Reinnervation of dystrophic muscles

To analyse the regenerating capability of the peripheral nerve fibers and the capability of the muscle fibers to accept the regenerating and new nerve sprouts in myotonic dystrophy (MD).

One male, aged 58 years, diagnosed of MD at the age of 30 years, suffered neuralgic amyotrophy in the right shoulder girdle 4 weeks before admission. Needle EMG and nerve conduction studies were performed on admission and 6, 12, and 18 months later.

On admission there were atrophy and absence of voluntary contraction in deltoids, supra- and infraspinatus muscles. EMG showed abundant fibrillations, positive sharp waves and myotonic bursts in these muscles without voluntary activity, consistent with axonal neuropathy of both axillary and suprascapular nerves. The follow-up showed signs of reinnervation 6 months later and slight loss of long duration and high amplitude MUPs at 18 months of evolution, with good clinical recovery. This is compatible with chronic neurogenic atrophy, presumably as an expression of type grouping.

The reinnervation capability of the nerve fibers and the capability of muscle fibers membrane to accept regenerating and new nerve sprout remain in MD. Myotonic bursts persist after total denervation.