Introduction: Despite being a relatively uncommon condition, cauda equina syndrome has a high profile due to its life altering consequences for patients. However, once imaging has ruled out a compressive cause for CES, other rarer pathologies must be considered. In the following case, there was significant difficulty in differentiating between an inflammatory, infective or infiltrative basis for the patient’s presentation.

Case Description:    A 69 year old lady with a background of sero-negative rheumatoid arthritis presented with a subacute history of progressive lower limb weakness, areflexia and paraesthesia with an accompanying maculopapular rash. Initial MRI of the spinal cord was unremarkable. However, CSF revealed elevated protein and NCS and EMG were in keeping with severe Guillain Barre Syndrome. The patient completed a course of IVIg with no clinical improvement. Subsequently, HSV-2 was isolated from the CSF, repeat imaging showed diffuse enhancement of the cauda equina and the patient received anti-viral therapy for Elsberg’s Syndrome. Several weeks after admission, a PET scan revealed FDG avid nodal disease and lymph node biopsy confirmed a T cell lymphoma.
 
Conclusion:
Infective, infiltrative and inflammatory conditions are important causes of cauda equina syndrome. In particular, Elsberg syndrome is a rare cause of acute inflammation of the lumbosacral nerve roots, often due to herpes simplex virus 2, and prompt diagnosis and initiation of anti-viral therapy may preserve neurological function.