Extraforaminal L5 Nerve Root Compression Caused by Intervertebral Osteophyte Accompanied by Lumbosacral Transitional Vertebra: A Case Treated by Anterior Approach

BACKGROUND: Several authors have reported the occurrence of extra-foraminal L5 nerve root compression between lumbosacral transitional vertebrae (LSTV) and sacral ala, but reports on a lesion caused by an intervertebral osteophyte on the ventral and contralateral side of a unilateral abnormality by LSTV are hardly available. CASE DESCRIPTION: A 67-year-old woman presented with pain along the distribution of the L5 nerve root; straight leg raise test, femoral nerve stretch test, and Kemp test were positive on the left. Following plain radiographs, computerized tomography, magnetic resonance imaging, and selective nerve root block, an osteophyte bridging the L5 and S1 vertebral bodies in the ventral side was identified compressing the L5 nerve root. On account of resistance to conservative therapy and the delicate position of the lesion, surgical treatment was performed by an anterior decompression. Subsequently, the patient attained adequate relief from pain and could walk normally. CONCLUSION: We herein present a very rare case of extraforaminal L5 nerve root compression caused by an intervertebral osteophyte on the ventral and contralateral side of a unilateral abnormality by LSTV, which was managed by anterior decompression.