[Two cases of thalamic infarction presenting with "thalamic astasia"].

We report two cases of so-called 'thalamic astasia', associated with thalamic infarction. A 76-year-old-man suddenly noted to fall down to the left side without severe hemiparesis. An MRI showed an infarction in the superolateral portion of the right thalamus. Over eight weeks, his astasia gradually disappeared. A 69-year-old-man suddenly noted inability to stand with loss of balance. He showed mild hemiparesis, hypesthesia and cerebellar signs on the right side. Although right hemiparesis was slight, he was unable to stand by himself. An MRI demonstrated an infarction in the ventrolateral to ventroposterior portion of the left thalamus. Three weeks later, his symptoms except for cerebellar ataxia remarkably disappeared. The overlapped MRI lesions of these two cases were localized in the ventrolateral thalamus, such as Vimi (nucleus ventrointermedii internus), Vci (nucleus ventrocaudalis internus), Cemc (nucleus centralis thalami magnocellularis). These lesions are so-called 'vestibular thalamic nuclei', in which fibers from vestibulocerebellum are terminated. Involvement of the thalamic connectivity explains that two patients noted inability to stand. Thus we concluded that these two patients had thalamic astasia, described by Masdeu and Gorelick.