Pathway for the Differential Diagnosis of Obstetrical Brachial Plexus Palsy

Abstract

Background:

Obstetrical brachial plexus palsy (OBPP) is a common birth injury, generally presenting as upper limb paralysis at birth. While diagnosis is straightforward when associated with known risk factors, misdiagnoses can nevertheless occur. This study aimed to elucidate the process of differential diagnosis for OBPP by analyzing cases of suspected OBPP, ultimately diagnosed with other conditions.

Methods:

We reviewed the electronic medical records of patients under 1 year of age presenting with suspected or previously diagnosed OBPP at 2 tertiary childrens’ centers in Osaka between 1994 and 2021. Cases were divided into the OBPP and non-OBPP groups, according to the final diagnosis, for comparison of demographic data and physical findings, to determine the clinical course that could be used to differentiate non-OBPP from OBPP.

Results:

Of the 414 enrolled cases, 387 (93%) were confirmed as OBPP, while 27 (7%) were diagnosed with other conditions. Statistically significant differences were found in gestational age, birth weight, and age of first visit, between the 2 groups, although these were not clinically meaningful for differential diagnosis. Shoulder dystocia was observed in 54% of OBPP cases, but not in non-OBPP cases. The key characteristics of OBPP included paralysis from birth, paralysis following an anatomic distribution, and paralysis that gradually improved without worsening. Conversely, joint contracture immediately after birth was a key indicator for ruling out OBPP. Using these criteria, 24 of 27 suspected cases were excluded from OBPP diagnosis. Of the remaining 3 cases, spinal cord infarction was detected on MRI in 1 case. In the remaining 2 cases, although normal MRI and surgical findings could rule out OBPP, a definite diagnosis could not be made.

Conclusions:

This study highlights that accurate OBPP diagnosis requires careful verification of specific characteristics. If these characteristics are not met, OBPP becomes less likely, and diagnostic uncertainty persists. An MRI of the brachial plexus is needed in such cases.

Level of Evidence:

Level III—retrospective cohort study.

Obstetrical brachial plexus palsy (OBPP) is a traction injury to the brachial plexus resulting from excessive traction on the fetal brachial plexus during delivery that occurs in 1.24 to 3.5 per 1000 live births.^1–3 Diagnosis is generally straightforward when patients present with flaccid paralysis is present at birth, particularly when associated with complications such as difficult delivery, macrosomia, breech presentation, vacuum or forceps extraction, or shoulder dystocia.^4–6 However, misdiagnoses occasionally occur among physicians unfamiliar with OBPP.

One contributing factor to misdiagnosis is the lack of a systematically-described differential diagnosis for OBPP in the literature. While conditions such as fractures of the clavicle or humeral shaft, septic arthritis of the shoulder, tumors involving the spinal cord or brachial plexus, and postinfectious plexopathy have all been mentioned as potential differential diagnoses, these have often been listed randomly, without any form of structured approach.

In this article, we analyze cases referred to our hospital with suspected OBPP that were ultimately diagnosed with other conditions, with the aim of elucidating the process of different diagnosis for OBPP, as distinguishing OBPP from other conditions is essential to allow proper treatment.

METHODS

Data were extracted from electronic medical records of patients under 1 year of age who presented to the orthopaedics departments of 2 tertiary children; centers in Osaka with suspected or diagnosed cases of OBPP between 1994 and 2021. Patients were divided into OBPP and non-OBPP groups based on their final diagnosis. Information on suspected diagnosis, birth history, date of first visit, physical and imaging findings, and clinical course was collected, and ethical approval was obtained from both centers. Further, verbal informed consent was obtained from the patient’s parents and/or legal guardians.

Statistical Analysis

Statistical analysis was performed using Microsoft Excel (Microsoft Corporation, Redmond, WA). The t test was used for continuous variables and the χ² test for categorical variables. A P-value <0.05 was considered statistically significant.

RESULTS

Of the 414 cases referred with a diagnosis of OBPP or suspected OBPP, 387 (93%) were ultimately confirmed as OBPP, while 27 (7%) were diagnosed with other conditions. The diagnoses in the referral letters in the non-OBPP group were OBPP (n=10), suspected OBPP (n=6), upper limb palsy (n=8), and others with no specific diagnosis, but with suspected OBPP mentioned in the text (n=3).

Statistically significant differences in gestational age (38.4/39.0 w), birth weight (3896/2910 g), and age of first visit (81/115 d) were found between the OBPP and non-OBPP groups; however, these were not clinically meaningful for differential diagnosis. Shoulder dystocia was observed in 54% of OBPP cases, but was not observed in non-OBPP cases. Cesarean section rates were 3%/33%, and neonatal asphyxia occurred in 51%/19% (Fig. 1).

