Obstetric brachial plexus lesions: CT myelography

Evaluation of Infantile Brachial Plexopathy Using 3T MRI and High-Resolution Ultrasound: Experience From a Tertiary Care Centre

BACKGROUND

Currently, clinical assessment is the main tool for the evaluation of brachial plexus injury, complemented by electrophysiologic studies (EPS), and imaging studies whenever available. Imaging plays an important role as it enables the differentiation of pre-ganglionic and postganglionic injuries, and adds objectivity to presurgical evaluation.

OBJECTIVES

The primary objective was to evaluate the utility of magnetic resonance imaging (MRI) and high-resolution ultrasonography (USG) in the localization and characterization of brachial plexus injury in infants.

MATERIALS AND METHODS

In this prospective study, 34 infants with signs and symptoms of brachial plexus injury were evaluated by clinical examination, EPS, MRI, and USG. Imaging findings were correlated with intraoperative findings in infants who underwent surgical management. The association between EPS and MRI findings, and USG and MRI findings were assessed using Fisher's exact test. Semi-quantitative subjective analysis of various MRI sequences was done as well.

RESULTS

The most common findings of preganglionic injury and postganglionic injury, in our study, were pseudomeningocele and nerve thickening, respectively. MRI detection of injuries had a significant association with EPS findings. All MRI-detected injuries had a muscle power of grade 3 or less. muscle. Three-dimensional (3D) short tau inversion recovery (STIR) sequence was found to be superior for detecting postganglionic injuries (P < 0.05).

CONCLUSION

Imaging studies enable localization of the site of injury, determining the extent, and nature/morphology of injury. The gamut of findings obtained from MRI is far wider compared to that from USG. USG can be used as the first-line screening investigation.

Shoulder Internal Rotation Contracture Formation in Surgically Managed C5, C6 Brachial Plexus Birth Injuries: Neurotmetic Lesions Fare Worse Than Avulsions

BACKGROUND

A typical feature in infants with severe C5-C6 brachial plexus birth injury (BPBI) requiring nerve repair is the formation of shoulder internal rotation contracture (IRC). The underlying pathophysiological mechanism is unknown, and the sequelae can be difficult to treat. The severity of the IRC differs among children. C5-C6 lesions are heterogeneous at the root level. Our null hypothesis was that the type of root-level lesion (axonotmesis or neurotmesis versus avulsion) was not associated with the extent of IRC formation over time in children with upper-trunk BPBI.

METHODS

We performed a retrospective analysis of all patients with upper-trunk BPBI who underwent primary surgery of the C5 and/or C6 spinal nerves between 1990 and 2020 and had follow-up of at least 2 years. The primary outcome was passive shoulder external rotation (ER) in adduction at 1, 3, 5, 7, and 15 years of age. The secondary outcome was whether additional shoulder surgery was performed. The relationship between the nature of the C5-C6 lesion and IRC formation was analyzed using linear mixed models. The Kaplan-Meier method was used to estimate the cumulative risk of secondary shoulder procedures.

RESULTS

In total, 322 patients were analyzed; mean follow-up was 7.2 ± 4.6 years. The C5-C6 root lesion type was significantly related to the passive range of ER (overall test in linear mixed model, p = 0.007). Children with avulsion of C5 and C6 (n = 21) had, on average, 18° (95% confidence interval [CI], 6.3° to 30°) less IRC formation than those with neurotmesis of C5 and C6 (n = 175) and 17° (2.9° to 31°) less than those with neurotmesis of C5 and avulsion of C6 (n = 34). IRC formation did not differ between the neurotmesis C5-C6 and neurotmesis C5-avulsion C6 groups. Secondary shoulder procedures were performed in 77 patients (10-year risk, 28% [95%CI, 23% to 34%]).

CONCLUSIONS

Shoulder IRC formation in infants with BPBI with surgically treated C5-C6 lesions occurs to a lesser degree if the C5 root is avulsed than when C5 is neurotmetic. This finding provides insight into the possible causative pathoanatomy and may ultimately lead to strategies to mitigate IRC.

LEVEL OF EVIDENCE

Prognostic Level III . See Instructions for Authors for a complete description of levels of evidence.

