Neck extensor hypertonia: a clinical sign of insult to the central nervous system of the newborn.

Abnormal hypertonia of the neck extensor muscles in newborns may be appreciated by observing spontaneous posture, evaluating resistance to repeated passive flexion of the head, and eliciting the head straightening reflexes. This sign correlates well with other signs of insult to the central nervous system. Of 1743 newborns over 37 wk gestational age, 17 appeared to have signs of cerebral insult according to the classical criteria of abnormal state of consciousness, tone, and reflexes. Of these 17, 12 (70%) had neck extensor hypertonia. 38 newborns appeared to have mild signs of cerebral insult with abnormalities of tone and excitability. Of these 38, 14 (37%) had neck extensor hypertonia. Only 12 (0.7%) of 1655 newborns with otherwise normal neurological examination had neck extensor hypertonia. Further studies are necessary to evaluate the prognostic value of neck extensor hypertonia in the neonatal period.