The evaluation of the sense of hearing in patients with carotid artery stenosis within the extracranial segments

Stenosis of arteries that supplies blood to the brain is one of the main causes of ischemic stroke which is the third most common cause of deaths in Europe. Atherosclerosis of carotid and vertebral arteries is responsible for 20% of the ischemic stroke cases. Stenosis may be either asymptomatic or manifested with typical neurological symptoms including motor and sensory disturbances as well as disturbances in vision and speech. However, discrete non-specific symptoms of ischemia, including headaches and vertigo, tinnitus and hearing loss, are also quite common. These symptoms may be indicative of a clinically significant stenosis of carotid and vertebral arteries, particularly within the internal carotid artery region, as well as of a risk of ischemic stroke. To date, research reports were unable to provide exact explanation of correlations between impaired hearing and the stenosis of carotid and vertebral arteries. Despite this, numerous articles list these symptoms as one of the first non-specific symptoms of this disorder. The ischemic mechanism within the inner ear region may lead to early symptoms of atherosclerosis of large vessels. However, no evidence of relationship and no explanation could be provided with this regard. The objective of the study was to assess the effect of carotid and vertebral artery stenosis on the function of the hearing and equilibrium organ on the basis of diagnostic audiological examinations including pure-tone threshold audiometry, impedance audiometry, otoacoustic emission tests and brainstem auditory evoked potential tests. The study was conducted in 63 patients (32 males, 31 females) aged 45–75 years, presenting with carotid and vertebral artery stenosis and treated at the Vascular Surgery Clinic of the University Clinical Hospital in Wrocław. Patients were stratified into two subgroups according to their age (45–60 years, 61–75 years). Patients were also divided into subgroups according to the stenotic arteries and to the symptomatic/asymptomatic status of the disorder. All patients were homogeneous in terms of the degree of artery stenosis. The control group consisted of 32 healthy persons (14 males, 18 females) aged 48–75 years. Patients qualified to the control group reported no history of middle or inner ear disorders, disturbed hearing, vertigo and balance disorders, as well as cardiovascular diseases; they also presented with unremarkable ultrasound scans of the arteries. All patients were subjected to precise audiological examinations. Prior to being qualified for the study, patients were subjected to the assessment of arteries by means of Doppler ultrasonography. The hearing organ function was assessed by means of pure-tone threshold audiometry, impedance audiometry, otoacoustic emission tests and brainstem auditory evoked potential tests. Reduction of the flow through the carotid arteries causes problems in the organ of hearing; abnormalities are reported especially in tone threshold audiometry, examinations of the stapedius muscle reflexes and brainstem auditory evoked potentials, which prove the presence of receptive cochlear–extracochlear hearing damage. Disturbances of the organ of hearing have similar severity in stenosis of the internal carotid artery and vertebral artery. Abnormalities found in audiologic examinations in patients with carotid artery stenosis are not always explicitly clinically expressed in patients with hearing loss; we should consider diagnostics for carotid artery stenosis.