Radiographic imaging modalities for perinatal brachial plexus palsy: a systematic review

PURPOSE

Perinatal brachial plexus palsy (PBPP) has a wide spectrum of clinical symptoms that can range from incomplete paresis of the affected extremity to flaccid arm paralysis. Although there is a high rate of spontaneous recovery within the first two years of life, it remains challenging to determine which patients will benefit most from surgical intervention. The diagnostic and predictive use of various imaging modalities has been described in the literature, but there is little consensus on approach or algorithm. The anatomic, pathophysiological, and neurodevelopmental characteristics of the neonatal and infant patient population affected by PBPP necessitate thoughtful consideration prior to selecting an imaging modality.

METHODS

A systematic review was conducted using six databases. Two reviewers independently screened articles published through October 2021.

RESULTS

Literature search produced 10,329 publications, and 22 articles were included in the final analysis. These studies included 479 patients. Mean age at time of imaging ranged from 2.1 to 12.8 months and investigated imaging modalities included MRI (18 studies), ultrasound (4 studies), CT myelography (4 studies), and X-ray myelography (1 study). Imaging outcomes were compared against surgical findings (16 studies) or clinical examination (6 studies), and 87.5% of patients underwent surgery.

CONCLUSION

This systematic review addresses the relative strengths and challenges of common radiologic imaging options. MRI is the most sensitive and specific for identifying preganglionic nerve injuries such as pseudomeningoceles and rootlet avulsion, the latter of which has the poorest prognosis in this patient population and often dictates the need for surgical intervention.

Brachial Plexus Birth Palsy: Practical Concepts for Radiologists

Brachial plexus birth palsy (BPBP) is classified as a preganglionic or postganglionic injury based on the site of injury. Most patients recover spontaneously and are followed up with clinical evaluation; however, permanent sequelae are not uncommon. For patients with persistent neurologic deficits, clinical and radiologic evaluation is crucial. Untreated BPBP can progress to significant sequelae, such as muscle contractures and glenohumeral dysplasia (GHD). Timely characterization of these entities based on different imaging modalities is a high priority for optimal patient outcomes. We describe the anatomy and pathogenesis, as well as the different imaging modalities involved in the evaluation and classification of BPBP and GHD.

Contemporary imaging of the pediatric shoulder: pearls and pitfalls

In skeletally immature patients, the presence of growth plates and articular cartilage of the shoulder can create a predisposition for unique injuries not observed in adults. Furthermore, increasing participation in sports by children and adolescents appears to be leading to a corresponding increase in the number of sports-related injuries. The importance of radiologists being familiar with pediatric shoulder imaging and its associated injuries is therefore growing. In this article, we review the normal development and maturation pattern of ossification centers of the shoulder from the early gestational period through adolescence. Brachial plexus birth palsy, physeal injuries, shoulder dislocation, and internal impingement are discussed within the context of the child's age and the mechanism of injury to guide radiologists to a correct diagnosis.

Comparative accuracies of electrodiagnostic and imaging studies in neonatal brachial plexus palsy

OBJECTIVEThe incorporation of ancillary testing in the preoperative setting for patients with neonatal brachial plexus palsy (NBPP) remains controversial, but the recommendation for early nerve reconstruction when a baby has a preganglionic lesion at the lower nerve roots is generally accepted. At some specialty centers, nerve surgeons use preoperative electrodiagnostic testing (EDX) and imaging to aid in lesion localization and the preoperative planning of the nerve reconstruction. EDX and imaging have been evaluated for their abilities to detect pre- and postganglionic lesions, but their accuracies have never been compared directly in the same set of patients. The aim of the present study was to evaluate the accuracy of imaging and EDX in an NBPP population.METHODSA retrospective review was conducted of 54 patients with operative NBPP seen between 2007 and 2017. The patients underwent EDX and imaging: EDX was performed, and the results were reviewed by board-certified electrodiagnosticians, and imaging was reviewed by board-certified neuroradiologists. The gold standard was considered to be the findings at surgical exploration. Descriptive and analytical statistics were utilized to compare the accuracies of imaging and EDX.RESULTSThe mean age at surgery was 6.94 mos (± 4 mos). Fifteen patients (28%) were Narakas grade I-II, and 39 (72%) were Narakas grade III-IV. For all nerve roots, the overall accuracy of detecting preganglionic lesions was 74% for EDX and 69% for imaging. The overall sensitivity of detecting preganglionic lesions by EDX was 31%, but the specificity was 90%. The overall sensitivity of detecting preganglionic lesions by imaging was 66%, and the overall specificity was 70%. However, at C8, EDX was 37.5% sensitive and 87.5% specific, whereas imaging was 67.7% sensitive but only 29.4% specific.CONCLUSIONSEDX outperformed imaging with regard to specificity and accuracy of identifying preganglionic injuries. This finding is especially relevant in the lower nerve roots, given that lower plexus preganglionic lesions are an accepted indication for early intervention.

