Pneumosinus dilatans: A report of three new cases and their surgical management.
Pneumosinus dilatans is a rare pathology that primarily involves the frontal sinus. We report three new cases, with special attention given to the pathophysiology and histologic data. Surgical management is reported.
Frontal pneumosinus dilatans is a rare condition in which facial deformity is caused by a gross enlargement of the sinus cavity. [1-4] Based on a review of the literature and an analysis of three new cases that involve the frontal sinus, we discuss the clinical findings and possible etiologies of this pathology.
Case 1. A 25-year-old man came to our institution with a complaint of progressive bilateral frontal bossing without other symptoms. Examination revealed a marked bilateral bony smooth swelling. Growth hormone levels were normal, and computed tomography (CT) revealed a bilateral enlargement of the frontal sinus without bone erosion or mucosal abnormalities (figures 1A, 1B).
Because of the persistent increase in the swelling, the patient underwent surgery. Before the procedure, the permeability of the nasofrontal duct was evaluated with a cannula introduced through the anterior wall of the sinus.  No obstruction was found, even though dynamic evaluation was performed to analyze the variation of the pressure according to the respiratory cycle. Surgery was secondarily performed to correct a deformity of the anterior wall. The mucosa was normal, and no purulent secretion was found. Mucociliary transport was observed and found to be normal. Ciliary beat frequency (10.53 [plus or mines] 1.4 Hz), histology of the mucosa, and the bone of the anterior wall of the frontal deformity were normal. After drilling and modification, the bone was replaced, and the cosmetic result was good (figure IC). No other mucosa was removed, and the nasofrontal duct was respected.
Case 2. A 49-year-old man had a 10-year history of progressive left frontal bossing and intermittent local pain. Acute frontal sinusitis was detected at the onset of his pathology. CT revealed a bilaterally well-aerated frontal sinus, with expansion of the left anterior wall; the right frontal sinus was normal (figures 2A, 2B). After trephination of the left anterior wall under local anesthesia, monitoring of the sinus pressure was carried out according to the respiratory cycle. Sinus pressure was identical to atmospheric pressure and varied with the respiratory cycle. During Valsalva's maneuver, sinus pressure increased to more than 250 mm[H.sub.2]O and returned to normal on completion of the maneuver.
In view of the cosmetic appearance, surgery was performed. After a coronal incision, the left anterior wall was removed. There was minimal edema of the frontal floor and no purulent secretion. Histology of the bone and mucosa of the anterior wall showed no abnormality on ciliary beat frequency analysis (11.5[plus or mines]0.9Hz). Drilling of the lateral part of the anterior wall and the septa allowed the frontal wall to be manipulated into the desired shape. No modification or obturation of the nasofrontal duct was performed.
Case 3. A 37-year-old man was seen for progressive bilateral frontal bossing. The history revealed no previous local trauma or infectious sinusitis. He had suffered from allergic rhinitis for 15 years. He reported rare occasions of frontal headache during the previous 10 years. CT demon- strated a normal aerated frontal sinus with bilateral enlargement; there was no evidence of hone erosion (figure 3). The patient elected not to undergo surgery at that time because his cosmetic deformity was only moderate.
Pneumosinus dilatans is rare. The first description was attributed to Meyes in 1898, but the first to assign the term pneumosinus dilatans was Benjamin in 1918.  The largest series was reported in 1970 by Bourdial, who collected 51 cases from previous publications, although there was considerable doubt about some of them because of the absence of radiologic documentation.  More recently, Urken et a1  and Legent et al  reported new cases of pneumosinus dilatans, giving special attention to the definition and possible etiologies of this unusual process. In this paper, we add information on three new cases of progressive frontal hyperpneumatization or pneumosinus dilatans to the body of knowledge, and we devote special attention to histologic and manometric data.
According to criteria suggested by Urken et al, [4,8] there are three categories of enlarged aerated frontal sinus: hypersinus, pneumosinus dilatans, and pneumocele. [9,10] In our three patients, progressive bossing and extension of the sinus beyond the normal boundaries of the frontal bone excluded the diagnosis of hypersinus. In patients 1 and 3, no pain or bone erosion was present; the lack of these two features provides evidence to suggest pneumosinus dilatans. In patient 2, the presence of frontal sinusitis 10 years earlier led us to consider a diagnosis of pneumocele. However, CT found no thinning of the bony anterior table, even at the site of frontal bossing, which is the feature that sometimes differentiates pneumocele from pneumosinus dilatans. 
