Other median neuropathies.

Median mononeuropathy is common, with carpal tunnel syndrome the most frequently encountered acquired mononeuropathy in clinical practice. However, other disorders of the median nerve and many known anatomical variants can lead to misdiagnosis and unexpected surgical complications if their presence is not correctly identified. A number of inherited and acquired disorders can affect the median nerve proximal to the wrist, alone or accompanied by other affected peripheral nerves. Recognizing other disorders that can masquerade as median mononeuropathies can avoid misdiagnosis and misguided management. This chapter explores median nerve anatomical variants, disorders, and lesions, emphasizing the need for careful examination and electrodiagnostic study in the localization of median neuropathy.

Thrombosed Persistent Median Artery with Coexisting Bifid Median Nerve in a Robotic Arthroplasty Surgeon: A Case Report.

CASE: A 47-year-old orthopaedic surgeon presented with acute volar left wrist pain. He performed over 250 robot-assisted knee arthroplasties each year. Color Doppler evaluation revealed bilateral persistent median arteries and bifid median nerves, with focal occlusive thrombosis of the left median artery. He was advised rest and oral aspirin. He could return to his professional activities after 1 month. He had no recurrence of symptoms at 1 year of follow-up. CONCLUSION: Orthopaedic surgeons use vibrating hand tools on a daily basis. The possibility of hand-arm vibration syndrome must be considered in the differential diagnosis of wrist pain among orthopaedic surgeons.

Concurrent spinal and brain imaging with optically pumped magnetometers.

BACKGROUND: The spinal cord and its interactions with the brain are fundamental for movement control and somatosensation. However, brain and spinal electrophysiology in humans have largely been treated as distinct enterprises, in part due to the relative inaccessibility of the spinal cord. Consequently, there is a dearth of knowledge on human spinal electrophysiology, including the multiple pathologies that affect the spinal cord as well as the brain. NEW METHOD: Here we exploit recent advances in the development of wearable optically pumped magnetometers (OPMs) which can be flexibly arranged to provide coverage of both the spinal cord and the brain in relatively unconstrained environments. This system for magnetospinoencephalography (MSEG) measures both spinal and cortical signals simultaneously by employing custom-made scanning casts. RESULTS: We evidence the utility of such a system by recording spinal and cortical evoked responses to median nerve stimulation at the wrist. MSEG revealed early (10 - 15 ms) and late (>20 ms) responses at the spinal cord, in addition to typical cortical evoked responses (i.e., N20). COMPARISON WITH EXISTING METHODS: Early spinal evoked responses detected were in line with conventional somatosensory evoked potential recordings. CONCLUSION: This MSEG system demonstrates the novel ability for concurrent non-invasive millisecond imaging of brain and spinal cord.

Metacarpal Small Incision for Carpal Tunnel Syndrome.

Endoscopic carpal tunnel release (ECTR) techniques have been established as a successful treatment for carpal tunnel syndrome and have proven equally effective as traditional open carpal tunnel release (OCTR) techniques in relieving pain and numbness. However, patients who undergo OCTR are more likely to experience scar tenderness and pillar pain and take longer to return to work. We present here a method of metacarpal small incision for carpal tunnel release (MSICTR) as a safe, reliable, cost-effective alternative surgical decompression of the median nerve of the wrist. This technique utilizes a metacarpal small incision and direct visualization of the median nerve and carpal tunnel contents, reducing the risk of permanent injury and neurasthenia when compared to traditional OCTR. MSICTR is also suitable for the examination of the median nerve, surrounding tendon sheath, or space-occupying lesions. MSICTR is associated with shorter operation times, less postoperative pain, faster recovery, and improved cosmetic results when compared to traditional OCTR. Therefore, MSICTR is an effective surgical decompression of the median nerve for the treatment of carpal tunnel syndrome.

Investigating the effects of dopamine on short- and long-latency afferent inhibition.