The current role of diagnostic imaging in the preoperative workup for refractory neonatal brachial plexus palsy

INTRODUCTION

Despite recent improvements in perinatal care, the incidence of neonatal brachial plexus palsy (NBPP) remains relatively common. CT myelography is currently considered to be the optimal imaging modality for evaluating nerve root integrity. Recent improvements in MRI techniques have made it an attractive alternative to evaluate nerve root avulsions (preganglionic injuries).

AIM

We demonstrate the utility of MRI for the evaluation of normal and avulsed spinal nerve roots. We also show the utility of ultrasound in providing useful preoperative evaluation of the postganglionic brachial plexus in patients with NBPP.

Utility of ultrasound in noninvasive preoperative workup of neonatal brachial plexus palsy

BACKGROUND

Ultrasound has been utilized in the evaluation of compressive and traumatic peripheral nerve pathology.

OBJECTIVE

To determine whether US can provide comprehensive evaluation of the post-ganglionic brachial plexus in the setting of neonatal brachial plexus palsy and whether this information can be used to guide preoperative nerve reconstruction strategies.

MATERIALS AND METHODS

In this retrospective cohort study, preoperative brachial plexus ultrasonography was performed in 52 children with neonatal brachial plexus palsy who were being considered for surgery. The 33 children who had surgery compose the patient cohort. The presence and location of post-ganglionic neuromas were evaluated by US and compared to the surgical findings. US evaluation of shoulder muscle atrophy was conducted as an indirect way to assess the integrity of nerves. Finally, we correlated glenohumeral joint laxity to surgical and clinical management.

RESULTS

Ultrasound correctly identified 21 of 25 cases of upper trunk and middle trunk neuroma involvement (84% sensitivity for each). It was 68% sensitive and 40% specific in detection of lower trunk involvement. US identified shoulder muscle atrophy in 11 of 21 children evaluated; 8 of these 11 went on to nerve transfer procedures based upon the imaging findings. US identified 3 cases of shoulder joint laxity of the 13 children evaluated. All 3 cases were referred for orthopedic evaluation, with 1 child undergoing shoulder surgery and another requiring casting.

CONCLUSION

Ultrasound can provide useful preoperative evaluation of the post-ganglionic brachial plexus in children with neonatal brachial plexus palsy.

Nerve Transfers in Birth Related Brachial Plexus Injuries: Where Do We Stand?

This article reviews the assessment and management of obstetrical brachial plexus palsy. The potential role of distal nerve transfers in the treatment of infants with Erb's palsy is discussed. Current evidence for motor outcomes after traditional reconstruction via interpositional nerve grafting and extraplexal nerve transfers is reviewed and compared with the recent literature on intraplexal distal nerve transfers in obstetrical brachial plexus injury.

Clinical and neurobiological advances in promoting regeneration of the ventral root avulsion lesion

Root avulsions due to traction to the brachial plexus causes complete and permanent loss of function. Until fairly recent, such lesions were considered impossible to repair. Here we review clinical repair strategies and current progress in experimental ventral root avulsion lesions. The current gold standard in patients with a root avulsion is nerve transfer, whereas reimplantation of the avulsed root into the spinal cord has been performed in a limited number of cases. These neurosurgical repair strategies have significant benefit for the patient but functional recovery remains incomplete. Developing new ways to improve the functional outcome of neurosurgical repair is therefore essential. In the laboratory, the molecular and cellular changes following ventral root avulsion and the efficacy of intervention strategies have been studied at the level of spinal motoneurons, the ventral spinal root and peripheral nerve, and the skeletal muscle. We present an overview of cell-based pharmacological and neurotrophic factor treatment approaches that have been applied in combination with surgical reimplantation. These interventions all demonstrate neuroprotective effects on avulsed motoneurons, often accompanied with various degrees of axonal regeneration. However, effects on survival are usually transient and robust axon regeneration over long distances has as yet not been achieved. Key future areas of research include finding ways to further extend the post-lesion survival period of motoneurons, the identification of neuron-intrinsic factors which can promote persistent and long-distance axon regeneration, and finally prolonging the pro-regenerative state of Schwann cells in the distal nerve.

