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Considerations on Anatomy and Pathophysiological Notions Concerning the Inner Ear

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Considerations on Anatomy and Pathophysiological Notions Concerning the Inner Ear Archives of the Balkan Medical Union vol. 52, no. 1, pp. 50-56 Copyright © 2017 Balkan Medical Union March 2017 REVIEW CONSIDERATIONS ON ANATOMY AND PATHOPHYSIOLOGICAL NOTIONS CONCERNING THE INNER EAR Iulia M. Burghiu-Hobeanu1, Viorel Zainea2,3 1 Clinical Emergency Hospital „St. Pantelimon”, Bucharest, Romania 2 University of Medicine and Pharmacy „Carol Davila”, Bucharest, Romania 3 Institute of Phonoaudiology and Functional ENT Surgery „Prof. Dr. D. Hociota”, Bucharest, Romania ABSTRACT RÉSUMÉ Sudden hearing loss is a medical emergency requiring Considérations sur l’anatomie et notions pathophy- immediate clinical and laboratory tests, as well as an siologiques concernant l’oreille interne adequate and quickly established treatment. Sudden hearing loss is disabling for the patient and its perma- La surdité brusquement installée est une urgence mé- nence has implications on the patient’s quality of life. dicale nécessitant des investigations cliniques et para- According to literature data, the earliness of treatment cliniques immédiates, ainsi qu’un traitement approprié initiation is directly correlated to therapeutic results. et rapidement installé. L’hypoacousie brusque est inva- An individual response to therapy exists, which is due lidante pour le patient et sa permanence a des implica- to anatomical particularities: individual vascular pat- tions sur la qualité de vie de celui-ci. Conformément tern, poor vascularity and fragility of cochlear vascular- aux données de la littérature, la précocité du début du ization, as well as the existence of some malformations. traitement est directement corrélée aux résultats théra- The knowledge of the pathophysiological mechanisms peutiques. La réponse à la thérapie est individuelle en of brain ischemia led to a new paradigm in the modern raison des particularités anatomiques: le terrain vascu- therapeutic protocols for acute and aggravated stroke: laire individuel, la vascularité pauci-immune et la fra- the neural growth factors. Nerve growth factors are a gilité de la vascularité cochléaire, ainsi que l’existence modern and advanced therapeutic approach through des malformations. La connaissance des mécanismes multimodal effects: neuroprotector, neurotrophic and physiopathologiques de l’ischémie cérébrale a conduit neuroregenerative effects. à un nouveau paradigme dans les protocoles thérapeu- tiques modernes pour les micro-accidents vasculaires Key words: cochlear vasculature, nerve growth factor, cérébraux ischémiques aigus et aggravés : les facteurs cochlear ischemia, sudden hearing loss treatment. de croissance nerveuse. Les facteurs de croissance nerveux représentent une approche thérapeutique Abbreviations: NGF – Nerve growth factor, moderne et prometteuse, par ses effets multimodaux, SHL – Sudden hearing loss, BDNF – Brain-derived Correspondence address: Iulia-Mihaela Burghiu-Hobeanu, M.D. e-mail: [email protected] ENT Compartment, Clinical Emergency Hospital „St. Pantelimon“ Archives of the Balkan Medical Union neurotrophic factor, AICA – anterior-inferior cerebel- parmi lesquels on mentionne: l’effet neuroprotecteur, lar artery, LTP/LDP – long-term potentiation/depres- neurotrophique et neurorégénérateur. sion, Ang 1 – Angiopoietin 1, tPA – tissue plasminogen activator, Shh – Sonic Hedgehog, miRs – microRNAs. Mots-clefs: vascularité cochléaire, facteur de crois- sance nerveuse, ischémie cochléaire , traitement d’hy- poacousie. INTRODUCTION one irrigating the middle ear and the bony labyrinth. However, in several cases, it was observed at the level Sudden hearing loss is a medical emergency of the inner ear canal the presence of a cerebellar requiring immediate clinical and laboratory tests, anse disposed between nerves VII-VIII and called ar- as well as an adequate and quickly established treat- cuate artery (Characon)5. It is the only anastomosis be- ment1. Sudden hearing loss is disabling for the pa- tween the inner and middle ear vascularization and tient and its permanence has implications on the pa- explains the relationship between the tubo-tympanic tient’s quality of life. According to literature data, the diseases and the cochlear-vestibular system. This ar- earliness of treatment initiation is directly correlated cuate artery arises from the middle cerebellar artery, to therapeutic results2. after exceeds the posterior edge of the acoustic-facial Sudden hearing loss treatment is one of the package, at several millimeters distance from the most controversial issue in otology literature in the labyrinthine artery, and which penetrates into the past years3. Regarding etiology, sudden hearing loss petro-mastoid canal where it branches on