Myelopathy in Behçet's disease: The Bagel Sign

Objective: To describe the clinical and distinctive imaging features of myelopathy associated with Behçet's disease (BD). Methods: We evaluated the records of patients meeting the following criteria: (1) fulfillment of the International Study Group criteria for BD; (2) clinically suggestive of myelopathy; (3) simultaneous spinal cord and brain magnetic resonance images (MRIs) within 1 month of acute worsening of myelopathy; and (4) follow-up duration ≥ 1 year after initial MRI evaluation. Patients not fulfilling all inclusion criteria and having MRIs with poor quality or missing sequences were excluded. Results: In 11 patients (9 men, 2 women), we studied 14 MRIs during distinct myelopathy episodes and nine follow-up MRIs. Two distinct MRI patterns of spinal cord involvement were described according to T2-weighted (T2W) axial images: (1) “Bagel Sign” pattern: a central lesion with hypointense core and hyperintense rim with or without contrast enhancement; and (2) “Motor Neuron” pattern: a symmetric involvement of the anterior horn cells. Bagel Sign was present in 13 of 14 myelopathy episodes whereas Motor Neuron pattern was observed in 1 of 14 MRIs. Of the 13 MRIs with Bagel Sign long myelopathy (n = 9), both long and short myelopathy (n = 2) and short myelopathy (n = 2) was observed. All patterns cleared with some residual lesions after steroid use and immunomodulation with associated clinical recovery in patients. Interpretation: The signal characteristics of the Bagel Sign potentially represent venous engorgement and/or acute blood products within the spinal cord. To our knowledge, Bagel Sign has not been observed in other forms of longitudinal myelopathy outside of BD, including neuromyelitis optica. Ann Neurol 2017;82:288–298.