Functional Capaсities of Limb Muscles in Patients with Partial Damage to the Cervical Spinal Cord

INTRODUCTION: In the long-term course of traumatic spinal cord disease (TSCD), neuroplastic adaptive and maladaptive changes occurred on different structural levels of the nervous system, which leads to a shift in the activation and strength characteristics of the limb muscles. The standard neurological assessment is approximate; therefore, objective instrumental studies of the motor sphere of patients with partial damage to the cervical spinal cord have not lost their significance. AIM: To study the activation and strength characteristics of the limb muscles of patients with partial injury of the cervical spinal cord in the long-term course of the disease (type B on the American Spinal Cord Injury Association (ASIA) scale). MATERIALS AND METHODS: The study enrolled 28 patients with fractures of the cervical spinal cord vertebrae in the late period of the TSCD of ASIA type B. The amplitude of motor responses (M-responses) of the upper and lower limbs was assessed using electroneuromyography. The strength of the upper limb muscles was evaluated using manual dynamometers. RESULTS: M-responses were absent in 9% and 64% in the upper and lower limbs, respectively. The amplitude of the most recorded M-responses of the upper and lower limb muscles was reduced relative to the norm. The reduction was not uniform, with significant differences in different leads. The average values of the amplitude asymmetry of M-responses did not exceed the norm. Moreover, 61% of the patients could perform hand-grip functions and hold the wrist dynamometer. Only 59% of the patients could make an effort and the results of strength measurement were obtained, whereas in 41% of cases, zero values were obtained. Statistical analyses revealed a clear relationship between the motor deficiency index of the upper limb and hand-grip strength. CONCLUSION: The degree of preservation of M-responses and evident asymmetry of evoked electrical activities of the upper and lower limb muscles indicate the existence of a certain level of neurotrophic interaction in the “muscle fiber–motor neuron” system. The level of reduction of the hand-grip strength and its relationship with the motor deficiency index allows discussion about the partial preservation of the voluntary control of the motor function of the upper limbs.