Dizziness and Vertigo Across the Lifespan

Bradley W. Kesser, A. Tucker Gleason

• Editorial: Elsevier
• Año: 2018
• ISBN:
  9780323551373
• Categoría: Medicine
• Categoría: Ear, Nose & Throat Medicine

Get a quick, expert overview of dizziness and vertigo from childhood through old age with this concise, practical resource. Drs. Bradley W. Kesser and Tucker Gleason have assembled a leading team of experts to address timely clinical topics of interest to otolarynologists and other health care providers who see patients with these common problems.

• Covers key topics such as the clinical exam and diagnostic techniques, assessment and differential diagnosis in the pediatric population, dizziness and vertigo in the adolescent and the elderly, evaluation of dizziness in the litigating patient, vHIT, positional vertigo in all age groups, vestibular neuritis, migraine-associated vertigo, Meniere's disease, medication-related dizziness in the older adult, and more.
• Includes information on dizziness demographics and population health, as well as development of the vestibular system and balance function.
• Consolidates today's available information and experience in this important area into one convenient resource.

Section IV

Elderly

Outline

Chapter 15. The Cardiovascular Dizziness Connection: Role of Vestibular Autonomic Interactions in Aging and Dizziness

Chapter 16. Vertebrobasilar Infarcts and Ischemia

Chapter 17. Dizziness in the Elderly

Chapter 18. Medication-Related Dizziness in the Older Adult

Chapter 19. Older Adults With Dizziness: Rehabilitation Strategies and Novel Interventions

Chapter 15

The Cardiovascular Dizziness Connection

Role of Vestibular Autonomic Interactions in Aging and Dizziness

Jorge M. Serrador, PhD

Abstract

Dizziness and vertigo symptoms are common across all ages. Although it is well known that vestibular dysfunction can cause these symptoms, other causes must also be considered. This chapter examines the role of blood pressure and cerebral blood flow regulation and their possible connections to the development of dizziness. Humans have several cardiovascular adaptations that are designed to maintain blood pressure and brain blood flow when upright. The role of the baroreflex in maintaining blood pressure when moving from the supine to upright position is reviewed. Brain blood flow regulation to maintain adequate flow when upright also has been examined. Reductions in brain blood flow have been shown to be associated with the development of dizziness as well as orthostatic hypotension. In addition, there is emerging evidence that the vestibular system assists in this cardiovascular adaptation. Therefore, it is important to consider how vestibular dysfunction may result in orthostatic hypotension or reduced brain blood flow that could cause or worsen symptoms of dizziness.

Keywords

Autonomic; Baroreflex; Cerebral blood flow; Orthostatic; Vestibular

Introduction

Without a doubt, vestibular dysfunction can cause dizziness; however, other systems that interact with the vestibular system can also be involved. The goal of this chapter is to discuss the role of cardiovascular reflexes in contributing to dizziness.

A common symptom that often causes a patient to seek medical attention for the evaluation of dizziness is presyncope: the feeling of “lightheadedness” before fainting. Even young healthy individuals with intact vestibular systems commonly report dizziness and lightheadedness during tilt table testing. Participants generally report dizziness but not true vertigo. So why are these individuals reporting dizziness during an upright tilt?

Although the mechanism remains unclear, the assumption is that reductions in cerebral blood flow (CBF) result in symptoms associated with presyncope. In fact, recent evidence has found that both orthostatic hypotension (decreased blood pressure when standing)¹ and cerebral hypoperfusion (reduction in brain blood flow)² are related to incidents of dizziness. To understand why CBF would be reduced during upright posture requires an understanding of how blood pressure and CBF are regulated when we are standing or when we rise from a supine or seated position. To explore this connection, blood pressure regulation and regulation of brain blood flow are described in this chapter.

In addition, fascinating evolving evidence suggests that the vestibular system provides important signals that assist in the regulation of blood pressure³ and brain blood flow.⁴ This chapter also explores these vestibular connections in the context of their impact on the development of dizziness and vertigo.

Regulation of Blood Pressure

Regulation of blood pressure is essential to health because blood flow through all organs is dependent on adequate driving pressure. To produce that pressure, the heart pumps approximately 86,000 times/day to maintain blood flow and pressure throughout the body. Pressure at the aorta, where blood is ejected from the left ventricle, is determined by the following equation:

MAP=CO×TPR

(15.1)

where MAP is the mean arterial pressure, CO is the cardiac output (total blood flow out of the heart each minute), and TPR is the total peripheral resistance of blood vessels throughout the body. Cardiac output is determined by the heart rate multiplied by the stroke volume, the amount of blood pumped in one contraction of the left ventricle. Thus to maintain adequate pressure we must maintain the stroke volume. Because the heart is a passive pump (i.e., it fills passively), the volume it ejects is based on how much blood is returned to the heart and how forcefully the heart contracts. The return of blood to the heart is determined by a number of properties, but because we are interested in the relationship to dizziness and vertigo, which are symptoms that normally occur when upright, we must consider the importance of the upright posture in cardiovascular regulation.

FIG. 15.1 Distribution of blood when upright in a human versus a quadruped. Note that a significant amount of blood volume is located below the heart in a standing human compared with the quadruped. From Rowell. Human Cardiovascular Control. Oxford University Press; 1993; with permission.

Humans are bipedal and, unlike quadrupeds, during upright standing, there is a significant distance between the head and the feet. This unique posture results in substantial movement of blood from the upper torso to the legs (Fig. 15.1).

Sufficient cardiac output is required to maintain blood pressure (MAP; Eq. 15.1). Cardiac output is the product of heart rate and stroke volume, and stroke volume is determined by venous return (the amount of blood returning to the heart); therefore, assumption of the upright position results in considerable reduction in venous return. The result of this reduction in venous return is a drop in mean arterial blood pressure, which if uncompensated results in syncope (i.e., loss of consciousness). An example of this response was demonstrated in a group of elderly males and females who participated in the Maintenance of Balance, Independent Living, Intellect and Zest in the Elderly (MOBILIZE) Boston study (Fig. 15.2).

Note that within 10 seconds of initiating the stand, the participants had roughly a 20-mmHg drop in mean arterial pressure (MAP). The decrease in pressure was transient, and by 30 seconds the blood pressure had returned to baseline levels. This regulation of blood pressure is essential to maintaining consciousness. Returning to Eq. (15.1), some variables can be modified to maintain pressure. One of these variables is cardiac output, which is dependent on the stroke volume and heart rate. When humans stand upright, there is translocation of blood to the lower limbs and reduction in stroke volume. This results in a reduction in arterial pressure as seen in Fig. 15.2. To return blood pressure to normal levels, there is a need to modify (increase) the heart rate and/or resistance, which is accomplished by the baroreflex.

FIG. 15.2 Changes in heart rate and blood pressure in group of elderly individuals (308 females, 236 males) when moving from a sitting position to a standing position and remaining standing for 1 min. Note the significant decrease in blood pressure upon standing with a compensatory increase in heart rate to return blood pressure to baseline levels...