They can be grouped into the following categories: Mental status alterations: Anxiety, agitation and restlessness, easy startling, delirium Autonomic hyperactivity: Tachycardia, hypertension, hyperthermia, diaphoresis, shivering, vomiting, diarrhea Neuromuscular hyperactivity: Tremor, muscle hypertonia or rigidity, myoclonus, hyperreflexia, clonus (including ocular clonus), extensor plantar responses Neuromuscular hyperactivity may be more pronounced in the lower than the upper extremities.