Jonathan Cheng

Topographic mapping of the superior transverse scapular ligament: a cadaver study to facilitate suprascapular nerve decompression.

&NA; Division of the superior transverse scapular ligament for decompression of suprascapular nerve entrapment can be curative. However, the superior transverse scapular ligament can be difficult to locate, and large incisions are often required. This study was designed to determine the topographic coordinates of the superior transverse scapular ligament to permit reproducible surgical localization and reduce incision size. In 20 cadavers, the superior transverse scapular ligament was identified through a superior approach. Measurements were obtained from the superior transverse scapular ligament to external landmarks. The superior transverse scapular ligament was located 1.3 ± 0.3 cm (± SD) posterior to the posterior border of the clavicle and 2.9 ± 0.8 cm from the acromioclavicular joint in a two‐dimensional surface plane. The depth of the superior transverse scapular ligament from the skin surface was 3.9 ± 0.7 cm. An incision (mean length, 6.3 ± 0.7 cm) derived from a novel system of planning marks facilitated access to the superior transverse scapular ligament. The authors conclude that the superior transverse scapular ligament can be located consistently through an incision located on the superior aspect of the shoulder on the basis of palpable topographic landmarks. The superior approach permits small incision size and the maintenance of local muscle anatomic integrity.

Evaluation of the scratch collapse test in peroneal nerve compression.

Background: The scratch collapse test is a recently described provocative test for diagnosis of peripheral nerve compression. Methods: The scratch collapse test was studied prospectively in 24 consecutive patients with a diagnosis of common peroneal nerve compression neuropathy. The diagnosis was confirmed by history, physical examination, and electrodiagnostic testing. Provocative testing by the scratch collapse test and Tinels sign was performed. Results: The scratch collapse test showed a sensitivity of 0.77 and a specificity of 0.99, while the Tinels sign showed 0.65 and 0.99, respectively. Conclusion: The scratch collapse test is a sensitive and specific provocative test that compares favorably to existing clinical tests and aids in the diagnosis of common peroneal neuropathy. CLINICAL QUESTION/LEVEL OF EVIDENCE: Diagnostic, II.

Magnetic resonance neurography in the management of peripheral trigeminal neuropathy: experience in a tertiary care centre

AbstractObjectiveThis tertiary care experience examines the utility of magnetic resonance neurography (MRN) in the management of peripheral trigeminal neuropathies.Materials and methodsSeventeen patients with clinically suspected peripheral trigeminal neuropathies (inferior alveolar nerve and lingual nerve) were imaged uniformly with 1.5-T examinations. MRN results were correlated with clinical and surgical findings in operated patients and the impact on clinical management was assessed.ResultsClinical findings included pain (14/17), sensory changes (15/17), motor changes (2/17) and palpable masses (3/17). Inciting events included prior dental surgery (12/17), trauma (1/17) and idiopathic incidents (4/17). Non-affected side nerves and trigeminal nerves in the intracranial and skull base course were normal in all cases. Final diagnoses on affected sides were nerve inflammation (4/17), neuroma in continuity (2/17), LN transection (1/17), scar entrapment (3/17), infectious granuloma (1/17), low-grade injuries (3/17) and no abnormality (3/17). Associated submandibular gland and sublingual gland oedema-like changes were seen in 3/17 cases because of parasympathetic effects. Moderate-to-excellent MRN-surgical correlation was seen in operated (8/17) patients, and neuroma and nerve transection were prospectively identified in all cases.ConclusionMRN is useful for the diagnostic work-up of suspected peripheral trigeminal neuropathy patients with significant impact on clinical management and moderate-to-excellent correlation with intra-operative findings.Key Points• MRN substantially impacts diagnostic thinking and management in peripheral trigeminal neuropathy. • MRN has moderate-to-excellent correlation with intra-operative findings. • MRN should be considered in pre-surgical planning of peripheral trigeminal neuropathy subjects.

