Extrapyramidal stiffness in patients with amyotrophic lateral sclerosis.

There is accumulating evidence that ALS is a multisystem degenerative disease, raising the question of whether some symptoms are of extrapyramidal origin. The objective was to better characterize the type of stiffness in a series of ALS patients and to study correlations with balance and postural impairment. We studied ALS patients who exhibited stiffness without noticeable motor deficit in the lower limbs. We analyzed the response to manual stretch velocity to differentiate between extrapyramidal (rigidity) or pyramidal (spasticity) stiffness, shortening reaction in the tibialis anterior muscles (abolished in pyramidal diseases and exaggerated in extrapyramidal diseases) and balance and posture impairment (UPDRS and Berg's scale). After a preliminary inter-rater reliability study, 39 consecutive ALS patients were prospectively recruited. Each patient was randomly assigned to one or other of two investigators who evaluated either stiffness or balance impairment. In the lower limbs, rigidity was observed in at least one muscle in 27/39 patients (69%), and shortening reaction was exaggerated in 20/39 patients (51%). Both were correlated with balance and posture impairment (UPDRS and Berg's scale, P < 0.001). This study suggests that extrapyramidal involvement plays a role in stiffness and balance impairment in a subset of ALS patients.