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

T2 TSE transverse with fat saturation
Thick Maximum Intensity Projection (MIP) of 3D SPACE
20 direction MDDW of the sacral plexus with inverted grey scale
Tractography of the sacral plexus using 20 direction MDDW


  • 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


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