Detergent-free decellularized nerve grafts for long-gap peripheral nerve reconstruction

Background: Long-gap peripheral nerve defects arising from tumor, trauma, or birth-related injuries requiring nerve reconstruction are currently treated using nerve autografts and nerve allografts. Autografts are associated with limited supply and donor-site morbidity. Allografts require administration of transient immunosuppressants, which has substantial associated risks. To overcome these limitations, we investigated the use of detergent-free decellularized nerve grafts to reconstruct long-gap nerve defects in a rodent model and compared it with existing detergent processing techniques. Methods: Nerve grafts were harvested from the sciatic nerves of 9 donor rats. Twenty-four recipient rats were divided into 4 groups (6 animals per group): (1) nerve grafts (NG, positive control), (2) detergent-free decellularized (DFD) grafts, (3) detergent decellularized grafts, and (4) silicone tube conduits (negative control). Each recipient rat had a 3.5-cm graft or conduit sutured across a sciatic nerve transection injury. All animals were harvested at 12 weeks postimplantation for functional muscle analysis and nerve histomorphometry. Results: Histomorphometry results indicated maximum growth in NG when compared with other groups. DFD and detergent decellularized groups showed comparable regeneration at 12 weeks. Silicone tube group showed no regeneration as expected. Muscle force data indicated functional recovery in NG and DFD groups only. Conclusions: This study describes a detergent-free nerve decellularization technique for reconstruction of long-gap nerve injuries. We compared DFD grafts with an established detergent processing technique and found that DFD nerve grafts are successful in promoting regeneration across long-gap peripheral nerve defects as an alternative to existing strategies.

Chronic sensory-motor activity in behaving animals using regenerative multi-electrode interfaces.

Regenerative peripheral nerve interfaces have been proposed as viable alternatives for the natural control and feel of robotic prosthetic limbs. We have developed a Regenerative Multi-electrode Interface (REMI) that guides re-growing axons through an electrode array deployed in the lumen of a nerve guide. While acute studies have shown the use of the REMI in the rat sciatic nerve, the quality of chronic signal recording has not been reported. Here we show that implantation of this interface in the sciatic nerve is stable with high quality recordings up to 120 days and failures mainly attributable to abiotic factors related to pedestal detachment and wire breakage. We further tested the interfacing of REMI with fascicles of the sciatic nerve that primarily innervate muscles (tibial) and skin (sural). When implanted into the tibial nerve, bursting activity was observed synchronous to stepping. However, implantation of REMI into the sural nerve failed due to its small size. While fascicles smaller than 300 μm are a challenge for regenerative interfacing, we show that a modified REMI can be used in an insertion mode to record sensory signals from skin. In summary, the REMI represents an effective tool for recording firing patterns of specific axon types during voluntary movement, which may be used to improve the motor control and sensory feedback in closed loop control systems for robotic prosthesis.

A rat model for long-gap peripheral nerve reconstruction.

Background: The rat model has had limited utility for the study of long nerve gaps because of the small size of the animal. The authors sought to develop a simple, effective rat model for reconstruction of long nerve gap defects. Methods: Fifteen rats had a sciatic nerve transection followed by reconstruction. Positive control rats received a 1-cm isograft. Negative control rats received a 3.5-cm hollow silicone conduit, and experimental rats received a 4-cm isograft; these were implanted in a looped configuration to accommodate the long length. Nerves were harvested at 6 weeks (1-cm grafts) and 12 weeks (3.5-cm conduits and 4-cm grafts) for histologic and histomorphometric evaluation. Results: The 1-cm and 4-cm isograft groups showed robust regeneration in the distal nerve segment. The 3.5-cm hollow conduits showed absolutely no initiation of nerve regeneration. Histomorphometric values were as expected for the specified gap length. Conclusions: This study describes a simple and effective long nerve gap rat model for experiments on nerve grafts and nerve conduits. The long nerve graft model can be useful for studying techniques such as processed nerve grafts, which are currently a topic of frequent investigation. The 3.5-cm hollow conduit “no-regrowth” long-gap model is ideal for investigating conduit-based tissue-engineering solutions for long-gap nerve repair. The authors’ approach overcomes the size limitation of the small animal while exploiting the features that make the rat the model of choice for preliminary nerve studies.

