David M. Brogan

Neural mechanisms underlying handedness remain poorly understood. We used functional magnetic resonance imaging (fMRI) to study performance of a visually guided drawing task with each hand. We hypothesized that the left superior parietal lobule supports drawing with either hand, and individuals with chronic peripheral nerve injury (PNI) to the dominant hand use the same mechanism as healthy adults. Thirty-three right-handed adults (23 healthy, 10 patients) underwent fMRI while performing a precision drawing task, alternating between the right hand (RH) and left hand (LH). BOLD magnitude and functional connectivity (FC) modulation via generalized psychophysiological interaction were analyzed in 12 a priori regions of interest, followed by additional exploratory areas identified via whole-brain magnitude analysis. During LH drawing (compared to RH drawing), contralateral primary motor cortex showed lower BOLD magnitude but greater FC with two networks: First, a left motor-premotor network with increased FC and equal-or-greater magnitude during LH drawing. Second, a right parietal network characterized by increased FC during LH drawing but increased magnitude during RH drawing. Exploratory whole-brain analyses supported and extended these motor and parietal networks, and additionally suggested that RH drawing may involve greater magnitude and FC within a bilateral parieto-premotor network centered on right paracingulate cortex. No significant group-related effects were observed in BOLD magnitude or FC. These results describe the first proposed mechanisms for LH precision drawing, both of which depend on differential engagement of bimanual control networks: a left hemisphere motor-premotor network for precision motor control, which engages intrahemispherically (directly) during RH drawing and interhemispherically (indirectly) during LH drawing; and a right hemisphere parietal network with greater distributed coordination during LH drawing. Although these mechanisms’ preservation after PNI requires confirmation in a larger sample, their differential involvement in LH precision drawing supports their potential relevance as neuromodulatory targets to enhance LH performance after RH impairment.

Background: Proximal peripheral nerve injuries may be accompanied by structural changes along the course of the nerve, including enlargement at distal sites. Ultrasound offers a noninvasive method to assess nerve caliber at anatomic tunnels where swelling may have clinical relevance. However, the prevalence and distribution of distal enlargement after proximal traumatic injury remain poorly defined. Objective: To evaluate the frequency of distal nerve enlargement at common entrapment locations in patients with proximal upper extremity peripheral nerve injuries. Methods: We retrospectively reviewed 76 patients (140 nerves) with proximal nerve injuries who underwent ultrasound evaluation. Cross‐sectional area (CSA) was measured at standard entrapment sites in the upper extremities. Enlargement was defined as CSA exceeding published reference thresholds. Distal enlargement was analyzed by entrapment site, injury pattern, and mechanism of injury. Results: Distal enlargement was identified in 66 of 140 nerve segments (47.1%) and in 44 of 76 patients (57.9%). Enlargement occurred across all injury patterns, with the highest prevalence in plexopathies (68.4%). It was also observed across all mechanisms of injury, including penetrating, blunt, and iatrogenic trauma, with the highest prevalence in iatrogenic injuries (80.0%). Conclusions: Distal nerve enlargement is a common ultrasound finding after proximal peripheral nerve injury. Although the mechanism cannot be determined from this retrospective, single‐time‐point dataset, the high prevalence underscores the importance of assessing for distal compression during evaluation and reconstructive planning. Future studies using standardized and serial ultrasound protocols are needed to clarify the temporal evolution of distal enlargement and its clinical significance.

Chronic, high‐resolution imaging of peripheral nerve injury and regeneration remains a major technical challenge due to the optical inaccessibility of peripheral nerves embedded in soft tissue. Here, we present a broadly applicable approach for longitudinal, high‐resolution optical imaging of peripheral nerves in vivo that combines a flexible, optically transparent polydimethylsiloxane (PDMS) window along with multimodal microscopy. The PDMS window is implanted in the skin above the mouse sciatic nerve, providing stable, motion‐tolerant optical access for over one month without impairing nerve function. Using confocal, two‐photon, and second‐harmonic generation microscopy, we simultaneously visualized fluorescently labeled axons and Schwann cells, endogenous collagen, and vasculature with high spatial and temporal resolution. This approach enabled real‐time tracking of axonal degeneration and regeneration, Schwann cell dynamics, and extracellular matrix‐guided axon pathfinding across multiple nerve injury models. The platform also supports longitudinal imaging of axonal regrowth within a clinically relevant model of nerve transection gap repair. Overall, our method enables new avenues for studying peripheral nerve biology and testing regenerative therapies in vivo.

