Which clinical sign is typically observed in lower motor neuron disease?

In lower motor neuron diseases, hyporeflexia is a hallmark clinical sign. This occurs due to the degeneration or dysfunction of motor neurons located in the spinal cord that directly innervate muscles. When these lower motor neurons are damaged, their ability to transmit signals effectively to the muscles is impaired, leading to reduced or absent reflexes in the affected area. Thus, the absence of the usual reflex responses results in hyporeflexia.

This sign is particularly important in differentiating between lower motor neuron and upper motor neuron lesions. While upper motor neuron damage often leads to increased reflexes (hyperreflexia) and spasticity due to loss of inhibitory control, lower motor neuron conditions characteristically present with diminished reflexes and muscle weakness or atrophy. Understanding these distinctions helps clinicians in diagnosing the underlying neurological issues effectively.