Not Such a Long Stretch

New research reveals an early process in amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA) that prefigures hallmarks of the diseases; muscle atrophy and weakness.

The study from the National Institute of Neurological Disease and Stroke finds communication between the sensory and motor neurons that make up the stretch reflex (a muscle contraction in response to stretching within the muscle and which is vital for motor function) showed massive and progressive failure early in the motor neuron disease process. Both amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA)  are motor neuron diseases.

Dr. George Z. Mentis and colleagues studied synaptic connections between sensory and motor neurons in the spinal cord of SMA-afflicted mice. They went to show that a drug designed to improve motor function and increase survival in SMA mice also improved sensory-motor circuitry.

The study results suggest that spinal circuit dysfunction marks "one of the earliest and most pronounced pathological features" of spinal muscular atrophy, according to Mentis.

Spinal muscular atrophy affects about 4 in 100,000 individuals in the United States. It is an inherited disease usually present at birth and characterized by breathing difficulty, feeding difficulty, poor muscle tone, lack of head control and little spontaneous movement, among other signs.