Nerve transfers for brachial plexus injuries: grading of volitional control

Area of Science:

• Neuroscience
• Orthopedic Surgery
• Rehabilitation Medicine

Background:

• Brachial plexus injuries (BPIs) often result in significant muscle function loss.
• Nerve transfers are a surgical option to restore function by rerouting nerves.
• Brain plasticity, involving disconnection and reconnection of neural programs, is crucial for regaining volitional control after nerve transfers.

Purpose of the Study:

• To systematically study the levels of neural disconnection and reconnection after nerve transfers for BPIs.
• To develop and validate a novel 4-point plasticity grading scale (PGS) to assess volitional control.
• To identify clinical correlations with the achieved level of volitional control.

Main Methods:

• A cohort of 153 patients with BPIs undergoing nerve transfers (phrenic, spinal accessory, median/ulnar fascicles) for biceps and deltoid restoration were studied.
• Patients attempted maximal muscle contraction using donor nerve programs and then actively avoiding donor nerve activation.
• The novel 4-point plasticity grading scale (PGS) was used to rate volitional control, with Medical Research Council (MRC) scale assessing muscle strength.

Main Results:

• The majority of patients achieved PGS grade 3 (67.3%), indicating substantial but incomplete volitional control.
• Only 18.3% of patients reached PGS grade 4, signifying maximum brain plasticity and complete independent control.
• No significant differences in median PGS grade were found between different donor nerves, nor correlations with age, time to surgery, follow-up duration, or rehabilitation compliance.

Conclusions:

• Approximately 20% of patients achieved complete disconnection of donor programs and full independent control over reinnervated muscles.
• Most patients demonstrated incomplete disconnection and varying degrees of volitional control, with about 15% showing poor outcomes.
• While brain plasticity is fundamental for recovery, its capacity for achieving complete volitional control after nerve transfer appears limited.