Short- and long-latency afferent inhibition (SAI and LAI respectively) are phenomenon whereby the motor evoked potential induced by transcranial magnetic stimulation (TMS) is inhibited by a sensory afferent volley consequent to nerve stimulation. It remains unclear whether dopamine participates in the genesis or modulation of SAI and LAI. The present study aimed to determine if SAI and LAI are modulated by levodopa (l-DOPA). In this placebo-controlled, double-anonymized study Apo-Levocarb (100 mg l-DOPA in combination with 25 mg carbidopa) and a placebo were administered to 32 adult males (mean age 24 ± 3 years) in two separate sessions. SAI and LAI were evoked by stimulating the median nerve and delivering single-pulse TMS over the motor hotspot corresponding to the first dorsal interosseous muscle of the right hand. SAI and LAI were quantified before and 1 h following ingestion of drug or placebo corresponding to the peak plasma concentration of Apo-Levocarb. The results indicate that Apo-Levocarb increases SAI and does not significantly alter LAI. These findings support literature demonstrating increased SAI following exogenous dopamine administration in neurodegenerative disorders. KEY POINTS: Short- and long-latency afferent inhibition (SAI and LAI respectively) are measures of corticospinal excitability evoked using transcranial magnetic stimulation. SAI and LAI are reduced in conditions such as Parkinson's disease which suggests dopamine may be involved in the mechanism of afferent inhibition. 125 mg of Apo-Levocarb (100 mg dopamine) increases SAI but not LAI. This study increases our understanding of the pharmacological mechanism of SAI and LAI.

Fascicular Involvement of the Median Nerve Trunk in the Upper Arm: Manifestation as Anterior Interosseous Nerve Syndrome With Unique Imaging Features.

Selective fascicular involvement of the median nerve trunk above the elbow leading to anterior interosseous nerve (AIN) syndrome is a rare form of peripheral neuropathy. This condition has recently garnered increased attention within the medical community owing to advancements in imaging techniques and a growing number of reported cases. In this article, we explore the topographical anatomy of the median nerve trunk and the clinical features associated with AIN palsy. Our focus extends to unique manifestations captured through MRI and ultrasonography (US) studies, highlighting noteworthy findings, such as nerve fascicle swelling, incomplete constrictions, hourglass-like constrictions, and torsions, particularly in the posterior/posteromedial region of the median nerve. Surgical observations have further enhanced the understanding of this complex neuropathic condition. High-resolution MRI not only reveals denervation changes in the AIN and median nerve territories but also illuminates these alterations without the presence of compressing structures. The pivotal roles of high-resolution MRI and US in diagnosing this condition and guiding the formulation of an optimal treatment strategy are emphasized.

Análisis de los parámetros ecográficos descritos en el estudio del síndrome del túnel del carpo. Una revisión sistemática / Analysis of the echographic parameters described in the study of carpal tunnel syndrome: A systematic review

El síndrome del túnel del carpo (STC) es la mononeuropatía por atrapamiento más frecuente; el diagnóstico se establece mediante pruebas electrodiagnósticas con un número sustancial de falsos positivos/negativos. Presentamos la siguiente revisión sistemática, cuyo objetivo es analizar la literatura más reciente en relación con los parámetros ecográficos descritos para estudiar el STC. Seleccionamos estudios que evaluasen parámetros ecográficos en pacientes con sospecha clínica, siguiendo las recomendaciones del manual Cochrane; incluimos revisiones sistemáticas, metaanálisis, estudios caso-control y de pruebas diagnósticas, valorando estudios retrospectivos y revisiones bibliográficas con buena calidad metodológica. La revisión se hizo de artículos publicados entre 2005-2019. Incluimos 8 artículos (2 revisiones sistemáticas/metaanálisis, 2 estudios caso-control, un estudio de pruebas diagnósticas, 2 revisiones literarias y un estudio retrospectivo). Los parámetros analizados fueron el área de sección transversa del nervio mediano, el índice muñeca-antebrazo, el índice entrada-salida, el rango de adelgazamiento del nervio mediano, el abombamiento del retináculo flexor y la vascularización/movilidad. La evidencia actual permite afirmar que la ecografía tiene utilidad en el cribado del STC.(AU)

Carpal tunnel syndrome (CTS) is the most common entrapment mononeuropathy; the diagnosis is established by electrodiagnostic tests with until 34% of false positives/negatives. We present the following systematic review which objective is to analyze the most recent literature related to the ultrasound parameters described to study CTS. We selected studies that evaluated ultrasound parameters in patients with clinical suspicion following the Cochrane manual's recommendations. We include systematic reviews, meta-analyses, case–control studies and diagnostic tests, evaluating retrospective studies and bibliographic reviews with proper methodological quality. Articles published between 2005 and 2019. We included eight articles (two systematic reviews/meta-analyses, two case–control studies, one diagnostic test study, two literature reviews, and one retrospective). The parameters analyzed were cross-sectional area, wrist–forearm index, entry–exit index, thinning range, palmar bowing of the flexor retinaculum, and vascularity/mobility. Current evidence allows us to affirm that ultrasound is useful in screening for CTS.(AU)

A bilateral four-headed brachialis muscle with a variant innervation: a cadaveric report with possible clinical implications.

