopontine tract and cerebellothalamocortical tract, but also due to the disturbance of sensory-motor integrity. In conclusion, etiologies of unilateral monoataxia may be heterogeneous. Furthermore, functional outcome may depend on the mechanism of unilateral monoataxia.