Non-Discogenic Sciatica

The most common cause of sciatica is a herniated disk that puts pressure on the nerve roots, typically at the L4/L5 or L5/S1 level. This condition is characterized by lower back pain that extends to the buttock, back of the thigh, and the front and side of the lower leg.

In some cases, the pain can even reach the foot. Approximately 90% of sciatica cases are attributed to herniated disks and other degenerative issues in the lumbosacral region.

Despite exhibiting mild to moderate disc disease on imaging, some patients with classic sciatica may receive a misdiagnosis related to disc issues. Unfortunately, this can result in unnecessary surgical procedures.

It is of utmost importance to explore alternative causes when patients continue to experience sciatica symptoms with normal or slightly altered lumbar images, including non-spinal origins.

In patients with non-discogenic sciatica (NDS), the neurological examination often reveals the absence of Lasègue’s sign, a positive Tinel’s sign with radiation along the sciatic nerve (SN) distribution, and tenderness upon deep palpation in the infragluteal region between the ischial tuberosity and the greater trochanteric area.

Frequent causes of non-discogenic sciatica (NDS) involve traumatic, inflammatory, tumoral, vascular, and gynecological factors. Conditions like schwannomas, neurofibromas, and malignant peripheral nerve sheath tumors can exert pressure on the sciatic nerve (SN). NDS can also be mimicked by metastasis from prostate cancer and uncommon conditions like extradural hemangioma.

These cases typically manifest with initial sciatic pain, along with neurological symptoms like weakness, changes in gait, reduced reflexes, tingling sensations, and abnormal sensations, which resemble discogenic sciatica.

Among the causes of sciatica, extra-uterine endometriosis has emerged as a prominent factor, particularly affecting the right side. This condition, referred to as cyclical sciatic, involves pain that aligns with the menstrual cycle. In cases of extra-uterine endometriosis, MRI scans demonstrate the presence of intense T1 and T2 signals.

Non-discogenic sciatica (NDS) is an infrequent condition that is often overlooked due to its similarity to more common causes of sciatica. In this study, we present a series of six patients treated at the Division of Neurosurgery at HUGG between 2010 and 2018. Treatment approaches varied, including surgery with lesion excision, incisional biopsy followed by radiotherapy, and drug therapy.

In a study reported by literature, the patients experienced significant sciatica symptoms, including persistent pain, tenderness in the buttock area, and a positive Tinel’s sign along the course of the sciatic nerve. It was observed a deep-seated lesions without apparent masses.

NDS, a form of sciatica not related to disc issues, is primarily documented in case reports, often involving tumor cases. However, there is currently no established standardized clinical approach for NDS.

To prevent misdiagnosis, it is vital to identify symptoms and signs associated with discogenic causes and establish a connection between physical examination and imaging findings.

Indicators of nerve root compression in individuals with lumbar disc herniation include localized pain following dermatomal patterns, leg coldness, heightened pain during specific activities, muscle weakness, limited finger-floor distance, absent reflexes, and a positive straight leg raise test.

However, there is a lack of literature addressing the specific neurological examination for non-discogenic sciatica (NDS).

Patients with endometriosis experienced cyclical sciatica during menstruation, indicating a gynecological cause. Extra-uterine endometriosis is a common contributor to gynecological non-discogenic sciatica (NDS).

The mechanism behind sciatica development in these cases is still debated, with theories ranging from pelvic peritoneal pain referral to perineural spread affecting the lumbosacral plexus. Imaging studies have shown compromised sciatic nerve (SN) in many cases. MRI confirmed SN enlargement, and hormonal therapy was effective, consistent with existing literature.

The literature presents differing opinions on whether piriformis syndrome is a possible cause of sciatica. In one case, initial symptom relief was observed after a piriformis injection; however, further examination revealed stage IV sarcoma instead of piriformis syndrome.

Given the similarities in clinical presentation between tumoral and non-tumoral non-discogenic sciatica (NDS), it is advisable to conduct an MRI of the gluteus region for individuals suspected of having piriformis syndrome to exclude more serious underlying conditions.

Radiological studies in the English literature have assessed the role of MRI in diagnosing non-discogenic sciatica (NDS). Literature has reported correlated histopathological cases with imaging findings, identifying the main causes of NDS. The importance of combining clinical and MRI findings for accurate diagnoses has been emphasized.

Authors have cautioned against overreliance on lumbosacral MRI results as disc-related findings may be incorrectly implicated as the cause of symptoms. In our study, abnormalities observed on lumbosacral MRI in two patients were considered insufficient to explain the severity of symptoms and neurological signs.

Literature has reported unsuccessful surgical treatment for lumbosacral disc disease, revealing a sciatic notch schwannoma. Another study reported lumbar arthrodesis, which failed to improve symptoms in a patient later diagnosed with a low-grade sarcoma. Tumor resection provided long-term pain relief.

Clinical findings such as sciatic pain, positive Tinel’s sign, and deep infragluteal tenderness prompted a gluteal MRI for accurate diagnosis. These findings strongly indicate non-discogenic sciatica (NDS) and highlight the importance of gluteal imaging when lumbar spine imaging is inconclusive.

Further investigation with a pelvic MRI is recommended if gluteal MRI results are negative. Misdiagnosis of non-discogenic sciatica as discogenic is common, even when lumbosacral MRI results are inconclusive.

When a patient with sciatica reports sitting-related pain, displays a positive Tinel’s sign, experiences marked tenderness upon deep infragluteal palpation, and presents inconclusive lumbosacral MRI findings, it is advisable to refer them for a gluteal ± pelvic MRI.

This recommendation applies irrespective of the presence of a detectable mass.

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