The Value of the “Trident Sign” and Flow Cytometry in Suspecting Spinal Cord Sarcoidosis: A Case Report and a Flow Chart of Diagnostic Imaging in Longitudinally Extensive Transverse Myelitis (LETM)

The diagnosis of sarcoidosis-related longitudinally extensive transverse myelitis (LETM) is challenging, requiring the exclusion of mimicking conditions along with histopathological confirmation of the diseases affecting the spinal cord. This report presents the case of a 68-year-old woman with complaints of low back pain and tingling dysesthesia in the limbs one month prior and finally developed paraparesis with the need for support from a third person for walking. Magnetic resonance imaging (MRI) of both the brain and spinal cord, total body computed tomography, lumbar puncture, flow cytometry of the cell sediment from cerebrospinal fluid (CSF), and whole-body 18-F-fluorodeoxyglucose positron emitting tomography (FDG-PET) assisted us to finalise the diagnosis. The presence of the "trident sign" in axial sequences of MRI is of exceptional value since it is a clue for sarcoidosis of the spinal cord. CSF flow cytometry may help clinicians to rule out lymphoma, and FDG-PET can help clinicians in identifying manifestations of sarcoidosis, which need to be biopsied so as to unveil the final diagnosis.