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.