What are endolymphatic sac decompression and vestibular nerve section?

Endolymphatic Sac Decompression and Vestibular Nerve Section: Surgical Interventions for Ménière's Disease

Endolymphatic sac decompression and vestibular nerve section are surgical interventions for medically refractory Ménière's disease, with endolymphatic sac decompression being preferred as a first-line surgical option due to its lower risk profile and hearing preservation capabilities. 1, 2

Endolymphatic Sac Decompression

Procedure Overview

• Endolymphatic sac decompression is a surgical procedure that aims to relieve pressure in the inner ear by decompressing the endolymphatic sac, which is thought to maintain hydrostatic pressure and endolymph homeostasis 3
• The procedure involves surgical exposure and decompression of the endolymphatic sac to potentially relieve vertigo symptoms in Ménière's disease 1
• Various modifications exist, including simple decompression, endolymphatic sac enhancement, and endolymphatic sac shunting, all with essentially equivalent therapeutic results 4
• A newer modification called endolymphatic duct and sac decompression (DASD) includes decompression of both the endolymphatic duct and sac from the posterior cranial fossa to the labyrinthine block 5

Risk Profile

• Considered a low-risk procedure with less than 2% incidence of complete sensorineural hearing loss 1
• Rare complications include cerebrospinal fluid leak, facial nerve paralysis, vertigo, and wound infection 4, 1
• The procedure is hearing-preserving, making it suitable for patients who still have usable hearing 4

Efficacy

• Retrospective studies show vertigo control rates ranging from 78% to 90% 4, 6
• Despite controversy regarding efficacy following the Danish Sham Surgery Study, the procedure has been widely adopted by the international neurotologic community 2
• Newer techniques with wider decompression of the sac and surgical manipulation of the endolymphatic duct may improve outcomes 5, 2

Recovery

• Typically classified as a "day case" or "short stay" procedure requiring 1-2 days of hospitalization 1
• Complete physiological and psychological recovery may take several weeks to months 1

Vestibular Nerve Section (VNS)

Procedure Overview

• Vestibular nerve section involves surgically cutting the vestibular portion of the eighth cranial nerve to eliminate vertigo while preserving hearing 4
• The procedure aims to disconnect the abnormal vestibular input from the affected ear while preserving cochlear function 7

Risk Profile

• More invasive than endolymphatic sac procedures, involving craniotomy 4
• Complications include hearing loss (despite being theoretically hearing-preserving), facial nerve injury, postoperative headache, and risks associated with craniotomy such as bleeding, meningitis, and cerebrospinal fluid leak 4
• Residual vestibular function may persist due to incomplete nerve section, as there is not a well-defined separation between vestibular and cochlear nerves 4

Efficacy

• Vertigo control rates range from 78% to 90% in retrospective cohort studies 4
• Considered very effective for abolishing vertigo in isolated cases 7
• Hearing is theoretically preserved but may be lost due to complications such as opening of the vertical canal or disruption of blood supply 7

Comparative Considerations and Decision-Making Algorithm

When to Consider Endolymphatic Sac Decompression:

• First-line surgical option for patients with medically refractory Ménière's disease 2
• Particularly suitable for patients with:
  • Preserved hearing that should be maintained 4
  • No evidence of contralateral disease 4
  • Failed conservative measures and medical management 4

When to Consider Vestibular Nerve Section:

• Should be offered only in select cases due to its invasive nature compared to other options 4
• May be appropriate for patients with:
  • Active vertigo unresponsive to all other therapies 4
  • Usable hearing that should be preserved 4
  • No evidence of contralateral disease 4
  • Reasonable expectation of compensation following surgery 4
  • Drop attacks associated with Ménière's disease (though labyrinthectomy may also be considered) 4

Important Caveats

• In bilateral Ménière's disease, endolymphatic sac surgery or vestibulotoxic drugs are advised rather than vestibular nerve section 7
• For patients with fixed non-fluctuating hearing loss, vestibular neurectomy may be more appropriate than sac surgery 7
• Patients should be evaluated with audio-vestibular function testing preoperatively to assess contralateral vestibular function, especially before considering ablative procedures 4