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Updated: Mar 28, 2026
Assessment and Evaluation of the High Risk Neonate: The NICU Network Neurobehavioral Scale
Published on: August 25, 2014
[Neurological prognosis of floppy infants after health examinations]
Insights
Many infants with benign congenital hypotonia, characterized by initial low muscle tone, later develop intellectual disabilities and autism spectrum disorder. Early diagnosis and intervention are crucial for these children with motor delays.
Area of Science:
- Pediatric Neurology
- Developmental Pediatrics
- Genetics
Context:
- Benign congenital hypotonia (BCH) describes infants with temporary low muscle tone.
- BCH can stem from various neurological or muscular conditions.
- Many affected infants exhibit motor delays and may later show cognitive impairments.
Purpose:
- To investigate the long-term neurodevelopmental outcomes of infants diagnosed with benign congenital hypotonia.
- To identify potential sequelae such as intellectual disability and autism spectrum disorder in this cohort.
- To emphasize the need for prospective follow-up and early diagnostic interventions.
Summary:
- Thirty-two floppy infants with motor delays were followed until age two.
- While most achieved motor milestones, a significant percentage developed intellectual disability (67%) and autism spectrum disorder (19%).
- Two infants were diagnosed with Rett syndrome and spinal muscular atrophy; others with persistent motor issues were suspected of congenital myopathies or malformation syndromes.
Impact:
- Highlights the high prevalence of neurodevelopmental issues post-recovery of muscle tone in BCH.
- Underscores the importance of comprehensive genetic testing and long-term monitoring for early detection of developmental disorders.
- Informs clinical practice regarding the need for early intervention strategies for floppy infants.
Objective:
The term benign congenital hypotonia is retrospective and refers to infants who are hypotonic at birth or shortly thereafter but later show a normal tone. It encompasses many different pathological processes that affect the brain, motor unit, or both. The majority of affected children have cerebral hypotonia. An increased incidence of mental retardation, learning disabilities, and other sequelae of cerebral abnormality are evident later in life, despite the recovery of a normal muscle tone. We followed floppy infants who were pointed out as showing motor delay on health examinations at 4 or 9 months of age until at least 2 years of age.
Methods:
We selected 32 floppy infants (15 males and 17 females) born uneventfully, with no family history, major anomalies, or abnormal findings on brain imaging, and no chromosomal study (G-banding and fluorescence in situ hybridization), serum creatine kinase level, blood lactate and pyruvate level, or blood amino acid abnormalities.
Results:
All 32 infants achieved head control, but 2 failed to learn to sit unsupported. These two were diagnosed based on gene analysis with Rett syndrome and spinal muscular atrophy, respectively. Although 27 among the 32 patients became ambulant, 18 (67%) showed mental retardation and 5 (19%) also had autism spectrum disorder. Five patients who could not walk were suspected to have congenital myopathy or congenital malformation syndrome.
Conclusions:
After learning to walk independently and recovery of the normal muscle tone, many floppy infants showing motor delay on health examinations at 4 or 9 months of age developed mental retardation and autism spectrum disorder. Prospective follow-up is necessary for early diagnosis and intervention. For patients showing no motor and mental development, further laboratory studies including appropriate gene analysis are important for a definite diagnosis.
