Peripheral nervous system maturation in preterm infants: longitudinal motor and sensory nerve conduction studies

Change in cross-sectional area of the median nerve with age in neonates, infants and children analyzed by high-resolution ultrasound imaging

AIM

To analyze age dependencies in the cross-sectional area (CSA) of the median nerve during early childhood.

METHOD

A total of 43 participants (32 of whom were children younger than 2 years) were included in this cross-sectional study to analyze the age dependency of the CSA of the median nerve at three locations (wrist, forearm and upper arm) using high-resolution ultrasound images.

RESULTS

A strong and highly significant correlation was found between age and CSA (p < 0.001). When plotted, the relationship followed a logarithmic curve (p < 0.001) with a growth rate that decreases with age. Based on the regression analysis, a temporally similar increase in CSA for all three locations was found. The nerve reaches 70% of its final CSA by 2 years of age at all three locations.

INTERPRETATION

Similar to the nerve conduction speed, the increase in CSA is greatest during the first 2 years of life. Then, the rate gradually and synchronously slows at the proximal and distal locations. Measurement of the CSA in the clinical setting might offer a new method to assess the maturation of the nervous system in infants with minimal interference.

A Systematic Review of the Electrodiagnostic Assessment of Neonatal Brachial Plexus

Despite improvements in obstetric care, neonatal brachial plexus palsy continues to significantly impact infants’ lives worldwide, with an incidence of 1 to 4 per 1000 live births. While a majority of affected infants recover spontaneously by three months, 20-30% suffer permanent functional deficits that significantly impair their quality of life. Anatomical complexity of the brachial plexus results in varying degrees of injury and pathological changes at multiple levels within the plexus. Current clinical diagnosis relies on electrodiagnostic techniques such as nerve conduction (i.e., motor and sensory) and electromyography studies. These techniques not only aid clinicians to differentiate between axonal and demyelinating lesions, evident by changes in signal shape and conduction, but also provide prognostic information in cases of brachial plexus injuries. The presented study offers a comprehensive review of existing literature on electrodiagnostic techniques employed for assessing neonatal brachial plexus injuries.

Utility and practice of electrodiagnostic testing in the pediatric population: An AANEM consensus statement

Nerve conduction studies and needle electromyography, collectively known as electrodiagnostic (EDX) studies, have been available for pediatric patients for decades, but the accessibility of this diagnostic modality and the approach to testing vary significantly depending on the physician and institution. The maturation of molecular diagnostic approaches and other diagnostic technologies such as neuromuscular ultrasound indicate that an analysis of current needs and practices for EDX studies in the pediatric population is warranted. The American Association of Neuromuscular & Electrodiagnostic Medicine convened a consensus panel to perform literature searches, share collective experiences, and develop a consensus statement. The panel found that electrodiagnostic studies continue to have high utility for the diagnosis of numerous childhood neuromuscular disorders, and that standardized approaches along with the use of high-quality reference values are important to maximize the diagnostic yield of these tests in infants, children, and adolescents.

Age-related characteristics and normative values of F waves in healthy infants

OBJECTIVE

To establish age-related characteristics and normative values of F waves in healthy Chinese infants.

METHODS

We studied median, ulnar and tibial nerves on one side distally in 229 healthy Chinese infants (108 males) ranging from 1 to 12 months old.

RESULTS

Minimal F-wave latencies (Fmin) showed a strong negative correlation to the age for median, ulnar and tibial nerves (P < 0.01) but no correlation to the height. Statistical analyses revealed a significant (P < 0.01) decrease of Fmin during the second month of life and no change (P > 0.05) thereafter. Dividing the infants into 1 month old (Group 1) and 2-12 months old (Group 2), normal values (Mean ± SD ms) of Fmin for tibial, median and ulnar nerves consisted of 23.38 ± 1.68, 17.19 ± 0.95 and 16.47 ± 1.06 for Group 1 and 21.42 ± 1.25, 14.50 ± 1.15 and 14.52 ± 0.90 for Group 2.

CONCLUSION

F-wave latencies shorten in the 2nd month of life and change little thereafter when age-related maturation counters the concomitant growth of the nerve length.

SIGNIFICANCE

F waves can assess infantile neuropathies as a reliable measure, complementing the technically difficult conventional nerve conduction study in short limbs.

Neuromuscular maturation in the neonate: Combined electroneurographic and ultrasonographic study

BACKGROUND

The combined electroneurography and muscle ultrasound examination (ENG-USM) in adult patients showed a correlation between the compound motor action potential (CMAP) and muscular thicknesses (MT). No similar studies exist regarding the neonatal period.

AIM

To evaluate the correlations between the maximum compound muscle action potential (CMAP) and maximum muscle thickness (MT) in term and premature newborns versus a group of young adults, as measured by combined electroneurography-ultrasonography (ENG-USM) to assess the stages.

STUDY DESIGN

Observational cohort study.

SUBJECTS

We studied 36 subjects (14 premature and 11 term infants, and 11 young adults), who underwent ENG-USM of the tibialis anterioris (TA) muscle.

OUTCOME MEASURES

We measured: 1) Onset-Peak (O-P) and Peak-to-Peak (P-P) maximum CMAP; 2) maximum MT; and 3) MT at the detected maximum CMAP.

RESULTS

The maximum CMAP in term newborns studied was about 1/3 of the mean value measured in the adults; the differences between O-P and P-P values of the term versus premature infants were not significant. We did not find a good correlation between maximum MT and maximum CMAP in the term (r = 0.63) newborns, contrary to what was found in preterms (r = 0.95) and in young adults (r = 0.98).

CONCLUSION

Our ENG-USM study shows that in newborns, the site of innervation of the neuromuscular plaque does not correspond to MT since muscle growth is related to the period of development, and depends on the progression of the nerve terminal branches that go to innervate the same muscle.