What is a carotid bruit?

Carotid Bruit: Definition and Clinical Significance

A carotid bruit is an innocent murmur with a medium-pitched, harsh character heard at the right or left upper sternal border, supraclavicular region, or anterior portion of the lower neck that disappears with bilateral shoulder hyperextension. 1

Characteristics of Carotid Bruits

• Sound quality: Medium-pitched, harsh sound detected during auscultation
• Location: Typically heard at the upper sternal border, supraclavicular region, or anterior portion of the lower neck
• Distinguishing feature: Disappears with bilateral shoulder hyperextension
• Auscultation technique: Best detected using the bell of the stethoscope positioned over the carotid artery just medial to the sternocleidomastoid muscle 2

Clinical Significance

Carotid bruits are often associated with carotid artery stenosis, though the relationship is not straightforward:

• Moderate predictive value: A carotid bruit has moderate value for detecting clinically relevant carotid stenosis (>70%), with high specificity (83%) but low sensitivity (53%) 3
• False positives: Normal carotid arteries are found in approximately 32% of patients with a bruit 4
• False negatives: The false negative rate for severe disease is approximately 43%, meaning many patients with significant stenosis have no bruit 4
• Non-linear relationship: The likelihood of a carotid bruit does not necessarily increase with increasing degrees of stenosis 3 - bruits may be absent in very high-grade stenosis or complete occlusion 5

Differential Diagnosis

When auscultating the neck, it's important to distinguish carotid bruits from other sounds:

• Venous hum: Medium-pitched, blowing sound with diastolic accentuation that disappears with jugular venous compression or supine position 2
• Mammary souffle: Continuous flow with systolic accentuation heard over breasts that disappears with compression of breast tissue 2
• Transmitted cardiac murmurs: Can be mistaken for carotid bruits 5
• External carotid artery turbulence: May be the true source of some bruits rather than internal carotid disease 5

Clinical Implications

When a carotid bruit is detected:

• Further evaluation: Carotid duplex ultrasonography is the recommended initial diagnostic test for suspected carotid stenosis 1, 2
• Diagnostic accuracy: Duplex carotid Doppler has approximately 90% sensitivity and 94% specificity in identifying clinically significant (>70%) stenosis 1
• Limitations of bruit auscultation: While useful as a screening tool (negative predictive value of 97%), the positive predictive value of a bruit for significant stenosis is only about 27% 6

Important Considerations

• All patients with suspected carotid territory ischemia should be referred for assessment whether a bruit is present or not 4
• The absence of a bruit does not rule out significant carotid stenosis
• Additional imaging modalities (CTA, MRA) may be necessary when ultrasound findings are equivocal or when planning interventions 1

Carotid bruits remain a useful clinical finding that should prompt further investigation with more definitive imaging studies, particularly in patients with cerebrovascular risk factors or symptoms.