Paraneoplastic subacute lower motor neuron syndrome associated with solid cancer

We retrospectively analyzed three patients with pure motor neuronopathy followed for more than four years in our center. The patients presented a rapidly progressive lower motor neuron syndrome (LMNS) over the course of a few weeks leading to a severe functional impairment. The neurological symptoms preceded the diagnosis of a breast adenocarcinoma and a thymoma in the first two patients, one of them with anti-CV2/CRMP5 antibodies. Cancer was not detected in the third patient who had circulating anti-Hu antibodies. A final diagnosis of paraneoplastic syndrome was made after investigations for alternative causes of lower motor neuron syndrome. Early diagnosis, combined treatment of the underlying cancer, and immunomodulatory treatment led to neurological improvement of the disease in two out of the three cases in which the cancer was diagnosed. Cases of subacute LMNS with rapid progression may occur as an expression of a paraneoplastic neurological syndrome. Identification of these syndromes is important, as the treatment of underlying malignancy along with immunomodulatory treatment may result in a favorable long-term outcome of these potentially fatal diseases.