Background: Opsoclonus-myoclonus syndrome and breast carcinoma were initially described as neurologic and oncologic accompaniments of antineuronal nuclear autoantibody type 2 (ANNA-2, also known as anti-Ri). However, the neurologic spectrum of ANNA-2 autoimmunity is broader, includes a syndrome of jaw dystonia and laryngospasm, and can be accompanied by lung carcinoma. Objective: To describe clinically (with a video) ANNA-2-associated jaw dystonia and laryngospasm, its pathologic correlates, and therapeutic outcomes. Design: Retrospective case series with prospective clinical follow-up. Setting: Mayo Clinic's Neuroimmunology Laboratory, Rochester, Minnesota. Patients: Consecutive patients with ANNA-2 seropositivity identified since January 1, 1990. Main OutcomeMethods: Clinical (in 9 patients) and neuropathologic (in 2 patients) findings were reviewed. Results: Of 48 patients with ANNA-2 seropositivity, 9 (19%) had multifocal neurologic manifestations that included jaw dystonia and laryngospasm. Among 6 patients with jaw dystonia, 5 had severely impaired nutrition, causing profound weight loss. Five patients had documented laryngospasm, which contributed to 1 patient's death. Neuropathologic examination revealed diffuse infiltration by CD8+ T lymphocytes, with axonal loss and gliosis in brain-stem and descending spinal cord tracts. Some patients improved symptomatically after immunosuppressant or cytotoxic therapies; 1 patient improved after treatment with botulinum toxin. One patient who underwent tracheostomy because of recurrent laryngospasm was alive and well longer than 3 years after symptom onset. Conclusions: Jaw dystonia and laryngospasm are common accompaniments of ANNA-2 autoimmunity and are associated with significant morbidity. We propose that selective damage to antigen-containing inhibitory fibers innervating bulbar motor nuclei by CD8 + T lymphocytes (histopathologically observed infiltrating brain-stem reticular formation) is the proximal cause of this syndrome. Early and aggressive therapy offers the prospect of neurologic improvement or stabilization.