Background: Despite the well-known functional impacts of peripheral nerve injury (PNI), little is understood about its financial burden (monetary strain), financial worry (stress), and return-to-employment outcomes. Financial toxicity has been studied in many different patient populations, but little is known in PNI patients. We aimed to use validated questionnaires to assess these aspects following PNI. Methods: In this retrospective study, we surveyed patients (≥18 years) who underwent operative treatment for PNI between May 2021 and November 2023 at a single institution. Data on employment status, financial difficulties, and disability applications were collected. Two validated scales, the Financial Burden Composite Score and Financial Worry Scale, were used to collect data on financial burden and worry. Participants were included if they were 6 to 36 months postsurgery. Univariate analyses were performed to identify factors associated with financial burden and worry. Results: Among 35 respondents in a 6- to 36-month postoperative timeframe, 51.4% had a financial burden score ≥4, and 45.7% had a financial worry score ≥4. Participants aged 40 to 60 years experienced the highest burden (mean = 4.5), compared with those aged 60 to 80 years (mean = 1.4, P < .01). High financial worry was significantly linked to employment status, job modifications, and inability to return to work ( P < .05). Overall, 61% of participants returned to work after an average absence of 7.3 months; 57.1% required job modifications, and 30% changed professions. Conclusions: Financial burden and worry are common among individuals recovering from PNI, particularly in those unable to return to work. This exploratory study begins to describe the interplay between financial burden and worry, return-to-work outcomes, and rehabilitation barriers. Beyond improving limb function, care teams may collaborate with social workers, community health workers, and vocational rehabilitation experts to support patient well-being and facilitate a successful return to employment.

Introduction: Peripheral nerve injuries (PNI) pose a major challenge in the intraoperative assessment of nerve viability. Wallerian degeneration (WD) is the degenerative process of axonal breakdown distal to the site of injury, with limited proximal extension, and progresses through spatiotemporally consistent stages facilitated by Schwann cell reprogramming and macrophage infiltration. We evaluated LS-301, a near-infrared (NIR) fluorophore previously used in human oncology trials, that targets phosphorylated annexin A2 (pANXA2), which is upregulated and redistributed to Schwann cell surfaces after nerve injury. Methods: Utilizing a sciatic nerve transection model in rats, LS-301 was compared with the untargeted control dye Cypate-3 using in vivo fluorescence imaging. Fluorescence intensities in proximal and distal bulbs and their adjacent segments were quantified, normalized to the contralateral sham nerve, and compared across time points chosen to represent documented stages of WD (5 h, 2 days, and 2 weeks). Results: LS-301 showed time-dependent accumulation in injured nerve in a spatial pattern consistent with the expected progression of WD, whereas Cypate-3 uptake was variable and lacked a consistent spatiotemporal gradient. Discussion: This study’s findings support the feasibility of using a targeted NIR probe to preferentially label degenerating versus uninjured peripheral nerve after transection, with potential for intra-operative application. This proof-of-concept study does not define per-nerve surgical decision thresholds yet, but this will be the focus of future work testing whether LS-301 mapping can complement existing intraoperative assessments and determine surgically actionable fluorescence cutoffs.

Several wearable devices, image analysis systems, and smartphone apps have been developed to increase the accuracy and reliability of hand range of motion measurement. While their performances have been assessed independently, there has been no comparison of devices across different groups. This study aims to compare the accuracy, reliability, and telehealth applicability of hand goniometry devices across methodological classes. PubMed, Embase, Scopus, and CINAHL were queried for studies evaluating the accuracy and reliability of hand goniometry technologies. The inquiry focused on tools that were directly compared to manual goniometry. 13 studies met inclusion criteria, representing 2 wearable devices, 7 image analysis systems, and 4 smartphone apps. Wearable devices had the highest accuracy (mean difference [MD] < 1 ^o ) but had low telehealth integration scores (TIS = 38 out of 50). Image analysis systems had high reliability (interclass correlation coefficient [ICC] > .67) and telehealth usability (TIS = 42) but lacked accuracy (MD 1°–35°). Similarly, smartphone apps had low accuracy (MD 1°–12°) but high reliability (ICC > 0.83). No single device class outperforms others across all metrics. Future studies should focus on creating technologies that combine the strengths of multiple device classes.