Neonatal loss of motor function in human spina bifida aperta.
OBJECTIVE
In neonates with spina bifida aperta (SBA), leg movements innervated by spinal segments located caudal to the meningomyelocele are transiently present. This study in neonates with SBA aimed to determine whether the presence of leg movements indicates functional integrity of neuronal innervation and whether these leg movements disappear as a result of dysfunction of upper motor neurons (axons originating cranial to the meningomyelocele) and/or of lower motor neurons (located caudal to the meningomyelocele).


METHODS
Leg movements were investigated in neonates with SBA at postnatal day 1 (n = 18) and day 7 (n = 10). Upper and lower motor neuron dysfunction was assessed by neurologic examination (n = 18; disinhibition or inhibition of reflexes, respectively) and by electromyography (n = 12; absence or presence of denervation potentials, respectively).


RESULTS
Movements, related to spinal segments caudal to the meningomyelocele, were present in all neonates at postnatal day 1. At day 1, leg movements were associated with signs of both upper (10 of 18) and lower (17 of 18) motor neuron dysfunction caudal to the meningomyelocele. In 7 of 10 neonates restudied after the first postnatal week, leg movements had disappeared. The absence of leg movements coincided with loss of relevant reflexes, which had been present at day 1, indicating progression of lower motor neuron dysfunction.


CONCLUSIONS
We conclude that the presence of neonatal leg movements does not indicate integrity of functional lower motor neuron innervation by spinal segments caudal to the meningomyelocele. Present observations could explain why fetal surgery at the level of the meningomyelocele does not prevent loss of leg movements.
Pediatric Neurology, Department of Pediatrics, University Hospital Groningen, PO Box 30.001, 9713 GZ Groningen, Netherlands. d.a.sival@bkk.azg.nl
Deborah A
DA
Sival
Tiemen W
TW
van Weerden
Johan S H
JS
Vles
Albert
A
Timmer
Wilfred F A
WF
den Dunnen
A L
AL
Staal-Schreinemachers
Eelco W
EW
Hoving
Krystyne M
KM
Sollie
Vivianne J M
VJ
Kranen-Mastenbroek
Pieter J J
PJ
Sauer
Oebele F
OF
Brouwer
D004576:Electromyography; D006801:Humans; D007231:Infant, Newborn; D007866:Leg / Q000502:physiology*; D009046:Motor Neurons / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology; D012018:Reflex / Q000502:physiology; D016137:Spina Bifida Cystica / Q000503:physiopathology*; D013116:Spinal Cord / Q000033:anatomy & histology