Parenchymal neuro-Behçet with cascade sign and movement disorders: a case report

Abstract

Case Presentation: A 33-year-old male was admitted to the neurology department due to progressive ataxia, diplopia, and right-sided hemiparesis with an insidious course over approximately 18 months. Initial contrast-enhanced brain magnetic resonance imaging (MRI) revealed T2/FLAIR hyperintense lesions in the nucleocapsular regions and left thalamus, extending to the mesodiencephalic junction, without diffusion restriction. The patient was initially evaluated by neurosurgery, and a neoplastic lesion was ruled out. Upon admission to the neurology ward, a history of recurrent oral and genital ulcers since adolescence was identified, raising the suspicion of central nervous system involvement in Behçet's disease. High-dose intravenous methylprednisolone (1,000 mg daily for 5 days) was initiated. The patient subsequently developed area postrema syndrome and showed partial improvement of ataxia and hemiparesis. A follow-up contrast-enhanced brain MRI demonstrated progression of the lesions, now involving the cerebral peduncles and mesencephalon, with contrast enhancement. The continuous distribution of lesions from the diencephalon to the brainstem, consistent with the “cascade sign,” supported the diagnosis of parenchymal neuro-Behçet, and intravenous cyclophosphamide was initiated, followed by hospital discharge. In February 2026, the patient was readmitted under the rheumatology service due to the onset of choreoathetosis and dystonia in the right upper limb, along with behavioral changes. A new course of high-dose methylprednisolone was administered, resulting in marked clinical and radiological improvement. Discussion: This case illustrates involvement of deep brain structures and the brainstem in Behçet's disease, resulting in a combination of pyramidal, ataxic, and hyperkinetic features. The initial presentation with insidious brainstem and diencephalic involvement, followed by radiological progression despite corticosteroid therapy, reflects high inflammatory activity. Behçet’s disease has variable prevalence; in countries such as Brazil and United States, it ranges from 1 case per 100.000 inhabitants, with neurological involvement in approximately 5–10% of patients. The evolution of MRI findings, particularly the extension from nucleocapsular and thalamic regions to the mesencephalon and cerebral peduncles with contrast enhancement, supports contiguous inflammatory spread. The “cascade sign” is a characteristic feature of parenchymal neuro-Behçet and may aid in differential diagnosis. Final Comments: Despite an aggressive initial course, the patient demonstrated a favorable response after intensification of immunosuppressive therapy, highlighting the importance of early recognition and appropriate management of neuro-Behçet. This case underscores the critical role of neuroimaging in diagnosis and longitudinal assessment, as well as the need for individualized therapeutic strategies in refractory cases.