SCIATIC NEUROPATHY
Section snippets
ANATOMY
The sciatic nerve derives its nerve fibers from the L4, L5, S1, and S2 nerve roots. It arises from the lumbosacral plexus and leaves the pelvis through the greater sciatic foramen (sciatic notch) (Fig. 1). It passes over the obturator internus muscle, and beneath the gluteal and the piriformis muscles. As it exits the gluteal compartment, the sciatic nerve runs posterior and medial to the hip joint. The nerve then courses deep in the thigh and posterior to the femur. The nerve consists of two
Symptoms
Weakness, numbness, and paresthesias are frequent symptoms of sciatic neuropathy.93 Foot drop is usually the most prominent symptom, for two reasons. First, foot drop as a result of tibialis anterior weakness causes greater gait disability compared with other sciatic-innervated muscles. Second, as discussed below, the peroneal-innervated muscles are more severely weak compared with tibial-innervated muscles. Weakness of toe extension or flexion, ankle plantar flexion, eversion, inversion, and
ELECTROPHYSIOLOGY
Electromyography (EMG) and nerve-conduction studies (NCS) play a vital role in localizing the lesion and in determining severity and prognosis. Evaluation of the sural and superficial peroneal sensory-nerve action potentials (SNAP) are important for documenting whether the lesion is preganglionic or postganglionic, the degree to which tibial and peroneal sensory axons are affected, and the severity of the lesion. The extensor digitorum brevis, the abductor hallucis compound muscle action
OTHER DIAGNOSTIC TESTS
Ancillary tests can play a role in confirming or excluding a diagnosis on the basis of the history, examination, and electrodiagnostic testing. Radiologic studies help to evaluate the possibility of a mass lesion or a compressed nerve. MRI provides the best resolution. Recent innovations in which MRI short tau inversion recovery (STIR) sequence has been used have further enhanced the ability to visualize the peripheral nerve (Fig. 3). CT of the sciatic nerve provides excellent visualization of
DIFFERENTIAL DIAGNOSIS
Lesions of the lumbosacral roots or plexus can mimic sciatic neuropathy. Involvement of sensory or motor fibers outside of the sciatic-nerve distribution places the lesion elsewhere. For example, an L5 or S1 radiculopathy can be distinguished from a sciatic neuropathy by electromyographic abnormalities in the paraspinal muscles, gluteus medius, gluteus maximus, or tensor fascia latae. Abnormalities of the sural or the superficial peroneal sensory responses on NCS would favor sciatic neuropathy
ORIGINS
The causes of sciatic neuropathies can be categorized into those occurring in the hip (gluteal) or the thigh regions. The majority of sciatic neuropathies occur in the hip, whereas only a minority are in the thigh.94 The causes of sciatic mononeuropathy are numerous (see table).9, 13, 40, 55, 78, 84
PRACTICAL MANAGEMENT
Management of sciatic neuropathy depends on the clinical setting and the suspected cause. The underlying cause of the neuropathy should be treated medically if possible, examples being vasculitis, endometriosis, systemic cancer, or diabetes mellitus. Surgical exploration and decompression may be required when compression of the nerve from mass lesions, (e.g., tumor or hemorrhage), compartment syndrome, or fibrous bands is suspected.16
Surgical repair with nerve grafts of the sciatic nerve is
PROGNOSIS
As with other mononeuropathies, prognosis of sciatic neuropathy depends on its origin etiology and severity. In a study of 52 patients who had acute sciatic neuropathy and removal of the inciting factor (caused by hip replacement, hip dislocation or fractures, gunshot wound, acute external compression, nerve infarction, femur fracture, or gluteal contusion), improvement in strength to Medical Research Council (MRC) grade 2 or by at least 2 MRC grades occurred in 30% by 1 year, 50% by 2 years,
ACKNOWLEDGMENT
We thank Cynthia So for assistance with Figures 1 and 2.
References (95)
Piriformis syndrome: A rational approach to management
Pain
(1991)- et al.
Indications for peripheral nerve and brachial plexus surgery
Neurol Clin
(1992) - et al.
Sciatic nerve injury following misplaced gluteal injection
J Pediatr
(1970) - et al.
High sciatic lesion mimicking peroneal neuropathy at the fibular head
J Neurol Sci
(1994) Operative management of major nerve lesions of the lower extremity
Surg Clin North Am
(1972)- et al.
Sciatic neuropathy complicating vaginal hysterectomy
Am J Obstet Gynecol
(1972) - et al.
Intraoperative cortical somatosensory evoked potentials for detection of sciatic neuropathy during total hip arthroplasty
J Clin Anesth
(1989) - et al.
Solitary extranodal lymphoma of sciatic nerve
J Neurol Sci
(1986) The pyriformis syndrome—report of four cases and review of the literature
S Afr J Surg
(1980)- et al.
