Balancing as a clinical test in the differential diagnosis of sensory-motor disorders.

During balancing on a seesaw normal individuals have a mean sway oscillation of 4.3 Hz, which is significantly lower (3.3 Hz) in patients with peroneal muscular atrophy. It is assumed that the oscillations in both cases are generated by spinal stretch reflexes and that the lower frequency in patients with peroneal muscular atrophy is due to their slower nerve conduction velocity. The balancing movements are altered when spinal stretch reflex activity is reduced by ischaemia but are normal in patients with a dorsal column lesion despite a similar sensory loss. The analysis of balancing movements can be a diagnostic tool in differentiating several sensory-motor disturbances.