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n. Pathology The state of being hypertonic.

n. An abnormal increase in tightness of muscle tone, common in cerebral palsy.

n. Extreme reflex irritability. Also called hypertonicity and hypertonus.

n. (of muscular tissue) the state of being hypertonic

"Signs and symptoms of Lithium toxicity such as hypertonia, hypothermia, cyanosis and ECG changes have been reported in some infants and neonates."

tonicity    tone    tonus