Journal of Neurology, Neurosurgery, and Psychiatry, 1995, Vol 58, 222-226
Partial restoration of blink reflex function after spinal accessory- facial nerve anastomosis
N Danziger, B Chassande, G Lamas, I Fligny, J Soudant and JC Willer
Department of Clinical Neurophysiology, Hopital Pitie-Salpetriere, Paris, France.
Functional motor control requires perfect matching of the central
connections of motoneurons with their peripheral inputs. It is not known,
however, to what extent these central circuits are influenced by target
muscles, either during development or after a lesion. Surgical
interventions aimed at restoring function after peripheral nerve lesions
provide an opportunity for studying this interaction in the mature human
nervous system. A patient was studied in whom the spinal accessory nerve
was anastomosed into a lesioned facial nerve, allowing voluntary
contractions of the previously paralysed muscles. This procedure, in
addition to replacing the facial neurons at peripheral synapses, allowed a
new short latency trigeminospinal accessory reflex of the R1 blink reflex
type to be demonstrated, implying that trigeminal neurons had sprouted
towards spinal accessory motoneurons over a distance of at least 1 cm.
These results show an unexpected influence of the periphery in remodelling
central connectivity in humans. The motoneuronal excitability for this R1
reflex response was therefore studied to compare the convergent properties
of facial motoneurons (normal side) with those of the spinal accessory
motoneurons (operated side) using a classic double shock technique with
variable interstimulus intervals (conditioning test stimulus). On the
normal side, conditioning stimuli (to the ipsilateral or contralateral
infraliminar supraorbital nerve) produced a clearcut facilitation of the R1
blink reflex when the interstimulus interval was 30-80 ms. By contrast, a
similar procedure had no effect on the R1 blink reflex mediated via the
trigeminal-spinal accessory reflex arc.(ABSTRACT TRUNCATED AT 250 WORDS)
