Hyperreflexia is a condition where muscles have an increased or overactive reflex response. It can be a sign of an underlying neurological condition, such as amyotrophic lateral sclerosis (ALS) and multiple sclerosis (MS), or it can be caused by non-neurological conditions such as anxiety disorders and hyperthyroidism. Hyperreflexia indicates an upper motor neuron lesion and reflects a loss of inhibitory modulation of the motor pathways. It is often associated with increased twitching and spastic tendencies. Autonomic hyperreflexia is a potentially life-threatening syndrome involving an abnormal, overreaction of the autonomic nervous system to painful sensory input. It most often happens after a spinal cord injury at or above the sixth thoracic vertebrae (T6) . Treatment depends on the cause of the hyperreflexia. If drugs cause it, treatment may require that they not be used. Recovery from hyperreflexia can occur several hours to several months after a spinal cord injury.