Objective

Hereditary spastic paraplegia (HSP) designates a rare genetic disorder characterized by the existence of a pyramidal syndrome and/or paresis of the lower limbs, resulting in locomotor disorders. The objective of this study was to investigate the HSP patients walking characteristics during a comfortable walking speed, to determinate the most deleterious impairments and their evolutivity during a prolonged standardized walk. A second goal was to study the co-contraction of targeted muscles during these two walking conditions.

Material/patients and methods

In this prospective study, the spatio-temporal parameters (GAITRITE ^® electronic walkway) and electromyographics (surface EMG) of twelve HSP patients were compared with those of nine matched subjects, for the walking conditions: « comfortable walk », « Six Minutes Walking Test » (SMWT). The perceived exertion was assessed by the Borg scale. HSP patients received a standardized interrogatory and neuro-orthopedic examination measuring angles joint values, spasticity (Tardieu scale) and muscle strength (MRC scale). For every subjects, muscle activations and co-contractions indices were analyzed for several muscles: semi-tendinosus (ST), rectus femoris (RF), gastrocnemius lateralis (GL) and tibialis anterior (TA) for all walking conditions.

Results

Median gait speed (0.85 m/s) and cadence (91 steps/min) were significantly lower in the HSP group compared with unaffected subjects. Walking speed was constant over the SMWT for a high level of exertion. Spasticity and weakness were greatest for the GL muscle that had a prolonged activation during the swing phase. Co-contraction indices in the GL/TA couple were significantly increased for the non-dominant lower-limb during swing phase. No significant differences were found for the RF/ST couple. The motor deficit was the only significant parameter correlate to walking speed.

Discussion–conclusion

HSP patients are characterized by a slow walk explained mainly by a motor deficit. Surface EMG seems to be an interesting tool in the therapeutic reflection to investigate walking disorders in HSP disease.