International Federation of Societies for Surgery of the Hand Committee report: the role of nerve transfers in the treatment of neonatal brachial plexus palsy

Nerve transfers have gained popularity in the treatment of adult brachial plexus palsy; however, their role in the treatment of neonatal brachial plexus palsy (NBPP) remains unclear. Brachial plexus palsies in infants differ greatly from those in adults in the patterns of injury, potential for recovery, and influences of growth and development. This International Federation of Societies for Surgery of the Hand committee report on NBPP is based upon review of the current literature. We found no direct comparisons of nerve grafting to nerve transfer for primary reconstruction of NBPP. Although the results contained in individual reports that use each strategy for treatment of Erb palsy are similar, comparison of nerve transfer to nerve grafting is limited by inconsistencies in outcomes reported, by multiple confounding factors, and by small numbers of patients. Although the role of nerve transfers for primary reconstruction remains to be defined, nerve transfers have been found to be effective and useful in specific clinical circumstances including late presentation, isolated deficits, failed primary reconstruction, and multiple nerve root avulsions. In the case of NBPP more severe than Erb palsy, nerve transfers alone are inadequate to address all of the deficits and should only be considered as adjuncts if maximal re-innervation is to be achieved. Surgeons who commit to care of infants with NBPP need to avoid an over-reliance on nerve transfers and should also have the capability and inclination for brachial plexus exploration and nerve graft reconstruction.

Results of nerve reconstructions in treatment of obstetrical brachial plexus injuries

BACKGROUND

The aim of this study was to evaluate the results achieved using various surgical techniques in patients with partial and total obstetrical brachial plexus palsy.

METHODS

From 2000 to 2013, 33 patients with obstetrical brachial plexus injury underwent surgery. Twenty had follow-up periods greater than 24 months and met the criteria for inclusion in the study. All patients were evaluated using the Active Movement Scale.

RESULTS

The outcomes of different nerve reconstructive procedures including nerve transfers, nerve grafting after neuroma resection and end-to-side neurorrhaphy are presented. The overall success rate in upper plexus birth injury was 80 % in shoulder abduction, 50 % in external rotation and 81.8 % in elbow flexion with median follow-ups of 36 months. Success rate in complete paralysis was 87 % in finger and thumb flexion, 87 % in shoulder abduction and 75 % in elbow flexion; the median follow-up was 46 months. Useful reanimation of the hand was obtained in both patients who underwent end-to-side neurotization.

CONCLUSION

Improved function can be obtained in infants with obstetrical brachial plexus injury with early surgical reconstruction.

Neonatal brachial plexus palsy with neurotmesis of C5 and avulsion of C6: supraclavicular reconstruction strategies and outcome

BACKGROUND

Nerve reconstruction strategies for restoration of elbow flexion and shoulder function in patients with neonatal brachial plexus palsy with neurotmesis of C5 and avulsion of C6 are not well defined and the outcomes are unclear.

METHODS

From 1990 to 2008, nerve surgery was performed in 421 patients with neonatal brachial plexus palsy. This study focused on thirty-four infants who had a neurotmetic lesion of C5 and avulsion or intraforaminal neurotmesis of C6, irrespective of C7. The C8 and T1 functions were intact. Intraplexal transfer of C6 to C5 with direct coaptation was preferred for restoration of elbow flexion. The suprascapular nerve was reconnected either by extra-intraplexal transfer of the accessory nerve or by grafting from C5 to restore shoulder function. Additional grafts were attached from C5 to the C5 contribution of the posterior division of the superior trunk when technically possible.

RESULTS

Transfer of either the C6 anterior root filaments or the entire C6 nerve to C5 was performed in seventeen patients (group A) with direct coaptation in fifteen of them. Grafting from C5 to the anterior division of the superior trunk was performed in the remaining seventeen infants (group B). An accessory-to-suprascapular nerve transfer was applied in twenty-nine infants. The suprascapular nerve was reconnected in five patients by grafting from C5. It was possible to attach one, two, or three additional grafts from C5 to the posterior division of the superior trunk in twenty-one patients. All infants had biceps muscle recovery to a Medical Research Council (MRC) grade of ≥4, twenty-two (65%) of the thirty-four patients obtained Mallet grade-IV abduction, and eleven (32%) of the thirty-four obtained Mallet grade-IV external rotation.

