Drug eluting stents in ent short note from Scott and brown

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"drug-eluting stent" ENT rhinosinusitis OR sinus

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Drug-Eluting Stents in ENT

Introduction

Drug-eluting stents (DES) in ENT are biodegradable or non-biodegradable implants that serve a dual purpose: acting as a mechanical spacer to maintain luminal patency while delivering sustained, localized pharmacological agents (most often corticosteroids or anti-proliferative drugs) directly to the target tissue. Their use in ENT spans sinonasal surgery, airway management, and emerging cochlear implant technology.

1. Sinonasal / Endoscopic Sinus Surgery (ESS)

The PROPEL Implant (Most Clinically Established DES in ENT)

The Propel corticosteroid-releasing implant (Intersect ENT, Palo Alto, CA) is the only FDA-approved drug-eluting stent in ENT practice for sinonasal use.

Structure:

Biodegradable, bioabsorbable scaffold
Drug: Mometasone furoate - a potent topical corticosteroid
Release period: Sustained drug release over 30 days

Mechanism of Action:

Acts as a mechanical spacer to keep the middle meatus open post-ESS, preventing adhesion (synechiae) formation
Simultaneously delivers mometasone locally to the sinus mucosa, reducing the local inflammatory response and polyp reformation

Indications:

Post-ESS to maintain patency of the ethmoid sinuses and frontal recess
Patients with chronic rhinosinusitis with nasal polyposis who are at high risk of postoperative adhesion or recurrence

Clinical Benefits (as cited in K.J. Lee's Essential Otolaryngology):

Reduces postoperative polyposis formation
Reduces adhesion (synechiae) formation
Provides controlled local drug delivery without the systemic side-effects of oral steroids

Patient Selection:

Patient-specific factors should dictate appropriateness
Particularly useful in revision sinus surgery or cases with extensive polyposis
K.J. Lee's Essential Otolaryngology, Section: Steroid-Eluting Stents

2. Frontal Sinus / Mucocele Surgery

Scott-Brown's Otorhinolaryngology Head & Neck Surgery addresses stenting in the context of frontal sinus mucoceles, though here the role is mechanical rather than pharmacological:

Stenting remains controversial in frontal sinus mucocele management; most authors do not advocate routine stenting to maintain patency except in smaller unilateral marsupializations
If a stent is placed, it must be loose fitting to prevent circumferential pressure necrosis that could paradoxically lead to stenosis
Drug-eluting variants (such as the Propel) represent an evolution from conventional passive stents by adding the anti-inflammatory benefit
Scott-Brown's Otorhinolaryngology Head & Neck Surgery - Vol 1, Section: Fronto-ethmoidal mucoceles

3. Airway: Drug-Eluting Bioabsorbable Tracheal Stents

Cummings Otolaryngology discusses emerging DES technology in the context of tracheomalacia and tracheal stenosis:

Background:

Conventional tracheal stents (silicone: Montgomery, Hood, Dumon; metallic: Palmaz, Ultraflex) have significant drawbacks including granuloma formation, mucus plugging, mucociliary impairment, and difficulty of removal
Bioabsorbable polydioxanone stents maintain rigid strength for ~6 weeks and dissolve by ~15 weeks, avoiding the need for removal

Drug-Eluting Bioabsorbable Tracheal Stents:

Zhu et al. reported on a mitomycin C drug-eluting bioabsorbable stent, which demonstrated:
- Decreased granulation tissue formation
- Lower rate of restenosis in a rabbit model
The concept extends to other drugs that modulate the tissue response (anti-proliferative, anti-inflammatory agents)
This technology holds "significant promise for the future" in combating the major complications of conventional stents - restenosis and granulation tissue

Note: The FDA (2005) issued an advisory against metallic airway stents in benign airway disorders due to high complication rates, which further motivates development of DES bioabsorbable alternatives.

Cummings Otolaryngology Head and Neck Surgery, Section: Treatment of Tracheomalacia

4. Inner Ear / Cochlear Implants

An emerging frontier for DES in ENT:

Drug-eluting electrode arrays for cochlear implants represent the most technologically advanced application
Growth factor-eluting cochlear implants have been shown to:
- Attenuate insertional trauma
- Promote neural recovery
- Protect against loss of cochlear neural elements, cochlear fibrosis, and residual hearing loss
Long-term steroid delivery via drug-eluting electrode arrays has also been tested in animal models, demonstrating protection against inflammatory changes
The first clinical trials using drug-eluting cochlear implants were underway at the time of publication
Cummings Otolaryngology Head and Neck Surgery, Section: Delivery Method (Cochlear implants)

Summary Table

Application	Drug Used	Device/Type	Key Benefit
Post-ESS (sinuses)	Mometasone furoate	PROPEL (biodegradable)	Reduces polyps, adhesions; FDA approved
Frontal sinus mucocele	- (mechanical stent)	Conventional loose stent	Maintains patency; DES variants evolving
Trachea / tracheomalacia	Mitomycin C	Bioabsorbable DES	Reduces granulation, restenosis (animal data)
Cochlear implant	Growth factors / steroids	Drug-eluting electrode array	Attenuates insertional trauma, preserves hearing

Key Points for Exams

The Propel implant is the only FDA-approved DES in ENT; it releases mometasone over 30 days post-ESS
DES combines the role of a mechanical spacer with sustained topical pharmacotherapy
Main benefit in ESS: reduction of polyposis and synechiae formation
In the trachea, mitomycin C-eluting bioabsorbable stents show promise in reducing granulation and restenosis
Drug-eluting cochlear implant arrays represent the frontier - growth factors protect the spiral ganglion post-insertion
Scott-Brown's cautions against routine sinus stenting; if used, stents must be loose-fitting to avoid pressure necrosis and stenosis

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