CURRENTLY, the antemortem diagnosis of sporadic amyotrophic lateral sclerosis (ALS) is based on a combination of clinical, electrophysiologic, and sometimes muscle biopsy findings, and exclusion of other conditions that might produce the clinical picture. There is no definitive diagnostic test for the disease, and there is no established technique for demonstrating upper motoneuron involvement except for the clinical neurologic examination. For these reasons, there has been an interest in the past decade in the use of in vivo magnetic resonance (MR) imaging and spectroscopy of the brain to diagnose ALS and to monitor its progression. The initial focus was on MR imaging features, such as hyperintensity in the corticospinal tracts on proton density–weighted images and hypointensity in the motor cortex on T2-weighted images.1 These features, however, are present in less than half of patients with clinically diagnosed ALS, and motor cortex hypointensity can be observed in normal volunteers and in subjects with other neurodegenerative diseases.
Bowen BC, Bradley WG. Amyotrophic Lateral SclerosisThe Search for a Spectroscopic Marker of Upper Motoneuron Involvement. Arch Neurol. 2001;58(5):714-716. doi:10.1001/archneur.58.5.714