Evaluation of peripheral nerve injury according to the severity of damage using 18F-FDG PET/MRI in a rat Model of sciatic nerve injury.

OBJECTIVES: We ascertained that the PET scan may be a valuable imaging modality for the noninvasive, objective diagnosis of neuropathic pain caused by peripheral nerve injury through the previous study. This study aimed to assess peripheral nerve damage according to severity using18F-FDG PET/MRI of the rat sciatic nerve. METHODS: Eighteen rats were divided into three groups: 30-second (G1), 2-minute (G2), and 5-minute (G3) crushing injuries. The severity of nerve damage was measured in the third week after the crushing injury using three methods: the paw withdrawal threshold test (RevWT), standardized uptake values on PET (SUVR), and intensity analysis on immunohistochemistry (IntR). RESULTS: There were significant differences between G1 and G3 in both SUVR and IntR (p = 0.012 and 0.029, respectively), and no significant differences in RevWT among the three groups (p = 0.438). There was a significant difference in SUVR (p = 0.012), but no significant difference in IntR between G1 and G2 (p = 0.202). There was no significant difference between G2 and G3 in SUVR and IntR (p = 0.810 and 0.544, respectively). DISCUSSION: Although PET did not show results consistent with those of immunohistochemistry in all respects, this study demonstrated that PET uptake tended to increase with severe nerve damage. If this research is supplemented by further experiments, PET/MRI can be used as an effective diagnostic modality.

Characterizing peroneal nerve injury clinicoradiological patterns with MRI in patients with sciatic neuropathy and foot drop after total hip replacement.

OBJECTIVE: Sciatic nerve injury following total hip arthroplasty (THA) predominantly affects the peroneal division of the sciatic nerve, often causing a foot drop. This can result from a focal etiology (hardware malposition, prominent screw, or postoperative hematoma) or nonfocal/traction injury. The objective of this study was to compare the clinicoradiological features and define the extent of nerve injury resulting from these two distinct mechanisms. METHODS: Patients who developed a postoperative foot drop within 1 year after primary or revision THA with a confirmed proximal sciatic neuropathy based on MRI or electrodiagnostic studies were retrospectively reviewed. Patients were divided into two cohorts: group 1 (focal injury), including patients with an identifiable focal structural etiology, and group 2 (nonfocal injury), including patients with a presumed traction injury. Patient demographics, clinical examinations, subsequent surgeries, electrodiagnostic study results, and MRI abnormalities were noted. The Student t-test was used to compare time to onset of foot drop and time to secondary surgery. RESULTS: Twenty-one patients, treated by one surgeon, met inclusion criteria (8 men and 13 women; 14 primary THAs and 7 revision THAs). Group 1 had a significantly longer time from THA to the onset of foot drop, with a mean of 2 months, compared with an immediate postoperative onset in group 2 (p = 0.02). Group 1 had a consistent pattern of localized focal nerve abnormality on imaging. In contrast, the majority of patients in group 2 (n = 11) had a long, continuous segment of abnormal size and signal intensity of the nerve, while the other 3 patients had a segment of less abnormal nerve in the midthigh on imaging. All patients with a long continuous lesion had Medical Research Council grade 0 dorsiflexion prior to secondary nerve surgeries compared with 1 of 3 patients with a more normal midsegment. CONCLUSIONS: There are distinct clinicoradiological findings in patients with sciatic injuries resulting from a focal structural etiology versus a traction injury. While there are discrete localized changes in patients with a focal etiology, those with traction injuries demonstrate a diffuse zone of abnormality within the sciatic nerve. A proposed mechanism involves anatomical tether points of the nerve acting as points of origin and propagation for traction injuries, resulting in an immediate postoperative foot drop. In contrast, patients with a focal etiology have localized imaging findings but a highly variable time to the onset of foot drop.

Early perioperative magnetic resonance findings in patients with foot drop following total hip Arthroplasty: A descriptive case-series.