CONCLUSIONS

In patients with neonatal brachial plexus palsy who have neurotmesis of C5 and avulsion of C6, elbow flexion can be successfully restored with supraclavicular intraplexal reconstruction with use of C5 as the proximal outlet. However, shoulder function recovery following suprascapular nerve reinnervation and additional grafting from C5 to the posterior division of the superior trunk is less successful.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Intercostal and pectoral nerve transfers to re-innervate the biceps muscle in obstetric brachial plexus lesions

In obstetric brachial plexus lesions with avulsion injury, nerve grafting for biceps muscle re-innervation may not be possible owing to the unavailability of a proximal stump. In such cases, the intercostal nerves or medial pectoral nerve can serve as donor nerves in an end-to-end transfer to the musculocutaneous nerve. The present study reports the results of both techniques from a single institution in a consecutive series of 42 patients between 1995 and 2008. From 1995 to 2000 we always used the intercostal nerve transfer, and from 2001 to 2008 both techniques were used. Biceps muscle force ≥ Medical Research Council Grade 3 was achieved in 37 of 42 patients after a mean follow-up of 44 months. There was no statistical difference in the results in the medial pectoral nerve transfer group (n = 25) and the intercostal nerve transfer group (n = 17).

The diagnostic value of CT myelography, MR myelography, and both in neonatal brachial plexus palsy

BACKGROUND AND PURPOSE

Although most infants with brachial plexus palsy recover function spontaneously, approximately 10-30% benefit from surgical treatment. Pre-operative screening for nerve root avulsions is helpful in planning reconstruction. Our aim was to compare the diagnostic value of CT myelography, MR myelography, and both against a surgical criterion standard for detection of complete nerve root avulsions in birth brachial plexus palsy.

MATERIALS AND METHODS

Nineteen patients who underwent a preoperative CT and/or MR myelography and subsequent brachial plexus exploration were included. Imaging studies were analyzed for the presence of abnormalities potentially predictive of nerve root avulsion. Findings of nerve root avulsion on surgical exploration were used as the criterion standard to assess the predictive value of imaging findings.

RESULTS

Ninety-five root levels were examined. When the presence of any pseudomeningocele was used as a predictor, the sensitivity was 0.73 for CT and 0.68 for MR imaging and the specificity was 0.96 for CT and 0.97 for MR imaging. When presence of pseudomeningocele with absent rootlets was used as the predictor, the sensitivity was 0.68 for CT and 0.68 for MR imaging and the specificity was 0.96 for CT and 0.97 for MR imaging. The use of both CT and MR imaging did not increase diagnostic accuracy. Rootlet findings in the absence of pseudomeningocele were not helpful in predicting complete nerve root avulsion.

CONCLUSIONS

Findings of CT and MR myelography were highly correlated. Given the advantages of MR myelography, it is now the single technique for preoperative evaluation of nerve root avulsion at our institution.

The evidence for nerve repair in obstetric brachial plexus palsy revisited

Strong scientific validation for nerve reconstructive surgery in infants with Obstetric Brachial Plexus Palsy is lacking, as no randomized trial comparing surgical reconstruction versus conservative treatment has been performed. A systematic review of the literature was performed to identify studies that compare nerve reconstruction to conservative treatment, including neurolysis. Nine papers were identified that directly compared the two treatment modalities. Eight of these were classified as level 4 evidence and one as level 5 evidence. All nine papers were evaluated in detail to describe strong and weak points in the methodology, and the outcomes from all studies were presented. Pooling of data was not possible due to differences in patient selection for surgery and outcome measures. The general consensus is that nerve reconstruction is indicated when the result of nerve surgery is assumedly better than the expected natural recovery, when spontaneous recovery is absent or severely delayed. The papers differed in methodology on how the cut-off point to select infants for nerve reconstructive surgical therapy should be determined. The justification for nerve reconstruction is further discussed.

High-resolution MRI evaluation of neonatal brachial plexus palsy: A promising alternative to traditional CT myelography

BACKGROUND AND PURPOSE

Despite recent improvements in perinatal care, the incidence of neonatal brachial plexus palsy remains relatively common. CT myelography is currently considered to be the optimal imaging technique for evaluating nerve root integrity. Recent improvements in MR imaging techniques have made it an attractive alternative to evaluate nerve root avulsions (preganglionic injuries). We aim to demonstrate utility of MR imaging in the evaluation of normal and avulsed spinal nerve roots.

