CSF AND PLASMA AMINO-ACID LEVELS IN MOTOR-NEURON DISEASE - ELEVATION OF CSF GLUTAMATE IN A SUBSET OF PATIENTS

Fasting plasma and/or CSF amino acid levels have been measured in a gr oup of 37 patients with motor neurone disease (MND) and in 35 neurolog ical control patients undergoing lumbar puncture prior to myelography. There were no significant differences in the plasma levels of 22 amin o acids between the two groups. In CSF, there was a significant elevat ion of the glutamate level in the MND patients (P = 0.008). However, t he MND group were heterogeneous with regard to CSF glutamate: 19/31 (6 1%) had levels within the normal range; eight (26%) had levels more th an twice the upper limit of normal (greater than or equal to 10 mu mol /l) and five (16%) had levels more than seven times normal (greater th an or equal to 30 mu mol/l). In a subset of seven MND patients there w as a significant inverse correlation (r(s) = -0.775, P < 0.03) between CSF glutamate levels in life and the density of pre-synaptic glutamat e re-uptake sites in the lumbar spinal cord measured in a post mortem autoradiographic study. A possible interpretation of these findings is that an abnormality of glutamate transport may underlie the increase in CSF glutamate. The identification of a subgroup of MND patients wit h high CSF glutamate levels may be important in evaluating the clinica l response to antiglutamate therapeutic agents.