We present the initial MR and PET work-up in a diabetic 31-year-old female patient presenting with spinal cord compression because of abnormal meningeal tissue and highlight the close correlation between the clinical course and the monitoring of the lesions on MR images. The combination of non-specific inflammatory signs at histopathological examination and of the negative results of a comprehensive bacteriological and serological testing led to the diagnosis of idiopathic hypertrophic spinal pachymeningitidis. The abnormal tissue showed mild glucose uptake at whole-body FDG-PET examination. Repeated MR follow-up examinations during corticoid treatment only demonstrated partial shrinkage of the abnormal tissue. Symptomatic relapse and re-increase in lesion size on MR images occurred concomitantly after an 11-month symptom-free remitting interval under tapering corticoid treatment.