Deconstruction the feedforward inhibition changes in the layer III of anterior cingulate cortex after peripheral nerve injury.

The anterior cingulate cortex (ACC) is one of the critical brain areas for processing noxious information. Previous studies showed that peripheral nerve injury induced broad changes in the ACC, contributing to pain hypersensitivity. The neurons in layer 3 (L3) of the ACC receive the inputs from the mediodorsal thalamus (MD) and form the feedforward inhibition (FFI) microcircuits. The effects of peripheral nerve injury on the MD-driven FFI in L3 of ACC are unknown. In our study, we record the enhanced excitatory synaptic transmissions from the MD to L3 of the ACC in mice with common peroneal nerve ligation, affecting FFI. Chemogenetically activating the MD-to-ACC projections induces pain sensitivity and place aversion in naive mice. Furthermore, chemogenetically inactivating MD-to-ACC projections decreases pain sensitivity and promotes place preference in nerve-injured mice. Our results indicate that the peripheral nerve injury changes the MD-to-ACC projections, contributing to pain hypersensitivity and aversion.

Iatrogenic Common Peroneal Nerve Injuries From Inside-out Lateral Meniscus Repair: A Report of 2 Cases.

CASES: We report 2 cases of common peroneal nerve (CPN) palsy after inside-out lateral meniscus (LM) repair with very different presentations, occurring despite the standard surgical precautions (open counter incision and proper retraction between the biceps femoris tendon, lateral gastrocnemius, and capsule). On exploration, needle was found to have penetrated the nerve in one case and the nerve sheath in the other case. Patient 1 had near-complete neurological recovery, while patient 2 had partial neurological recovery after suture removal and neurolysis. CONCLUSION: CPN palsy can occur despite following all precautions during LM repair and should be managed as an iatrogenic injury unless proven otherwise.

Continuous muscle pump activation by neuromuscular electrical stimulation of the common peroneal nerve in the treatment of patients with venous leg ulcers: A position paper.

The standard treatment for patients with confirmed Venous Leg Ulcers (VLUs) is compression therapy to improve the function of the calf muscle pump. There is a significant cohort of patients who are unable to tolerate optimal compression therapy or indeed any level of compression therapy. In addition, there is a cohort of patients who can tolerate compression whose ulcers show little or no evidence of healing. There is a need for ways to further improve calf muscle pump function and to improve venous ulcer healing in these patients. Published data were reviewed on the use of Muscle Pump Activation (MPA) using common peroneal nerve neuromuscular electrical stimulation (NMES) to improve calf muscle pump function. There is physiological evidence that MPA can improve calf muscle pump function and venous return in both control subjects and in patients with venous disease. The use of MPA has also been shown to improve venous flow volume and venous flow velocity on ultrasound scanning in patients with venous disease. MPA has been shown to improve microcirculation in the skin using Laser Doppler and laser Doppler Speckle Contrast Imaging, in both normal subjects as well as in patients with venous disease and VLU. A recent randomized controlled trial of MPA plus compression therapy compared with compression therapy alone, found significantly faster rates of healing with the use of MPA in addition to compression therapy. There are indications for the use of MPA as an adjunctive treatment to enhance calf muscle pump function in patients with VLU: who cannot tolerate compression therapy who can only tolerate suboptimal, low-level compression whose ulcer healing remains slow or stalled with optimal compression.

Initial findings using high-resolution magnetic resonance imaging for visualisation of the sural nerve and surrounding anatomy in healthy volunteers at 7 Tesla.

