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UNASSIGNED: Common etiologies of sciatic mononeuropathy are compressive, infiltrative, traumatic, or diabetic. However, in a proportion of patients, the etiology remains elusive despite extensive serological, electrophysiological, radiological, and histological investigations.
UNASSIGNED: Patients with unexplained sciatic mononeuropathy were studied with regard to their clinical, radiological, pathological, and treatment aspects.
UNASSIGNED: We could identify five cases of sciatic mononeuropathy wherein the etiology remained unknown even after a comprehensive evaluation. The compressive, metabolic, hematological, and immune causes were ruled out with necessary investigations. The clinical, electrophysiological, radiological, and histological features of these patients are discussed.
UNASSIGNED: The etiology of sciatic mononeuropathy can remain obscure in certain instances in spite of the comprehensive workup. The role of investigations and the exclusion process of various diagnostic entities are discussed.

BACKGROUND: The formation of abscesses with necrosis within large, striated muscles leads to pyomyositis, a condition relatively rarely encountered outside the tropics. Intravenous drug users and other immunocompromised individuals are predisposed toward this infection, which may occur due to local or haematogenous spread of infection to skeletal muscles previously damaged by trauma, exercise, or rhabdomyolysis.
METHODS: We report a young male intravenous drug user with rhabdomyolysis due to use of a synthetic opioid, in whom disseminated pyomyositis was detected following evaluation for sciatic and radial neuropathies and Horner\'s syndrome and review available reports of peripheral nerve dysfunction in the setting of this uncommon infection. We searched online databases to identify all published reports on adult patients with pyomyositis complicated by peripheral nerve dysfunction.
CONCLUSIONS: Peripheral nerve dysfunction may rarely occur via local spread of infection or compression from abscesses.

Pelvic floor hernias represent a rare type of hernia and a rare etiology of pelvic symptoms. The rarest type of pelvic floor hernias are sciatic hernias, which present with a variety of symptoms depending on the hernia contents and location. Many different treatment approaches are described in the literature. A 73-year-old female presented to our outpatient minimally invasive surgery (MIS) clinic with one year of colicky left flank pain. She had previously presented to an emergency department, at which time a computed tomography (CT) scan demonstrated left-sided hydronephrosis in the setting of a left-sided ureterosciatic hernia. She was asymptomatic and had no palpable hernia bulge. An operative repair was offered based on her prolonged symptoms. The patient was brought electively to the operating room with minimally invasive and urological surgeons. A left ureteral stent was placed over a guidewire. A robotic repair was performed with a round piece of biosynthetic mesh, secured in place with fibrin glue. Sciatic hernias are an extremely rare etiology of pelvic symptoms and require a high index of suspicion to identify. Obstructive and neuropathic symptoms may be intermittent, so diagnosis is often made using CT imaging. We report a successful treatment with pre-operative ureteral stenting followed by a robotic repair using biologic mesh secured with fibrin glue fixation. We believe this is a durable repair although acknowledge that longer follow-up is needed to establish the longevity of our treatment modality.

Regional anesthesia is an integral component of successful orthopedic surgery. Neuraxial anesthesia is commonly used for surgical anesthesia while peripheral nerve blocks are often used for postoperative analgesia. Patient evaluation for regional anesthesia should include neurological, pulmonary, cardiovascular, and hematological assessments. Neuraxial blocks include spinal, epidural, and combined spinal epidural. Upper extremity peripheral nerve blocks include interscalene, supraclavicular, infraclavicular, and axillary. Lower extremity peripheral nerve blocks include femoral nerve block, saphenous nerve block, sciatic nerve block, iPACK block, ankle block and lumbar plexus block. The choice of regional anesthesia is a unanimous decision made by the surgeon, the anesthesiologist, and the patient based on a risk-benefit assessment. The choice of the regional block depends on patient cooperation, patient positing, operative structures, operative manipulation, tourniquet use and the impact of post-operative motor blockade on initiation of physical therapy. Regional anesthesia is safe but has an inherent risk of failure and a relatively low incidence of complications such as local anesthetic systemic toxicity (LAST), nerve injury, falls, hematoma, infection and allergic reactions. Ultrasound should be used for regional anesthesia procedures to improve the efficacy and minimize complications. LAST treatment guidelines and rescue medications (intralipid) should be readily available during the regional anesthesia administration.

A growing number of case reports and series have described a wide spectrum of neurological manifestations of COVID-19 disease including encephalopathy, cerebrovascular disease, and Guillain-Barre syndrome (GBS). However, peripheral neuropathy associated with COVID-19 disease has been uncommonly reported. Here, we describe a young patient with a COVID-19 infection who developed unilateral sciatic neuropathy during the course of treatment requiring prolonged physical medicine and rehabilitation stay. She was treated in the intensive care unit (ICU) for hypoxic respiratory failure for 22 days total, during which she was intubated, sedated, and paralyzed for 14 days. She received dexamethasone, convalescent plasma, and remdesivir for COVID-19; she also received ceftriaxone and azithromycin for possible superimposed bacterial pneumonia. The hypoxic respiratory failure was improved progressively, and she was extubated. On day 17 of ICU stay, she reported numbness and weakness in left leg and had 0/5 motor strength at the left ankle in all directions. She was able to move left hip and knee and had decreased sensation to light touch and pain from the level of the left knee to the toes. Imaging of the brain and spine showed no obvious findings that would explain the neurological symptoms. On electromyography (EMG), there was acute denervation in the left tibialis anterior muscle. She required prolonged physical medicine and rehabilitation care, greater than 60 days during which she had some improvement in sensation, but remained without ankle movement for two more months. This could be a rare manifestation of COVID-19-induced sciatic mono-neuropathy given her symptoms, EMG reports, clinical exam, and normal imaging studies.

