Abstract
The study was performed on a group of 17 patients with spastic paraparesis: 12 with hereditary spastic paraparesis, 3 with cord compression and 2 with complete spinal transection. 10 healthy volunteers acted as controls. Recurrent inhibition of the soleus alpha-motoneurones was estimated at rest and during voluntary contraction of triceps surae. At rest, there was evidence for a substantial decrease in the excitability of Renshaw cells in 9 out of the 12 patients with complete spastic paraparesis; this was also observed in the 2 patients with complete spinal transection, while the 3 patients with cord compression exhibited a normal Renshaw cell activity. In 3 out of 4 patients with hereditary spastic paraparesis, the changes in Renshaw cell excitability expected to occur during voluntary contraction were not found, whereas in one patient with hereditary spastic paraparesis and one with spastic paraparesis due to cord compression recurrent inhibition was normally influenced by the motor command. Our results indicate that recurrent inhibition is likely to be differently affected according to the type and/or localization of the lesion. It is also suggested that the central nervous system might control the excitability of Renshaw cells at rest and during voluntary contraction via partly separate pathways. The role of recurrent inhibition in spasticity is discussed.
Sommario
Lo studio è stato realizzato su 17 pazienti con paraparesi spastica: 12 erano affetti da paraparesi spastica ereditaria, 3 da compressione midollare e 2 da sezione completa del midollo spinale. Il materiale di controllo era costituito da 10 volontari sani. L'inibizione ricorrente dei motoneuroni del muscolo soleo è stata studiata a riposo e durante contrazione volontaria del muscolo tricipite della sura. A riposo, era presente un consistente decremento dell'eccitabilità delle cellule di Renshaw in 9 dei 12 pazienti con paraparesi spastica ereditaria e nei due pazienti con sezione midollare completa. Nei 3 pazienti con compressione midollare, l'attività delle cellule di Renshaw a riposo era normale. In 3 pazienti con paraparesi spastica ereditaria era assente la modulazione dell'inibizione ricorrente che normalmente accompagna la contrazione volontaria. In un paziente con paraparesi spastica ereditaria ed in uno con paraparesi spastica da compressione midollare, l'inibizione ricorrente era normalmente influenzata dal comando volontario. I nostri risultati indicano che, nei soggetti spastici, l'inibizione ricorrente a riposo e durante contrazione volontaria può essere interessata in modo diverso a seconda del tipo e/o localizzazione delle lesioni. È inoltre suggerito che il Sistema Nervoso Centrale può controllare l'eccitabilità di questi interneuroni a riposo e durante contrazione volontaria tramite vie almeno in parte separate. Il ruolo dell'inibizione ricorrente nella spasticità è discusso.
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Mazzocchio, R., Rossi, A. Recurrent inhibition in human spinal spasticity. Ital J Neuro Sci 10, 337–347 (1989). https://doi.org/10.1007/BF02333781
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DOI: https://doi.org/10.1007/BF02333781