To identify radiographic clues in myelitis suggestive of neurosarcoidosis.

Inflammatory myelitis is challenging to differentiate during the acute evaluation, especially in those disorders lacking a biomarker. Understanding the specific radiographic abnormalities in myelitis from neurosarcoidosis may improve diagnosis.

Patients with biopsy-proven sarcoidosis with radiographic evidence of spinal cord parenchymal involvement were included. Those without images for review by the authors were excluded. 

Twenty-nine patients (21 males, 8 females; 22 Black, 6 white, 1 unknown; median age 45 years) were included. Myelitis was the initial manifestation of neurosarcoidosis in 27 (93.1%). A longitudinally-extensive lesion was observed on post-contrasted T1 in 12 (41.4%) and non-contrasted T2 in 25 (86.2%). The median lengths of the longest sagittal enhancing lesion and T2 hyperintensity were 2 (range 0.5-21) and 9.5 vertebral bodies (range 0.5-21), respectively. Enhancing lesions were present in 28 (96.6%) and located in the cervical (24, 82.8%), thoracic (16, 55.2%), and conus medullaris (6, 20.7%) segments. On T2, lesions were expansile in 26 (89.7%) and located axially in the anterolateral (23, 79.3%), lateral (19, 65.5%), and dorsal (26, 89.7%) columns and central canal (23, 79.3%). A partial or full enhancing trident sign was seen dorsally in 14 (48.3%) and ventrally in 4 (13.8%). Additional findings included leptomeningeal disease (10, 34.5%), cauda equina involvement (6, 20.7%), vertebral disease (3, 10.3%), and lymphadenopathy (9, 31.0%). On brain MRI, intracranial inflammation was present in 8/27 (29.6%) with involvement of the optic nerves (4/27, 14.8%), leptomeninges (3/27, 11.1%), and brain parenchyma (3/27, 11.1%) being most common.

MRI lesions are usually longer on sagittal T2 than post-contrasted T1-weighted imaging. They typically involve the subpial cord parenchyma with extension towards the central canal, producing a dorsal or ventral “trident sign.” Involvement of the leptomeninges and lymph nodes, unusual for demyelinating disorders, may support the diagnosis.