BACKGROUND AND AIMS: Histopathological diagnosis is the gold standard in many acquired inflammatory, infiltrative and amyloid based peripheral nerve diseases and a sensory nerve biopsy of sural or superficial peroneal nerve is favoured where a biopsy is deemed necessary. The ability to determine nerve pathology by high-resolution imaging techniques resolving anatomy and imaging characteristics might improve diagnosis and obviate the need for biopsy in some. The sural nerve is anatomically variable and occasionally adjacent vessels can be sent for analysis in error. Knowing the exact position and relationships of the nerve prior to surgery could be clinically useful and thus reliably resolving nerve position has some utility. METHODS: 7T images of eight healthy volunteers' (HV) right ankle were acquired in a pilot study using a double-echo in steady-state sequence for high-resolution anatomy images. Magnetic Transfer Ratio images were acquired of the same area. Systematic scoring of the sural, tibial and deep peroneal nerve around the surgical landmark 7 cm from the lateral malleolus was performed (number of fascicles, area in voxels and mm2, diameter and location relative to nearby vessels and muscles). RESULTS: The sural and tibial nerves were visualised in the high-resolution double-echo in steady-state (DESS) image in all HV. The deep peroneal nerve was not always visualised at level of interest. The MTR values were tightly grouped except in the sural nerve where the nerve was not visualised in two HV. The sural nerve location was found to be variable (e.g., lateral or medial to, or crossing behind, or found positioned directly posterior to the saphenous vein). INTERPRETATION: High-resolution high-field images have excellent visualisation of the sural nerve and would give surgeons prior knowledge of the position before surgery. Basic imaging characteristics of the sural nerve can be acquired, but more detailed imaging characteristics are not easily evaluable in the very small sural and further developments and specific studies are required for any diagnostic utility at 7T.

Inhibition of muscle sympathetic nerve activity in premenopausal women: responses to sudden sensory stimuli predict responses to mental stress.

Muscle sympathetic nerve responses to sudden sensory stimuli have been elucidated in several studies on young healthy men, showing reproducible interindividual differences ranging from varying degrees of inhibition to no significant change, with very few subjects showing significant excitation. These individual response patterns have been shown to predict the neural response to mental stress and coupled blood pressure responses. The aim of this study was to investigate whether premenopausal healthy women show similar neural and blood pressure responses. Muscle sympathetic nerve recordings from the peroneal nerve were performed in 34 healthy women (mean age 27 ± 8 yr) during sudden sensory stimuli (electrical stimuli to a finger) and 3 min of mental stress (forced arithmetics). After sensory stimuli, 18 women showed varying degrees of inhibition of muscle sympathetic nerve activity (burst amplitude mean reduction 60%, range 34-100%). The remaining 16 showed no inhibition (mean 5%, range -31 to 28%; one subject exhibiting excitation). During 3 min of mental stress, the normalized change in burst incidence for muscle sympathetic nerve activity correlated with the percentage change of muscle sympathetic nerve activity induced by the sensory stimulation protocol (r = 0.64, P = 0.0042). In contrast to men, the neural responses did not predict changes in blood pressure. Thus, premenopausal females show a similar range of individual differences in defense-related muscle sympathetic neural responses as men, but no associated differences in blood pressure responses. Whether these patterns are unchanged after menopause remains to be investigated.NEW & NOTEWORTHY Muscle sympathetic neural responses to sudden sensory stimuli in premenopausal women showed interindividual differences and the distribution of sympathetic responses was similar to that previously found in men. Despite this similarity, the associated differences in transient blood pressure responses seen in men were not found in women. The increased risk of developing hypertension in postmenopausal women warrants an investigation of whether these response patterns are altered after menopause.

Giant Common Peroneal Nerve Schwannoma Mimicking Synovial Sarcoma: An Unusual Case Report.

Schwannoma, also known as neurilemmoma or Schwann cell tumor, is one of the most common neoplasms of the nerve sheath which usually appears at the head, neck, or upper extremity. Schwannoma occurrence in the lower extremity originating from the common peroneal nerve is rarely reported according to literary findings. We report a case of a 32-year-old man who presented with a 6-month history of a growing lump in the left knee. MRT revealed a well-defined 9.6 cm × 7.8 cm × 6.5 cm multilobular mass of heterogeneous consistency with areas of necroses with a likely diagnosis of synovial sarcoma. After surgery, a final histopathological assessment of the tumor demonstrated Antoni A and B patterns with nuclear palisading, hallmarks of a schwannoma. Postoperatively the patient suffered a neurological complication-impaired dorsiflexion of the left foot. The patient started immediate physiotherapy in the Department of Rehabilitation. Three weeks after the operation, gradual improvement in neurological function was observed. To date, complete tumor excision combined with microscopic analysis and immunohistochemical staining remains the gold standard in diagnosing and treating a peripheral nerve schwannoma. Moreover, the use of additional nerve monitoring tools during surgery could help to prevent complications.

