Selective stimulation of the equilibrium organ using monochromatic near infrared

BACKGROUND: The aim of this study was, to establish, if a selective thermal warm-stimulation using monochromatic near infrared radiation (NIR) in healthy persons, patients with chronic otitis media (chronic mucosal inflammation) and after radical surgery of one ear shows quantitative or qualitative changes of the nystagmus reaction. PATIENTS AND METHODS: Healthy persons (n = 3), patients with a large central defect of the tympanic membrane (n = 5) and after radical ear surgery (n = 6) were examined. In healthy persons a stimulation with monochromatic NIR (lambda = 980 nm) of several areals of the external auditory canal was performed. In patients with large defects of the tympanic membrane the promontorium was stimulated. In patients with a radical cave of the ear a selective NIR-stimulation of the region of the vertical and the anterior semicircular canal was performed. The horizontal semicircular canal was visible as a landmark. Registration of the nystagmus was performed by means of videonystagmography. RESULTS: In healthy persons the mean slow phase velocity of the nystagmus depended on the stimulated region. But there was no qualitative change of three dimensional eye movement. Stimulation of the promontorium showed a strong directional horizontal nystagmus. In patients with a radical cave the stimulation of the regions of the three semicircular canals showed a qualitative difference in three dimensional eye movement. NIR-stimulation showed in all cases a nystagmus into the stimulated ear. CONCLUSIONS: The method of monochromatic near infrared stimulation can be used for selective stimulation of several regions of the external auditory canal, the promontorium and the regions of the semicircular canals in a radical cave of the ear as well as to prove the warm reaction of the equilibrium organ. A specific nystagmus after stimulation of the semicircular canal-region in a radical cave of the ear could be an indication for a normal semicircular canal function.