A Rare Case of Subdural Hematoma Associated with Intracranial Hypotension Following Rituximab Therapy in a Patient with Myasthenia Gravis

Background: Spontaneous intracranial hypotension (SIH) is an underdiagnosed disorder most often presenting with postural headache and attributable to cerebrospinal fluid (CSF) leakage. Complications include brain sagging and subdural hematoma (SDH), which may carry significant morbidity. Rituximab, a chimeric monoclonal antibody targeting CD20, is widely prescribed for autoimmune diseases, including myasthenia gravis (MG). Although its safety profile is generally favorable, rare neurological complications have not been fully characterized. Case presentation: We describe a 40-year-old woman with a history of generalized MG, thymectomy, hypothyroidism, and chronic migraine who developed persistent headache following Rituximab infusion. The infusion on this occasion was administered more rapidly than in previous cycles. Her pain was severe, positional, and unresponsive to escalation of migraine prophylaxis. Neurological examination was unremarkable. Brain MRI revealed bilateral non-traumatic SDH, diffuse pachymeningeal enhancement, and cerebellar tonsillar descent, consistent with SIH. CT angiography and MR venography ruled out vascular abnormalities. Comprehensive autoimmune and infectious work-up was negative, and CSF analysis was normal. Conservative therapy with intravenous fluids and caffeine led to marked symptom improvement. Conclusion: This case highlights a rare occurrence of SIH complicated by bilateral SDH in temporal association with Rituximab infusion. While causality cannot be confirmed, the temporal relationship, absence of alternative risk factors, and response to conservative management suggest a possible drug-related contribution. Clinicians should consider SIH in patients with refractory or atypical headache after Rituximab therapy, as early recognition can prevent unnecessary interventions and allow for effective, non-invasive treatment. Further reports are needed to clarify whether Rituximab may predispose susceptible individuals to disturbances in CSF dynamics.