Brain changes after peripheral nerve repair: limitations of neuroplasticity

[Rare case of reconstruction of the anterior thigh compartment after resection of high-grade sarcoma by hybrid technique: Latissimus dorsi free flap associated with a medial gastrocnemius pedicled flap]

INTRODUCTION

The soft tissue sarcomas of the limbs require extensive surgical excision. Reconstructive surgery plays an essential role in its management to preserve the limb, as exposed in a case of thigh sarcoma.

CLINICAL CASE

A 73-year-old patient has a large sarcoma within the quadriceps. Its excision requires resection of the entire anterior thigh compartment. Preservation of the limb is permitted by reconstruction by latissimus dorsi free flap and medial gastrocnemius pedicled flap. The patient resumed walking using an orthosis at 3 months.

CONCLUSION

Surgery to remove a sarcoma of a limb can threaten the integrity of the limb. Plastic surgery, with all the reconstruction techniques, contributes to the preservation of a functional limb.

Efficacy of cervical perivascular sympathectomy in improving upper limb motor function in children with cerebral palsy and construction of a predictive model

BACKGROUND

The effectiveness of cervical perivascular sympathectomy (CPVS) in enhancing upper limb motor function in children with cerebral palsy is unclear, and the factors that influence the effectiveness of the surgery have not been documented.

OBJECTIVE

To investigate the effectiveness of CPVS in enhancing upper limb motor function in children with cerebral palsy and develop a predictive chart for potential associated adverse outcomes METHODS: The study included 187 children with cerebral palsy who underwent CPVS at the Cerebral Palsy Center, Second Affiliated Hospital of Xinjiang Medical University, between January 2018 and January 2022. Patients were categorized into two groups based on prognostic outcomes: those with adverse and favorable prognoses. Demographic and laboratory data were collected and analyzed from both groups. To identify independent predictors of poor post-CPVS upper limb motor function outcomes, statistical techniques, including univariate analysis and binary logistic regression, were applied. Subsequently, these predictors were integrated to formulate a comprehensive predictive model.

RESULTS

In this cohort of 187 children with cerebral palsy undergoing CPVS, 68 (36.36%) exhibited a favorable prognosis for upper limb motor function and 119 (63.64%) demonstrated an adverse prognosis. Age, motor function, and serum albumin levels were identified as significant prognostic factors via logistic regression analysis. To develop the model, we divided the sample into a training set (70%, n = 131) and a validation set (30%, n = 56). Employing motor function, serum albumin levels, and age as variables, we crafted a predictive model. The model's performance, reflected by the area under the curve was 0.813 (0.732, 0.894) in the training set and 0.770 (0.647, 0.892) in the validation set, demonstrating its robust predictive capability for post-CPVS adverse outcomes. Furthermore, the consistency curve and Hosmer-Lemeshow test (χ2 = 8.808, p = 0.359) illustrated a strong concordance between the model's predictions of poor prognosis and the actual incidence rate.

CONCLUSION

CPVS has been shown to be effective in improving upper limb motor function in patients with cerebral palsy. Independent prognostic factors identified encompass motor function, age, and serum albumin levels. The composite predictive model shows potential for clinical applications.

Brain plasticity in neonatal brachial plexus palsies: quantification and comparison with adults' brachial plexus injuries

PURPOSE

To compare two populations of brachial plexus palsies, one neonatal (NBPP) and the other traumatic (NNBPP) who underwent different nerve transfers, using the plasticity grading scale (PGS) for detecting differences in brain plasticity between both groups.

METHODS

To be included, all patients had to have undergone a nerve transfer as the unique procedure to recover one lost function. The primary outcome was the PGS score. We also assessed patient compliance to rehabilitation using the rehabilitation quality scale (RQS). Statistical analysis of all variables was performed. A p ≤ 0.050 set as criterion for statistical significance.

RESULTS

A total of 153 NNBPP patients and 35 NBPP babies (with 38 nerve transfers) met the inclusion criteria. The mean age at surgery of the NBPP group was 9 months (SD 5.42, range 4 to 23 months). The mean age of NNBPP patients was 22 years (SD 12 years, range 3 to 69). They were operated around sixth months after the trauma. All transfers performed in NBPP patients had a maximum PGS score of 4. This was not the case for the NNBPP population that reached a PGS score of 4 in approximately 20% of the cases. This difference was statistically significant (p < 0.001). The RQS was not significantly different between groups.

