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Differential diagnosis of intraspinal and extraspinal non-discogenic sciatica

Available online at Journal of Clinical Neuroscience 15 (2008) 1246–1252 Differential diagnosis of intraspinal and extraspinal non-discogenic sciatica Duygu Geler Kulcu a,*, Sait Naderi b a Department of Physical Medicine and Rehabilitation, Yeditepe University School of Medicine, Yeditepe University Hospital, Devlet Yolu Ankara Caddesi No. 102/104 Kozyatag˘ı, Istanbul, Turkey b Department of Neurosurgery, Yeditepe University School of Medicine, Istanbul, Turkey Received 10 December 2007; accepted 5 January 2008 The aim of this study is to present a series of 11 patients with non-discogenic sciatica (NDS), and to review the diagnostic techniques of careful clinical and radiological examination. The cases include lumbar radicular herpes zoster, lumbar nerve root schwannoma,lumbar instability, facet hypertrophy, ankylosing spondylitis, sacroiliitis, sciatic neuritis, piriformis syndrome, intrapelvic mass andcoxarthrosis. The pain pattern and accompanying symptoms were the major factors suggesting a non-discogenic etiology. PelvicMRI and CT scans, and sciatic nerve magnetic resonance neurography were the main diagnostic tools for diagnosis of NDS. The treat-ment of choice depended on the primary diagnosis. Detailed physical examinations with special attention paid to the extraspinal causesof sciatica and to pain characteristics are the major components of differential diagnosis of NDS.
Ó 2008 Elsevier Ltd. All rights reserved.
Keywords: Magnetic resonance neurography; Non-discogenic sciatica; Piriformis syndrome; Sacroiliitis; Sciatica NDS, and overviews the different causes of intraspinaland extraspinal sciatica.
Sciatica is common, and is frequently caused by lumbar disk herniation.However, some intraspinal or extraspinal pathologic processes along the sciatic nerve may also causesciatica. Whereas lumbar spine imaging reveals the causes The patients, 6 female and 5 male, were aged between 25 of intraspinal non-discogenic sciatica (NDS), extraspinal and 65 years old. There were 4 patients with extraspinal sciatica is often misdiagnosed because routine diagnostic NDS, 4 with intraspinal NDS, and 3 with sciatica second- tests focus on the lumbar Extrapelvic causes affect ary to both spinal and extraspinal processes.
the nerve as it progresses distally from the sciatic notch.
A careful patient history and clinical examination are 2.1. Intraspinal non-discogenic sciatica important in identifying extraspinal sciatica. Further diag-nostic imaging may clarify the diagnosis.
2.1.1. Lumbar radicular herpes zoster (Patient 1) In general, studies of NDS tend to focus on only one dis- A 64-year-old woman was admitted with a 1-week his- order.This study reports a series of 11 patients with tory of left leg pain that was not responding to analgesics.
A neurological examination revealed no abnormal findings.
A lumbar MRI showed degenerative changes A physical examination revealed typical skin lesions along Corresponding author. Tel.: +90 216 5784100; Mob.: +90 505 the L3 and L4 dermatomes The patient was re- E-mail address: (D.G. Kulcu).
ferred to the dermatology department, where the lesions 0967-5868/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.

D.G. Kulcu, S. Naderi / Journal of Clinical Neuroscience 15 (2008) 1246–1252 Fig. 1. (A) Sagittal T1-weighted lumbar MRI showing degenerative changes. (B) Skin lesions along the trajectories of the L3 and L4 nerve roots.
Fig. 2. (A) Sagittal postcontrast T1-weighted lumbar MRI, and (B) axial fat-saturated T1-weighted lumbar MRI showing multiple schwannomatosis.
were determined to be caused by herpes zoster. After tive. The patient had pain with extension of the trunk.
receiving medication for herpes zoster, the patient's symp- There was no neurological deficit. A lumbosacral antero- toms resolved.
posterior (AP) radiograph showed sclerotic and degenera-tive changes in the L5–S1 facet joint on the left side. A 2.1.2. Schwannomatosis (Patient 2) lumbar MRI showed a L4–L5 and L5–S1 central disc pro- A 27-year-old female patient was admitted with a 2- trusion. After physical therapy and flexion exercises, the month history of low back pain (LBP) and left leg pain.
symptoms resolved partially.
