Astasia without abasia due to peripheral neuropathy

K. Hirayama, M. Nakajima, M. Kawamura and Y. Koguchi
Department of Neurology, School of Medicine, Chiba University, Japan.

OBJECTIVE: To describe an unusual symptom characterized by an inability to stand still despite the ability to walk in eight patients with paraparesis due to peripheral neuropathy. DESIGN: Case series during the past 18 years. SETTING: Referral center. PATIENTS: Six patients with acute or subacute polyneuropathies recovering from flaccid paralysis of the lower limbs and two patients with chronic progressive polyneuropathy for more than 10 years were studied. Weakness around the ankle joints was profound, while muscle strength around the hip joints was well recovered or preserved. MAIN OUTCOME MEASURES: Standing and walking were recorded and reviewed on videotape or motion pictures. Spectral content of postural sway was analyzed in three recent cases. RESULTS: The symptom was transient in acute or subacute cases and was continual in chronic cases. The patients were compelled to take a series of steps forward and backward while standing until they initiated locomotion. They swayed rapidly around the hip joints before stepping. The anteroposterior component of postural sway in three patients had frequency peaks around 1 Hz. CONCLUSION: We have termed this symptom astasia without abasia, or stilts phenomenon, in which maintenance of the body mass depends on a moving base of support. Both an abnormal pattern of postural movements and defective somatosensory feedback for postural stabilization may be responsible for the symptom.