Peroneal Nerve Entrapment in Diabetes Mellitus.

This narrative mini-review discusses the association between peroneal nerve entrapment (PEN) and diabetes mellitus (DM). Generally, PEN is not a common cause of peripheral neuropathy in DM. Poor glycaemic control and DM duration are powerful risk factors for PEN. Underlying mechanisms involve neurodegeneration and entrapment of the peroneal nerve. Patients tend to present with chronic leg pain, gradual foot drop, steppage gait, or weakness of ankle dorsiflexion. Electrodiagnostic and imaging studies are very useful in diagnosis to determine the level at which entrapment occurs. Treatment varies based on the aetiology and severity of symptoms. It is initially conservative. Surgical nerve decompression management is required when entrapment is refractory to non-operative options.

Palsy of Both the Tibial Nerve and Common Peroneal Nerve Caused by a Ganglion Cyst in the Popliteal Area.

A ganglion cyst is a benign mass consisting of high-viscosity mucinous fluid. It can originate from the sheath of a tendon, peripheral nerve, or joint capsule. Compressive neuropathy caused by a ganglion cyst is rarely reported, with the majority of documented cases involving peroneal nerve palsy. To date, cases demonstrating both peroneal and tibial nerve palsies resulting from a ganglion cyst forming on a branch of the sciatic nerve have not been reported. In this paper, we present the case of a 74-year-old man visiting an outpatient clinic complaining of left-sided foot drop and sensory loss in the lower extremity, a lack of strength in his left leg, and a decrease in sensation in the leg for the past month without any history of trauma. Ankle dorsiflexion and great toe extension strength on the left side were Grade I. Ankle plantar flexion and great toe flexion were Grade II. We suspected peroneal and tibial nerve palsy and performed a screening ultrasound, which is inexpensive and rapid. In the operative field, several cysts were discovered, originating at the site where the sciatic nerve splits into peroneal and tibial nerves. After successful surgical decompression and a series of rehabilitation procedures, the patient's neurological symptoms improved. There was no recurrence.

Nadir blood pressure responses to longer consecutive cardiac cycle sequences absent of sympathetic bursts are associated with popliteal endothelial-dependent dilation.

PURPOSE: The nadir pressure responses to cardiac cycles absent of muscle sympathetic nerve activity (MSNA) bursts (or non-bursts) are typically reported in studies quantifying sympathetic transduction, but the information gained by studying non-bursts is unclear. We tested the hypothesis that longer sequences of non-bursts (≥8 cardiac cycles) would be associated with a greater nadir diastolic blood pressure (DBP) and that better popliteal artery function would be associated with an augmented reduction in DBP. METHODS: Resting beat-by-beat DBP (via finger photoplethysmography) and common peroneal nerve MSNA (via microneurography) were recorded in 39 healthy, adults (age 23.4 ± 5.3 years; 19 females). For each cardiac cycle absent of MSNA bursts, the mean nadir DBP (ΔDBP) during the 12 cardiac cycles following were determined, and separate analyses were conducted for ≥8 or < 8 cardiac cycle sequences. Popliteal artery endothelial-dependent (via flow-mediated dilation; FMD) and endothelial-independent vasodilation (via nitroglycerin-mediated dilation; NMD) were determined. RESULTS: The nadir DBP responses to sequences ≥8 cardiac cycles were larger (-1.40 ± 1.27 mmHg) than sequences <8 (-0.38 ± 0.46 mmHg; p < 0.001). In adjusting for sex and burst frequency (14 ± 8 bursts/min), larger absolute or relative FMD (p < 0.01), but not NMD (p > 0.53) was associated with an augmented nadir DBP. This overall DBP-FMD relationship was similar in sequences ≥8 (p = 0.04-0.05), but not <8 (p > 0.72). CONCLUSION: The DBP responses to non-bursts, particularly longer sequences, were inversely associated with popliteal endothelial function, but not vascular smooth muscle sensitivity. This study provides insight into the information gained by quantifying the DBP responses to cardiac cycles absent of MSNA.

