Cutaneous silent period in masseter muscles: a clinical and electrodiagnostic evaluation.

Abstract

SYNOPSIS In 35 normal subjects electromyographic silent periods were constantly evoked bilaterally in the masseter muscles during maximal contraction after unilateral electrical stimulation over the infraorbital or mental nerve. Findings in this study and data obtained in 30 patients suffering from trigeminal (26) and facial (four) nerve lesions suggest that the silent period evoked according to our methods is cutaneous in origin. The trigeminal sensory root forms the afferent limb of the silent period reflex. Its central pathway is thought to pass both crossed and uncrossed through the pons. Determination of the cutaneous silent period might be of value for the demonstration of trigeminal nerve lesions and to supplement results concerning other brain-stem reflexes.The electromyographic silent period (SP) refers to a transitory, relative or absolute decrease of EMG activity evoked in the midst of an otherwise sustained contraction (Shahani and Young, 1973). The term SP should be reserved for reflex pauses following a stimulus of some kind -for example, an electrical shock-to peripheral nerves and the skin overlying them; phasic reflex contractions-for instance, a tendon tap; or sudden decreases in the load against which a muscle is contracting (unloading reflex). Several factors are involved in the SP, including recurrent inhibition of motoneurones (Renshaw inhibition), Golgi tendon organ inhibitory activity, a pause in muscle spindle input, cutaneous factors, and descending impulses from subcortical or cortical areas, as well as other mechanisms yet to be described (Shahani and Young, 1973;Struppler, 1975).In the masseter muscles SPs have been observed after acoustic stimuli, a tap on the chin, and stimulation applied to the surface of the tongue and to the masseter muscle belly (Hoffman and Tonnies, 1948;Struppler et al., 1960;

Effects of different stimulus locations on inhibitory responses in human jaw-closing muscles

“…This study together with our previous findings (23) indicated that both the appearance and magnitude of RMS‐EMG values in the 400–500 ms following 450 ms train stimuli may not be directly linked to pain and may not be affected by the location of the stimulation in the oro‐facial areas used in this study. This is particularly likely to happen if a long‐duration pulse is used (10); if a train of high frequency and short‐duration pulses are delivered, the reflex threshold decreases, falling below the pain threshold. This is in accordance with our previous study (22), when non‐painful ultra‐long (450 ms pulse train) stimuli were used in settings for the contingent electrical stimulation applied to temporalis muscle to reduce the EMG activity during sleep.…”

Neurophysiological evidence for generalized sensory neuronopathy in cerebellar ataxia with neuropathy and bilateral vestibular areflexia syndrome

“…Median nerve somatosensory evoked potentials (SSEPs) and brainstem auditory evoked responses (BAERs; Keypoint Classic; Medtronic, Skovlunde, Denmark) were recorded using previously established protocols. Small (Aδ) fiber involvement was assessed by measurement of the cutaneous silent period (CSP) in the upper and lower limbs bilaterally . We randomly chose left‐ or right‐sided data for the limb (non‐cranial region) studies in our analysis and tested both sides for confirmation that the abnormality was bilateral.…”

Cutaneous silent periods

“…Trigeminal stimulation produces silent periods (SPs) in a variety of cranial muscles, as recently reviewed 2. The masseteric inhibitory reflex (MIR) refers to silent periods that occur bilaterally in the active masseter muscle following stimulation of the face, gums, or teeth 49. The MIR has certain similarities to CSPs in limb muscles.…”