Physical examination revealed a positive straight leg raising(SLR) test at 45°, and hypoesthesia at the left S1 derma- 2.1.4. Lumbar instability (Patient 4) tome. Lumbar MRI showed multiple schwannomatosis of A 31-year-old male was admitted with a 12-year history the bilateral L5 and left S1 nerve roots (). The symp- of LBP and a 1-month history of left leg pain. Physical toms improved after medical therapy. Because of the lack examination showed a positive SLR test at 60°. The patient of neurological deficit and the small size of the schwanno- was mistakenly diagnosed as having a lumbar disc hernia mas, surgical treatment was not indicated.
(LDH) at another center and was treated with physiother-apy, which was not beneficial. Sagittal lumbar MRI 2.1.3. Facet syndrome and lumbar disk herniation showed no disc herniation, and axial MRI showed pars de- fects of L5. Oblique radiographs showed bilateral pars int- A 63-year-old woman was admitted with a history of erarticularis defects. The LBP was attributed to the lumbar LBP, left leg pain and numbness. The SLR test was nega- instabilty related to the isthmic defects.

D.G. Kulcu, S. Naderi / Journal of Clinical Neuroscience 15 (2008) 1246–1252 2.2. Extraspinal cases nerve root compression and bilateral sacroiliitis. Thesciatica was attributed to the sacroiliitis. The patient reci- 2.2.1. Sciatic neuritis (Patient 5) eved indomethacin at 150 mg/day for 15 days. The A 64-year-old woman was admitted to hospital with left patient's symptoms resolved. The visual analogue scale buttock pain. The patient had undergone surgery for lum- (VAS) pain score decreased from 7 to 2. Further analyses bar spondylolisthesis 10 years previously. The results of a were performed to identify the etiology of the sacroiliitis physical examination were unremarkable. A lumbar MRI showed left sciatic neuritis between the piriformis muscle and the proximal femur ).
2.2.3. Sacroiliitis (Patient 7) 2.2.2. Bilateral sacroiliitis (Patient 6) A 53-year-old woman was admitted with left leg pain.
A 25-year-old female was admitted with a 2-month his- Physical and neurological examinations yielded no abnor- tory of LBP, left-side buttock and posterior thigh pain. The mal findings. Lumbar MRI showed no abnormality. Sacro- patient had no lower limb weakness or paresthesias and iliac MRI showed sacroiliitis and edema in the joint had no history of morning stiffness or night pain. On phys- compressing the sciatic nerve ). The erythrocyte sed- ical examination the SLR test was limited to 60° on the left imentation rate (ESR) was 88 mm/h. After further exami- side. There was no other neurologic deficit in the lower nation, the patient was diagnosed with seronegative limbs. Her range of motion of the trunk was not limited spondyloarthropathy. The patient started to recieve indo- and was not painful. Deep palpation of the left buttock methacin at 300 mg/day, salazosulphapyridine at 400 mg/ over the sciatic nerve course was painful. Gaenslen's test day and prednisolone acetate at 7.5 mg/day. Pain de- was positive on the left side. The sacroiliac compression creased and the ESR was 68 mm/h after 2 weeks. Symp- test was positive on the left side. MRI of the lumbar spine toms completely resolved after completion of the medical and sacroiliac joint showed L4–L5 disc protrusion with no 2.2.4. Soft tissue tumor (Patient 8) A 55-year-old male was admitted with a 1-month history of right buttock pain. The patient had undergone L4–L5discectomies five and three years previously. Neurologicalexamination revealed no deficit. The buttock was painfulupon palpation. Lumbar spine MRI showed modicchanges at the L4–L5 level. A pelvic MRI showed a 6 cmsoft tissue mass anterior and right to the sacrum. Examina-tion of a pelvic CT scan revealed destruction of the anteriorsurface of the sacrum (A CT-guided needle biopsyrevealed an angiosarcoma.
2.2.5. Piriformis syndrome and hamstring tendinopathy(Patient 9) A 59-year-old woman was admitted with a 2-month his- tory of left-side buttock and posterior thigh pain. The pa-tient had an antalgic gait with knee flexed and hip Fig. 3. Axial fat saturated T2-weighted lumbar MRI showing hyperin- adducted and was not able to walk further than 10 m tensity at the left sciatic nerve.
