Neuro-Otology

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• Publisher: Elsevier
• Year: 2016
• ISBN:
  9780444634474
• Topic: Medicine
• Subtopic: Neurology

Neuro-Otology: a volume in the Handbook of Clinical Neurology series, provides a comprehensive translational reference on the disorders of the peripheral and central vestibular system. The volume is aimed at serving clinical neurologists who wish to know the most current established information related to dizziness and disequilibrium from a clinical, yet scholarly, perspective.

This handbook sets the new standard for comprehensive multi-authored textbooks in the field of neuro-otology. The volume is divided into three sections, including basic aspects, diagnostic and therapeutic management, and neuro-otologic disorders. Internationally acclaimed chapter authors represent a broad spectrum of areas of expertise, chosen for their ability to write clearly and concisely with an eye toward a clinical audience.

The Basic Aspects section is brief and covers the material in sufficient depth necessary for understanding later translational and clinical material. The Diagnostic and Therapeutic Management section covers all of the essential topics in the evaluation and treatment of patients with dizziness and disequilibrium. The section on Neuro-otologic Disorders is the largest portion of the volume and addresses every major diagnostic category in the field.

• Synthesizes widely dispersed information on the anatomy and physiology of neuro-otologic conditions into one comprehensive resource
• Features input from renowned international authors in basic science, otology, and neuroscience
• Presents the latest assessment of the techniques needed to diagnose and treat patients with dizziness, vertigo, and imbalance
• Provides the reader with an updated, in-depth review of the clinically relevant science and the clinical approach to those disorders of the peripheral and central vestibular system

Chapter 1

Anatomy, physiology, and physics of the peripheral vestibular system

H. Kingma*; R. van de Berg Department of Oto-Rhino-Laryngology and Head and Neck Surgery, Maastricht University Medical Centre, Maastricht, the Netherlands and Faculty of Physics, National Research State University Tomsk, Tomsk, Russian Federation
^* Correspondence to: Herman Kingma, Department of ORL and Head and Neck Surgery, Maastricht University Medical Centre, Maastricht, the Netherlands. email address: [email protected]

Abstract

Many medical doctors consider vertigo and dizziness as the major, almost obligatory complaints in patients with vestibular disorders. In this chapter, we will explain that vestibular disorders result in much more diverse and complex complaints. Many of these other complaints are unfortunately often misinterpreted and incorrectly classified as psychogenic. When we really understand the function of the vestibular system, it becomes quite obvious why patients with vestibular disorders complain about a loss of visual acuity, imbalance, fear of falling, cognitive and attentional problems, fatigue that persists even when the vertigo attacks and dizziness decreases or even disappears. Another interesting new aspect in this chapter is that we explain why the function of the otolith system is so important, and that it is a mistake to focus on the function of the semicircular canals only, especially when we want to understand why some patients seem to suffer more than others from the loss of canal function as objectified by reduced caloric responses.

Keywords

vertigo; dynamic visual acuity; balance and posture; semicircular canals; otolith or statolith system

Introduction

In their preface to the book, Mammalian Vestibular Physiology, published in 1979, the famous vestibular scientists Wilson and Melvill Jones made a perceptive statement: “It is easy to underrate the importance of a sensory system whose receptor is buried deep within the skull and of whose performance we are usually not aware” (Wilson and Melvill Jones, 1979). This statement is still up to date, as many doctors are unaware of the relevance of the vestibular system in daily life and also think that central compensation and sensory substitution almost completely deal with vestibular loss and reduce complaints to a minimum. Also, in unilateral loss, it is often stated that the healthy labyrinth will take over. How absurd such a statement is, becomes clear if we claim that losing one ear or one eye is of no importance as we can still hear with one ear and see with one eye. Losing one vestibular organ, like losing one ear or eye, results in a disturbing asymmetry. Bilateral vestibular areflexia (there is not even a common word for it in lay language) is a major handicap like deafness or blindness. But apparently, symptoms associated with bilateral vestibular areflexia are often not recognized, leading to a delay of many years before a correct diagnosis is made (van de Berg et al., 2011; Guinand et al., 2015a; Guyot, 2015). The major reason is that the function of the vestibular system is poorly understood by both doctors and patients. This unawareness also led to problems in obtaining permission to develop a vestibular implant for humans, very different from the development of cochlear implants several decades ago. Only after publication of a number of scientific articles showing the impact and incidence of severe bilateral vestibular loss was a Swiss–Dutch research team allowed to execute the first human vestibular implantation in August 2012 (Pelizzone et al., 2014; Perez Fornos et al., 2014; Guinand et al., 2015b).