The effects of electrical stimulation of ventromedial prefrontal cortex on skin sympathetic nerve activity.

Skin sympathetic nerve activity (SSNA) is primarily involved in thermoregulation and emotional expression; however, the brain regions involved in the generation of SSNA are not completely understood. In recent years, our laboratory has shown that blood-oxygen-level-dependent signal intensity in the ventromedial prefrontal cortex (vmPFC) and dorsolateral prefrontal cortex (dlPFC) are positively correlated with bursts of SSNA during emotional arousal and increases in signal intensity in the vmPFC occurring with increases in spontaneous bursts of SSNA even in the resting state. We have recently shown that unilateral transcranial alternating current stimulation (tACS) of the dlPFC causes modulation of SSNA but given that the current was delivered between electrodes over the dlPFC and the nasion, it is possible that the effects were due to current acting on the vmPFC. To test this, we delivered tACS to target the right vmPFC or dlPFC and nasion and recorded SSNA in 11 healthy participants by inserting a tungsten microelectrode into the right common peroneal nerve. The similarity in SSNA modulation between ipsilateral vmPFC and dlPFC suggests that the ipsilateral vmPFC, rather than the dlPFC, may be causing the modulation of SSNA during ipsilateral dlPFC stimulation.

Diagnostic accuracy of ultrasound and MR imaging in peroneal neuropathy: A prospective, single-center study.

INTRODUCTION/AIMS: Magnetic resonance imaging (MRI) findings in peroneal neuropathy are not well documented and the prognostic value of imaging remains uncertain. Upper limits of cross-sectional area (CSA) on ultrasound (US) have been established, but uncertainty regarding generalizability remains. We aimed to describe MRI findings of the peroneal nerve in patients and healthy controls and to compare these results to US findings and clinical characteristics. METHODS: We prospectively included patients with foot drop and electrodiagnostically confirmed peroneal neuropathy, and performed clinical follow-up, US and MRI of both peroneal nerves. We compared MRI findings to healthy controls. Two radiologists evaluated MRI features in an exploratory analysis after images were anonymized and randomized. RESULTS: Twenty-two patients and 38 healthy controls were included. Whereas significant increased MRI CSA values were documented in patients (mean CSA 20 mm2 vs. 13 mm2 in healthy controls), intra- and interobserver variability was substantial (variability of, respectively, 7 and 9 mm2 around the mean in 95% of repeated measurements). A pathological T2 hyperintense signal of the nerve was found in 52.6% of patients (50% interobserver agreement). Increased CSA measurements (MRI/US), pathological T2 hyperintensity of the nerve and muscle edema were not predictive for recovery. DISCUSSION: Imaging is recommended in all patients with peroneal neuropathy to exclude compressive intrinsic and extrinsic masses but we do not advise routine MRI for diagnosis or prediction of outcome in patients with peroneal neuropathy due to high observer variability. Further studies should aim at reducing MRI observer variability potentially by semi-automation.

Fibular (peroneal) neuropathy.

Fibular neuropathy has variable presenting features depending on the site of the lesion. Anatomical features make it susceptible to injury from extrinsic factors, particularly the superficial location of the nerve at the head of the fibula. There are many mechanisms of compression or other traumatic injury of the fibular nerve, as well as entrapment and intrinsic nerve lesions. Intraneural ganglion cysts are increasingly recognized when the mechanism of neuropathy is not clear from the medical history. Electrodiagnostic testing can contribute to the localization as well as the characterization of the pathologic process affecting the nerve. When the mechanism of injury is unclear from the analysis of the presentation, imaging with MRI and ultrasound may identify nerve lesions that warrant surgical intervention. The differential diagnosis of foot drop includes fibular neuropathy and other neurologic conditions, which can be distinguished through clinical and electrodiagnostic assessment. Rehabilitation measures, including ankle splinting, are important to improve function and safety when foot drop is present. Fibular neuropathy is less frequently painful than many other nerve lesions, but when it is painful, neuropathic medication may be required. Failure to spontaneously recover or the detection of a mass lesion may require surgical management.