Fig. 4. (A) Coronal STIR-weighted and (B) axial postcontrast fat-saturated T1-weighted sacroiliac joint MRIs showing inflammation on the left side.

D.G. Kulcu, S. Naderi / Journal of Clinical Neuroscience 15 (2008) 1246–1252 Fig. 5. (A) Axial postcontrast T1-weighted and (B) sagittal T2-weighted pelvic MRIs revealing a 4 cm  5 cm soft tissue tumor right and anterior to thesacrum.
partially but the patient still complained of left thigh painafter prolonged sitting and hip internal rotation. MRIneurography showed no abnormal signal at the sciaticnerve. The patient underwent a tetracosactrin injectionprotocol but received no benefit. A new examination re-vealed negative SLR. Freiberg's sign was positive at theleft side. Although MRN showed no abnormality, giventhe results of a physical examination, the patient wasdiagnosed as having PS and the physical therapy protocolfor PS was applied.The patient received 15 sessions of Fig. 6. (A) Axial T1-weighted pelvic magnetic resonance neurography physical therapy. At the end of the physical therapy (MRN) showing left piriformis muscle asymmetry and atrophy, and (B) regimen, the VAS score decreased from 9 to 2 points.
axial postcontrast fat-saturated T1-weighted pelvic MRN showing leftischial bone marrow edema and hamstring tendinopathy. Note that the The patient was comfortable after prolonged sitting and left arrow in (A) shows an atrophic and asymmetric piriformis muscle, and internal rotation of the hip.
the arrow in (B) shows bone marrow edema and tendinopathy.
2.2.7. Degenarative lumbar spine and coxarthrosis (Patient11) because of increasing symptom intensity. At physical exam- A 65-year-old male was admitted with bilateral buttock ination the SLR test was negative. Freiberg's sign was posi- pain and neurogenic claudication. The FABER test was tive. The range of trunk motion was not limited. The left leg also positive at the left side. A lumbar MRI showed L3– was paresthetic. Tenderness in the piriformis muscle and L4 disc herniation, lumbar spinal stenosis, and L4–L5 ischium pubis was noted on deep palpation. MRI of the spondylolisthesis. Pelvic radiographs showed grade IV lumbar spine yielded no abnormal findings. Magnetic reso- osteoarthritis of the left hip. After discussion with the nance neurography (MRN) revealed piriformis asymmetry patient regarding a treatment plan, the patient underwent on the left side, high signal at the sciatic nerve at this loca- L3–4–5 decompression and instrumentation, and inter- tion and bone marrow edema at the ischium pubis at the transverse fusion. Two months after spinal intervention hamstring muscle insertion site (). A physical therapy the patient underwent total hip arthroplasty. The symp- protocol for piriformis syndrome (PS) was applieAt the toms resolved after surgery.
end of the physical therapy, the VAS score decreased from10 to 3 points. The antalgic gate was corrected andFreiberg's sign became negative. Tenderness of the ischium pubis remained due to hamstring tendinopathy.
Many intraspinal and/or extraspinal pathologic pro- 2.2.6. Lumbar disc hernia and piriformis syndrome (Patient cesses along the lumbar nerve roots and sciatic nerve can cause sciatica. In 20% of cases, the sciatica is of both disco- A 48-year-old male was admitted with a 6-week history genic and non-discogenic origin.However, in practice, of LBP and left leg pain. MRI of the lumbar spine causes of NDS are often overlooked, partly due to the high showed L5–S1 disc herniation compressing the left S1 nerve root. Electromyography showed S1 radiculopathy.
He underwent L5 hemipartial laminectomy, and left L5– The causes of NDS may be classified into two major cat- S1 microdiscectomy. After surgery, the symptoms resolved egories: intraspinal and extraspinal. Differential diagnosis

D.G. Kulcu, S. Naderi / Journal of Clinical Neuroscience 15 (2008) 1246–1252 Fig. 7. An algorithm for the diagnosis of discogenic and non-discogenic sciatica. Sacroiliitis may cause posterior pelvic and sacroiliac pain during theFABER test, whereas coxarthrosis may cause groin pain during that test. In a few cases there is coincidence of spinal and extraspinal processes. In patientswhose spinal pathology has additional findings, extra examinations for extraspinal processes should be carried out. AP = anteroposterior radiography,DPP = deep piriformis palpation, SICT = sacroiliac compression test, SLR = straight leg raise test.
requires a careful and detailed physical and radiological ever, may complicate the symptomatology, and require examination based on a schema careful evaluation.
