Eur J Pediatr DOI 10.1007/s00431-012-1837-y
CASE REPORT
Your diagnosis? Congenital foot drop C. P. Hawkes & B. McNamara & O. O’Mahony & E. M. Dempsey
Received: 15 July 2012 / Revised: 31 August 2012 / Accepted: 5 September 2012 # Springer-Verlag 2012
Abstract A term infant was noted to have right-sided foot drop. We discuss the role of neurophysiology and diagnostic imaging. Keywords Foot drop . Neonate . Peroneal nerve . Congenital . Neuropathy
movements at the ankle joint, without any discomfort. Passive flexion at the ankle joint showed that her right calf was slightly more resistant to stretch than her left. Ankle and knee reflexes were absent. She had torticollis to the left side, but there was no evidence of hypotonia or further neuropathy.
Case A female infant was born following vaginal delivery at 41 weeks of gestation. Birth weight was 3.49 kg (P50) and head circumference was 35 cm (P50), both of which were on the 50th centile for gestation. Delivery had been induced as a result of gestational age, and her presentation was cephalic. She was vigorous at delivery and required no active resuscitation. Her mother was a primigravida, and there was neither relevant maternal history nor relevant family history. Following delivery, the infant was noted to have right-sided foot drop (Fig. 1). There was occasional spontaneous active movement of her big toe, but there were no further movements of the foot. It was held in plantar flexion, but there was full range of passive
Fig. 1 Infant at presentation
C. P. Hawkes : E. M. Dempsey (*) Department of Neonatology, Cork University Maternity Hospital, Cork, Ireland e-mail:
[email protected]
What is your diagnosis?
C. P. Hawkes : O. O’Mahony Department of Paediatrics and Child Health, Cork University Hospital, Cork, Ireland
Electromyography (EMG) and nerve conduction studies (NCS) were performed on day 2. Her right gastrocnemius showed no spontaneous activity and a full interference pattern with normal-appearing motor units. The common peroneal nerve had an absent motor response. Needle EMG showed a reduced interference pattern of the tibialis anterior with intact voluntary motor units. This suggested a
B. McNamara Department of Neurophysiology, Cork University Hospital, Cork, Ireland
Discussion
Eur J Pediatr
Fig. 2 Peroneal nerve conduction studies at the ankle (top) and below the knee (middle). a Left peroneal nerve on day 2. b Right peroneal nerve on day 2. c Right peroneal nerve at 6 months of age
neurapraxia with axonal interruption to the common peroneal nerve or L5 nerve root. MRI of her brain and spinal cord was also performed and was normal. Motor NCS normalised by 6 months of age (Fig. 2). The diagnosis was a right common peroneal nerve mononeuropathy. The EMG findings in this case suggested a neuropraxia with axonal interruption to the common peroneal nerve or L5 root. Physiotherapy and occupational therapy including splinting of the affected limb were initiated pre hospital discharge. At 3 weeks of age, she began to show some spontaneous evidence of dorsiflexion of the foot, which had improved over the next 2 months. Repeat EMG at 12 weeks of age was normal, and by 6 months of age, there was full voluntary dorsiflexion. Of note, this patient’s father had a background of lower limb paraesthesia in the past. He had neuroimaging performed and had been investigated for hereditary neuropathy with liability for pressure palsies. These investigations were negative. Dorsiflexion at the ankle joint utilises a pathway from the motor cortex to the spinal cord, sciatic nerve, common peroneal nerve and anterior tibialis muscle. Intact surrounding structures such as bones and ligaments are also required. Foot drop can be a result of pathology involving this pathway. Isolated peroneal nerve palsy is a rare phenomenon in the neonate, and there have been few previously reported cases [1, 2, 6]. Foot drop has also been described in older neonates as a result of ischaemic necrosis of the gluteal region following umbilical artery catheterisation [3], pelvic fibrosarcoma in a 10-day old [4] and group B streptococcal osteomyelitis [8]. In older children, the likely aetiology is compression, trauma or entrapment [5]. Mononeuropathies in neonates are most commonly results of trauma during delivery or of compression in utero, e.g. constriction bands [7]. They may also be a component
of a systemic disorder (e.g. hereditary sensory motor neuropathy) or an indication of an underlying structural central nervous system disorder. The investigation of congenital foot drop should include neurophysiology assessment (EMG and NCS) and neuroimaging. Nerve conduction studies and electromyography (EMG) can aid in defining the exact location of the nerve injury. The peroneal nerve is a division of the sciatic nerve, which splits above the popliteal fossa to form the tibial and common peroneal nerves. The latter nerve extends anterolaterally around the neck of the fibula where it is exposed to potential injury. We postulate that the most likely cause of this mononeuropathy was compression of the common peroneal nerve in utero at the lateral margin of the knee secondary to abnormal posture in utero as evidenced by the torticollis to the left side. The outcome for this rare condition in the newborn infant is variable and will depend on the underlying aetiology. Investigations including EMG, NCS and neuroimaging can help isolate the lesion and prognosticate on outcome. Early physiotherapy and occupational therapy should be initiated in an attempt to improve longterm outcome.
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Eur J Pediatr 5. Jones HR Jr, Felice KJ, Gross PT (1993) Pediatric peroneal mononeuropathy: a clinical and electromyographic study. Muscle Nerve 16:1167–1173 6. Jones HR Jr, Herbison GJ, Jacobs SR, Kollros PR, Macones GA (1996) Intrauterine onset of a mononeuropathy: peroneal neuropathy in a newborn with electromyographic findings at age one day compatible with prenatal onset. Muscle Nerve 19:88–91
7. Jones NF, Smith AD, Hedrick MH (2001) Congenital constriction band syndrome causing ulnar nerve palsy: early diagnosis and surgical release with long-term follow-up. J Hand Surg Am 26:467–473 8. Obando I, Martin E, Alvarez-Aldean J, Chileme A, Baca M, Barrio F (1991) Group B Streptococcus pelvic osteomyelitis presenting as foot drop in a newborn infant. Pediatr Infect Dis J 10:703–705