Sciatic notch tumors are rare and have numerous etiologies. Tumor presentation varies widely and no uniform recommendations exist for approaching resection. Most studies on the topic have been small case series, with the approach dictated by surgeon experience and comfort. We provide an overview of surgical approaches for resecting sciatic notch tumors reported in the literature, as well as a conceptual framework for application of these approaches based on standard oncologic principles. The advantages and disadvantages of each approach are described on the basis of anatomic location of the tumor. For tumors that span the notch with intra- and extra-pelvic extension, notchplasty is a novel technique that provides superior visualization and access for en-bloc excision.

Schwannomas are the most common peripheral nerve sheath tumors. Benign schwannomas with malignant transformation are rarely reported. Most common schwannomas occur in the head and neck region. Sciatic schwannomas are rare, as are completely cystic schwannomas. Sciatic nerve schwannomas represent less than 1% of all schwannomas. Benign tumors in the sciatic nerve consist of 60% neurofibromas and 38% schwannomas. In general, a schwannoma induces chronic symptoms. It can be misleading, sometimes mimicking degenerative spinal pathology due to disc herniation. Schwannoma involving the sciatic nerve can be asymptomatic or may present with sciatica or neurological deficits. Most schwannomas are solid or heterogeneous tumors, and completely cystic schwannomas are rare. The differential diagnoses of nondiscogenic sciatica include lumbar disc herniation, tumor, abscess, hematoma, facet syndrome, lumbar instability, sacroiliitis, piriformis syndrome, and sciatic neuritis. We report a rare case of a long completely cystic sciatic schwannoma in the left foraminal L5-S1 zone extending to the left ischial groove with chronic sciatica that was diagnosed radiologically with a combination of conventional MRI and MR neurography and confirmed histopathologically by surgical resection. The patient previously had conservative therapy, but the complaints were not reduced. Nonsurgical therapy is considered the first choice, and surgical therapy is indicated in cases that do not respond to conservative therapy, with recurrent cysts, severe pain, or neurological deficits.

Obstetric paralysis is a generic term used to describe postpartum locomotor alterations resulting from nerve damage, widely reported in cattle, but rare in equines. The aim of this study is to report a case of a peripheral polyneuropathy in a primiparous mare, 3 years old, of Mangalarga Marchador breed, after a dystocia lasting approximately 12 hours. At the time of delivery, the head of the fetus was exposed in the vulva and there was flexion of the thoracic limbs. These events culminated in a framework of extreme abduction of the pelvic limbs, thus generating functional impotence and leading the animal to adopt a frog anddecubitus position. After three days of treatment with no improvement in the clinical framework, the animal was euthanized. In the postmortem examination, perineural hemorrhagic lesions were observed in the obturator and sciatic nerves, characterizing the diagnosis of obstetric paralysis. It is possible the outcome of the case would have been satisfactory if there had been an early fetotomy or postpartum treatment had been more prolonged; however, these measures depend on the availability of equipment, conditions of care, and consideration of the owner.

OBJECTIVE: It is compulsory to make a tension-free, end-to-end repair in transected injuries. However, when it comes to longer defects, placement of an autograft or nerve conduits is required. The present study was designed to assess regenerative potential of silymarin nanoparticles loaded into chitosan conduit on peripheral nerve regeneration in a transected sciatic nerve model in rat.
METHODS: In NML group left sciatic nerve was exposed through a gluteal muscle incision and after careful hemostasis skin was closed. In TSC group left sciatic nerve was transected and stumps were fixed in adjacent muscle. In CTN group, 10-mm sciatic nerve defects were bridged using a chitosan. In CTN/NSLM group, 10-mm sciatic nerve defects were bridged using a chitosan conduit and 100 µL silymarin nanoparticles were administered into the conduit. The regenerated fibers were studied 4, 8, and 12 weeks after surgery. Assessment of nerve regeneration was based on behavioral, functional, biomechanical, histomorphometric, and immuohistochemical criteria.
RESULTS: The behavioral, functional, electrophysiological, and biomechanical studies confirmed significant recovery of regenerated axons in CTN/NSLM group (P < 0.05). Quantitative morphometric analyses of regenerated fibers showed number and diameter of myelinated fibers in CTN/NSLM group were significantly higher than in CTN group (P < 0.05).
CONCLUSIONS: This demonstrated potential of using chitosan-silymarin nanoparticles in peripheral nerve regeneration without limitations of donor-site morbidity associated with isolation of autograft. It is also cost saving and may have clinical implications for surgical management of patients after peripheral nerve transection.