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News -> March, 2003 News
Minimally Invasive Sinus Techniques (MIST): A Surgical Model for the Treatment of Chronic Sinusitis
Peter Catalano, M.D.
Functional Endoscopic Sinus Surgery (FESS)
David Kennedy, M.D.
Minimally Invasive Sinus Techniques (MIST): A Surgical Model for the Treatment of Chronic Sinusitis
Peter Catalano, M.D.
MIST, for the treatment of chronic sinusitis, has become increasingly popular since its introduction in 1996. This surgical model is the true embodiment of functional concepts originally described by Messerklinger between 1968-1978. Application of the "functional theory", originally termed FESS, was based on conservatism, with surgical intervention limited to the sinus transition spaces (i.e. ethmoidal infundibulum, hiatus semilumaris superior, and retroagger space). The goal - "to re-establish ventilation and drainage of the dependent larger sinuses through their natural ostia, usually without touching the larger sinuses themselves" (1). Pathologic mucosal change, even when "massive", was considered reversible in all cases (1). The definition of what constitutes irreversible mucosal disease after re-establishing normal sinus drainage and ventilation remains elusive and controversial (2). The foundation statements of Messerklinger's functional concepts are indistinguishable from those of MIST. Thus, the MIST surgical model applies a literal translation of this philosophy.
MIST, in it's simplest form, is a targeted intervention, or 'threshold' surgical procedure. It is much more than not performing a middle meatal antrostomy. The MIST philosophy, based on tissue preservation and transition space surgery, has established the only intranasal procedure based on a stepwise, anatomic progression of surgery that has a defined beginning and end. Other forms of conventional endoscopic sinus surgery are far less disciplined, often allowing the surgeon excessive freedoms within the nasal cavity. Turbinates may or may not be resected, middle meatal antrostomies (MMA) may or may not be performed. The uncertainties and possibilities are numerous. If a patient tells us he/she had a parotidectomy, we have confidence in what was done; if they claim to have had sinus surgery, we can only guess. However, if a patient states they had a MIST procedure, we know exactly what surgery was performed. The MIST surgical model standardizes the procedure for surgeons and patients alike. Although the majority of the dissection is performed with powered instrumentation, a few pediatric hand instruments are needed. The former provides real time suction for better visualization, and true cutting blades to preserve birth membranes.
The advantages of MIST are numerous. Because the surgery is based on conservatism and mucosal preservation, potential for scarring within the nasal cavity is minimized, and iatrogenic sinusitis, especially of the frontal sinuses, is rare. Problems/revisions related to creation of a MMA are eliminated. Operative time and intra-operative bleeding are reduced, obviating the need for postoperative nasal packing. Because the healing burden placed on the nasal cavity is limited, overall peri-operative patient morbidity is reduced allowing most patients to return to work or school within 24-48 hours after surgery.
Recent outcome studies at 24 months post-MIST have shown significant clinical improvement across the spectrum of disease severity, with revision rates following MIST under 6% (3). These studies show that patient outcome following MIST is at least equal to those of other endoscopic intranasal procedures. These findings, coupled with the numerous other advantages offered by MIST, support the consideration of MIST as the initial procedure for patients undergoing endoscopic sinus surgery for chronic sinusitis.
References:
- Stammberger H. Endoscopic Endonasal Surgery - Concepts in Treatment of Recurring Rhinosinusitis. Part I: Anatomic and Pathophysiologic Considerations. Otol. Head & Neck Surgery, Vol. 94 (2), Feb. 1986, 143-47.
- Kennedy DW, Zinreich SJ, Rosenbaum AE, Johns ME. Functional Endoscopic Sinus Surgery: Theory and Diagnostic Evaluation. Arch. of Otolaryngology; Vol. 111, Sept. 1985, 576-582.
- Catalano PJ, Roffman E. Outcome in Patients with Chronic Sinusitis following Minimally Invasive Sinus Techniques (MIST). Amer. J. Rhin, Vol. 17 (1), Feb. 2003, 17-22.
Functional Endoscopic Sinus Surgery (FESS)
David Kennedy, M.D.
Proponents of minimally invasive sinus surgery (MIST) proselytize that they are ones who are performing the true functional techniques envisioned by Messerklinger, because what they are doing is providing drainage of the sinuses with a minimal mucosal preserving procedure. Indeed they claim just to have further improved upon an already good technique. Unfortunately, (or fortunately) our knowledge of the pathogenesis of chronic rhinosinusitis has progressed since the early days of Messerklinger.1 We have increasingly identified and demonstrated that chronic rhinosinusitis is not merely an issue of plumbing and of providing appropriate drainage. 2 We have learned that the adjacent bone becomes actively involved in the disease process and that, at least in an animal model, this inflammation can spread widely through the Haversian canals within the bone.3 Thus it becomes unlikely that just creating an opening, leaving the bone in place, is really sufficient. We have also learned that if you leave bony partitions during a surgical procedure and inflammation continues, the bone then this residual bone becomes thickened over time. Thus it becomes dramatically more difficult to remove this bone at a later time without causing significant mucosal trauma. Proponents of MIST will also argue that the results of MIST are similar to those of more extensive surgery. However, these are subjective results of combined surgery and medical therapy, and subjective results are uniformly good with all endoscopic sinus surgery techniques. Moreover, as we know, early postoperative subjective improvement does not necessarily translate into resolution of disease.4 Indeed, persistent asymptomatic disease frequently continues and may take many years to again become symptomatic.
MIST certainly has advantages in that it provides rapid healing and good mucosal preservation. For children who have not had longstanding problems it is probably an appropriate approach. Similarly in very minor disease in adults it may have a role. However, most adults with such minor disease are probably better treated with medical therapy directed at the underlying causes of the disorder rather than with a surgical intervention, for we now know that anatomic issues are not the most significant factor in the pathogenesis of chronic rhinosinusitis. Persistent mucosal inflammation is a major issue and in more extensive and longstanding chronic rhinosinusitis the bone clearly becomes involved, frequently devitalized and may present a pathway for the spread of the inflammation.3,5 Accordingly, it makes sense to completely remove these bony partitions within the area involved in the disease process while, at the same time, carefully preserving the mucosa on the surrounding bone that cannot be removed. This is not an easy task and it takes more time, making technically more difficult and less remunerative to the surgeon than MIST. However, given our current knowledge of the disease process, complete removal of the bony partitions within the region of disease is the approach that makes sense, and it is also the approach that has demonstrated both subjectively and objectively, excellent results over a true long term follow up period, when combined with appropriate medical management.
References:
- Messerklinger W. Endoscopy of the Nose (Urban and Schwarzenberg, Baltimore, 1978.
- Kennedy DW, Bolger WE, and Zinreich J, Diseases of the Sinuses: Diagnosis and Management. Anonymous B.C. Decker, Hamilton, Ontario 2001.
- Khalid AN, Hunt J, Perloff JR and Kennedy DW. The Role of Bone in Chronic Rhinosinusitis. Laryngoscope, 112:1951-1957, 2002
- Senior BA, Kennedy DW, Tanabodee J, Kroger H, Hassab M and Lanza D. Long-term Results Of Functional Endoscopic Sinus Surgery. Laryngoscope, 108: 151-157, 1998.
- Perloff J, Gannon FH, Bolger WE, Montone KT, Orlandi RR, and Kennedy DW. Bone Involvement in Chronic Sinusitis: An Apparent Pathway for the Spread of Infection. Laryngoscope, 2000
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