Chronic Frontal Sinusitis
Chronic frontal sinus infection is one of the most difficult entity to manage. This is due to the varying anatomical relationships of frontal sinus outflow tract.
Chronic frontal sinusitis is defined as infection / inflammation of frontal sinus mucosa lasting for more than 3 months. In order to understand the pathophysiology of chronic frontal sinus infections it is imperative that we should understand the anatomy of frontal outflow tract. Complications are more common in chronic frontal sinusitis.
Anatomy of frontal outflow tract:
Eventhough anatomically there is no duct leading from the frontal sinus into the nasal cavity the term "naso frontal duct" has become well entrenched in out literature. Recent anatomic studies have revealed the variations in the frontal sinus drainage tract. The term frontal sinus outflow tract is slowly replacing the term "naso frontal duct". The frontal sinus outflow tract could be considered to be shaped like an "Hour glass" with three basic components. The superior most portion of the hour glass shaped out flow tract is also known as the "frontal sinus infundibulum". This lies in the inferior aspect of the frontal sinus into which the mucous generated by frontal sinus pours. The middle narrowest portion of the outflow tract is the frontal sinus ostium, which lies at the inferior most portion of the frontal sinus proper. It is this area which swells up commonly inresponse to inflammation causing obstruction to the frontal outflow tract. The third component of the hour glass shaped outflow tract is the frontal recess area. This area is the most variable of all the components of frontal sinus outflow tract.
The frontal recess space is dependent on the pneumatization of various anterior ethmoidal air cells. The degree of pneumatization of these cells plays a role in determining the anatomical complexities of this region.
Diagramatic representation of frontal sinus outflow tract
Boundaries of frontal recess area:
Anterior - Posterior wall of agger nasi region
Posterior - Anterior wall of bulla ethmoidalis
Laterally - Lamina papyracea
Medially - Anterior vertical portion of middle turbinate
Superiorly - Roof of ethmoid
Agger Nasi: The term "agger nasi" means mound in the nose. This area pneumatizes under all circumstances. The degree and size of pneumatization can vary influenzing the dimensions of frontal recess and frontal sinuses. Ethmoidal cells located above the level of aggernasi cell are termed as frontal cells. These frontal cells are classified according to their location and number. The frontal cells that could influenze the size of frontal recess include: supra bullar, supraorbital ethmoidal cells and intersinus septal cells. The ethmoidal cells above the level of frontal recess may confuse the surgeon who can mistake it for frontal sinus opening. Hence careful evaluation of this area using CT scan images is advisable before endoscopic sinus surgery.
Diagnostic criteria for chronic frontal sinusitis:
1. Continuous symptoms / findings lasting for more than 3 months
2. One inflammatory sign associated with symptoms:
- Discolored mucous, polyp, inflammatory swelling of nasal mucosa
- Oedema / erythema of middle meatus
2. Imaging modalities
- CT scan showing diffuse signs of inflammation
- Plain radiographs showing 5mm or more of mucosal thickening / opacification of sinuses
Diagnostic nasal endoscopy:
Diagnostic nasal endoscopy should be performed with the nose in normal and decongested state. Middle meatal area should be carefully examined for the presence of discharge, polyp, mucosal oedema etc. Abnormal discharge any should be collected with care and sent for culture and sensitivity.
Frontal sinusitis in operated patients should be suspected in patients with:
- Lateralized / amputated middle turbinate
- Polypoidal oedema in anterior ethmoid area
CT scan study is a must in these patients.
Microbiology of chronic frontal sinusitis:
1. H. Influenza
3. S. Pneumoniae
Suggested adjuvant medial treatment:
1. Intranasal / systemic steroids
2. Topical / systemic decongestants
4. Leucotreine modifiers
6. Nasal saline irrigations
Definitive surgical therapy for chronic frontal sinusitis:
1. Endoscopic anterior ethmoidectomy - Indicated in patients with limited frontal sinus mucosal thickening
2. Intranasal frontal sinusotomy - Indicated in patients with extensive frontal sinus mucosal thickening, frontal sinus polyp / opacification of frontal sinus / failed anterior ethmoidectomy.
3. Frontal sinus rescue procedure - Indicated in patients with failed intranasal frontal sinusotomy
4. Draf II & III procedure - Indicated in patients with extensive frontal disease, tumors of frontal sinus and previous failed frontal sinus surgery
5. Frontal sinus trephination - Indicated when intranasal frontal sinus approach is not possible
6. External frontal sinusotomy - Neoplasm, trauma, CSF leak requiring extensive exposure