In research published in the journal Multiple Sclerosis in November 2014, a team of researchers led by Associate Professor Michael Barnett at the Brain and Mind Centre in Sydney have shown that combining MRI measurements with electrical studies of nerve conduction can help to identify lesions within nerve pathways in the brain, and to measure the extent of myelin repair and permanent nerve damage.
This type of information is going to prove crucial in testing the next generation of MS therapies that target neuroprotection and myelin repair.
This is because the measures of disability progression traditionally used in clinical trials are too slow, making clinical trials for progressive forms of MS very long and expensive. New biomarkers for repair need to be developed to assess whether the new drugs are able to effectively stimulate repair and halt progression.
In this study, Associate Professor Barnett and his colleagues have investigated if combining measurements of the electrical conduction speed in nerves, with a specialised form of MRI scan that can detect disruption to the integrity of myelin, can provide an accurate measure of myelin loss and repair.
In people with MS who have lesions in a particular bundle of nerve fibres known as the medial longitudinal fasiculus (MLF) in the brain, the sideways movements of the eyes become uncoordinated, leading to a breakdown in normal binocular vision, as well as symptoms such as double vision and impaired depth perception, with accompanying reduction in quality of life.
The speed of electrical impulses in the MLF is relatively easy to measure using specialised techniques, and the speed of conduction reflects whether the nerve fibres (axons) are insulated with myelin (fast conduction) or demyelinated and exposed (slow conduction).
The team used both the electrical and MRI tests in eighteen people with MS with lesions in the MLF. They were able to show that the speed of nerve conduction was closely associated with the extent of myelin disruption as visualised by the specialised MRI test. Combining the results of the two tests allowed the researchers to clearly differentiate between demyelination and remyelination.
Further fine tuning of the techniques may allow more accurate assessment of the extent of myelin loss, and better distinguish between slowed electrical conduction as a result of myelin loss and nerve axon loss (degeneration).
The researchers conclude that further development of combinations of non-invasive tests, such as these studied here, may play a crucial role in the assessment of new therapies designed to stimulate myelin repair in people with MS, paving the way towards faster clinical trials for progressive MS.