PURPOSE: This study aims to characterize iatrogenic sciatic nerve injury patterns in the early, perioperative period following posterior-approach total hip arthroplasty (THA) with magnetic resonance imaging (MRI). METHODS: This was an IRB-approved retrospective analysis of patients acquired from a longitudinal, single site radiology database of patients who underwent MRI for "foot drop" within 4 weeks following posterior-approach THA surgery, over a 20-year period. RESULTS: MRI exams from 51 patients (mean age 62 years; 32 females) who met inclusion criteria were evaluated. Mean time to MRI was 2.4 days. Of 51 patients, 43 underwent primary THA, 6 revision THA and 2 explantation with antibiotic spacer placement. Ten exams revealed a normal appearance of the sciatic nerve. Nineteen showed compression of the sciatic nerve by edema or a fluid collection, without intrinsic nerve abnormality. Fifteen demonstrated perineural tethering or scar/granulation tissue encasement of the nerve, and in half of these cases the sciatic nerve was enlarged and/or hyperintense on fluid-sensitive sequences. Six patients had sciatic nerve compression secondary to quadratus femoris retraction. Six patients had complete resolution of the foot drop at a mean follow-up of 37.3 months following surgery, and in these cases the sciatic nerve appeared normal on the initial postoperative MRI. Remaining patients all had persistent weakness and paresthesias in the sciatic nerve distribution at a mean follow-up duration of 34.3 months. CONCLUSION: This retrospective case series demonstrates various sciatic nerve injury patterns in the early perioperative period on MRI and proposes a targeted MRI protocol to evaluate the sciatic nerve post THA surgery.

Study on the Crush Injury Model of the Sciatic Nerve in Rabbits by Conventional Ultrasound and Elastography.

BACKGROUND: The crush injury model of the sciatic nerve in rabbits is a common nerve injury model, but there is little literature on the evaluation of nerve stiffness by ultrasound elastography. PURPOSE: To explore the value of ultrasound elastography in diagnosing crush injury of the sciatic nerve in rabbits. MATERIALS AND METHODS: Forty cases of crush injury model of the sciatic nerve in rabbits were examined by conventional ultrasound and elastography. The sonographic manifestations and stiffness of the model were analyzed, and the regularity of nerve injury with time was summarized. RESULTS: Ultrasound could clearly show the location, range, and thickness of the injured nerve in this model. The thickness of the injured area reached a peak in the 2nd week and returned to normal thickness in the 8th week. The nerve stiffness of the injured area increased gradually with time. CONCLUSION: Conventional ultrasound combined with elastography can comprehensively and quantitatively evaluate the morphological changes and mechanical properties of the injured sciatic nerve in rabbits, which may be of great significance to the repair and rehabilitation of peripheral nerve crush injuries.

A Sciatic Neuralgia Case of an Entrapment Neuropathy Mimicking Piriformis Syndrome Due to Soft Tissue Hemangioma.

BACKGROUND: Lumbosacral pain is commonly seen in daily clinical practice. In fact, entrapment of the part of the sciatic nerve after the sacral foramen causes some of these pains, which should not be overlooked. The sciatic nerve may be compressed during its course after the sacral foramen for a variety of reasons. We aimed in this article to review extra-spinal compressive sciatic neuropathy reasons and abnormal magnetic resonance imaging (MRI) by presenting a sciatic neuralgia case of an entrapment neuropathy mimicking piriformis syndrome due to soft tissue hemangioma. CASE PRESENTATION: A 30-year-old male patient was admitted with complaints of lumbosacral pain spreading to the leg that had been worsening over the previous 10 days. With the preliminary diagnosis of labral damage and piriformis syndrome, the patient was referred to the radiology clinic for a hip MRI. In the hip MR images, a mass lesion suggestive of heterogeneously enhanced soft tissue hemangioma after the injection of paramagnetic contrast material was observed in the proximal left thigh. The soft tissue hemangioma extends towards the obturator foramen and compresses the sciatic nerve proximal to the femur after the sciatic foramen. CONCLUSION: The diagnosis of lower extremity entrapment neuropathy is frequently misdiagnosed. In these cases, MRI becomes more important for accurate diagnosis. The radiologists' knowledge of the sciatic nerve in MRI, regional anatomy during the course of the sciatic nerve, and abnormal nerve imaging findings will aid in the diagnosis.

Ciática extrarraquídea: caso clínico y revisión de la literatura / Persistent sciatic artery: A case report and literature review

La arteria ciática persistente es una entidad poco frecuente, considerada como una malformación vascular congénita de tipo axial por falta de involución de la arteria ciática durante el desarrollo embrionario. Puede, o no, asociarse con alteraciones en el desarrollo de las arterias iliaca, femoral común y/o femoral superficial. Clínicamente los pacientes pueden ser asintomáticos, o pueden manifestar un dolor crónico tipo neuralgia ciática, por irritación nerviosa, al estar en contigüidad con el vaso anómalamente persistente, o por dolor isquémico, al sufrir trombosis de un aneurisma que con relativa frecuencia suele desarrollarse en este vaso anómalamente persistente, o por embolia arterial distal, pudiendo llegar a comprometer la viabilidad de la extremidad (AU)

