[Three patients with a paraneoplastic neurological syndrome: the significance of paraneoplastic antibodies]. / Drie patiënten met een paraneoplastisch neurologisch syndroom; de betekenis van paraneoplastische antistoffen.

Establishing the presence of paraneoplastic antibodies is important in identifying an often severe neurological syndrome as paraneoplastic and hence directing the search for an underlying neoplasm. A paraneoplastic neurological syndrome was diagnosed in 3 patients. The first was a 64-year-old woman in whom paraneoplastic encephalomyelitis was diagnosed. The diagnosis was strongly supported by a high titre of serum anti-Hu antibodies, despite three negative biopsies from a mediastinal mass. The patient died of a non-convulsive status epilepticus; autopsy revealed not only paraneoplastic encephalomyelitis but also small-cell lung cancer. The second patient was a 55-year-old woman with metastatic breast cancer. After a three-year period of progressive neurological deterioration, a high titre of anti-CV2/CRMP5 antibodies was detected, on the basis of which the clinical syndrome was diagnosed as paraneoplastic. She received immunotherapy and her condition stabilised. The third patient, a 41-year-old man, presented with severe limbic encephalitis. Biopsy from a paraaortic mass was positive for undifferentiated carcinoma. The patient had a high titre ofanti-Ma2 antibodies and was subsequently tested positive for serum alpha-foetoprotein (AFP) and beta-human-chorionic gonadotrophin (bta-HCG). During chemotherapy for a non seminoma testicular cancer, the limbic encephalitis improved both clinically and radiologically, but the patient died as a result of the toxicity of the treatment.

Extracellular detection of active membrane currents in the neuron-electrode interface.

Although measurement of sealing resistance is an important tool in the assessment of the electrical contacts between cultured cells and substrate embedded microelectrodes, it does not offer information about the type of cell, i.e. neuron or non-neuronal cell. Also, rules for translation of a measured sealing resistance into parameters for successful stimulation, i.e. eliciting an action potential, are not available yet. Therefore, a method is proposed for the detection of active membrane currents, elicited by extracellular current stimulation. The method is based on the prediction of the linear part of the response to an applied stimulus current pulse using an impedance model of the neuron-electrode contact. Active membrane currents are detected in the nonlinear response, which is obtained by subtraction of the predicted linear response from the measured response. The required impedance model parameters are extracted from impedance spectroscopy or directly from the measured responses.