PURPOSE: Anterior compartment muscles of the arm present high morphological variability, with possible clinical significance. The current cadaveric report aims to describe a bilateral four-headed brachialis muscle (BM) with aberrant innervation. Emphasis on the embryological background and possible clinical significance are also provided. METHODS: Classical upper limb dissection was performed on an 84-year-old donated male cadaver. The cadaver was donated to the Anatomy Department of the National and Kapodistrian University of Athens. RESULTS: On the left upper limb, the four-headed BM was supplied by the musculocutaneous and the median nerves after their interconnection. On the right upper limb, the four-headed BM received its innervation from the median nerve due to the musculocutaneous nerve absence. A bilateral muscular tunnel for the radial nerve passage was identified, between the BM accessory heads and the brachioradialis muscle. CONCLUSION: BM has clinical significance, due to its proximity to important neurovascular structures and frequent surgeries at the humerus. Hence, knowledge of these variants should keep orthopedic surgeons alert when intervening in this area. Further dissection studies with a standardized protocol are needed to elucidate the prevalence of BM aberrations and concomitant variants.

Changes in the excitability of anterior horn cells in a mental rotation task of body parts.

INTRODUCTION/AIMS: Mental rotation (MR), a tool of implicit motor imagery, is the ability to rotate mental representations of two- or three-dimensional objects. Although many reports have described changes in brain activity during MR tasks, it is not clear whether the excitability of anterior horn cells in the spinal cord can be changed. In this study, we examined whether MR tasks of hand images affect the excitability of anterior horn cells using F-wave analysis. METHODS: Right-handed, healthy participants were recruited for this study. F-waves of the right abductor pollicis brevis were recorded after stimulation of the right median nerve at rest, during a non-MR task, and during an MR task. The F-wave persistence and the F/M amplitude ratio were calculated and analyzed. RESULTS: Twenty participants (11 men and 9 women; mean age, 29.2 ± 4.4 years) were initially recruited, and data from the 18 that met the inclusion criteria were analyzed. The F-wave persistence was significantly higher in the MR task than in the resting condition (p = .001) or the non-MR task (p = .012). The F/M amplitude ratio was significantly higher in the MR task than in the resting condition (p = .019). DISCUSSION: The MR task increases the excitability of anterior horn cells corresponding to the same body part. MR tasks may have the potential for improving motor function in patients with reduced excitability of the anterior horn cells, although this methodology must be further verified in a clinical setting.

[Rare nerve compression neuropathies] / Seltene Nervenkompressionssyndrome.

UNCOMMON NERVE COMPRESSION SYNDROMES: In regard to the complex anatomical relationship of peripheral nerves and muscles, tendons, fasciae as well as their long course within those anatomical structures and additional close contact to bony structures, they are prone to suffer from local compression syndromes. Hence creating a vast majority of entrapment syndromes - well described in literature for almost every single nerve. The purpose of this article is to give an overview of symptoms, signs, diagnostic studies and treatment options, addressing especially the less known syndromes. Compression syndromes of the upper arm and shoulder region include the suprascapular nerve syndrome the compression of the axillary nerve within the spatium quadrilaterale and the compression of the long thoracic nerve at the chest wall. The upper extremity offers a variety of infrequent entrapment syndromes, as the pronator teres syndrome and anterior interosseus syndrome, both resulting from pressure to the median nerve in the forearm. Compression neuropathy in the course of the radial nerve in the distal upper extremity is also known as supinator syndrome. Guyon's canal syndrome is the ulnar side equivalent to the well-known carpal tunnel syndrome. In the case of a Cheiralgia paresthetica, a compression of a sensory branch of the superficial radial nerve can be seen. In the lower extremities, a variety of nerves especially in the groin and thigh area can be compressed as they pass through the narrow spaces between the abdominal muscles or underneath the inguinal ligament. Compression of the lateral femoral cutaneous nerve is the most common syndrome. Compression syndromes of the femoral and obturator nerves are most often iatrogenic. Pain around the knee, especially the lateral part and following orthopedic procedures of the knee, can arise from a compression or a lesion of a small infrapatellar branch of the saphenous nerve. Another probably underdiagnosed syndrome is piriformis syndrome, resulting from an entrapment of the sciatic nerve as it passes through certain muscular structures. In the distal lower extremity, the peroneal and tibial nerves can be compressed at multple sites, clinically known as peroneal nerve paralysis resulting from nerve compression around the fibular head, the anterior and posterior tarsal tunnel syndrome, and Morton's metatarsalgia.

