Proton magnetic resonance spectroscopy and transcranial magnetic stimulation for the detection of upper motor neuron degeneration in ALS patients.

Transcranial magnetic stimulation (TMS) was compared to proton magnetic resonance spectroscopy (1H-MRS) for the detection of upper motor neuron loss or dysfunction in 49 ALS patients classified according to the El Escorial criteria. Abnormal NAA/Cho ratios were detected in 53% of ALS patients. Abnormal TMS results (i.e. cortical inexcitability or prolonged CMCT's) were obtained in 63% of ALS patients. If one or both methods were considered for diagnosis of upper motor neuron degeneration/dysfunction, the percentage of abnormal findings was 77%, whilst in 39% of all patients both methods produced abnormal results. Compared to TMS, 1H-MRS detected more patients with upper motor neuron involvement in the suspected El Escorial subgroup (42% versus 25%), whereas TMS detected more patients with upper motor neuron involvement in the possible (81% versus 50%), probable (71% versus 57%) and definite El Escorial subgroup (71% versus 64%). We conclude that the combined use of 1H-MRS and TMS increases diagnostic accuracy for the detection of upper motor neuron involvement in ALS patients.