Posterior reversible encephalopathy syndrome associated with anti-N-methyl-ᴅ-aspartate receptor encephalitis: a case report.

Posterior reversible encephalopathy syndrome (PRES) is a clinicoradiological syndrome characterized by vasogenic edema, predominantly involving the posterior regions of the brain, and can be triggered by various conditions. PRES has rarely been reported in patients with autoimmune encephalitis, and no cases have been reported in anti-N-methyl-ᴅ-aspartate receptor (NMDAR) encephalitis before the initiation of immunotherapy. We report a case of a 36-year-old woman who presented with recurrent seizures and severe hypertension, with brain magnetic resonance imaging showing subcortical fluid-attenuated inversion recovery hyperintensities in both occipital regions, consistent with PRES. Blood pressure control and antiseizure medication therapy markedly reduced seizure frequency and resulted in near-complete resolution of the occipital lesions; however, occasional brief seizures continued, and psychomotor slowing and gait disturbance persisted despite sustained blood pressure control. Further evaluation revealed anti-NMDAR antibodies in both serum and cerebrospinal fluid and a small mature teratoma in the right ovary. She received corticosteroid immunotherapy, followed by laparoscopic ovarian cystectomy, and achieved complete neurological recovery. Notably, brain lesions consistent with PRES were present at disease onset, excluding immunotherapy as a potential cause. Severe hypertension likely played a major role in the development of PRES, and autonomic instability associated with anti-NMDAR encephalitis may have contributed to blood pressure dysregulation. Immune-mediated endothelial dysfunction and recurrent seizures may also have contributed to the development of the occipital lesions. This case expands the radiological spectrum of anti-NMDAR encephalitis and highlights the importance of considering autoimmune encephalitis in patients with PRES, particularly when there is no apparent precipitating factor or the clinical course is atypical.