Bilateral sensory deprivation of trigeminal afferent fibres on corticomotor control of human tongue musculature: a preliminary study

Abstract

Transcranial magnetic stimulation (TMS) has demonstrated changes in motor evoked potentials (MEPs) in human limb muscles following modulation of sensory afferent inputs. The aim of this study was to determine whether bilateral local anaesthesia (LA) of the lingual nerve affects the excitability of the tongue motor cortex (MI) as measured by TMS. The effect on MEPs after bilateral LA of the lingual nerve was studied, while the first dorsal interosseous (FDI) muscle served as a control in ten healthy participants. MEPs were measured on the right side of the tongue dorsum in four different conditions: (i) immediately prior to anaesthesia (baseline), (ii) during bilateral LA block of the lingual nerve, (iii) after anaesthesia had subjectively subsided (recovery) and (iv) 3 h after bilateral lingual block injection. MEPs were assessed using stimulus-response curves in steps of 10% of motor threshold (T). Eight stimuli were given at each stimulus level. The amplitudes of the tongue MEPs were significantly influenced by the stimulus intensity (P < 0·001) but not by condition (P = 0·186). However, post hoc tests showed that MEPS were statistically significantly higher during bilateral LA block condition compared with baseline at T + 40%, T + 50% and T + 60% (P < 0·028) and also compared with recovery at T + 60% (P = 0·010) as well as at 3 h after injection at T + 50% and T + 60% (P < 0·029). Bilateral LA block of the lingual nerve seems to be associated with a facilitation of the corticomotor pathways related to the tongue musculature.

Bite or brain: Implication of sensorimotor regulation and neuroplasticity in oral rehabilitation procedures

“…The slope of the curve is interpreted as the measure of cortical excitability. Figure shows a schematic representation of the protocol implemented in these studies which demonstrate an increased performance with facilitation of MEPs and MI map areas after oral motor training paradigm . However, one may note that the relationship between excitability and the activity of the region is quite complex and the factors determining MI plasticity are not yet clear .…”

“…Previous studies in rodents have suggested that the reorganisation of the MI may occur after peripheral nerve injuries . Further, experimental studies in humans have shown that manipulation of peripheral sensory inputs from oro‐facial structures alters the cortical excitability of the oro‐facial muscles …”

“…Figure 1 shows a schematic representation of the protocol implemented in these studies which demonstrate an increased performance with facilitation of MEPs and MI map areas after oral motor training paradigm. [82][83][84]95,99,100,103,104 However, one may note that the relationship between excitability and the activity of the region is quite complex and the factors determining MI plasticity are not yet clear. 101,105 Skill acquisition and practicing of motor tasks with high degree of precession are more likely to be associated with cortical changes compared to non-skilled movement.…”

“…114 Further, experimental studies in humans have shown that manipulation of peripheral sensory inputs from oro-facial structures alters the cortical excitability of the oro-facial muscles. 103,115,116…”

Alteration of occlusal vertical dimension induces signs of neuroplastic changes in corticomotor control of masseter muscles: Preliminary findings

“…The face sensorimotor cortex plays an important role in adaptive and learning processes in animals and humans . Previous studies have shown a reorganisation of the jaw and tongue motor representations or changes in motor cortex excitability following intra‐oral alterations or learning of novel oral motor tasks . More recent animal studies in rats have shown significant neuroplastic changes within the face motor cortex following modification of the dental occlusion .…”