Meniere's Disease Part 1 - Definition, Etiology, Pathophysiology & Histopathology
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👂 Meniere's Disease - Definition, Etiology & Pathophysiology
📝 Definition of Meniere's Disease
Meniere's disease is an idiopathic inner ear disorder characterized by recurrent spontaneous vertigo, accompanied by fluctuating or progressive sensorineural hearing loss, tinnitus and aural fullness in the affected ear, occurring due to distension of the endolymphatic system.
What does the term Idiopathic mean?
👨⚕️ Eponym
Named after Prosper Meniere, who first reported the disease.
📊 Epidemiology of Meniere's Disease
| Parameter | Detail |
|---|---|
| Incidence | 7.5 to 157 per 1 lakh persons |
| Race | More common in Caucasians |
| Age | 2nd to 6th decade of life |
| Sex | No sex preponderance; equal incidence in males and females |
| Laterality | Mostly unilateral |
What is the prevalence of Meniere's disease in the pediatric age group?
What is the percentage of Bilateral involvement of Meniere's disease?
What is the percentage of sporadic and familial Meniere's disease?
What are the Features of Familial Meniere's Disease?
What are the Genes Associated with Meniere's Disease?
⚖️ Meniere's Disease vs Meniere's Syndrome
Distension of the endolymphatic system is termed endolymphatic hydrops.
| Feature | Meniere's Disease | Meniere's Syndrome |
|---|---|---|
| Type of hydrops | Primary (idiopathic) endolymphatic hydrops | Secondary endolymphatic hydrops |
| Underlying cause | No identifiable cause | Identifiable underlying cause present |
| Clinical features | Same | Same |
What are the causes of Meniere's Syndrome?
🔍 Etiology of Meniere's Disease
1- Endolymphatic Hydrops
⭐ The main etiological factor.
Distension of the endolymphatic system occurs due to an increased volume of endolymph, which may result from:
a. Increased production of endolymph
b. Reduced or faulty absorption of endolymph
c. Both occurring together
What is the Sequence of Events leading to the development of vertigo in Meniere's disease?
⚠️ Endolymphatic hydrops is not pathognomonic of Meniere's disease, as it is seen in other conditions too.
What other conditions do you see Endolymphatic hydrops in?
2- Autoimmune Factor
What are the Theories of Autoimmunity in Meniere's disease?
Why is an Autoimmune etiology considered in Meniere's disease?
3- Viral Factor
What is the most common virus associated with Meniere's disease?
4- Allergy
Potential Mechanisms
- The endolymphatic sac is targeted by the allergic reaction
- Deposition of circulating immune complexes in the fenestrated blood vessels of the endolymphatic sac and the stria vascularis
- Viral antigen and allergic interaction, with T cell homing to the endolymphatic sac
5- Vasomotor Disturbance
How does vasomotor disturbance cause Meniere's disease?
6- Hormonal Factor
⭐ About 3% of cases are associated with hypothyroidism, and these patients often benefit from thyroid replacement therapy.
🧠 Pathophysiology of Meniere's Disease
Increased production or faulty absorption of endolymph
→ Increased volume of endolymph
→ Distension of the endolymphatic system
→ Thinning and atrophy of the Reissner's membrane, which bulges into the scala vestibuli
→ Rupture of the Reissner's membrane, with sudden release of a large volume of endolymph into the perilymphatic space
→ Sensory and neural structures exposed to potassium rich endolymph
→ Sudden hearing loss and vertigo
→ Excess pressure is released and the perilymphatic compartment is restored to normal
→ Symptoms subside and the patient goes into remission
→ The rupture heals, pressure builds up again and the whole cycle repeats
What are the Histopathological changes seen in Meniere's Disease?
🧠 Viva Pearls
- Meniere's disease is an idiopathic inner ear disorder due to distension of the endolymphatic system.
- Named after Prosper Meniere.
- Most common in the 2nd to 6th decade of life, with no sex preponderance.
- Mostly unilateral.
- Meniere's disease is primary (idiopathic) endolymphatic hydrops.
- Meniere's syndrome is secondary endolymphatic hydrops with an identifiable cause.
- Endolymphatic hydrops is not pathognomonic of Meniere's disease.
- Increased endolymph volume results from increased production or faulty absorption.
- Reissner's membrane bulges into the scala vestibuli and may rupture.
- Rupture causes mixing of endolymph and perilymph, producing an attack of vertigo.
- Bulging may herniate through the helicotrema into the apical part of the scala tympani.
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