We present the case of a female patient with a subacute paraneoplastic brainstem neurological syndrome associated with breast cancer and the development of anti-Ri antineuronal antibodies (ANNAs). It is an important syndrome to identify because of the need for urgent investigation and management to reduce progressive and irreversible neurological deterioration and to recognise the associated risks of bulbar and central respiratory failure. Diagnosis can be confounded if the anticipated normality of imaging and cerebrospinal fluid (CSF) studies is not appreciated. Positive antineuronal screening can provide rapid support for a paraneoplastic aetiology. Urgent and extensive investigation to identify the underlying tumour is imperative since neurological outcome is dependent on the rapidity of commencement and efficacy of tumour therapy. We discuss the symptoms, pathophysiology, diagnosis, treatment and prognosis of paraneoplastic neurological syndromes.