This all illustrates how poorly the function and relevance of the vestibular system is understood in clinical practice, and this is what has motivated us to write this chapter in the hope that the real value of this complex vestibular system in human life will become obvious for everyone and that this awareness can lead to an earlier diagnosis and better patient management.

A major misperception is that vertigo is the major vestibular symptom of a peripheral vestibular function disturbance, which only holds for abrupt asymmetries of vestibular function. A slowly decreasing or relatively stable but permanent function loss is more frequent (e.g., aging) and – despite central compensation and sensory substitution – leads to a diversity of other complaints due to the impaired ability of the normally extremely sensitive labyrinthine sensors to detect head motion and head orientation relative to gravity (Kingma and Janssen, 2013). These persisting complaints are: a loss of visual (dynamic) acuity, imbalance, fear of falling and actual falls, visual vertigo, chronically enhanced cognitive load, and fatigue reflecting the various functions of the labyrinth.

To serve all disciplines, we choose a multidisciplinary approach, including clinical sciences, physiology, and physics.

General introduction to the labyrinth

The two balance organs located in the left and right temporal bone of the skull, the vestibular nerves, the vestibular nuclei, the vestibulocerebellum, and the vestibular cortex are not the only but the major structures that together form the vestibular system. In this chapter we will focus on the balance organs providing sensory input to the central vestibular system.

The vestibular system contributes to optimize visual acuity during head motion, enhances balance control, and allows detection of self-motion and orientation relative to gravity. As these tasks are quite complicated in many conditions of daily life, we also use vision, proprioception (including gravity receptors along the large blood vessels), and learning processes. In fact, the brain seems to neglect vestibular input under several conditions when no other sensory input is available to verify the interpretation of motion or spatial orientation (divers in deep, dark water and skiers covered by snow in an avalanche). Only very fast vestibulo-ocular and vestibulospinal reflexes seem to be an exception to this rule. The vestibular system makes use of specialized sensors located in the head to monitor angular accelerations (rotations in three dimensions (3D)) and linear accelerations (translations in 3D and tilt relative to the gravity vector) of the head in space. During head movements, many forces act upon these sensors and often all sensors are stimulated simultaneously. On earth, head movements always occur within the gravitational field and are often composed of both rotations and translations. Physical principles teach us that the position and orientation of the sensors in the head are irrelevant for a precise detection of rotations but crucial for detection of additional translational components and centrifugal forces (Kingma and Janssen, 2013). If we rotate around any axis, both labyrinths will always sense the same rotational acceleration (Fig. 1.1) and translational acceleration. In contrast, centrifugal forces during rotation increase with eccentricity (Fig. 1.2).

Fig. 1.1 A movement of an object is generally the sum of rotations and translations. Any movement can be divided into a rotation around a freely chosen rotation axis combined with an appropriate translation. So, the rotation component of the labyrinth...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Handbook of Clinical Neurology 3rd Series
• Foreword
• Preface
• Contributors
• Chapter 1: Anatomy, physiology, and physics of the peripheral vestibular system
• Chapter 2: Physiology of central pathways
• Chapter 3: Neurotransmitters in the vestibular system
• Chapter 4: Multisensory integration in balance control
• Chapter 5: The epidemiology of dizziness and vertigo
• Chapter 6: Vestibular symptoms and history taking
• Chapter 7: Bedside examination
• Chapter 8: Eye movements in vestibular disorders
• Chapter 9: The caloric irrigation test
• Chapter 10: Vestibular-evoked myogenic potentials
• Chapter 11: Audiometry and other hearing tests
• Chapter 12: Rotational testing
• Chapter 13: An overview of vestibular rehabilitation
• Chapter 14: Principles of vestibular pharmacotherapy
• Chapter 15: Acute unilateral loss of vestibular function
• Chapter 16: Chronic unilateral vestibular loss
• Chapter 17: Bilateral vestibulopathy
• Chapter 18: Benign paroxysmal positional vertigo and its variants
• Chapter 19: Menière's disease
• Chapter 20: Otologic disorders causing dizziness, including surgery for vestibular disorders
• Chapter 21: Posttraumatic dizziness and vertigo
• Chapter 22: Vestibular migraine
• Chapter 23: Ischemic syndromes causing dizziness and vertigo
• Chapter 24: Functional and psychiatric vestibular disorders
• Chapter 25: Vertigo and dizziness in children
• Chapter 26: The conundrum of cervicogenic dizziness
• Chapter 27: Motion sickness
• Chapter 28: Mal de débarquement syndrome
• Index