Читать книгу Advances in Neurolaryngology - Группа авторов - Страница 59

Nerve conduction studies play an important role in diagnostics of neuropathies of peripheral nerves of the upper and lower limbs. LEMG only analyses the recorded muscle and gives indirect information about the related nerve. Due to the short distances and the anatomical situation of the laryngeal nerves, nerve conductions studies allowing a direct investigation of the laryngeal nerves are not established yet for the clinical routine. Current experimental techniques are hampered by volume conduction from stimulation in the neck and the inability to record compound muscle action potentials in the intrinsic laryngeal muscles transcutaneously through the thyroid cartilage [3]. Recently, a novel conduction study of the laryngeal nerves using the laryngeal closure reflex was established [26, 27]. The laryngeal mucosa in the sensory territory of the superior laryngeal nerve was stimulated by a wire inserted via a transnasal flexible laryngoscope. The stimulus was delivered through the working channel of the laryngoscope. Bilateral hookwire electrodes recorded the result in the TA. They revealed normal values ipsilateral to the side of stimulation (LR1; right 13.2 ± 0.80 ms; left 15.2 ± 1.20 ms), and late bilateral responses (ipsilateral LR2 [LR2i] and contralateral LR2 [LR2c]), with greater variation in latency and morphology (right LR2i 50.5 ± 3.38 ms; left LR2i 52.2 ± 3.32 ms; right LR2c 50.7 ± 4.26; left LR2c 50.6 ± 4.07), right similar to the blink reflex. Nerve conduction testing resulted in significant delay in patients with VFP. Reflex testing will open up new indications for LEMG in the future. There are several laryngeal reflex systems with sensory-motor reflex responses involving glossopharyngeal, pharyngeal, laryngeal, and tracheobronchial sensory receptors. Reflex testing will allow for the diagnosis of sensory reductions, as well as sensory hypersensitivity may account for laryngeal disorders such as chronic cough, paradoxical vocal fold disorder and muscular tension dysphonia [28].

Other important future directions are more LEMG studies to understand the natural history and mechanisms of laryngeal synkinesis. Further research should help to ultimately minimize this process through rehabilitative training or medications [3]. Finally, we need more international standardization in LEMG, possibly a tool for quantitative and automated LEMG analysis, and prospective trials showing the effect of LEMG on clinical decision making and outcome.