Sacral PlexusClinical case and images provided by Avneesh Chhabra, M.D., Johns Hopkins University School of Medicine, Baltimore, USA

30-year-old man with 3 year history of pain involving the right lower extremity, at times, radiating into the bottom of the foot.

• Pain clearly aggravated by driving
• Patient had good range of motion of lumbar spine with no weakness
• Negative straight leg raise
• EMG showed a normal study without any denervation
• Patient referred to MR Neurography
• Patient's outside MR lumbar spine imaging showed slight asymmetry of the S1 root with the nerve appearing slightly enlarged
• No clear enhancement

• Fusiform enlargement of the right L5 nerve and mild asymmetric hyperintensity of the right S1 nerve. Diffuse fascicular enlargement suggesting diffuse neuronal involvement
• Minimal enhancement
• DTI - Low FA values (0.2-0.3) and high ADC values - 1.4 - 2.0. Tractography shows mildly disrupted tracts
• Diagnosis - Benign peripheral nerve sheath tumor, likely segmental schwannoma 

• It was inadvisable to operate on the lesion, since only limited improvement was expected
• Final diagnosis - Benign peripheral nerve sheath tumor
• The diagnosis was proven for a benign peripheral nerve sheath tumor as it did not change over two year follow-up