The persistent sciatic artery is an uncommon disease, considered an axial congenital vascular malformation due to the lack of involution of the sciatic artery during embryonic development. It may be associated with abnormalities in the development of the iliac, common femoral and superficial femoral arteries. Patients may be asymptomatic, or they could present chronic pain, such as sciatic neuralgia, caused by nerve damage, since it is close to the abnormal persistent vessel, or due to ischemic pain, as a result of a thrombosis or embolism of an aneurysm, which could compromise the viability of the limb (AU)

Nerve conduction assessment and magnetic resonance imaging for the diagnosis of localized hypertrophic neuropathy of the sciatic nerve and the lumbo-sacral plexus.

Localized hypertrophic neuropathy (LHN) are slowly growing nerve lesions causing progressive nerve deficit and weakness. We present the case of a 32-year old woman with long history of motor and sensory deficit complains along the sciatic nerve territory. The muscles involved were featured by delay in F waves at nerve conduction assessment. Magnetic resonance imaging (MRI) showed specific patterns, low intense on T1 and abnormally hyper intense on short tau inversion recovery (STIR) and T2, with no obvious enhancement, features compatible with either LHN or intraneural perineurioma (IP) of the sciatic nerve and/or the lumbosacral plexus. Focal thickening and hypertrophy of the sciatic nerve with preserved fascicular configuration and progressive enlargement of the right lumbosacral plexus could be noted. A nerve conduction assessment followed by an MRI eventually allowed to diagnose LHN, without performing a nerve biopsy. Although similar, LHN and IP are two distinct lesions which should be diagnosed and differentiated as soon as possible, to avoid potential complications due to delayed diagnosis and/or misdiagnosis.

Sciatic Nerve Hematoma - Case Report.

Hemorrhagic neuropathy is an extremely rare condition. This condition refers to bleed into or around a peripheral nerve, causing either an extra neural or an intraneural hematoma. When they do occur, it is usually due to iatrogenic/inherited coagulopathies or as a consequence of injections targeting nerves. We present a case of sciatic nerve palsy developed secondary to anticoagulant therapy (Warfarin). MRI imaging showed features of sciatic nerve hematoma following which warfarin was withdrawn. The patient showed symptomatic improvement and a follow up ultrasound of left thigh showed resolution of hematoma with normal sciatic nerve diameter. To the best of our knowledge there is limited available literature regarding nerve hematomas secondary to anticoagulation therapy. This complication should be promptly recognized and immediate steps should take place because of the favorable results of the early treatment.

Snapping of the Sciatic Nerve and Sciatica Provoked by Impingement Between the Greater Trochanter and Ischium: A Case Report.

CASE: A 64-year-old woman developed worsening sciatica associated with snapping at the hip over a period of 4 years. The physical examination and dynamic ultrasound revealed the snapping of the sciatic nerve (SN) provoked by impingement between the greater trochanter (GT) and the ischium. Additional imaging studies demonstrated hyperintense signal in the SN at the hip, sagittal imbalance, decreased ischiofemoral space, and increased femoral torsion. CONCLUSION: Snapping and entrapment of the SN provoked by impingement between the GT and the ischium should be considered in the differential diagnosis of snapping hip and/or sciatica.

Magnetic resonance imaging of enhanced nerve repair with mesenchymal stem cells combined with microenvironment immunomodulation in neurotmesis.

INTRODUCTION: The immuno-microenvironment of injured nerves adversely affects mesenchymal stem cell (MSC) therapy for neurotmesis. Magnetic resonance imaging (MRI) can be used noninvasively to monitor nerve degeneration and regeneration. The aim of this study was to investigate nerve repair after MSC transplantation combined with microenvironment immunomodulation in neurotmesis by using multiparametric MRI. METHODS: Rats with sciatic nerve transection and surgical coaptation were treated with MSCs combined with immunomodulation or MSCs alone. Serial multiparametric MRI examinations were performed over an 8-week period after surgery. RESULTS: Nerves treated with MSCs combined with immunomodulation showed better functional recovery, rapid recovery of nerve T2, fractional anisotropy and radial diffusivity values, and more rapid restoration of the fiber tracks than nerves treated with MSCs alone. DISCUSSION: Transplantation of MSCs in combination with immunomodulation can exert a synergistic repair effect on neurotmesis, which can be monitored by multiparametric MRI.

