Transient Tone Abnormalities in "High Risk" Infants and Cognitive Outcome at Five Years

Objective: To identify transient tone abnormalities and determine its prevalence in "high risk" infants and their cognitive outcome at 5 years. Design: Prospective cohort observational study. Setting: High risk infants discharged from a level II neonatal unit in a 12 month period, and followed upto 5 years. Methods: High risk infants and normal controls were assessed for abnormalities of tone using the method described by Amiel-Tison at 3, 6, 9, 12 months. An IQ by Stanford-Binet method and a preschool inventory by Ayres, Bobath was done at 5 years. Those infants who had normal tone at 6 and 12 months were called normal high risk (HR) group and those who had abnormalities at 6 months, which disappeared at 12 months, were called the transient tone abnormalities (TTA) group. Results: Out of 190 high risk infants, 113 were normal HR and 67 (35.2%) were labeled as TTA. Ten infants with cerebral palsy had abnormal tone throughout the first year. Controls had normal tone throughout the follow-up period. Although there was no difference in the IQ of the TTA group (98.5 + 12.4) and the normal HR (99.1+13.1) group, it was significantly less (P=0.04) than that of controls (106.1 + 9.1). Preschool inventory in TTA children showed poor language development (P=0.014). Conclusion: Many of the tone abnormalities detected at 6 months resolve by 12 months, hence a hasty diagnosis of cerebral palsy should not be made. High risk infants with transient tone abnormalities have a normal cognitive outcome at 5 years, except for poor language skills.