This study aimed to assess the relationship between the physiological loss of motor units and spinal excitability in aging process of healthy person. Multiple point stimulation technique was used to calculate MUNE and 100 F-wave were analyzed to determine the spinal excitability by F-wave persistence (FP) and the amplitude ratio between F-wave and CMAP (F%M) at right median nerve of sixty-four healthy volunteers (mean age, 43.1 years). We divided the subjects into four groups, young adult (18 to 30 years), adulthood (31 to 45 years), middle-aged (46 to 59 years), and older group (above 60 years). MUNE decreased in elder group compared with young and middle age groups. Whereas, FP and F%M increased in high-middle and elder groups compared with young group. Multiple regression analysis showed significant relation between the MUNE decrease with FP increase and aging. We concluded the aging process, which was known as motor neuron loss, was compensated with excessive spinal motoneuron excitability which was the result of dysregulation of inhibitory process from central nervous system.

Previous reports showed that some patients with X-linked Charcot–Marie–Tooth disease type 1 (CMTX1) showed favorable response after intravenous immunoglobulin therapy (IVIg). Immunological vulnerability of the myelin is hypothesized to underlie mechanism of such groups. Here, we report a patient with CMTX1 who responded to IVIg. A 51-year-old male became to be easy to stumble from about 46 years old, and developed subacute progression of gait disturbance three months before admission. Examination revealed hammer toes, muscle weakness in the distal four extremities, diminished tendon reflexes, and sensory ataxia. Nerve conduction study showed demyelinating features, fulfilled the criteria for CIDP. IVIg showed favorable effect. However, his symptom gradually worsened several months after IVIg. His mother also had peripheral neuropathy predominantly in the lower limbs. CMT was suspected and genetic test revealed P70S mutation in GJB1. The diagnosis of CMTX1 was made. His symptom improved again after second IVIg, and then, repeated IVIg maintained his symptoms.