High Resolution MRI Confirms Torsional Injury as Mechanism for Combined Ankle and Common Fibular (Peroneal) Nerve Injuries.

Common fibular nerve (CFN) injury due to ankle fracture is an underreported complication. The authors have proposed that torsional injury to the ankle can be translated along the interosseous membrane (IOM), producing tension on the CFN at the fibular neck. A 23-year-old woman presented to our clinic for left foot drop. Three months prior, the patient sustained a fall with left ankle inversion injury while running. She was diagnosed with a minor ankle fracture and placed in an orthopaedic boot. Unfortunately, her swelling worsened and one week later the patient was diagnosed with foot drop, which was further corroborated with EMG studies showing severe CFN injury localizing to the fibular neck. Because of the lack of recovery, she underwent decompression of the CFN. She experienced immediate symptomatic relief. High resolution imaging in this case supports our previous mechanism for indirect trauma to the ankle resulting in CFN injury. (Journal of Surgical Orthopaedic Advances 33(1):053-055, 2024).

[Superficial peroneal nerve entrapment: ultrasound-guided hydrodissection. A case report]. / Atrapamiento de nervio peroneo superficial: hidrodisección ecoguiada. A propósito de un caso.

Peripheral nerve entrapment is an underdiagnosed pathology when it is not the most common syndromes such as carpal tunnel syndrome or cubital tunnel syndrome. The symptomatic lesion of the superficial peroneal nerve (SPN) has a low incidence, being its diagnosis sometimes complex. It is based on a exhaustive physical examination and imaging tests such as ultrasound (US) or magnetic resonance imaging (RMI). Conservative treatment may sometimes not be sufficient, requiring surgical techniques in refractory cases. We present a patient diagnosed with superficial peroneal nerve entrapment by ultrasound and diagnostic nerve block that was subsequently resolved by hydrodissection technique at the level of the deep crural fascia tunnel. The results were satisfactory with a complete resolution of the clinical process since the application of this technique.

Peroneal Nerve Decompression in Patients with Multiple Hereditary Exostoses: Indications, Complications, and Recurrence.

BACKGROUND: To our knowledge, there have been no studies examining peroneal nerve decompression and proximal fibular osteochondroma excision exclusively in patients with multiple hereditary exostoses (MHE). The purpose of this study was to evaluate the indications, complications, and recurrence associated with nerve decompression and proximal fibular osteochondroma excision in patients with MHE. METHODS: The records on patients with MHE undergoing peroneal nerve decompression from 2009 to 2023 were retrospectively reviewed. Indications, clinical status, surgical technique, recurrence, and complications were recorded and were analyzed using the Fisher exact test, logistic regression, and the Kaplan-Meier method. RESULTS: There were 126 limbs identified in patients with MHE who underwent peroneal nerve decompression. The most common indications were pain over the proximal fibula, tibialis anterior and/or extensor hallucis longus weakness, and dysesthesias and/or neuropathic pain. Seven cases experienced postoperative foot drop as a complication of the decompression and osteochondroma excision. Logistic regression found significant relationships between complications and excision of anterior osteochondromas (odds ratio [OR], 5.21; p = 0.0062), proximal fibular excision (OR, 14.73; p = 0.0051), and previous decompression (OR, 5.77; p = 0.0124). The recurrence rate was 13.8%, and all recurrences occurred in patients who were skeletally immature at the index procedure. The probability of skeletally immature patients not experiencing recurrence was 88% at 3 years postoperatively and 73% at 6 years postoperatively. CONCLUSIONS: Indications for peroneal nerve decompression included neurologic symptoms and pain. The odds of a complication increased with excision of anterior osteochondromas and previous decompression. Recurrence of symptoms following decompression and osteochondroma excision was found exclusively in skeletally immature patients. LEVEL OF EVIDENCE: Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.

