Distinction between Intraspinal and Extraspinal
causes in Non-Discogenic Sciatica

Sciatica is a prevalent condition that is commonly attributed to lumbar disc herniation. However, it can also be caused by various factors within or outside the spine that affect the sciatic nerve.

While intraspinal non-discogenic sciatica can be detected through lumbar spine imaging, extraspinal causes are often misdiagnosed since standard diagnostic tests primarily focus on the lumbar spine.

Extrapelvic factors affect the nerve as it progresses from the sciatic notch. Accurate diagnosis of extraspinal sciatica relies on thorough patient history, clinical examination, and potentially additional diagnostic imaging.

Lumbar Radicular Herpes Zoster

Literature has reported a woman in her sixties sought medical attention due to ongoing left leg pain that was not relieved by painkillers. No abnormal findings were observed during a neurological examination

. A lumbar MRI revealed degenerative changes, and subsequent physical examination identified distinct skin lesions along specific dermatomes. Referral to the dermatology department confirmed the cause of the lesions as herpes zoster.

The patient experienced relief from symptoms following treatment for herpes zoster.


Literature has reported a young female patient who was hospitalized due to an extended period of low back pain and left leg pain. Upon physical examination, a positive outcome was observed on the straight leg raising test, and there was reduced sensation in a specific region of her skin.

Diagnostic imaging indicated the existence of multiple schwannomatosis affecting specific nerve roots in the lower back. The patient obtained relief from symptoms following medical treatment.

Surgical intervention was deemed unnecessary as there were no neurological impairments and the size of the schwannomas was relatively small.

Facet Syndrome And Lumbar Disc Herniation

Literature has reported an adult woman was hospitalized due to a previous occurrence of lower back pain, along with pain and numbness in her left leg. The straight leg raising test yielded normal results, and no neurological impairments were observed.

Radiographic evaluations detected degenerative alterations in the left-sided facet joint of the L5-S1 region. Furthermore, a lumbar MRI demonstrated a central disc protrusion at the L4-L5 and L5-S1 levels.

Through the implementation of physical therapy and targeted flexion exercises, the patient experienced partial alleviation of symptoms.

Lumbar Instability

Literature has reported a young male patient who was admitted to the hospital after experiencing chronic lower back pain (LBP) for 12 years, along with recent persistent left leg pain. During the physical examination, a positive result was obtained on the straight leg raising (SLR) test at a 60-degree angle.

The patient had previously received an inaccurate diagnosis of lumbar disc herniation (LDH) and underwent unsuccessful physiotherapy treatment. However, subsequent imaging, including sagittal lumbar MRI and axial MRI, revealed the presence of pars defects specifically at the L5 level.

Further confirmation came from additional oblique radiographs, which indicated bilateral pars interarticularis defects. Lumbar instability resulting from these isthmic defects was identified as the main cause of the lower back pain (LBP).

Sciatic Neuritis

Literature has reported that hospitalization was required for a 64-year-old female patient experiencing pain in her left buttock. The patient had previously undergone lumbar spondylolisthesis surgery ten years ago.

The physical examination did not yield any notable results. However, a lumbar MRI revealed the existence of left sciatic neuritis situated between the piriformis muscle and the proximal femur.

Bilateral Sacroiliitis

Literature has reported a young woman, aged 25, was hospitalized due to a two-month duration of lower back pain, along with pain in the left buttock and posterior thigh.

The physical examination revealed limited straight leg raising on the left side, discomfort in the left buttock, and positive indications of sacroiliitis. MRI findings displayed disc protrusion and bilateral sacroiliitis.

Symptom relief was achieved through indomethacin treatment, and a diagnosis of seronegative spondyloarthropathy was made.


Literature has reported a 53-year-old woman was admitted with left leg pain. Physical and neurological examinations were normal, but sacroiliac MRI revealed sacroiliitis and sciatic nerve compression.

Further evaluation led to a diagnosis of seronegative spondyloarthropathy. Treatment with indomethacin, salazosulfapyridine, and prednisolone acetate resulted in decreased pain and resolution of symptoms.

Soft Tissue Tumor

Literature has reported a middle-aged man, aged 55, was hospitalized due to right buttock pain lasting for one month. The patient had a history of L4-L5 discectomies performed several years prior.

Neurological examination did not show any abnormalities. Palpation of the buttock elicited pain. Diagnostic imaging revealed modic changes at the L4-L5 level on the lumbar spine MRI, and a 6 cm soft tissue mass located anteriorly and to the right of the sacrum on the pelvic MRI.

A CT-guided needle biopsy confirmed the presence of an angiosarcoma, indicating a malignant growth.

Piriformis Syndrome and Hamstring Tendinopathy

Literature has reported hospitalization was necessary for a 59-year-old woman experiencing pain in the left buttock and thigh. The examination identified an abnormal gait, positive Freiberg’s sign, and tenderness in the piriformis muscle and ischium pubis.

Although the lumbar spine MRI did not reveal any irregularities, magnetic resonance neurography (MRN) demonstrated piriformis muscle asymmetry, abnormal sciatic nerve signals, and bone marrow edema at the hamstring insertion site.

Pain in the ischium pubis persisted due to hamstring tendinopathy, despite physical therapy for piriformis syndrome resulting in pain relief and improved mobility.

Lumbar Disc Hernia and Piriformis Syndrome

Literature has reported a 48-year-old man was hospitalized with a six-week duration of lower back pain (LBP) and left leg pain. MRI revealed compression of the left S1 nerve root due to L5-S1 disc herniation.

Surgical intervention partially alleviated the symptoms, but persistent left thigh pain occurred with prolonged sitting and hip internal rotation. Although MRI neurography did not show any abnormalities, a positive physical examination led to a diagnosis of piriformis syndrome (PS).

Following a physical therapy protocol, the patient experienced a significant reduction in pain, improved comfort during prolonged sitting, and hip rotation.

Degenerative Lumbar Spine and Coxarthrosis

Literature has reported a 65-year-old man was hospitalized with bilateral buttock pain and neurogenic claudication. Diagnosis revealed disc herniation, spinal stenosis, and spondylolisthesis in the lumbar region, along with severe osteoarthritis in the left hip.

The patient underwent spinal decompression, instrumentation, and fusion surgery, followed by total hip arthroplasty. These interventions successfully resolved the symptoms.

Sciatica can result from various pathological processes affecting the lumbar nerve roots and sciatic nerve, both within and outside the spine.

While 20% of cases involve both discogenic and non-discogenic causes, non-discogenic sources of sciatica are frequently missed in practice, possibly due to the highly sensitive nature of lumbar spine MRI in detecting abnormalities even in asymptomatic individuals.

Dr. Nakul Karkare

I am fellowship trained in joint replacement surgery, metabolic bone disorders, sports medicine and trauma. I specialize in total hip and knee replacements, and I have personally written most of the content on this page.

You can see my full CV at my profile page.