Hyperreflexia describes an overactive or overresponsive reflex. This often manifests as twitching or a spastic reaction. It is usually a symptom of a serious condition typical of motor neuron diseases or an inability of the higher brain centers to exercise control over lower neural pathways.
It's most common cause is an injury to the spinal cord, but can also be caused by a side effect of medication, hyperthyroidism, an imbalance of electrolytes, serotonin syndrome, severe brain trauma, multiple sclerosis, Reye's syndrome and preeclampsia.
Treatment focuses on the underlying cause of the condition.