Post-labyrinthectomy balance compensation with preplacement of cerebellar vermis lesion.

Post-unilateral labyrinthectomy compensation was compared between squirrel monkeys; one group with the pre-placement of posterior vermectomy next group with uvulonodulectomy, and the other group without any vermic lesions. The comparison was made by characterizing behavioral locomotor imbalance (by squirrel monkey platform runway test) and oculomotor imbalance (spontaneous nystagmus). Post-posterior vermectomy + unilateral labyrinthectomy group showed a much slower regainment of locomotor balance function when compared to that after uvulonodulectomy + unilateral labyrinthectomy group (which results was almost identical to that after unilateral labyrinthectomy alone). In contrast, the former group exhibited faster decay in spontaneous nystagmus, whereas the latter group showed delayed reduction of slow phase eye velocity. Thus, posterior vermis could have more functional linkage to the vestibulo-spinal system, whereas, uvula and nodulus, to the vestibulo-oculomotor system.