Development of flexion pyramidal signs in preterm infants

Area of Science:

• Neonatal Neurology
• Developmental Pediatrics
• Neurodevelopmental Disorders

Background:

• Flexion pyramidal signs (FPS), including Rossolimo's and Mendel-Bechterew's signs, indicate upper motor neuron lesions in older individuals.
• These reflexes are transient in healthy newborns, typically disappearing by 12 weeks of age.
• Understanding the typical developmental trajectory of FPS is crucial for identifying neurological abnormalities in infants.

Purpose of the Study:

• To characterize the developmental course of flexion pyramidal signs (FPS) in preterm and small-for-dates infants.
• To determine the gestational age at which typical FPS responses emerge and resolve.
• To compare FPS development in healthy preterm infants versus small-for-dates infants.

Main Methods:

• Follow-up of 42 infants (birthweights 800-2000g, gestational ages 25-40 weeks) over several weeks.
• Conventional neurological examinations focusing on specific flexion pyramidal signs (Rossolimo's and Mendel-Bechterew's).
• Developmental testing to assess reflex maturation.

Main Results:

• Early in development (25-34/36 weeks gestational age), FPS manifest as toe abduction and great toe extension.
• After 34-36 weeks gestational age, the typical downward flexion of all toes becomes the standard response.
• This developmental progression of FPS was observed to be similar in both healthy preterm and small-for-dates infants.

Conclusions:

• The developmental course of flexion pyramidal signs in infants follows a predictable pattern, transitioning from abnormal to typical responses by late preterm gestation.
• The findings suggest that the developmental trajectory of FPS is not significantly altered by being small-for-dates, provided other factors are normal.
• This study provides normative data for FPS development, aiding in the early detection of potential neurodevelopmental issues in vulnerable infant populations.