Malignant peripheral nerve sheath tumor of the sciatic nerve presenting with leg pain in the setting of lumbar scoliosis and spinal stenosis.

STUDY DESIGN: Case report. OBJECTIVE: We present a case of malignant peripheral nerve sheath tumor (MPNST) presenting as neuropathic pain in the setting of lumbar scoliosis and spinal stenosis. Most peripheral nerve sheath tumors are benign, and malignant cases are more commonly associated with neurofibromatosis type 1 or prior radiation exposure. MPNST is a rare tumor with a poor prognosis. We report a case of MPNST that presented as neuropathic pain following lumbar decompression and fusion surgery. METHODS: A 60-year-old woman presented for management of lumbar scoliosis, stenosis, and left leg pain. After lumbar decompression and fusion surgery, the patient was readmitted to the hospital after falling 10 weeks post-op. She reported gradual recurrence of leg pain. Left foot drop was noted on exam. Imaging studies showed no spinal changes postoperatively or residual stenosis. Obesity limited electrodiagnostic studies. Hip MRI revealed a lobular soft tissue mass in the left sciatic notch. Surgical resection and pathology provided the diagnosis of MPNST. The patient declined wide resection and other interventions after seeking a second opinion. Palliative pain management was implemented. RESULTS: The patient expired 15 months after her index spinal surgery. CONCLUSIONS: MPNST is an extremely rare tumor that can present with symptoms similar to radiculitis. Clinical signs and symptoms of MPNST are vague and nonspecific due to compression of surrounding structures. Surgical wide resection is the first line of treatment for MPNST with chemotherapy and radiotherapy as adjuvant treatments. MPNST has a poor prognosis with reported 5-year survival ranging from 16 to 54%. This case demonstrates the need to pursue additional workup when diagnostic imaging and objective findings do not satisfactorily explain the clinical presentation. LEVEL OF EVIDENCE: IV.

Diagnostic Efficacy of 18F-FDG PET/MRI in Peripheral Nerve Injury Models.

The aim of this study was to evaluate the diagnostic efficacy of 18F-FDG PET/MRI in two different peripheral neuropathic pain models using the injured rat sciatic nerves. Twelve rats, with operation on left sciatic nerves, were evenly divided into three groups: sham surgery (control group), crushing injury and chronic constriction injury (CCI) (experimental groups). The nerve damage was assessed at 3 weeks postoperatively using following methods: paw withdrawal threshold values (RevWT), maximum standardized uptake values on PET/MRI images (SUVR), and counting the number of myelinated axons in proximal and distal sites of nerve injury (MAxR). The results were quantified and statistically analyzed. Compared to the control group, the crushing injury demonstrated significant differences in RevWT (p < 0.0001) and SUVR (p = 0.027) and the CCI group demonstrated significant differences in RevWT (p < 0.0001), SUVR (p = 0.001) and MAxR (p = 0.048). There were no significant differences between the two experimental groups for all assessments. Correlation analysis demonstrated that RevWT and SUVR assessments were highly correlated (r = -- 0.710, p = 0.010), and SUVR and MAxR were highly correlated (r = 0.611, p = 0.035). However, there was no significant correlation between RevWT and MAxR. The PET scan may be a valuable imaging modality to enable noninvasive, objective diagnosis of neuropathic pain caused by peripheral nerve injury. Also, MRI fused with PET may help clarify the anatomic location of soft tissue structures, including the peripheral nerves.

Division of Sacrospinous and Sacrotuberous Ligaments Expands Access Through Greater Sciatic Foramen: Anatomic Study with Application to Resection of Greater Sciatic Foramen Tumors.

OBJECTIVE: Tumors of the greater sciatic foramen remain difficult to treat. They often have both intrapelvic and extrapelvic components that may limit visualization and make safe resection of the tumor difficult. Therefore the goal of the present anatomic study was to quantitate how much additional surgical working space could be gained by transection of the sacrospinous and sacrotuberous ligaments. METHODS: Sixteen sides from 9 fresh-frozen Caucasian cadaveric torsos underwent transgluteal dissection and exposure of the greater sciatic foramen and associated liagments. With the piriformis in place, the vertical and horizontal diameters of the greater sciatic foramen were measured. Next, the sacrotuberous and sacrospinous ligaments were cut at their ischial attachments. The vertical diameter of the now confluent greater and lesser sciatic foramina (V2) was measured. RESULTS: The mean vertical diameter of the greater sciatic foramen (V1) was 54.8 ± 9.7 mm. The horizontal diameter of the greater sciatic foramen had a mean of 44.3 ± 6.1 mm with a range of 30-52 mm. After transection of the sacrotuberous and sacrospinous ligaments, the vertical distance of the greater and lesser sciatic foramina (V2) had a mean of 74.8 ± 6.8 mm with a range of 60.1-90 mm. The mean ratio of V2 to V1 was 1.40. CONCLUSIONS: The vertical length of the greater sciatic foramen increased, on average, 40% after resection of the sacrotuberous and sacrospinous ligaments. The results of this study support an alternative technique for resecting large intrapelvic tumors via a transgluteal approach.

