Sacral Plexus

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

Clinical question

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

Clinical images

Interpretation

  • 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 

Consequences for treatment

  • 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