OPM-MEG Measuring Phase Synchronization on Source Time Series: Application in Rhythmic Median Nerve Stimulation.

The magnetoencephalogram (MEG) based on array optically pumped magnetometers (OPMs) has the potential of replacing conventional cryogenic superconducting quantum interference device. Phase synchronization is a common method for measuring brain oscillations and functional connectivity. Verifying the feasibility and fidelity of OPM-MEG in measuring phase synchronization will help its widespread application in the study of aforementioned neural mechanisms. The analysis method on source-level time series can weaken the influence of instantaneous field spread effect. In this paper, the OPM-MEG was used for measuring the evoked responses of 20Hz rhythmic and arrhythmic median nerve stimulation, and the inter-trial phase synchronization (ITPS) and inter-reginal phase synchronization (IRPS) of primary somatosensory cortex (SI) and secondary somatosensory cortex (SII) were analysed. The results find that under rhythmic condition, the evoked responses of SI and SII show continuous oscillations and the effect of resetting phase. The values of ITPS and IRPS significantly increase at the stimulation frequency of 20Hz and its harmonic of 40Hz, whereas the arrhythmic stimulation does not exhibit this phenomenon. Moreover, in the initial stage of stimulation, the ITPS and IRPS values are significantly higher at Mu rhythm in the rhythmic condition compared to arrhythmic. In conclusion, the results demonstrate the ability of OPM-MEG in measuring phase pattern and functional connectivity on source-level, and may also prove beneficial for the study on the mechanism of rhythmic stimulation therapy for rehabilitation.

Capitate Proximal Fragment Migration Compressing the Median Nerve in Scaphocapitate Fracture: A Case Report.

BACKGROUND Scaphocapitate syndrome is a rare clinical entity consisting of a combined scaphoid and capitate fracture along with a 90- or 180-degrees rotation of the proximal capitate fragment. The syndrome is scarcely described in the literature, with proximal migration of the capitate fragment being reported only by Mudgal et al in 1995. Concurrent compression of the median nerve is a highly unfortunate event, suggesting a unique case presented here. CASE REPORT We present a unique case of scaphocapitate fracture-dislocation in a 25-year-old man with volar dislocation of the capitate's fragment deep to the median nerve. X-rays and CT scan were performed and the patient was treated few hours after the injury by a hand specialist, in order to prevent median neuropathy and avascular necrosis of the fragment. Open reduction and internal fixation utilizing a Herbert screw for the scaphoid fracture and 3 additional K-wires was performed. Immediately post-operatively, the acute neurological symptoms had subsided and good reduction was acquired radiologically. One year post-operatively the patient had regained good hand and wrist functionality, with no extension or flexion ROM deficits. CONCLUSIONS Immediate intervention in a specialized center with reduction and fixation utilizing a Herbert screw and K-wires showed favorable 1-year results in our case of scaphocapitate syndrome. The impending complications of median neuropathy and capitate avascular necrosis were avoided despite the high-risk injury pattern.

Relationship between Gravidity, Parity, and Neurophysiological Features in Carpal Tunnel Syndrome (CTS) Patients with a History of Pregnancy.

