Acute motor axonal neuropathy associated with anal carcinoma: Paraneoplastic neurological syndrome or coincidence?

AimAssessment of the association of an acute motor axonal neuropathy with a squamous cell anal carcinoma.BackgroundParaneoplastic neurologic syndromes are not a direct consequence of neither primary tumor nor its metastasis. They often parallel the course of the malignancy but may be the presenting sign of an occult cancer. Sometimes it is very difficult to distinguish if it is a paraneoplastic syndrome or just a coincidence.Materials and methodsWe report a 60-year-old man that presented with an acute motor deficit of the four limbs. Clinical examination found a pure and severe motor deficit in the four limbs. No sensory abnormality was found and all motor nerves were unexcitable. Electromyography suggested the diagnosis of acute motor axonal neuropathy (AMAN). Four months after developing the AMAN, blood in the stool revealed anal carcinoma. The patient was treated with concurrent chemoradiotherapy. Radiation was given to the tumor and to the pelvis, including inguinal nodes, over a five-week period plus fluorouracil and mitomycin. We investigated the presence of antiganglioside antibodies as studies suggest that carcinomas can express antigens shared with Schwann cells.ResultsAnti-GM1 IgG antibodies were detected by an enzyme-linked immunosorbent assay method. Other antibodies, including antinuclear nucleoprotein antibody (anti-Hu), anti-Tr, anti-Ri, anti-CV2, anti-amphiphysin and anti-Yo, were negative. Clinical improvement of the motor state was observed at the fourth week of oncologic treatment.ConclusionThe presence of anti-GM1 IgG antibodies and the clinical improvement of the motor state after concurrent chemoradiotherapy lead us to believe there is an association between anal carcinoma and this severe impairment.