3.1. Intraspinal causes of sciatica 3.2. Extraspinal causes of sciatica Many intraspinal disorders can cause sciatica. There Detection of extraspinal causes of sciatica is much more may also be multiple processes, for instance intradural or difficult than detection of intraspinal ones, and requires a extradural cysts and tumors (mainly schwannomas), adult high degree of caution. The main causes of extraspinal sci- tethered cord syndrome, spinal epidural abscesses and atica include sacroiliitis,intrapelvic processes, hematomas, facet syndrome, lumbosacral deformities and The pain pattern, and the presence or abscence of 3.3. Sacroiliitis and seronegative spondyloarthropathies accompanying symptoms, are the most important compo-nents of the differential diagnosis.
Sacroiliitis, as one of the major causes of sciatica The tumor-related pains commonly cause patients to should be considered during the differential diagnosis wake in the night. Whereas small schwannomas lead to of LDHs, particularly when there is posterior thigh radicular pain, larger tumors lead to accompanying symptoms due to multiple nerve root and spinal cord There are two potential mechanisms by which sacroiliitis compressions. Epidural abscesses and hematomas may can generate sciatica: (i) referred pain (e.g. patient 6), and present with symptoms similar to intradural tumors.
(ii) direct involvement of the nerve by inflammatory medi- Adult tethered cord syndrome may lead to sciatica asso- ators released from the sacroiliac joint (e.g. patient 7).
ciated with a stretched thigh, resulting in gait distur- Sacroiliitis is a common feature of seronegative spond- bance. The pain of facet origin is located commonly in yloarthropathies; the others include spondylitis, morning the low back, buttock and thigh. It rarely extends to stiffness, LBP, decreased mobility of the lumbar spine, the lower levels. The pain secondary to deformities and and peripheral arthritis.
instabilities is commonly associated with LBP and in- The history of the patient and characteristics of the pain creases in spine loading.
allow diagnosis of sacroiliitis and its etiology. The pain in Fortunately, because lumbar MRI shows anatomical de- sacroiliitis has an insidous onset, is commonly localized tails of the lumbar spine, and other neural structures and in the deep gluteal region and may refer to the posterior soft tissues, making a diagnosis of spinal NDS is relatively thigh. The pain decreases with activity and increases in easy. Coincidental spinal and extraspinal disorders, how- the late evening.
D.G. Kulcu, S. Naderi / Journal of Clinical Neuroscience 15 (2008) 1246–1252 The presence of LBP in patients with sacroiliitis makes muscle tone not only produces local muscle pain but also differential diagnosis complex. This is because LBP may may result in sciatica.
indicate both ankylosing spondylitis and degenerative lum- Patients with PS exhibit significantly different symptoms bar spine. The patient needs to be questioned carefully to and results of physical examination to those of patients determine the symptoms that indicate the disease. Disc her- with discogenic sciatica.Pain is the predominant symp- niation-related LBP increases after activity and decreases tom in both, but there are some differences in pain patterns.
after rest, whereas spondylitis-related LBP decreases after There is usually sciatic notch tenderness or pain at the but- activity, and increases during the latter half of the night.
tock in both patient groups. The pain of discogenic origin Morning stiffness is another characteristic of spondylitis- refers to the buttock and posterior thigh without any spe- related LBP.
cific focal tenderness in the buttock. Unlike patients with Physical examinations should include a Sacroiliac Com- LDH, patients with PS typically experience symptoms in pression Test, Gaenslen's test and a FABER test. The loca- multiple dermatomes rather than either the lateral (S1 tion of the aggrevating pain after the FABER test may radiculopathy) or the medial (L5 radiculopathy) derma- reflect the pathology. Posterior pain in the pelvis may re- tome alone. Numbness or weakness is quite uncommon flect sacroiliitis, whereas pain in the groin may reflect in PS. Unlike in LDH, the SLR test is generally negative in patients with PS. Most patients with PS report that pro- The early clinical diagnosis of sacroiliitis may be difficult longed sitting and walking exacerbate their pain and that and the diagnosis should be proven radiologically. Both CT their symptoms reaggravate after internal rotation of the and MRI are sensitive methods of demonstrating sacroiliitis.