BACKGROUND: It is not yet clear if gravidity and parity have any relationships with the electrodiagnostic parameters of carpal tunnel syndrome (CTS). OBJECTIVE: To determine whether there is a relationship between electrodiagnostic findings, gravidity, and parity number in CTS. MATERIALS AND METHODS: Female patients over 18 years of age with CTS were included in this retrospective cohort study. The gravidity/parity number, median nerve compound muscle action potential (CMAP), and compound nerve action potential (CNAP) of the patients were analyzed. The two subgroups of the Boston carpal tunnel syndrome questionnaire (BCTSQ): The Symptom Severity Scale (SSS) and Functional Severity Scale (FSS) were applied to the patients. CTS patients were divided into two groups aged at first pregnancy ≤20 years and >20 years. RESULTS: One hundred and eight CTS extremities (seven right-sided CTS, three left-sided CTS, 49 bilateral CTS) of 59 patients were included. The median (interquartile range: 25%-75%) number of gravidity, parity, and abortion were 3 (2-5), 3 (2-4), and 0 (0-0), respectively. Right-sided CTS patients at the age of first pregnancy ≤20 years had higher BCTSQ-SSS/FSS scores and median nerve CMAP latency compared to patients at the age of first pregnancy >20 years (P = 0.029 for SSS; P = 0.042 for FSS; and P = 0.041 for CMAP latency). A negative correlation was found between the gravidity/parity numbers and median nerve CNAP/CMAP amplitudes (P = 0.028/0.031, r = -0.293/-0.289 for CNAP amplitude; and P = 0.006/0.035, r = -0.363/-0.283 for CMAP amplitude). CONCLUSION: Neurophysiological findings worsen as the number of gravidity and parity increase. Electrodiagnostic and clinical features of CTS may be worsening in females below 20 years at first pregnancy.

Ultrasound-guided thrombin injection in the management of brachial artery pseudoaneurysm with median nerve compression.

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Effects of finger pinch motor imagery on short-latency afferent inhibition and corticospinal excitability.

Motor imagery is a cognitive process involving the simulation of motor actions without actual movements. Despite the reported positive effects of motor imagery training on motor function, the underlying neurophysiological mechanisms have yet to be fully elucidated. Therefore, the purpose of the present study was to investigate how sustained tonic finger-pinching motor imagery modulates sensorimotor integration and corticospinal excitability using short-latency afferent inhibition (SAI) and single-pulse transcranial magnetic stimulation (TMS) assessments, respectively. Able-bodied individuals participated in the study and assessments were conducted under two experimental conditions in a randomized order between participants: (1) participants performed motor imagery of a pinch task while observing a visual image displayed on a monitor (Motor Imagery), and (2) participants remained at rest with their eyes fixed on the monitor displaying a cross mark (Control). For each condition, sensorimotor integration and corticospinal excitability were evaluated during sustained tonic motor imagery in separate sessions. Sensorimotor integration was assessed by SAI responses, representing inhibition of motor-evoked potentials (MEPs) in the first dorsal interosseous muscle elicited by TMS following median nerve stimulation. Corticospinal excitability was assessed by MEP responses elicited by single-pulse TMS. There was no significant difference in the magnitude of SAI responses between motor imagery and Control conditions, while MEP responses were significantly facilitated during the Motor Imagery condition compared to the Control condition. These findings suggest that motor imagery facilitates corticospinal excitability, without altering sensorimotor integration, possibly due to insufficient activation of the somatosensory circuits or lack of afferent feedback during sustained tonic motor imagery.

The 2-by-2 Inch "Key Window" in the Upper Extremity: An Anatomical Appraisal of the Accessibility and Proximity of the Major Nerves and Vessels.

BACKGROUND: The brachial plexus is a network of nerves located between the neck and axilla, which receives input from C5-T1. Distally, the nerves and blood vessels that supply the arm and forearm form a medial neurovascular bundle. The purpose of this study was to illustrate that a peripheral nerve dissection via a 2 × 2 inch window would allow for identification and isolation of the major nerves and blood vessels that supply the arm and forearm. METHODS: A right side formalin-fixed latex-injected cadaveric arm was transected at the proximal part of the axillary fold and included the scapular attachments. Step-by-step anatomical dissection was carried out and documented with three-dimensional digital imaging. RESULTS: A 2 × 2 inch window centered 2 inches distal to the axillary fold on the medial surface of the arm enabled access to the major neurovascular structures of the arm and forearm: the median nerve, ulnar nerve, medial antebrachial cutaneous nerve, radial nerve and triceps motor branches, musculocutaneous nerve and its biceps and brachialis branches and lateral antebrachial cutaneous nerve, basilic vein and brachial artery and vein, and profunda brachii artery. CONCLUSIONS: Our study demonstrates that the majority of the neurovascular supply in the arm and forearm can be accessed through a 2 × 2 inch area in the medial arm. Although this "key window" may not be entirely utilized in the operative setting, our comprehensive didactic description of peripheral nerve dissection in the cadaver laboratory can help in safer identification of complex anatomy encountered during surgical procedures.

