What causes pulsatile tinnitus in pregnancy?

Causes of Pulsatile Tinnitus in Pregnancy

Pulsatile tinnitus during pregnancy is most commonly caused by cardiovascular changes including increased blood volume, cardiac output, and heart rate, which can lead to altered vascular flow dynamics and increased awareness of normal blood flow through vessels near the ear.

Physiological Mechanisms

Pregnancy induces significant hemodynamic changes that can contribute to pulsatile tinnitus:

• Cardiovascular adaptations:

  • Increased blood volume (40-50% increase by third trimester)
  • Elevated cardiac output (30-50% increase)
  • Increased heart rate (10-20 beats per minute higher than pre-pregnancy)
  • Decreased peripheral vascular resistance

• Hormonal influences:

  • Estrogen and progesterone cause vasodilation
  • Relaxation of vascular smooth muscle

Common Causes of Pulsatile Tinnitus in Pregnancy

1. Increased cerebral blood flow:

   • Heightened awareness of normal vascular sounds due to increased blood flow
   • More pronounced in vessels near the temporal bone

2. Venous causes (14% of pulsatile tinnitus cases 1):

   • Venous hum due to increased venous return
   • Venous anomalies or normal variants becoming symptomatic under increased flow

3. Arterial causes:

   • Increased awareness of carotid artery pulsations
   • Arterial turbulence due to increased cardiac output

4. Pregnancy-associated arrhythmias 2:

   • Supraventricular tachycardias occur in up to 20-44% of pregnancies
   • Arrhythmias become more frequent during pregnancy due to hemodynamic, hormonal, and emotional changes

5. Intracranial hypertension:

   • Pregnancy can exacerbate or trigger idiopathic intracranial hypertension
   • Associated with venous pulsatile tinnitus

Evaluation Algorithm

1. Initial assessment:

   • Determine if tinnitus is truly pulsatile (synchronous with heartbeat)
   • Check if it's unilateral or bilateral
   • Assess for associated symptoms (headache, visual changes, dizziness)

2. Physical examination:

   • Otoscopic examination to rule out visible vascular abnormalities
   • Auscultation of the ear, neck, and skull
   • Check blood pressure and heart rate

3. Basic investigations:

   • Complete blood count to rule out anemia
   • Thyroid function tests to exclude hyperthyroidism
   • ECG if arrhythmia is suspected

4. Advanced imaging (if red flags present):

   • Ultrasound examination of cervical vessels
   • MRI/MRA if concerning symptoms persist or worsen

Management Approach

1. For physiologic pulsatile tinnitus:

   • Reassurance that this is often a normal finding in pregnancy
   • Monitoring of blood pressure and heart rate
   • Positional changes (elevating head while sleeping)

2. For arrhythmia-related tinnitus 2, 3:

   • Rate control with selective beta-blockers (metoprolol) if symptomatic
   • Electrical cardioversion for hemodynamically unstable arrhythmias

3. For intracranial hypertension:

   • Neurological consultation
   • Careful monitoring of symptoms

Important Considerations and Pitfalls

• Persistent or severe pulsatile tinnitus requires thorough evaluation to rule out serious vascular abnormalities 4
• Unilateral pulsatile tinnitus is more concerning than bilateral and warrants closer investigation
• New onset of pulsatile tinnitus with headache may indicate increased intracranial pressure and requires prompt evaluation
• Pulsatile tinnitus with hypertension during pregnancy should raise concern for preeclampsia 5
• Post-partum monitoring is important as some cases may persist or worsen after delivery 3

Prognosis

Most cases of pregnancy-related pulsatile tinnitus are benign and resolve spontaneously after delivery when hemodynamic parameters return to pre-pregnancy state. However, persistent symptoms warrant further investigation to rule out underlying pathology.