An implantable, designed-for-human-use peripheral nerve stimulation and recording system for advanced prosthetics

Complex suture prostheses that deliver sensory and position feedback require a more sophisticated integration with the human user. Here a micro-size active implantable system that provides many-degree-of-freedom neural feedback in both sensory stimulation and motor control is shown, as one potential human-use solution in DARPAs HAPTIX program. Various electrical and mechanical challenge and solutions in meeting both sensory /motor performance as well as ISO 14708 FDA-acceptable human use in an aspirin-size active implementation are discussed.Complex suture prostheses that deliver sensory and position feedback require a more sophisticated integration with the human user. Here a micro-size active implantable system that provides many-degree-of-freedom neural feedback in both sensory stimulation and motor control is shown, as one potential human-use solution in DARPAs HAPTIX program. Various electrical and mechanical challenge and solutions in meeting both sensory /motor performance as well as ISO 14708 FDA-acceptable human use in an aspirin-size active implementation are discussed.

Asymmetric Sensory-Motor Regeneration of Transected Peripheral Nerves Using Molecular Guidance Cues

Neural interfaces are designed to decode motor intent and evoke sensory precepts in amputees. In peripheral nerves, recording movement intent is challenging because motor axons are only a small fraction compared to sensory fibers and are heterogeneously mixed particularly at proximal levels. We previously reported that pain and myelinated axons regenerating through a Y-shaped nerve guide with sealed ends, can be modulated by luminar release of nerve growth factor (NGF) and neurotrophin-3 (NT-3), respectively. Here, we evaluate the differential potency of NGF, glial cell line-derived neurotrophic factor (GDNF), brain-derived neurotrophic factor (BDNF), pleiotrophin (PTN), and NT-3 in asymmetrically guiding the regeneration of sensory and motor neurons. We report that, in the absence of distal target organs, molecular guidance cues can mediate the growth of electrically conductive fascicles with normal microanatomy. Compared to Y-tube compartments with bovine serum albumin (BSA), GDNF and NGF increased the motor and sensory axon content, respectively. In addition, the sensory to motor ratio was significantly increased by PTN (12.7:1) when compared to a BDNF + GDNF choice. The differential content of motor and sensory axons modulated by selective guidance cues may provide a strategy to better define axon types in peripheral nerve interfaces.

Peripheral neuropathy: Surgical approaches simplified for the imagers

Peripheral nerves traverse through different soft tissue compartments in the upper and lower extremities via specific anatomical tunnels, where they are susceptible to entrapment. Common sites in the upper extremity include carpal tunnel, cubital tunnel and radial tunnel. Common sites in the lower extremity include piriformis, fibular neck, and tarsal tunnel. Compressive peripheral neuropathy can develop in these sites, and are amenable for surgical decompression.

An Association between Carpal Tunnel Syndrome and Migraine Headaches-National Health Interview Survey, 2010.

Background: Migraine headaches have not historically been considered a compression neuropathy. Recent studies suggest that some migraines are successfully treated by targeted peripheral nerve decompression. Other compression neuropathies have previously been associated with one another. The goal of this study is to evaluate whether an association exists between migraines and carpal tunnel syndrome (CTS), the most common compression neuropathy. Methods: Data from 25,880 respondents of the cross-sectional 2010 National Health Interview Survey were used to calculate nationally representative prevalence estimates and 95% confidence intervals (95% CIs) of CTS and migraine headaches. Logistic regression was used to calculate adjusted odds ratios (aORs) and 95% CI for the degree of association between migraines and CTS after controlling for known demographic and health-related factors. Results: CTS was associated with older age, female gender, obesity, diabetes, and smoking. CTS was less common in Hispanics and Asians. Migraine was associated with younger age, female gender, obesity, diabetes, and current smoking. Migraine was less common in Asians. Migraine prevalence was 34% in those with CTS compared with 16% in those without CTS (aOR, 2.60; 95% CI, 2.16–3.13). CTS prevalence in patients with migraine headache was 8% compared with 3% in those without migraine headache (aOR, 2.67; 95% CI, 2.22–3.22). Conclusions: This study is the first to demonstrate an association between CTS and migraine headache. Longitudinal and genetic studies with physician verification of migraine headaches and CTS are needed to further define this association.