CONCLUSION

We found that babies with NBPP have a significantly greater capacity for plastic rewiring than adults with NNBPP. The brain in the very young patient can process the changes induced by the peripheral nerve transfer better than in adults.

[Contralateral C7 Nerve Transfer]

Complex brachial plexus injuries with multiple or complete root avulsions make intraplexic reconstruction impossible in some cases. Such cases necessitate the use of extraplexic nerve donors such as the spinal accessory nerve or intercostal nerves. The contralateral C7 root represents a donor with a high axon count and can be used as an axon source in such cases. We summarise current indications, surgical technique and functional results after a contralateral C7 transfer in cases of brachial plexus injury, describing some of our own cases and including a selective literature review.

Nerve transfers for brachial plexus injuries: grading of volitional control

OBJECTIVE

After brachial plexus injuries (BPIs), nerve transfers are used to restore lost muscle function. Brain plasticity underlies the process of regaining volitional control, which encompasses disconnection of the original donor nerve-related programs and reconnection to acceptor nerve programs. To the authors' knowledge, the levels of disconnection and reconnection have never been studied systematically. In this study, the authors developed a novel 4-point plasticity grading scale (PGS) and assessed the degree of volitional control achieved, identifying clinical correlations with this score.

METHODS

Patients with BPI who underwent a phrenic, spinal accessory, median, and/or ulnar fascicle nerve transfer to restore biceps and deltoid function were asked to maximally contract their target muscle as follows: 1) by using only the donor nerve program, and 2) by activating the target muscle while consciously trying to avoid using the donor nerve, with assessment each time of the Medical Research Council (MRC) scale grade for muscle strength. The authors' PGS was used to rate the level of volitional control achieved. PGS grade 1 represented the lowest independent volitional control, with MRC grade 4 obtained in response to the donor command and MRC grade 0 in response to the acceptor command (minimum brain plasticity), whereas PGS grade 4 was no noticeable contraction in response to the donor command and MRC grade 4 in response to the acceptor command (maximum brain plasticity).

RESULTS

In total, 153 patients were studied. For biceps restoration, the phrenic nerve was used as a donor in 44 patients, the spinal accessory nerve in 40 patients, and the median and/or ulnar fascicles in 44 patients. A triceps branch was used to restore deltoid function in 25 patients. The level of volitional control achieved was PGS grade 1 in 1 patient (0.6%), grade 2 in 21 patients (13.7%), grade 3 in 103 patients (67.3%), and grade 4 in 28 patients (18.3%). The median PGS grade did not differ significantly between the four donor nerves. No correlations were observed between age, time from BPI to surgery, duration of follow-up, or compliance with rehabilitation and PGS grade.

CONCLUSIONS

Just around 20% of the authors' patients developed a complete disconnection of the donor program along with complete independent control over the reinnervated muscle. Incomplete disconnection was present in the vast majority of the patients, and the level of disconnection and control was poor in approximately 15% of patients. Brain plasticity underlies patient ability to regain volitional control after a nerve transfer, but this capacity is limited.

Plasticity of the Central Nervous System Involving Peripheral Nerve Transfer

Peripheral nerve injury can lead to partial or complete loss of limb function, and nerve transfer is an effective surgical salvage for patients with these injuries. The inability of deprived cortical regions representing damaged nerves to overcome corresponding maladaptive plasticity after the reinnervation of muscle fibers and sensory receptors is thought to be correlated with lasting and unfavorable functional recovery. However, the concept of central nervous system plasticity is rarely elucidated in classical textbooks involving peripheral nerve injury, let alone peripheral nerve transfer. This article is aimed at providing a comprehensive understanding of central nervous system plasticity involving peripheral nerve injury by reviewing studies mainly in human or nonhuman primate and by highlighting the functional and structural modifications in the central nervous system after peripheral nerve transfer. Hopefully, it will help surgeons perform successful nerve transfer under the guidance of modern concepts in neuroplasticity.