Reflexes in prior polio and their relation to weakness and anterior horn cell loss

The aim of this study was to evaluate the reflex pattern in patients with prior polio and to relate these findings to the degree of anterior horn cell (AHC) involvement and loss of muscle force. Twenty-five prior polio subjects were investigated with electromyography (EMG), force testing and reflex studies, which included the patellar and Achilles reflex, H-reflex, T-response and interlimb reflex (ILR). The clinical reflexes, H/M-ratio and T-response amplitude at rest were positively correlated with force and negatively correlated with the degree of AHC loss. The H/M-ratio was decreased compared with age matched controls. ILR was present in 68% of the prior polio patients but did not exist in controls. The presence of the ILR was not correlated with the degree of AHC loss or force. The reflex studies gave two main findings. The first is reduced excitability of monosynaptic connections in the motor neuron pool, which is related to weakness. The other is the presence of ILR as an indicator of interneuronal hyper-excitability, which is not related to weakness.