Atypical manifestations of lumbar discogenic pain: a case of thigh and testicular pain associated with a high-intensity zone.

INTRODUCTION: The high-intensity zone (HIZ) is a distinct finding on T2-weighted MRI (T2WI), clearly demarcated from the nucleus pulposus and localized within the posterior or posterolateral annulus fibrosus of the intervertebral disc. Histopathological studies suggest that this finding represents an inflammatory process occurring within the HIZ lesion. This paper describes a case of radiculopathy and testicular pain presumed to be caused by an inflammatory HIZ lesion. CASE PRESENTATION: A 55-year-old man presented with severe pain and numbness extending from the left inguinal region to the anteromedial thigh, accompanied by left testicular pain. A plain MRI revealed no evidence of spinal canal stenosis or intervertebral disc herniation; however, an HIZ was clearly observed within the left L3-L4 intraforaminal zone. Given that the patient's left thigh symptoms corresponded to the left L3 dermatome, a left L3 nerve root block was planned. Following the left L3 nerve root block, the aforementioned symptoms promptly and completely resolved. Follow-up MRI at 3 months post-block revealed a reduction in the size of the HIZ. CLINICAL DISCUSSION: The presence of an HIZ has been interpreted as a surrogate marker of annular fissures and internal disc disruption and has been reported to correlate with discogenic low back pain. It is suggested that a HIZ within the left L3/4 intervertebral foramen irritated the left L3 nerve root, which subsequently stimulated the genitofemoral nerve via the sinuvertebral nerve, resulting in left thigh and testicular pain. CONCLUSION: This study demonstrates the pathogenesis in an atypical case of radiculopathy and testicular pain associated with an intraforaminal HIZ without evidence of lumbar canal stenosis or disc herniation.