Proprioceptive organs which regulate muscular tonus through the γ motor system play an important role in the maintenance of body equilibrium.
Niki has proved that hypertonicity of cervical and lumbar muscles can be induced through the sympathetic nervous system in certain cases of head and neck injuries. It is conceivable that in addition to the y motor system, the sympathetic nervous system may enhance muscular tonus and thereby. impair body equilibrium, especially when the subject is positive for the equilibrium test with adrenalin loading (hyper-sensitivity of the sympa-thetic component of the central autonomic system).
To test the above-mentioned hypothesis, we carried out the following experiments. The equilibrium test with adrenalin loading and the occipital nerve block were carried out in 96 patients with vertigo having the tenderness in the nuchal region. Changes in the righting reflex after the occipital nerve block were examined.
The result was such that improvement in the righting reflex was more often observed in patients who had a positive sign in the equilibrium test with adrenalin loading. This improvement in equilibrium is due to the blockade of abnormal impulses through γ fibers and sympathetic fibers which have caused hypertonicity of cervical muscles.
