[Disordered higher functions in a smoker].

Introduction: Paraneoplastic syndromes sometimes lead to the discovery of an intrathoracic tumour, notably small cell lung cancer (SCLC).

Materials And Methods: We report the case of a patient presenting with a paraneoplastic syndrome characterised by disordered higher functions and convulsions, representing a paraneoplastic encephalo-myelitis (PEM). This PEM led to the diagnosis of SCLC. The diagnostic features and progress of the PEM are discussed.

Conclusion: Recognition of PEM allows the diagnosis and early treatment of the underlying cancer, strongly influencing the prognosis, particularly in SCLC.