Astasia refers to the inability to maintain upright posture during standing, despite having full motor strength. Impairment of the vestibulocerebellar pathway, graviceptive system, and cingulate motor area have been proposed to be related to astasia. However, the responsible neural pathways remain unclear. We hypothesize that there is a common neural network behind astasia. To test the hypothesis, we reviewed all reported cases with astasia, including ours, and focused on the correlation between anatomical destruction and symptom presentation. A total of 26, including ours, non-psychogenic astasia patients were identified in the English literature. Seventy-three percent of them were associated with other neurologic symptoms and sixty-two percent of reported lesions were on the right side. Contralateral lateropulsion was very common, followed by retropulsion, when describing astasia. Infarction (54%) was the most reported cause. The thalamus (65%) was the most reported location. Infarctions were the fastest to recover (mean: 10.6 days), while lesions at the brainstem needed a longer time (mean: 61.6 days). By combining the character of lateropulsion in astasia and the presentation of an interrupted graviceptive system, we concluded that the primary graviceptive system may be the common neural network behind astasia. Future studies on astasia should focus on the pathological changes in the perception of verticality in the visual world and the body.
Keywords: astasia; graviceptive system; subjective posture vertical; subjective visual vertical; thalamo-cortical projections; vestibule-thalamic pathway.