Foraminal Stenosis at L5–S1 as an Overlooked Pathology of Bilateral Radiculopathy: A Case Series

INTRODUCTION: The classical symptom of foraminal stenosis is unilateral radiculopathy. Bilateral radiculopathy caused purely by foraminal stenosis is rare. Here, we report five cases of bilateral L5 radiculopathy caused purely by L5–S1 foraminal stenosis and describe the clinical and radiological features of these patients in detail. CASE PRESENTATION: Among the five patients, two were men and three were women with an average age of 69 years. Four patients had undergone surgeries at L4–5 level, previously. All the patients showed an improvement in symptoms in the post-operative period. After a certain period, the patients complained of bilateral leg pain and numbness. An additional surgery was performed in two patients; however, there was no improvement in symptoms. One patient, who did not undergo surgery, was treated conservatively for 3 years. All the patients had been suffering from bilateral leg symptoms before their first visit to our hospital. The neurological findings in these patients were consistent with bilateral L5 radiculopathy. The average pre-operative Japanese Orthopedic Association (JOA) score was 13 out of 29 points. Bilateral foraminal stenosis at L5–S1 level was confirmed using a three-dimensional magnetic resonance imaging or computed tomography. Posterior lumbar interbody fusion was performed in one patient and bilateral lateral fenestration using Wiltse’s approach was performed in four patients. The neurological symptoms recovered immediately after surgery. The average JOA score at 2-year follow-up was 25 points. CONCLUSIONS: Spine surgeons may overlook the pathology of foraminal stenosis, particularly in patients with bilateral radiculopathy. Familiarity with the clinical and radiological features of symptomatic lumbar foraminal stenosis is necessary to properly diagnose bilateral foraminal stenosis at L5–S1 level.