Concordance and Discordance of Intraoperative Nerve Root Findings in Brachial Plexus Birth Injury

Accurate preoperative characterization of brachial plexus birth injury (BPBI) is important for counseling and surgical planning, but the prediction of root-level injury remains challenging. We evaluated the agreement between preoperative injury classification and intraoperative nerve root findings, patterns of discordance, and the influence of Horner syndrome (HS).

A retrospective review identified 162 infants who underwent primary brachial plexus exploration and reconstruction at a single institution between 2004 and 2023. Preoperative injury classification was assigned from clinical examination and Active Movement Scale (AMS) scores using a root level classification (2025): Injury A (C5-6), B (C5-7), C (C5-8), and D (C5-T1). Intraoperative class was assigned from operative findings, including nerve stimulation and direct assessment of root integrity.

Preoperative and intraoperative classifications were concordant in 135 of 162 patients (83.3%) and discordant in 27 (16.7%), with substantial overall agreement (Cohen kappa=0.700). Concordance was highest for Injury D (C5-T1) and poorest for Injury C (C5-C8). Preoperative classification was least accurate for Injury C, with only 1 of 14 cases correctly identified. Among the 27 discordant cases, undercalls were more common than overcalls (19 [70.4%] vs. 8 [29.6%]), most frequently involving B-to-C and A-to-B misclassification. C7 and C8 were the roots most often misidentified. Concordance did not differ significantly before versus after adoption of differential nerve stimulation (86.9% vs. 81.2%, P=0.070). All undercalls occurred without HS. All 5 overcall events in which preoperative Injury D was downgraded intraoperatively to Injury B or C occurred in patients with HS, injuries of which had higher preoperative AMS scores than concordant D-D injuries.

This intraoperative BPBI classification provides reliable broad categorization preoperatively with substantial agreement but is vulnerable at the C7-C8 transition. Focused assessment of the C8 nerve root is important because this injury pattern is commonly misidentified and may affect diagnosis and treatment. Viewing HS as a marker of severity rather than a standalone sign of global injury may improve preoperative assessment.

Level IV-retrospective case series.