Terminal innervation ratio (TIR) of axons was measured in 251 neuromuscular biopsy specimens. In those from weak or atrophic muscles in denervation, TIR could not be measured in 15% owing to rarefaction of axons and paucity of motor endings. In remaining specimens, it was increased in 97%. Specimens from normal muscles with neuropathy showed increased TIR in 74%.
In samples from muscular dystrophies, TIR was normal in 82%, including all cases of Duchenne dystrophy. In some limb girdle and facioscapulohumeral syndromes, an increased TIR suggested a neural disorder. In myotonic dystrophy, mean TIR was significantly greater than in controls and exceeded normal in five cases.
Mean TIR was normal in 41 cases of myasthenia. It was slightly greater than normal in two cases. In acquired myopathy mean TIR was significantly increased, presumably in response to intramuscular denervation.
Coërs C, Telerman-Toppet N, Gerard J. Terminal Innervation Ratio in Neuromuscular Disease: II. Disorders of Lower Motor Neuron, Peripheral Nerve, and Muscle. Arch Neurol. 1973;29(4):215–222. doi:10.1001/archneur.1973.00490280027003
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