The effect of muscle-tone-reducing procedures in athetotic head movements: partial nerve block by lidocaine and surgical release of the neck muscles.
OBJECTIVE
To investigate the effect of muscle-tone-reducing procedures (MTRPs), i.e. partial nerve block by lidocaine (PNB) and surgical release of muscle attachment to bone (SRMAB), on incessant involuntary head movements in athetotic patients.


METHODS
Pre/post-MTRP changes in neck-muscle activities, glabella movement and maximum isometric forces of the head were measured in six athetotic patients with severe spondylotic myelopathy resulting from incessant involuntary head movements.


RESULTS
Pre/post-MTRP changes in neck-muscle activities resembled those after gamma-block. In four patients, PNB reduced the maximum isometric force by no more than 40% of pre-PNB force, while decreasing the amount of involuntary head movements to 37-65% of the pre-PNB value in the frontal plane. MRSAB reduced the force by less than 40% of pre-SRMAB force in 4 MRSAB tested patients, while decreasing the amount of involuntary head movements to 12-45% of the pre-SRMAB value in all 6 patients.


CONCLUSIONS
MTRPs reduced involuntary head movements significantly while preserving voluntary muscle forces relatively well. PNB and SRMAB procedures have in common the effect of reducing gain in the myotatic reflex pathway by decreasing the excitatory inflows to alpha-motoneurons via muscle spindle Ia-afferents, which resulted from blocking mainly gamma-efferent conduction by PNB, and reducing background tension in muscle spindles by SRMAB.
Saiki
K
K
Department of Orthopedic Surgery, Saitama Medical Center, Saitama Medical School, Kawagoe, Japan. saikik@saitama-med.ac.jp
Tsuzuki
N
N
Tanaka
R
R
D000328:Adult; D002547:Cerebral Palsy / Q000503:physiopathology* / Q000601:surgery; D004576:Electromyography; D005260:Female; D019416:Head Movements / Q000502:physiology*; D006801:Humans; D008012:Lidocaine; D008297:Male; D008875:Middle Aged; D009129:Muscle Tonus / Q000502:physiology*; D009132:Muscles / Q000503:physiopathology; D009334:Neck Muscles / Q000503:physiopathology / Q000601:surgery*; D009407:Nerve Block; D013997:Time Factors
D008012:Lidocaine