Common Peroneal Nerve and Tarsal Tunnel Release Surgery in an Adolescent Male with Hunter Syndrome: Illustrative Case.

BACKGROUND: Children with Hunter syndrome have a high prevalence of nerve compression syndromes given the buildup of glycosaminoglycans in the tendon sheaths and soft tissue structures. These are often comorbid with orthopedic conditions given joint and tendon contractures due to the same pathology. While carpal tunnel syndrome and surgical treatment has been well-reported in this population, the literature on lower extremity nerve compression syndromes and their treatment in Hunter syndrome is sparse. OBSERVATIONS: We report the case of a 13-year-old male with a history of Hunter syndrome who presented with toe-walking and tenderness over the peroneal and tarsal tunnel areas. He underwent bilateral common peroneal nerve and tarsal tunnel releases, with findings of severe nerve compression and hypertrophied soft tissue structures demonstrating fibromuscular scarring on pathology. Post-operatively, the patient's family reported subjective improvement in lower extremity mobility and plantar flexion. LESSONS: In this case, peroneal and tarsal nerve compression were diagnosed clinically and treated effectively with surgical release and postoperative ankle casting. Given the wide differential of common comorbid orthopedic conditions in Hunter syndrome and the lack of validated electrodiagnostic normative values in this population, the history and physical examination and consideration of nerve compression syndromes are tantamount for successful workup and treatment of gait abnormalities in the child with Hunter syndrome.

Estimation of the number of motor units in the human extensor digitorum brevis using MScanFit.

OBJECTIVE: Our aim was to determine the number and size parameters of EDB motor units in healthy young adults using MScanFit, a novel approach to motor unit number estimation (MUNE). Since variability in MUNE is related to compound muscle action potential (CMAP) size, we employed a procedure to document the optimal EDB electromyographic (EMG) electrode position prior to recording MUNE, a neglected practice in MUNE. METHODS: Subjects were 21 adults 21-44 y. Maximum CMAPs were recorded from 9 sites in a 4 cm2 region centered over the EDB and the site with the largest amplitude was used in the MUNE experiment. For MUNE, the peroneal nerve was stimulated at the fibular head to produce a detailed EDB stimulus-response curve or "MScan". Motor unit number and size parameters underlying the MScan were simulated using the MScanFit mathematical model. RESULTS: In 19 persons, the optimal recording site was superior, superior and proximal, or superior and distal to the EDB mid-belly, whereas in 3 persons it was proximal to the mid-belly. Ranges of key MScanFit parameters were as follows: maximum CMAP amplitude (3.1-8.5 mV), mean SMUP amplitude (34.4-106.7 µV), mean normalized SMUP amplitude (%CMAP max, 0.95-2.3%), largest SMUP amplitude (82.7-348 µV), and MUNE (43-103). MUNE was not related to maximum CMAP amplitude (R2 = 0.09), but was related to mean SMUP amplitude (R2 = -0.19, P = 0.05). CONCLUSION: The EDB CMAP was highly sensitive to electrode position, and the optimal position differed between subjects. Individual differences in EDB MUNE were not related to CMAP amplitude. Inter-subject variability of EDB MUNE (coefficient of variation) was much less than previously reported, possibly explained by better optimization of the EMG electrode and the unique approach of MScanFit MUNE.

Permanent Iatrogenic Fibular Nerve Injury following Tibial Plateau Levelling Osteotomy.

The aim of this study was to describe three dogs with permanent fibular nerve injury following tibial plateau levelling osteotomy (TPLO). Fibular nerve injury following TPLO led to atrophy of the cranial tibial muscle, absent hock flexion and a mild lameness. Fibular nerve injury was confirmed in one case with electrodiagnostics. All three cases had a drill tract in the same location, on the caudal aspect of the tibia, immediately distal to the tibial osteotomy. Permanent fibular nerve injury following TPLO occurred with a more caudally positioned plate and care should be taken when drilling the tibia from medial to lateral in the region described. Careful gait assessment at routine follow-up was required to identify this complication.