MATERIALS AND METHODS

All study patients with clinically diagnosed neonatal brachial plexus palsy underwent MR imaging by use of a high-resolution, heavily T2-weighted (driven equilibrium) sequence. MR imaging findings were reviewed for presence of nerve root avulsion from C5-T1 and for presence of pseudomeningocele. The intraoperative findings were reviewed and compared with the preoperative MR imaging findings.

RESULTS

Thirteen patients (9 male, 4 female) underwent MR imaging; 6 patients underwent nerve reconstruction surgery, during which a total of 19 nerve roots were evaluated. Eight avulsions were noted at surgery and in the remainder, the nerve injury was more distal (rupture/postganglionic injury). Six of the 8 nerve root avulsions identified at surgery were at C5-6 level, whereas 1 nerve root avulsion was identified at C7 and C8 levels, respectively. The overall sensitivity and specificity of MR imaging for nerve root avulsions was 75% and 82%, respectively.

CONCLUSIONS

Our preliminary results demonstrate that high-resolution MR imaging offers an excellent alternative to CT myelography for the evaluation of neonatal brachial plexus palsy with similar sensitivity compared with CT myelography.

Diagnostic performance of ultrasound in patients with suspected brachial plexus lesions in adults: a multicenter retrospective study with MRI, surgical findings and clinical follow-up as reference standard

PURPOSE

To evaluate brachial plexus ultrasound (US) performance in a large multicenter study.

MATERIALS AND METHODS

The research was approved by the Institutional Review Boards, and all patients gave written informed consent. A multicenter retrospective trial including three centers was performed between March, 2006 and April, 2011. A total of 204 patients who received a brachial plexus ultrasound requested by the referring physician were enrolled: magnetic resonance imaging, surgical findings and clinical follow-up of at least 12 months were used as the reference standard. Sensitivity, specificity with 95 % confidence intervals (CIs), positive predictive value (PPV), pre-test-probability (the prevalence), negative predictive value (NPV), pre- and post- test odds (OR), likelihood ratio for positive results (LH+), likelihood ratio for negative results (LH-), accuracy and post-test probability (post-P) were reported on a per-patient basis.

RESULTS

The overall sensitivity and specificity with 95 % CIs were: 0.76 (0.75-0.97); 0.96 (0.77-0.89). Overall PPV, pre-test probability, NPV, pre-OR, post-OR, LH+, LH-, Accuracy and post-P were: 0.93/0.43/0.84/0.75/0.75/13.4/17.6/0.25/0.88/0.93, respectively.

CONCLUSIONS

The specificity of brachial plexus US in patients suspected of having a brachial plexus lesion is very high.

Severe obstetric brachial plexus palsies can be identified at one month of age

OBJECTIVE

To establish whether severe obstetric brachial plexus palsy (OBPP) can be identified reliably at or before three months of age.

METHODS

Severe OBPP was defined as neurotmesis or avulsion of spinal nerves C5 and C6 irrespective of additional C7-T1 lesions, assessed during surgery and confirmed by histopathological examination. We first prospectively studied a derivation group of 48 infants with OBPP with a minimal follow-up of two years. Ten dichotomous items concerning active clinical joint movement and needle electromyography of the deltoid, biceps and triceps muscles were gathered at one week, one month and three months of age. Predictors for a severe lesion were identified using a two-step forward logistic regression analysis. The results were validated in two independent cohorts of OBPP infants of 60 and 13 infants.

RESULTS

Prediction of severe OBPP at one month of age was better than at one week and at three months. The presence of elbow extension, elbow flexion and of motor unit potentials in the biceps muscle correctly predicted whether lesions were mild or severe in 93.6% of infants in the derivation group (sensitivity 1.0, specificity 0.88), in 88.3% in the first validation group (sensitivity 0.97, specificity 0.76) and in 84.6% in the second group (sensitivity of 1.0, specificity 0.66).

INTERPRETATION

Infants with OBPP with severe lesions can be identified at one month of age by testing elbow extension, elbow flexion and recording motor unit potentials (MUPs) in the biceps muscle. The decision rule implies that children without active elbow extension at one month should be referred to a specialized center, while children with active elbow extension as well as active flexion should not. When there is active elbow extension, but no active elbow flexion an EMG is needed; absence of MUPs in the biceps muscle is an indication for referral.