Hypocalcemia causes neuromuscular excitability and cardiac electrical instability due to a reduced nerve and muscle cell depolarization threshold. Its most common early symptoms are paresthesias, or numbness and tingling, of the perioral region and the fingertips. Muscle stiffness, cramps, and spasms are also common. Neuropsychiatric symptoms include confusion, anger, depression, lightheadedness, and irritability. More sustained muscle contraction may lead to laryngospasm, and more severe neural excitability may lead to seizures.Signs of hypocalcemia include observed or elicited tetany. Classic bedside findings are a positive Chvostek sign (facial muscle twitching upon tapping the preauricular region over the facial nerve; present at baseline in up to 25% of people), or a positive Trousseau sign (flexion of the wrist, thumb, and metacarpophalangeal joints and hyperextension of the fingers, upon brachial artery occlusion by inflation of a blood pressure cuff above systolic blood pressure). Cardiovascular signs observed with progressive hypocalcemia include prolongation of the QT interval that can result in torsades de pointes, a form of ventricular tachycardia that may degenerate into ventricular fibrillation.