- Magnetic resonance spectroscopic imaging (MRSI) is a noninvasive technique that can be used to measure the presence of small molecules called metabolites in the brain.
- Levels of a metabolite called n-acetyl aspartate (NAA), which is produced by healthy motor neurons, often are reduced in some areas of the brain in people with ALS. (Motor neurons are the nerve cells lost in ALS.)
- Using MRSI, a research team has shown that NAA levels can be used to distinguish people with ALS from people without the disease, and that the levels correlate with a person's degree of ALS-associated disability.
Advances in technology have led to greater sensitivity in imaging techniques, increasing scientists' ability to see into the brain and spinal cord. Now, a research team reports that a technique called magnetic resonance spectroscopic imaging (MRSI) can distinguish people with amyotrophic lateral sclerosis (ALS) from people without the disease.
When enhanced by a processing component called MIDAS (Metabolite Imaging and Data Analysis System), MRSI is able to detect the presence of small molecules called metabolites in the brain, including one called n-acetyl aspartate (NAA), which is produced by healthy motor neurons (the muscle-controlling nerve cells that are lost in ALS). NAA levels in the brain may be a biomarker — a reliable biological indicator — of the presence and progression of ALS.
The researchers determined NAA levels in the brains of 16 people with ALS, three with a related disease called primary lateral sclerosis (PLS), and 14 unaffected controls. They found:
- People with ALS or PLS had significantly lower levels of NAA than did unaffected participants.
- Among the participants with ALS or PLS, those who had a lower degree of disability had higher NAA levels. (ALS disability was measured by the ALSFRS-R, or ALS Functional Rating Scale-Revised, a validated ratings scale used by physicians to assess symptom progression in ALS.)
- No significant relationship was found between NAA levels and duration of disease or rate of disease progression.
The results, the investigators wrote, require validation in larger studies.
Reliable indicators of disease presence and progression (biomarkers) could help speed ALS diagnosis and provide trustworthy indicators about the treatment effects of experimental therapies in ALS clinical trials.
The research team published its findings online Feb. 12, 2013, in Neurology. Read the full report, for a fee: Whole-Brain Magnetic Resonance Spectroscopic Imaging Measures are Related to Disability in ALS.