Figure 236.1.— Neonate with a left foot drop at rest [A]. During action he is unable to lift the left foot up [B]. The patient had a lumbar meningocele and a lipoma of the phylum terminalis.
nerve (Figure 236.2 [SN]) lesions may be complete or fascicular.A
complete sciatic nerve lesion produces foot drop, but unlike a lumbosacral
plexus lesion, it spares hip movements (iliopsoas nerve), knee extension
(femoral nerve), and adduction (obturator) of the leg. A complete sciatic
nerve lesion involves all muscles of the thigh. Fascicular sciatic nerve
lesions are more frequent than complete sciatic nerve lesions. Fascicular
lesions of the sciatic nerve may involve the lateral or the medial fascicles.
Lateral fascicle sciatic nerve injury occurs more frequently than medial
fascicle sciatic nerve injury. Lateral fascicles sciatic nerve injury
spares all the muscles of the thigh except the short head of the biceps
(Figure 236.2 [BshM]). This finding (the sparing or involvement of the
short head of the biceps) is an important EMG finding to distinguish a
lateral fascicle sciatic nerve injury from a common peroneal nerve lesion
(both present with foot drop). A neonate with a lateral fascicular sciatic
nerve lesion shows evidence of denervation of the short head of the biceps
femoralis, whereas a neonate with a common peroneal nerve lesion does
Figure 236.2.— Schematic representation of the lumbosacral plexus and most important intermedial nerves. IPN: iliopsoas nerve; SGN: superior gluteal nerve; IGN: inferior gluteal nerve; ON: obturator nerve; FN: femoral nerve; LST: lumbosacral trunk; SN: sciatic nerve; TN: tibial nerve; CPN: common peroneal nerve; AdM: adductor muscle of the thigh; HSM: hamstring muscles; PostTM: posterior tibialis muscle; B(sh)M: short head of the biceps femoralis muscle; PlNs: plantar nerves; DPN: deep peroneal nerve; SPN: superficial peroneal nerve.