Article

The contribution of spasticity to postural imbalance in patients with
upper motor neuron syndrome is still unclear. This study aimed to evaluate the
responses to support-surface perturbations in patients with hereditary spastic
paraparesis (HSP). These patients typically suffer from bilateral spasticity with
relatively preserved muscle strength of the lower limbs. Particularly toes-up
rotations were expected to be destabilizing due to insufficient suppression of
calf muscle stretch reflexes. METHODS: Participants were seventeen symptomatic
community-dwelling patients with autosomal dominant pure HSP and seventeen
healthy controls. All patients had increased muscle tone of the triceps surae
(TS) but no muscle contractures. Perturbations were applied by rotating or
translating a platform with increasing intensity in four sagittal-plane
directions. The primary outcome was maximum intensity
('limit of stability')
sustained without stepping or grabbing in each type of perturbation. Leg muscle
tone and strength were assessed with the Modified Ashworth Scale and Medical
Research Council (MRC) scale, respectively. RESULTS:
For toes-up perturbations,
limits of stability in patients were substantially lower than in controls, which
were related to TS muscle tone but not to tibialis anterior (TA) strength.
Toes-down rotations were indiscriminative. For backward perturbations, patients
also had lower limits of stability, unrelated to TA strength or TS muscle tone.
In forward perturbations, patients with TS strength MRC 4 were less stable than
patients with normal TS strength and controls. CONCLUSION:
Calf muscle spasticity
and weakness differently contribute to postural imbalance in patients with HSP.
This notion could have implications for the clinical management of spasticity.
CI - Copyright (c) 2012 Elsevier B.V. All rights reserved.

Langue : ANGLAIS