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.

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.

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.

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.

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.

Examination of metal mobilization from a gunshot by scanning acoustic microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and inductively coupled plasma optical emission spectroscopy: a case report.

BACKGROUND: Projectile foreign bodies are known to cause chronic heavy metal toxicity due to the release of metal into the bloodstream. However, the local effect around the metallic object has not been investigated and the main goal of our study is to examine the influence of the object in close proximity of the object. CASE PRESENTATION: A 36-year-old Caucasian woman with one metallic pellet close to her sciatic nerve due to a previous shotgun injury at the gluteal area presented with a diagnosis of recurrent lumbar disk herniation at L4-5 level. A physical examination confirmed chronic neuropathy and she underwent a two-stage surgery. The surgery included removal of the foreign body, followed by discectomy and fusion at the involved level. During the removal of the metallic foreign body, a tissue sample around the pellet and another tissue sample from a remote area were obtained. The samples were analyzed by scanning acoustic microscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Lead, chromium, copper, cadmium, iron, manganese, selenium, and zinc elements in tissue, blood, and serum specimens were detected by inductively coupled plasma optical emission spectroscopy. CONCLUSIONS: An acoustic impedance map of the tissue closer to the metallic body showed higher values indicating further accumulation of elements. Energy-dispersive X-ray spectroscopy results confirmed scanning acoustic microscopy results by measuring a higher concentration of elements closer to the metallic body. Scanning electron microscopy images showed that original structure was not disturbed far away; however, deformation of the structure existed in the tissue closer to the foreign body. Element analysis showed that element levels within blood and serum were more or less within acceptable ranges; on the other hand, element levels within the tissues showed pronounced differences indicating primarily lead intoxication in the proximity of the metallic body. We can state that residues of metallic foreign bodies of gunshot injuries cause chronic metal infiltration to the surrounding tissue and induce significant damage to nearby neural elements; this is supported by the results of scanning acoustic microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and inductively coupled plasma optical emission spectroscopy.

Sciatic Nerve Entanglement Around a Femoral Prosthesis During Closed Reduction of a Dislocated Total Hip Prosthesis: The Role of Metal-Suppression MRI: A Case Report.

CASE: A 68-year-old woman who had undergone a right total hip arthroplasty presented with a right posterior hip dislocation, and subsequently developed an ipsilateral sciatic nerve palsy after closed reduction. Magnetic resonance imaging (MRI) with metal suppression demonstrated sciatic nerve entanglement around the prosthetic femoral neck. A sciatic nerve release was performed, resulting in poor early neurologic recovery. CONCLUSION: Sciatic nerve entanglement following closed reduction of a dislocated total hip prosthesis is a rare injury. Assessment of neurovascular status before and after reduction is imperative. We recommend prompt MRI with metal suppression in patients with acute neurologic symptoms following reduction of a dislocated hip prosthesis to evaluate for acute nerve pathology and assess the need for emergency surgery.

Application of amniotic fluid stem cells in repairing sciatic nerve injury in minipigs.

Many studies have demonstrated that combining nerve conduits with neural stem cells or growth factors can repair peripheral nerve injury in rodents. However, nerve damage does occur with longer gaps in human than in rodents, thus findings from rodent studies are difficult to translate to clinical practice. Minipigs have a longer gap that is more closely applicable to the challenge of human nerve grafting in extensive traumatic nerve damage. In this study, human amniotic fluid stem cells (AFSCs) and polylactate nerve conduits were used to repair sciatic nerve injury in minipigs. The AFSCs exhibited the properties of mesenchymal stem cells with a propensity toward neural stem cells. Measurements of compound muscle action potential implied that administration of conduits with AFSCs was beneficial in function recovery in the minipig model compared with conduits alone. The results of diffusion tensor magnetic resonance imaging (DTI) based fiber tractography assay in the minipig model suggest that combining AFSCs with conduits could expedite the repair of sciatic nerve injury. Further, MR-based DTI provides an effective and non-invasive method to visualize the sciatic nerve and to monitor the regeneration progress of injured nerve in a longitudinal study.

Transected sciatic nerve repair by diode laser protein soldering.

BACKGROUND AND OBJECTIVE: Despite advances in microsurgical techniques, repair of peripheral nerve injuries (PNI) is still a major challenge in regenerative medicine. The standard treatment for PNI includes suturing and anasthomosis of the transected nerve. The objective of this study was to compare neurorraphy (nerve repair) using standard suturingto diode laser protein soldering on the functional recovery of transected sciatic nerves. STUDY DESIGN/MATERIALS AND METHODS: Thirty adult male Fischer-344 Wistar rats were randomly assigned to 3 groups: 1. The control group, no repair, 2. the standard of care suture group, and 3. The laser/protein solder group. For all three groups, the sciatic nerve was transected and the repair was done immediately. For the suture repair group, 10.0 prolene suture was used and for the laser/protein solder group a diode laser (500mW output power) in combination with bovine serum albumen and indocyanine green dye was used. Behavioral assessment by sciatic functional index was done on all rats biweekly. At 12weeks post-surgery, EMG recordings were done on all the rats and the rats were euthanized for histological evaluation of the sciatic nerves. The one-way ANOVA test was used for statistical analysis. RESULTS: The average time required to perform the surgery was significantly shorter for the laser-assisted nerve repair group compared to the suture group. The EMG evaluation revealed no difference between the two groups. Based on the sciatic function index the laser group was significantly better than the suture group after 12weeks (p<0.05). Histopathologic evaluation indicated that the epineurium recovery was better in the laser group (p<0.05). There was no difference in the inflammation between the suture and laser groups. CONCLUSION: Based on this evidence, laser/protein nerve soldering is a more efficient and efficacious method for repair of nerve injury compared to neurorraphy using standard suturing methods.

Piriformis muscle syndrome with assessment of sciatic nerve using diffusion tensor imaging and tractography: a case report.

Piriformis muscle syndrome (PMS) is difficult to diagnose by objective evaluation of sciatic nerve injury. Here we report a case of PMS diagnosed by diffusion tensor imaging (DTI) and tractography of the sciatic nerve, which can assess and visualize the extent of nerve injury. The patient was a 53-year-old man with a 2-year history of continuous pain and numbness in the left leg. His symptoms worsened when sitting. Physical examination, including sensorimotor neurologic tests, the deep tendon reflex test, and the straight leg raise test, revealed no specific findings. The hip flexion adduction and internal rotation test and resisted contraction maneuvers for the piriformis muscle were positive. There were no abnormal findings on magnetic resonance imaging (MRI) of the lumbar spine. The transverse diameter of piriformis muscle was slightly thicker in affected side on MRI of the pelvis. A single DTI sequence was performed during MRI of the pelvis. Fractional anisotropy (FA) and the apparent diffusion coefficient (ADC) of the sciatic nerve were quantified at three levels using the fiber-tracking method. FA values were significantly lower and ADC values were significantly higher distal to the piriformis muscle. We performed endoscopic-assisted resection of the piriformis tendon. Intraoperatively, the motor-evoked potentials in the left gastrocnemius were improved by resection of the piriformis tendon. The patient's symptoms improved immediately after surgery. There was no significant difference in FA or ADC at any level between the affected side and the unaffected side 3 months postoperatively. MRI-DTI may aid the diagnosis of PMS.