Sciatic neuropathy
Indian Pediatr
(1984)
Sciatic neuropathy secondary to migration of trochanteric wire following total hip arthroplasty
Clin Orthop
Endometriosis within the sheath of the sciatic nerve. Report of two patients with progressive paralysis
J Neurosurg
Sciatic entrapment neuropathy. Case report
J Neurosurg
Cement burn of the sciatic nerve
J Bone Joint Surg
Traumatic dislocation of the hip: Army experience and results over a twelve-year period
J Bone Joint Surg
Injuries of peripheral nerves in two world wars
Br J Surg
Sciatic and peroneal nerve injury: A complication of vaginal operations
Obstet Gynecol
Sciatic pain from arteriosclerotic aneurysm of pelvic arteries
N Engl J Med
Sciatica due to piriformis pyomyositis.Report of a case
J Bone Joint Surg
The late consequences of sciatic nerve injury
J Bone Joint Surg
Trochanteric sciatic neuropathy
Neurology
An unusual case of sciatic nerve paralysis
JAMA
Contributory factors and etiology of sciatic nerve palsy in total hip arthroplasty
Clin Orthop
Delayed sciatic palsy after total hip replacement: Case report
Neurosurgery
Idiopathic, progressive mononeuropathy in young people
Arch Neurol
Primary malignant lymphoma of sciatic nerve. Report of a case
Am J Surg Pathol
Injury of the sciatic nerve associated with acetabular fracture
J Bone Joint Surg
Cyclic sciatica of endometriosis
JAMA
Sciatic nerve entrapment in an osseous tunnel as a late complication of fracture dislocation of the hip
Orthopedics
Sciatic neuropathy associated with persistent sciatic artery
Arch Neurol
Migration of fractured greater trochanteric osteotomy wire with resultant sciatica. A report of two cases
Orthopedics
The involvement of the external and internal popliteal nerves in lesions of the sciatic nerve
BMJ
Sciatic nerve paralysis in posterior dislocation of the hip. A case report
Clin Orthop
Extrapelvic compression of the sciatic nerve.An unusual cause of pain about the hip: Report of five cases
J Bone Joint Surg
Nerve injury in total hip arthroplasty
Clin Orthop
Sciatic nerve palsy following delivery
Postgrad Med
Myositis ossificans in the biceps femoris muscles causing sciatic nerve palsy.A case report
J Bone Joint Surg
Sciatic neuropathies in childhood: A report of ten cases and review of the literature
J Child Neurol
Painful sciatic neuropathy following cardiac surgery
Aust N Z J Med
Bilateral footdrop after craniotomy in the sitting position
Anesthesiology
Late sciatic-nerve palsy following posterior fracture-dislocation of the hip.A case report
J Bone Joint Surg
Extraspinal causes of lumbosacral radiculopathy
J Bone Joint Surg
Comment to “The piriformis muscle syndrome: A simple diagnostic maneuver”
Neurosurgery
Sciatic nerve paralysis following anticoagulant therapy
J Bone Joint Surg
Sciatic nerve entrapment secondary to trochanteric wiring following total hip arthroplasty. A case report
Clin Orthop
Benign joint hypermobility with neuropathies: Documentation and mechanism of median, sciatic, and common peroneal nerve compression
Clin Rheumatol
Sciatic neuropathy with giant-cell arteritis [letter]
N Engl J Med
Cited by (60)
Electrodiagnostic Assessment of Uncommon Mononeuropathies
2021, Neurologic ClinicsCitation Excerpt :Etiologies of sciatic neuropathy include direct trauma (eg, penetrating trauma of the buttock or posterior thigh), femur fracture, after gluteal intramuscular injections, hip dislocation, hip surgery (eg, hip replacement), and hardware degradation and disintegration within the hip. It can also present during cesarean section or vaginal delivery owing to positioning (greater thigh flexion is associated with a greater risk for sciatic nerve traction), or compression by a tumor or hematoma.44–51 In a recent study of 109 patients from a single institution with sciatic neuropathy from nonpenetrating trauma, 56% were related to LE injury such as hip replacement, 15% related to compression, and a small percentage related to inflammation, radiation, ischemia, or other causes.52
Clinical neurophysiology of lower extremity focal neuropathies
2019, Handbook of Clinical NeurologyCitation Excerpt :The fibular (peroneal) division is more prone to external compression, as it is located anterolaterally in relation to the tibial fascicles. At times a proximal sciatic lesion may present clinically as a peroneal neuropathy (Yuen et al., 1995; Yuen and So, 1999; Feinberg and Sethi, 2006). Sciatic mononeuropathy is the second most common lower extremity mononeuropathy (Yuen et al., 1995).
Piriformis Syndrome
2018, Essentials of Physical Medicine and Rehabilitation: Musculoskeletal Disorders, Pain, and RehabilitationSciatic Neuropathy Caused by Focal Venous Engorgement Associated With Deep Vein Thrombosis: A Case Report
2016, PM and RCitation Excerpt :Sciatic neuropathy is the second most frequent neuropathy in the lower extremities; it can be caused by a number of mechanisms, including acute or chronic nerve entrapment, ischemia, tumor, aneurysm, laceration, toxic injury, vasculitis, hematoma, gluteal muscle contusion, or iatrogenic injury [1,2].
Foot drop resulting from degenerative lumbar spinal diseases: Clinical characteristics and prognosis
2014, Clinical Neurology and NeurosurgeryCitation Excerpt :For lower motor neuron lesions, it is important, as a next step, to differentiate between a peripheral neuropathy and radiculopathy from spinal causes. Peripheral neuropathies, such as sciatic or peroneal neuropathy [2,11], are the most common causes of foot drop. Etiologies include trauma, external compression, nerve entrapment, infection, mass/tumor, and iatrogenic factors [5].
Clinical and Electrodiagnostic Features of Sciatic Neuropathies
2013, Physical Medicine and Rehabilitation Clinics of North AmericaCitation Excerpt :Partial entrapment of the sciatic nerve at the hip affects the lateral (fibular) division more commonly. Etiologies include hip arthroplasty, dislocation, and fracture in up to 30% of patients.10,30 Acute external compression can occur in patients in coma, with or without compartment syndrome, or after prolonged sitting.
Address reprint requests to Eric C. Yuen, MD, Department of Neurology, University of Washington, Box 356115, Seattle, WA 98195