[Astasia without abasia due to peripheral neuropathy]

Ten patients with paraparesis due to peripheral neuropathies showed an unusual symptom characterized by an inability to stand still despite the ability to walk. The symptom was transient in the eight cases recovering from profound paraparesis due to acute or subacute polyneuropathies, and has continued for several years in two chronic polyneuropathy cases who have been suffering over ten years. All the patients take a series of to-and-fro steps forward and backward while standing until they initiate locomotion. We call this symptom "astasia without abasia", or the "stilts phenomenon", because the symptom reminds us of children's play with stilts. Weakness of the lower limbs was predominant in the ankle joints and muscle strength about the hip joints was relatively preserved. This pattern of weakness produced abnormal mechanical properties of the body in an upright posture. Postural movements of the patients thus consisted mainly of the movement about the hip joints (hip sway). The movement about the ankle joints (ankle sway) which maintains forward and backward leaning in upright posture was impaired. Although clinical examination revealed no significant sensory disturbances, impairment of the somatosensory system which stabilizes postural sway was proven in four patients by antero-posterior sway components around 1 Hz. Astasia without absia consists of maintaining body mass not on a fixed base but on a moving one. BOth abnormalities of postural movements and defective somatosensory feedback for postural stabilization may be responsible for this symptom.