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The findings in paediatric obstetric brachial palsy differ from those in older patients: a suggested explanation
J W Vredeveld1, G Blaauw, B A Slooff
1Department of Clinical Neurophysiology, Atrium Medisch Centrum, Heerlen, The Netherlands.
Insights
Electromyography (EMG) and nerve conduction studies in obstetric brachial palsy (OBP) can overestimate recovery. Early denervation in infants differs significantly from traumatic injuries, suggesting a central mechanism for OBP improvement.
Area of Science:
- Neurology
- Pediatric Neurology
- Clinical Electrophysiology
Background:
- Established EMG and nerve conduction study protocols are used for brachial plexus lesions.
- Current electrodiagnostic findings in obstetric brachial palsy (OBP) often suggest a falsely optimistic prognosis.
- Understanding early nerve integrity in OBP is crucial for accurate prognostication.
Purpose of the Study:
- To analyze the discrepancy in electrodiagnostic findings between OBP and traumatic brachial plexus injuries.
- To investigate the extent of denervation in infants with OBP compared to adults with similar lesions.
- To explore the potential role of C7 contribution and central mechanisms in OBP recovery.
Main Methods:
- Selection of infants (4-14 months) with OBP and child/adult patients (6-74 years) with traumatic brachial plexus lesions.
- Focus on patients with complete C5/C6 root avulsion or upper trunk rupture verified surgically.
- Comparison of EMG findings (motor unit recruitment, denervation) in biceps and deltoid muscles between OBP infants and traumatic injury patients.
Main Results:
- Infants with OBP (approx. 4 months) showed near-normal motor unit recruitment and minimal denervation in biceps and deltoid muscles.
- Adults with traumatic brachial plexus lesions (similar C5/C6 or upper trunk injury) exhibited complete denervation in the same muscles.
- OBP infants with additional C7 lesion or middle trunk rupture showed near-complete denervation, indicating C7's early contribution.
Conclusions:
- Electrodiagnostic studies in OBP may not accurately reflect the severity of nerve injury at birth.
- The C7 root significantly contributes to biceps and deltoid innervation in neonates, a contribution that diminishes later.
- A central mechanism may underlie the clinical presentation and spontaneous improvement observed in obstetric brachial palsy.
Abstract:
An EMG and nerve-conduction-study protocol has been developed and used in all patients with brachial plexus lesions since 1985. The findings of EMG and nerve-conduction studies in obstetric brachial palsy (OBP) mostly suggest a falsely optimistic prognosis. To analyse this, all subjects were selected with complete avulsion of both roots C5 and C6 and/or complete rupture of the upper trunk verified during operation from a group of 162 infants with OBP (aged 4 to 14 months) and a group of 184 child and adult patients (aged 6 to 74 years) with a traumatic brachial plexus lesion. Fourteen infants, approximately 4 months old, with OBP, and 19 adults (aged 16 to 30 years) met the selection criteria. The infants from the group with OBP had at 4 months a nearly normal recruitment pattern of motor units in the biceps brachii and deltoid muscles, with little or no denervation. However, in the older group with traumatic brachial palsy, the same lesion caused complete denervation of both muscles. From the group with OBP, a third group (N=3) with the same lesion plus an additional lesion of C7 or a rupture of the middle trunk was selected. This additional lesion resulted in nearly complete denervation of both muscles. This means that C7 largely contributes to the innervation of both muscles at the time of birth, but this innervation is lost during later life in normally developing individuals (apoptosis). A central mechanism might be responsible for the clinical palsy and later spontaneous improvement which is always found in the infants with OBP.