68Ga-PSMA Uptake in Prostate Cancer Sciatic Nerve Metastasis.

Most prostate cancers spread to regional lymph nodes, axial skeleton and lungs. Perineural malignant involvement is very rare. We present a Ga-PSMA PET/CT image of a sciatic nerve metastasis in a 65-year-old man with recurrent prostate cancer.

Noninvasive Measurement of Sciatic Nerve Stiffness in Patients With Chronic Low Back Related Leg Pain Using Shear Wave Elastography.

OBJECTIVES: The purpose of this study was to determine whether sciatic nerve stiffness is altered in people with chronic low back-related leg pain by using shear wave elastography. METHODS: In this cross-sectional study, the sciatic nerve shear wave velocity (ie, an index of stiffness) was measured in both legs of 16 participants (8 with unilateral low back-related leg pain and 8 healthy controls). Sciatic stiffness was measured during a passive ankle dorsiflexion motion performed at 2°/s in an isokinetic dynamometer. The ankle range of motion and passive torque, as well as muscle activity, were also measured. RESULTS: In people with low back-related leg pain, the affected limb showed higher sciatic nerve stiffness compared to the unaffected limb (+11.3%; P = .05). However, no differences were observed between the unaffected limb of people with low back-related leg pain and the healthy controls (P = .34). CONCLUSIONS: People with chronic low back-related leg pain have interlimb differences in sciatic nerve stiffness, as measured by a safe and noninvasive method: shear wave elastography. The changes found may be related to alterations in nerve mechanical properties, which should be confirmed by future investigations.

The High-Frequency Ultrasound Detection of Rat Sciatic Nerve in a Crushed Injury Model.

OBJECTIVE: This study aimed to visualize sciatic nerve injury in rats using ultrasound imaging in a crushed injury model. METHODS: Adult male Sprague-Dawley rats were subjected to a left sciatic nerve crush operation. Then, high-frequency ultrasound was used to image both sciatic nerves at 2 days and at 1, 2, 3, 4, and 6 weeks after surgery. RESULTS: Normal uninjured nerves have uniform thickness, display a smooth epineurium and inner adventitia, and are oblong in transverse sections. After the crush operation, nerve thickness increased, the inner echo signal decreased, the image of the epineurium became obscured and coarse before becoming smooth again, and transverse sections of the nerve fibers changed from being semicircular to oval in shape before becoming elliptical again. These observations were consistent with pathological changes associated with nerve injury. CONCLUSIONS: High-frequency ultrasound is capable of capturing dynamic changes in rat sciatic nerves in a crushed injury model. This can be used as an auxiliary method of evaluation in traditional peripheral nerve injury experiments.

Clinical and Electrodiagnostic Features Of Nontraumatic Sciatic Neuropathy.

INTRODUCTION: In this study we sought to characterize etiologies and features of sciatic neuropathy unrelated to penetrating nerve trauma. METHODS: This investigation was a retrospective review of 109 patients with electrodiagnostically confirmed sciatic neuropathies. RESULTS: Hip replacement surgery represented the most common (34.9%) etiology, whereas inflammatory sciatic neuropathy was seen in 7.3%. Electrodiagnostic testing revealed an axonal neuropathy in 95.4% and a demyelinating neuropathy in 4.6%. Predominant involvement of the peroneal division was seen in 39.4% and was tibial in 5.5%. Nine of 31 (29.0%) patients who had MRI or neuromuscular ultrasound study showed abnormalities within the sciatic nerve. At the final visit, 46.4% of patients required assistance for ambulation. Young age, lack of severe initial weakness, and presence of tibial compound muscle action potential or sural sensory nerve action potential were predictors of favorable outcome. DISCUSSION: Sciatic neuropathies are usually axonal on electrodiagnostic testing, affect preferentially the peroneal division, and are commonly associated with incomplete recovery. Muscle Nerve 59:309-314, 2019.