Sick sinus syndrome as the initial manifestation of neuromyelitis optica spectrum disorder: a case report

Background Sick sinus syndrome (SSS) is known to occur due to lesions in the medulla oblongata. Although medullary lesions have occurred in patients with neuromyelitis optica spectrum disorder (NMOSD), there are few reports of SSS associated with NMOSD. We report a patient with NMOSD who developed refractory nausea, vomiting and SSS as the initial manifestation. Case presentation A 77-year-old female developed refractory nausea and frequent episodes of syncope. The patient was diagnosed with SSS because sinus pauses lasting five to six seconds were observed, and pacemaker implantation was performed. Two months later, she was referred to our hospital because of limb weakness and sensory impairment that progressed over a month. The patient was confirmed to have muscle weakness; manual muscle testing revealed grade 4 in the upper extremities and grade 3 in the lower extremities. Tendon reflexes were diminished, while no pathological reflexes were present. Thermal and pain sensations were impaired in the upper and lower extremities, and vibration sensation was impaired in both lower extremities. Bladder and rectal disturbances were also noted. Optic neuritis was not detected. T2-weighted magnetic resonance imaging (MRI) showed high-intensity lesions in the dorsal part of the medulla oblongata and C3-6 cervical cord. Her serum was positive for antibodies against aquaporin 4, and a diagnosis of NMOSD was made. She was treated with two courses of an intravenous methylprednisolone pulse and one course of plasma exchange. Then, she was transferred to another hospital for rehabilitation. Conclusions Because SSS is a life-threatening complication, clinicians should be aware of the possibility that medullary lesions in NMOSD can cause SSS as the initial manifestation.