Retro-labyrinthine Lesion Site Detected by Galvanic Vestibular Stimulation Elicited Vestibular-evoked Myogenic Potentials in Patients with Auditory Neuropathy

Objective Auditory neuropathy(AN)is a unique pattern of hearing loss with preservation of hair cell function.The condition is characterized by the presence of otoacoustic emissions(OAE)or cochlear microphonic(CM)responses with severe abnormalities of the auditory brainstem response(ABR).The vestibular branches of the VIII cranial nerve and the structures innervated by it can also be affected.However,the precise lesion sites in the vestibular system are not well characterized in patients with AN.Methods The air-conducted sound(ACS)vestibular-evoked myogenic potentials(VEMPs)and galvanic vestibular stimuli(GVS)-VEMPs were examined in 14 patients with AN.Results On examination of VEMPs(n=14,28 ears),the absent rates of ACS-cervical VEMP(cVEMP),ACS-ocular VEMP(oVEMP),GVS-cVEMP,GVS-oVEMP and caloric test were 92.9%(26/28),85.7%(24/28),67.9%(19/28),53.6%(15/28),and 61.5%(8/13),respectively.Impaired functions of the saccule,inferior vestibular nerve,utricle,superior vestibular nerve,and horizontal semicircular canal were found in 25.0%(7/28),67.9%(19/28),32.1%(9/28),53.6%(15/28)and 61.5%(8/13)patients,respectively.On comparing the elicited VEMPs parameters of AN patients with those of normal controls,both ACS-VEMPs and GVS-VEMPs showed abnormal results in AN patients(such as,lower presence rates,elevated thresholds,prolonged latencies,and decreased amplitudes).Conclusion The study suggested that patients with AN often have concomitant vestibular disorders.Retro-labyrinthine lesions were more frequently observed in this study.GVS-VEMPs combined with ACS-VEMPs may help identify the lesion sites and facilitate detection of areas of vestibular dysfunction in these patients.

Random noise stimulation in the treatment of patients with neurological disorders

Random noise stimulation technique involves applying any form of energy(for instance,light,mechanical,electrical,sound)with unpredictable intensities through time to the brain or sensory receptors to enhance sensory,motor,or cognitive functions.Random noise stimulation initially employed mechanical noise in auditory and cutaneous stimuli,but electrical energies applied to the brain or the skin are becoming more frequent,with a series of clinical applications.Indeed,recent evidence shows that transcranial random noise stimulation can increase corticospinal excitability,improve cognitive/motor performance,and produce beneficial aftereffects at the behavioral and psychological levels.Here,we present a narrative review about the potential uses of random noise stimulation to treat neurological disorders,including attention deficit hyperactivity disorder,schizophrenia,amblyopia,myopia,tinnitus,multiple sclerosis,post-stroke,vestibular-postural disorders,and sensitivity loss.Many of the reviewed studies reveal that the optimal way to deliver random noise stimulation-based therapies is with the concomitant use of neurological and neuropsychological assessments to validate the beneficial aftereffects.In addition,we highlight the requirement of more randomized controlled trials and more physiological studies of random noise stimulation to discover another optimal way to perform the random noise stimulation interventions.