CHRONIC STIMULATION OF THE LEFT VAGUS NERVE IN EPILEPSY - BALANCE EFFECTS

Background: Stimulation of the left vagus nerve (VNS) has been shown t o control seizures in double blinded crossover studies in man, Animal studies have reported vagal a afferent induced depression of nocicepti ve and motor reflexes which may be caused by an effect on the descendi ng reticular system controlling spinal cord function. Anticonvulsant d rug therapy may cause postural instability, The effects of VNS are ass essed not only from the perspective of seizure control but also from t he view of potential harm to other bodily systems. Long term (2% years ) effects of VNS were compared to postural stability analyses. Methods : 8 subjects, 2 were females, mean age 34.5 +/- 8.23 SD years, with in tractable complex partial seizures, taking 3 anticonvulsant drugs wen assessed for postural stability in quiet standing and while moving for wards, backwards and sideways with eyes open (EO) and eyes closed (EC) . Data were collected and collated using an AMTI Biomechanics immovabl e forceplate, Newton M.A. U.S.A. The study design was longitudinal wit h pre-operative baseline data collected prior to neurostimulation and at intervals post operatively, Results: 4/8 balance measures showed si gnificant changes from pre-operative values and after 2% years of stim ulation. Area af sway (EO) in quiet standing p = .022 and total sway ( EC) in the moving state p = .019 and total sway (EC) in quiet standing showed an increase in sway p = .003, Area of sway (EC) p = .004 tende d to decrease. Regression analysis for frequency of stimulation showed an increase in sway with higher frequencies T = 1.99, P = .05, Conclu sion: Chronic VNS does not augment postural instability.