Why Cardiovascular Health Should Be Added to the Hearing Case History

Figure: © iStock/Blend_Images

The relationship between cardiovascular health and hearing is strong, and has been confirmed by a sizeable number of investigators. Therefore, if the case history of the audiologist's patient is to be complete, it should include cardiovascular health.

Figure: Dr. Hull

The case history should ask questions about coronary infarction, heart surgery as a result of coronary blockage, congenital heart conditions, vascular hypertension, and related disorders.

Here's why: Heart disease, hypertension, or any other restriction of blood supply to the peripheral and central auditory system can reflect itself in terms of audiometry and communication, and can be progressive in nature.

EXTENDS TO YOUNGER ADULTS

The association of human cardiovascular health with the peripheral and central auditory systems, including cognitive ability into advanced age, was first shown 80 years ago by the work of Bunch and Raiford¹ and of Crowe, Guild, and Polvogt.² A restriction of blood supply can compound other damaging influences, including noise, injury, and disease.^1-13

For example, Rubinstein, Hildesheimer, Zohar, and Chilarovitz found that adults who had cardiovascular disease and signs of peripheral circulation disorders had significantly poorer thresholds in the 500-Hz to 8,000-Hz frequency range compared with participants who did not have cardiovascular disease.⁹

Even among younger adults, there seems to be a relationship between early-onset arteriosclerosis and changes within the cochlea.

Nomiya et al compared temporal bones of six young adults who had arteriosclerosis with temporal bones from seven age-matched patients without arteriosclerosis.¹⁴

The temporal bones from the arteriosclerosis group possessed significantly fewer ganglion cells at the basal turn of the cochlea and had an atrophic spiral ganglion, which typically is associated with high-frequency sensorineural hearing loss. However, audiograms had not been obtained on the arteriosclerotic subjects.

Additional work has focused on the relationship between circulation and hearing loss.

For example, Schuknecht and Gacek believed that varying degrees of degenerative changes in the cochlea are attributable, at least in part, to changes in blood supply to the peripheral and central auditory systems over time.⁷

They stressed that any degeneration in the stria vascularis can affect the quality of the endolymph, which, in turn, can disrupt the processes by which electrochemical energy is created within the organ of Corti.

Along the same lines, Johnsson and Hawkins confirmed a positive relationship between stria vascularis atrophy and degenerative changes along the basilar membrane, which contribute to a decline in the electrosensory function of the cochlea.³

Other early work by Fisch, Dobozi, and Greig,¹⁵ as well as by Makishima,⁴ studied degenerative changes within the internal auditory artery. The investigators correlated the extent of narrowing of the internal auditory artery with atrophy of the spiral ganglion and degree of hearing loss.

CENTRAL AUDITORY INVOLVEMENT

The consequences of a decline in cardiovascular health are not restricted to the peripheral auditory system. The central auditory pathways also can be affected.

The involvement of the central auditory pathways can compound the sensorineural symptoms of impaired hearing, exacerbating not only individual difficulties in speech understanding but also the ability to process the phonemic elements of spoken speech with the speed and accuracy necessary for decoding.

Several studies have addressed the relationship between the central nervous system auditory pathways and cardiovascular health, as Stacy R. Kerschen and I have noted.¹⁶

These investigations have postulated a positive relationship between cardiovascular health and the structure and function of the brainstem auditory pathways and auditory cortex.^12,17-22

EFFECTS ON COGNITION

Research also has uncovered relationships among cardiovascular health, cognitive function, and aging.^13,20,21,23

For example, a study by Kramer et al suggests that the impact of age and cardiovascular health on the frontal and prefrontal areas of the brain can lead to significant changes in the control of executive processing, negatively influencing the speed and accuracy of decision making, higher language processing, and other similar executive language-based abilities.²⁰

Further, a comparative literature review by Colcome and Kramer showed consistently similar results.²¹ The analysis concluded that improvements in cardiovascular health will likewise improve cognitive function in older adults.

The authors took their conclusion a step further, stating, “Cardiovascular improvements might even ‘turn back the clock,’ biologically speaking, and lead to patterns of neurocognitive activation that are more similar to the patterns of young adults.”

This possibility prompts a rather thought-provoking question that would be interesting to investigate: Could better cardiovascular health, therefore, become a new component of a patient's aural rehabilitation program?

CAUTION: RED FLAGS

Given the strength and consistency of the relationship between cardiovascular health and the nature and degree of peripheral and central hearing loss, cardiovascular disease should be included in the case history information provided by the audiology patient.

In addition to the obvious inclusion of coronary blockage, congenital heart disease, and heart surgery in the case history, several other disease processes that potentially relate to peripheral or central hearing loss should also be considered red flags by the audiologist.

• Diabetes: Among people with diabetes who are between age 40 and 69, about 67 percent have high-frequency hearing loss, and one-third have low- or mid-frequency sensorineural hearing loss.

Since diabetic complications can include hypertensive retinopathy, nephropathy, and peripheral arterial disease, all of which are vascular in origin, the cochlea, and even the central auditory pathways, also can be involved.^24,25

• Thrombosis of the anterior inferior cerebellar artery, a branch of the basilar artery, has been found to affect almost all the structures of the brainstem, including auditory pathways and nuclei, as well as the VIIIth nerve.

Vestibulo-cochlear damage, due to involvement of the cochlear and vestibular nuclei as a result of brainstem infarction, is also noted in patients with thrombosis of the anterior inferior cerebellar artery.²⁶

• Pulsatile tinnitus: Patients with vascular abnormalities may complain of pulsatile tinnitus. Pulsing arterial sounds may be transmitted to the ear from arterial vessels near the temporal bone. The petrous carotid system is the most common source. Patients notice the tinnitus most at night and may have no other otologic symptoms.^27,28
• Sudden onset of sensorineural hearing loss is a medical emergency, but reaching a definitive medical diagnosis of the cause can be difficult.

There are a number of possible causes, including infectious diseases, particularly those of a viral nature; autoimmune diseases; and perilymphatic fistula. A vascular cause is always considered. Immediate physician referral is critical.²⁹

• Hypertensive retinopathy, which is described as end-organ damage of the vascular system due to chronic high blood pressure, has been substantiated as a cause of sensorineural hearing loss, particularly at high frequencies, although decreased hearing for other frequencies is found as well.

In patients with Grade I retinopathy, the poorest thresholds are seen at 4 kHz and 8 kHz.^30,31

A CASE FOR CARDIOVASCULAR HEALTH

In other words, it appears that the audiologist would do well to include the patient's cardiovascular health as part of the intake exam.

Of course, relying on the patient's memory can be risky in terms of ensuring accuracy, but most aspects of a rather dramatic occurrence such as a heart attack or a history of high blood pressure will likely be recalled by the patient, patient's spouse, or other family member.

Further, as stated by Richard Navarro, “While it is uncommon for hearing healthcare practitioners to measure a patient's blood pressure, there is no reason why this step should not be a routine part of the intake exam, particularly for patients being seen for dizziness or tinnitus,” or for a rather sudden increase of hearing loss.³²

For more information about cardiovascular disease and hearing healthcare, see our coverage on page 20 of the June 2013 issue, available athttp://www.bit.ly/HJ-CVD

References on Tap

Access the hyperlinks (shown in gray) in this article and throughout the issue by reading it on HJ's free iPad app: http://bit.ly/AppHearingJ.