Delays in latencies of median-nerve evoked magnetic fields in patients with succinic semialdehyde dehydrogenase deficiency.

OBJECTIVE: Succinic semialdehyde dehydrogenase deficiency (SSADHD) is a genetic disorder resulting in abnormal regulation of γ-aminobutyric acid, lipid metabolism, and myelin biogenesis, leading to ataxia, seizures, and cognitive impairment. Since the myelin sheath is thinner in a murine model of SSADHD compared to a wild type, we hypothesized that this also holds for human brain. We tested whether the conduction velocity in the somatosensory pathway is accordingly delayed. METHODS: Somatosensory evoked magnetic fields (SEF) produced by transcutaneous electrical stimulation of the median nerve were measured in 13 SSADHD patients, 11 healthy and 14 disease controls with focal epilepsy. The peak latencies of the initial four components (M1, M2, M3 and M4) were measured. RESULTS: The SEF waveforms and scalp topographies were comparable across the groups. The latencies were statistically significantly longer in the SSADHD group compared to the two controls. We found these latencies for the SSADHD, healthy and disease controls respectively to be: M1: (21.9 ± 0.8 ms [mean ± standard error of the mean], 20.4 ± 0.6 ms, and 21.0 ± 0.4 ms) (p < 0.05); M2: (36.1 ± 1.0 ms, 33.1 ± 0.6 ms, and 32.1 ± 1.1 ms) (p < 0.005); M3: (62.5 ± 2.4 ms, 54.7 ± 2.0 ms, and 49.9 ± 1.8 ms) (p < 0.005); M4: (86.2 ± 2.3 ms, 78.8 ± 2.8 ms, and 73.5 ± 2.9 ms) (p < 0.005). CONCLUSIONS: The SEF latencies are delayed in patients with SSADHD compared with healthy controls and disease controls. SIGNIFICANCE: This is the first study that compares conduction velocities in the somatosensory pathway in SSADHD, an inherited disorder of GABA metabolism. The longer peak latency implying slower conduction velocity supports the hypothesis that myelin sheath thickness is decreased in SSADHD.

Efficacy of focused shockwave therapy in patients with moderate-to-severe carpal tunnel syndrome: a preliminary study.

OBJECTIVE: To evaluate the efficacy of focused extracorporeal shockwave therapy for symptoms and function in patients with moderate-to-severe carpal tunnel syndrome. DESIGN: A single-blind randomized controlled trial. SUBJECTS: Twenty-four outpatients with moderate-to-severe carpal tunnel syndrome. METHODS: Patients were randomly allocated into 2 groups: a focused extracorporeal shockwave therapy group and a control group. The focused extracorporeal shockwave therapy group received conservative treatment in addition to focused extracorporeal shockwave therapy with an energy flux density ranging from 0.01 to 0.15 mJ/mm2, a frequency of 4-5 Hz, and 1500 pulses per session once a week for a total of 3 sessions. The control group received only conservative treatment, which comprised gliding exercises for carpal tunnel syndrome, a night wrist splint, and lifestyle modification. The Thai version of the Boston Carpal Tunnel Questionnaire (T-BCTQ), a nerve conduction study, and ultrasonography of the median nerve cross-sectional area were performed before treatment and at 3 and 6 weeks after baseline. RESULTS: The T-BCTQ symptom and function scores had significantly decreased in both groups, favouring focused extracorporeal shockwave therapy at all time-points. In addition, distal sensory and motor latency were significantly different between the groups at 3 weeks from baseline. CONCLUSION: Focused extracorporeal shockwave therapy plus conservative treatment effectively provided short-term improvement in symptoms, hand function, and nerve conduction in patients with moderate-to-severe carpal tunnel syndrome compared with conservative treatment alone.