FIGURE 1.

Comparison between the OBPP and non-OBPP groups.

Final diagnoses in the non-OBPP cases included congenital abnormalities such as arthrogryposis, hemiplegia due to cerebral palsy, nonobstetrical trauma, monoplegia including acute flaccid paralysis, intrauterine molding syndrome, spinal cord infarction, and intramuscular abscess (Fig. 2).

FIGURE 2.

Final diagnoses in patients in the non-OBPP group (number:cases).

In the OBPP group, upper limb paralysis without contractures was present immediately after birth, with most cases achieving partial recovery within a few months. The most frequent reason for ruling out OBPP was the presence of contractures in the upper limbs immediately after birth (n=9). Other reasons included paralysis not following the anatomic distribution (n=8) and palsy not being present immediately after birth (n=7). The other 3 patients with suspected OBPP underwent cervical MRI examination revealing a flattened spinal cord in 1 case, and normal findings in 2 cases. For these 2 cases with normal findings, we performed a diagnostic exploration of the brachial plexus, which revealed no abnormalities in either case (Table 1).

TABLE 1.

Points for Ruling Out OBPP

Points	Cases
Paralysis absent at birth	9
Paralysis does not follow anatomy	8
Contractures of limbs	7
Flattening of the spinal cord in MRI	1
Normal MRI and intact brachial plexus	2
Total	27

DISCUSSION

The prognosis is favorable for most cases of birth palsy;⁷ however, some severe cases exist, necessitating early nerve surgery.^8,9 Misdiagnosis or failure to definitively diagnose OBPP can result in missing the optimal timing for surgery. While surgical exploration or MRI examination can provide absolute confirmation of brachial plexus injury, these methods are both invasive and complex, precluding their use in all suspected cases. Generally, OBPP is diagnosed when paralysis of the upper extremity is present immediately after birth, accompanied by a history of abnormal or difficult labor, such as shoulder dystocia and breech presentation.¹⁰

In our study, 27 cases (7%) were misdiagnosed as OBPP. These infants presented with upper extremity immobility, leading referring doctors to suspect OBPP. Demographic data including gestational age at birth, birth weight, and age at initial visit, showed statistically significant differences between the OBPP and non-OBPP groups. However, these differences were not clinically meaningful for different diagnosis, although the presence of shoulder dystocia may strongly supports the diagnosis of OBPP.

On the basis of the findings of the present study, we propose that paralysis present from birth that gradually improves without worsening is a key characteristic of OBPP, with paralysis theoretically following anatomic distribution. Conversely, the presence of joint contractures immediately after birth can rule out OBPP. However, it should be noted that OBPP can coexist with other conditions. In addition, with the same brachial plexus injury, contractures are seen at birth in nontraumatic causes of paralysis seen at birth such as congenital brachial plexus abnormalities or absence, bicornuate uteri, and intrauterine molding syndrome, which are very rare among brachial nerve injuries, but they can be differentiated from traumatic brachial plexus palsy, whose prognosis depends on the timing of treatment. By applying these criteria, we were able to exclude 24 out of 27 suspected cases from OBPP diagnosis.

Cervical spinal cord MRI was performed in 14 cases, including 3 for which a definitive diagnosis remained elusive.¹¹ While nerve root abnormalities on cervical MRI strongly suggest OBPP, normal findings do not exclude this diagnosis.^12,13 In our study, MRI results were normal except in 1 case of spinal cord infarction. Brachial plexus exploration was performed as a therapeutic necessity in 5 cases (combination of intercostal nerve transfer, neurolysis, tendon transfer, arthrolysis, and muscle biopsy) and to facilitate definitive diagnosis in 2 cases, revealing no abnormal findings in any of the 7 cases. A normal MRI of the brachial plexus could be helpful in ruling out OBPP.

Although infant kinesthetic function tests may present a challenge to inexperienced physicians, we believe that the main reason for misdiagnosis was a lack of knowledge. Therefore, educating general practitioners about the different diagnoses of OBPP is crucial. Our study's limitation lies in its conduction at only 2 centers, potentially limiting the generalizability of our findings. Future multicenter research with larger sample sizes is required to confirm our results and explore potential population differences. Nevertheless, our study included 414 cases, a relatively large sample size for this type of study.

In conclusion, accurate diagnosis of OBPP requires careful verification of the aforementioned criteria. If any criteria are not met, OBPP becomes less likely. In such cases, continued close observation is essential. If recovery is unsatisfactory, an MRI examination should be considered.