the internal is a cochlear vasculopathy with multiple pathological wall of the mastoid antrum5. mechanisms: spasm, thrombosis, embolism, hemor- rhage. This theory is sustained by the anatomy of ARTERIAL VASCULATURE OF INNER EAR the cochlea, as well as the frequent association with different cardiovascular diseases (arterial hyperten- Arterial vasculature of the membranous sion, atrial fibrillation, carotid atheromatosis). The labyrinth originates from the vessels situated within changes of cerebral vasculature and the default of the cranial cavity, being ensured through the laby- the cochlear vasculature can be highlighted through rinthine artery (internal auditory artery), which imaging studies like Doppler carotid and vertebral often is a branch of the anterior-inferior cerebellar ar- ultrasound and angio-MRI. The correct diagnosis tery (AICA). The anterior-inferior cerebellar artery of the etiology is very important to establish an ade- is a branch of the basilar artery (basilar trunk), issued quate treatment4. from the union of the two vertebral arteries, which Treatment of sudden hearing loss must be cho- are branches of the subclavian artery5. sen from a variety of therapeutic solutions and should According to Guerrier, in 17.5 % of cases, the be individualized depending on the pathogenic con- labyrinthine artery may be detached from the basi- ditions of each patient4. The therapeutic results de- lar artery or more rarely, from the vertebral artery. pend on many factors such as the time until presen- The anterior-inferior cerebellar artery may have the tation to medical exam, the degree of hearing loss, following relationships with the acoustic-facial pedi- the presence of other comorbidities. An individual cle, as mentioned by Guerrier: response to therapy exists, which is due to anatomical anterior – the most frequently – the common particularities. There is mild hearing loss rebellious trunk of the middle cerebellar artery and labyrin- to treatment and severe hearing loss that answers thine artery is divided at large distance from the spectacular to medical treatment. The evolution of inner ear canal, the recurrent branches arising each case depends on individual vascular pattern, from the common trunk or from the middle cere- poor vascularity and fragility of cochlear vasculariza- bellar artery itself; tion, as well as the existence of some malformations. median – less frequently – the common trunk The fundamental and comparative studies regarding is divided in the vicinity of the facial nerve, into embryology, anatomy and physiology of the cochlea two branches: the middle cerebellar artery and the and cochlear vestibular nerve still remain full of un- cerebellar-labyrinthine artery; known aspects. posterior – the common trunk is very short and The anatomical studies showed that inner ear’s immediately bifurcates, after crossing the external vascularity is composed of arteries and veins, while oculomotor nerve, in the middle cerebellar artery, the lymphatic vascularity is still unknown. The in- which slides back, and the cerebellar-labyrinthine ner ear’s vascularity is generally separated from the artery; the cerebellar-labyrinthine artery will divide March 2017 / 51 Considerations on anatomy and pathophysiological notions concerning the inner ear – BURGHIU-HOBEANU et al in the internal auditory artery and two recurrent vessels, which makes them very fragile, so that they cerebellar branches, which will form two storeyed can be damaged at the smallest injury6. anses advance-back, passing one over and the oth- The complete model of cochlea vascularization er beneath the nerve VIII. From the anterior re- incited numerous discussions, some of the schemes current branch arises the internal auditory artery. widely accepted in the scientific literature is the one The origin of the auditory artery can be variable, presented by Hawkins (1968) as follows6,7: according to Mazzoni (1969)6: the main cochlear artery vascularizes ¾ of the co- In 80% of cases it is a main branch of the anteri- chlea, including the modiolus; or-inferior cerebellar artery. the cochlear branch irrigates ¼ from the basal In 17% of cases it is a branch of the basilar artery. trunk of the cochlea and adjacent modiolus; in 3% of cases it is a branch of the vertebral artery. the anterior vestibular artery irrigates the utricle’s Localization of the labyrinthine artery in the re- macula, a small part of the saccule’s macula, the gion of inner ear canal also presents a high individual crista and membranous portions of the superior variability, as demonstrated by Mazzoni in a study and lateral semi-circular canals, the upper face of made on 100 human specimens, as follows6: utricle and saccule; 40% of cases within inner ear canal; the posterior vestibular artery irrigates the macula 27% of cases at the level of the internal acoustic of saccule,
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