The early CT scan findings include cortical erosions and sub- The differential diagnosis of PS requires special tests chondral sclerosis of the sacroiliac joints. The later CT scan including Pace's sign, Freiberg's sign and deep digital pal- findings include sacroiliac joint narrowing and ankylosi pation of the piriformis muscle. If some of these tests are MRI has a similar capacity to CT for detecting the disease; positive, advanced radiological tests such as pelvic MRI however, MRI can detect the early stages of sacroiliitis and MRN should be performed since the pelvic MRI alone because it can reveal bone marrow edema before morpho- may fail to show the extraspinal parts of the sciatic nerve.
logic changes can be determined by a CT scan.
MRN may identify the sciatic nerve and its relationshipwith the surrounding structures.
3.4. Intrapelvic compressive processes In one study, MRN had 93% specificity and 64% sensi- tivity for distinguishing patients with PS from those with Intrapelvic compressive processes may affect the nerve similar symptoms by presenting piriformis muscle asymme- as it passes from the neural foramina to the greater sciatic try and sciatic nevre hyperintensity at the sciatic notch.
notch. Reported intrapelvic compressing processes include Although piriformis muscle hypertrophy has been demon- strated by MRI,Filler et al. also observed ipsilateral mus- scesspresacral abscessand aneu cle atrophy in some patieThis finding may be Pelvic and femoral bone tumors may compress the sci- secondary to disuse of the muscle in the chronic stage. In atic nerve. Bickel et al. analyzed a surgical database of 32 the present study, MRN of patient 9 showed piriformis patients with bone tumors that caused sciatica. According muscle atrophy and asymmetry, and sciatic nerve hyperin- to their analysis, the characteristics of the patient's pain tensity. However, the MRI of patient 11 (who had PS), are very important in the differential diagnosis of bone tu- similar to Lee et showed that the piriformis muscle mors. Sciatica due to bone tumors generally has an insi- was not compressing the sciatic nerve. The absence of the dous onset, causes constant pain, awakening at night, positive finding in the neutral (static) position can be ex- and is progressive and unresponsive to position changes.
plained by the dynamic nature of the piriformis muscle: Local compression may reveal local tenderness. As most as the pain is positive in Freiberg's position, MRI and bone tumors occur in the pelvis or proximal femur, initial MRN should be performed in both static and dynamic pelvic radiography is recommended for patients with atyp- positions (i.e. Freiberg's position).
ical sciatica. A simple pelvic radiograph may show tumor-related bony destruction, as in patient 8. Three-phase bone 3.6. Hip disorders scintigraphy, CT scanning, and MRI seem to be sensitive indetecting bone tumors. MRI and MRN may show the rela- The pattern of pain distribution in hip disorders may tionship between the tumor and the sciatic nerve in detail.
create difficulty in determining the source of pain (spinevs. Swezey et al. reviewed patients who were treated 3.5. Piriformis syndrome for lumbar spinal stenosis while the primary source of thepain was osteoarthrosis of the hip, and patients who were Sciatica is caused by PS in 6% of patieHypertro- treated for osteoarthrosis of the hip while the primary phy, inflammation, anatomic variations, myositis ossificans source of pain was lumbar spinal stenosis. Symptoms for and traumatic injury of the piriformis muscle may com- both disorders are frequently present in the same pa- press the sciatic nerve.Any increase in the piriformis tients.The presence of limb or groin pain, and limited D.G. Kulcu, S. Naderi / Journal of Clinical Neuroscience 15 (2008) 1246–1252 internal rotation of the hips is predictive of a hip disorder 14. Naderi S, Manisali M, Acar F, et al. Factors affecting reduction in rather than a spine disorder. The occurence of groin pain during the FABER test may suggest a hip disorder. Pelvic 15. Chen WS. Chronic sciatica caused by tuberculous sacroiliitis. A case radiography may show hip osteoarthritis.
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