Case Report

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American Journal of Emergency Medicine

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American Journal of Emergency Medicine 34 (2016) 756.e1-756.e2

An infant not moving her leg

Abstract

A 4-week-old female infant presented to the emergency department (ED) due to a 1-week history of not moving her Left lower extremity as well as crying during diaper changes. She had been seen 6 days prior at an ED, had normal x-rays, and was discharged home. The infant was afebrile and well appearing and had been feeding well all week. Labora- tory tests in our department, including a complete blood count with differential and inflammatory markers, were all normal. Repeat x-rays showed a subtle Distal tibial lucency, initially overlooked. The infant was admitted to the hospital and received a magnetic resonance imaging, which demonstrated distal tibial osteomyelitis with an accom- panying ankle effusion. Cultures from the bone grew group B Streptococcus, and the infant received 6 weeks of antibiotic therapy.

This case demonstrates the need for aggressive evaluation and likely admission for any infant younger than 1 year presenting with decreased use of an extremity, termed pseudoparalysis. Despite being afebrile and often having normal laboratory tests and normal x-rays, these patients should be considered to have a bone or joint infection until proven otherwise. Magnetic resonance imaging is the best imaging modality, and blood cultures should be drawn. Despite appearing systemically well for 1 week, this infant had a serious bacterial infection. Infants with pseudoparalysis should not be discharged from the ED having undergone only Laboratory workup and x-rays.

A 4-week-old female infant presented to the emergency department (ED) because of decreased movement of her left lower extremity for 1 week and crying during diaper changes. X-rays at an outside ED on day 1 of symptoms did not show a fracture, and she was discharged to follow up with her physician. The decreased movement continued, so her pediatrician sent her to our ED.

The infant had remained afebrile; had no swelling or erythema reported; and had been feeding, urinating, and stooling normally. She had not been irritable but had continued to cry with diaper changes. Pregnancy and delivery had been uneventful. Maternal serologies and group B Streptococcus (GBS) status were not known. Multiple family members cared for the child.

On our physical examination, she had normal vital signs: temperature of 37?C, heart rate of 122 beats per minute, respiratory rate of 38 breaths per minute, pulse oximetry of 98%, and a mean arterial pressure of 41. She was well-appearing and had a normal examination except that she held her left hip in flexion and became upset when it was extended. When placed prone, she was willing to extend the hip and did not seem uncom- fortable. No other areas of swelling or tenderness were apparent.

Repeat x-rays of her left hip, femur, and tibia/fibula were initially re- ported as normal. Laboratory tests revealed the following: white blood cell count 13 x 10³/uL with 20% neutrophils, C-reactive protein (CRP)

less than 0.3 mg/dL, and an erythrocyte sedimentation rate of 13 mm/h. An ultrasound of the hip showed no effusion. On further review of the x-rays, the radiologist noticed a “focal lytic area within the medial and posterior aspect of the distal left tibia with periosteal reaction” (Fig. 1). The child was admitted to the pediatric service for magnetic resonance imaging and orthopedic evaluation. Magnetic resonance imaging demonstrated findings consistent with a distal tibial osteomyelitis and possibly septic ankle joint (Fig. 2). Aspirates of the tibia and a bone biopsy grew GBS. The ankle joint fluid did not grow an organism. Antibiotics were started after the aspiration was complete, initially with clindamycin and ceftriaxone but after the cultures grew, the regimen was switched to ampicillin. She received 2 weeks of intra- venous ampicillin and then 4 weeks of oral amoxicillin.

This case demonstrates the emergent nature of working up an infant who is not moving an extremity, often termed pseudoparalysis. Despite a week of mild symptoms, a lack of fever, and normal laboratory results, this infant had a serious bacterial infection.

Osteomyelitis and Septic arthritis often coexist in infants due to the persistence of transphyseal blood vessels, connecting the joint space to the bone [1-3]. Staphylococcus aureus remains the most commonly reported organism causing osteomyelitis in all ages, but in neonates, GBS and Escherichia coli are important pathogens to consider [2].

The usual workup for suspected bone or joint infection involves an ESR, CRP, and a white blood cell count. The Kocher criteria, applicable to pedia- tric patients with hip pain to define the likelihood of septic arthritis, include non-weight-bearing on the effected side, ESR greater than 40 mm/h, fever, and a leukocyte count greater than 12000/mm³ [3,4] and are often applied to workup other potentially infected joints. There are no clear probability criteria for defining osteomyelitis based on laboratory tests, but practi- tioners tend to rely on them, as well as on x-rays [5]. Elevations in CRP and ESR have been shown but in small studies [6,7]. Neonatal osteomyelitis is often unaccompanied by fever and can be indolent for days to weeks, until severe bone or Joint destruction has already occurred. Crying with diaper changes, pseudoparalysis, and swelling may be the only initial clini- cal manifestations [7]. Surprisingly, GBS osteomyelitis is often not associa- ted with an abnormal white blood cell count or an ill-appearing infant [7,8]. Laboratory tests cannot reliably be used to rule out these infections.

We are often challenged with whether to be worried about well- appearing infants. Management of an infant with pseudoparalysis is based on far less data and experience than febrile but well-appearing infants. Given the data available from case studies and the potential serious adverse outcomes from missed infections in this age group, pseudoparalysis in infants, especially neonates, regardless of their overall appearance, vital signs, or laboratory tests, should be considered a skeletal infection until proven otherwise. The decision to start empiric antibiotic therapy before definitive diagnosis must balance the risk between losing a microbiological diagnosis and the risk of rapid decompensation if bacteremia develops.

0735-6757/(C) 2015

T. Berkowitz, D. Young / American Journal of Emergency Medicine 34 (2016) 756.e1–756.e2 756.e2

Fig. 1. X-ray of the tibia and fibula demonstrating a lytic lesion in the distal tibia. Fig. 2. Magnetic resonance imaging demonstrating osteomyelitis in the distal tibia with

adjacent ankle Joint effusion.

Tal Berkowitz, MD^? Deborah Young, MD

Division of Pediatric Emergency Medicine, Department of Pediatrics

Emory University, Atlanta, GA

^?Corresponding author. 1645 Tullie Circle, Atlanta, GA 30329

Email address: [email protected] http://dx.doi.org/10.1016/j.ajem.2015.07.073

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