These findings, along with complaints of local pressure as previously reported by other authors, [1,3,7] strongly suggested pneumosinus dilatans. In all three patients, the entire sinus was abnormally expanded, and it extended beyond the normal boundaries of the frontal bone. Such an extension differentiates pneumosinus dilatans from hypersinus. According to recommendations suggested by Urken et al,  plain-film examination was carried out (Caldwell's view) to obtain two measurements in the vertical portion of the frontal bone (table). Axial and coronal CT cuttings were also performed to determine the maximum depth of the frontal sinus. Findings confirmed the hyperpneumatization of all sinus cavities.
All three patients were male, and their ages at diagnosis ranged from 25 to 49, demographic information that is consistent with previous reports. [4,7,12] In patients 1 and 3, the progressive enlargement was bilateral. In patient 2, enlargement was unilateral, even though the hyperpneumatization involved both cavities; unilateral enlargement is not common, although Lombardi et al reported in a review of the literature in 1968 that most cases of pneumosinus dilatans that they analyzed were unilateral. 
The cause of the condition remains obscure. Three possibilities that have been suggested are a disturbance of the nasofrontal duct, a dysregulation of growth or sex hormones, or excessive osteoblastic activity. In two of our patients (cases 1, 2), intrasinus pressure and permeability of the nasofrontal duct was studied. The frontal sinus was trephined, and a transfrontal cannula was inserted to monitor sinus pressure. The cannula was connected by a three-way valve to a water manometer (U tube) and a syringe. In patient 1, the sinus pressure was identical to the atmospheric pressure, and passive permeability of the nasofrontal duct was considered to be normal according to the technique used by Drettner.  Nevertheless, no dynamic evaluation was available during general anesthesia. Inpatient 2, the procedure was initially performed under local anesthesia. Later, the patient performed Valsalva's s maneuver to test the hypothesis that there was a valve trap or dyspermeability of the nasofrontal duct. During V alsalva's s challenge, no abnormality was found. No obstruction was found in patients 1 and 2, and no abnormal modification of the pressure during the respiratory cycle was noted in patient 2. [5,13,14]
The primary local factor that has been suspected of causing sinus enlargement is osteoblastic activity secondary to chronic pressure.  No thinning of the overlying bone was observed in any of our patients, and their histologic examinations were normal in this respect. Local production of gas by bacteria was not suspected because all cultures of the mucosa of the anterior part of the sinus cavity were sterile. During surgery, patients 1 and 2 were found to have no nasofrontal duct blockage, and the mucosa of the floor was normal in both. Legent et al had also reported the absence of dyspermeability of the nasofrontal duct in the two cases of frontal pneumosinus dilatans that they studied.  In patients 1 and 2, histologic examination of the mucosa and the bone of the anterior wall of the frontal sinus revealed a pseudostratified epithelium associated with a moderate inflammatory reaction without any characteristic modification, especially with regard to the bone analysis. Ciliary activity of the mucosa was normal.
During cosmetic surgery on patients 1 and 2, no exclusion of the frontal sinus was carried out; this was in accordance with the long-term results published by Legent et al,  but contrary to the standard method recommended by Urken et al.  In both patients, an osteoplastic flap created by the drilling of the septa allowed the frontal wall to be manipulated to the desired shape. There was no nasofrontal drainage, and the duct was preserved in its entirety. A good cosmetic result was obtained in both patients 1 and 2, and there were no postoperative complaints.
From the Department of Otolaryngology, University Hospital, Poitiers, France (Dr. Klossek, Dr. Dufour, and Dr. Fontanel), and the Department of Otolaryngology-Head and Neck Surgery, University of Southern California, Los Angeles (Dr. Toffel).
Reprint requests: Jean-Michel Klossek, MD, Department d'Oto-RhinoLaryngologie, Hopital Jean Bernard, CHU Poitiers, 86021 Poitiers Cedex, France. Phone: 33-549-51-6004; fax: 33-549-44-3848; e-mail: firstname.lastname@example.org
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(3.) Smith IM, Maran AG, von Haacke NP. Pneumosinus dilatans. Ann Otol Rhinol Laryngol 1987;96:210-2.
(4.) Urken ML, Som PM, Lawson W, et al. Abnormally large frontal sinus. II. Nomenclature, pathology, and symptoms. Laryngoscope 1987;97:606-l1.
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Measurements of the sinus cavities in three patients with pneumosinus dilatans Patient 1 Patient 2 Length (mm) Left Right Left Right Midline to the lateral extent 62 67 65 58 of the hemifrontal sinus Base of the crista galli to the point 73 85 79 81 of maximum distance along the perimeter of the hemifrontal sinus Maximum depth of the frontal cavity 39 35 20 16 Patient 3 Length (mm) Left Right Midline to the lateral extent 63 64 of the hemifrontal sinus Base of the crista galli to the point 69 72 of maximum distance along the perimeter of the hemifrontal sinus Maximum depth of the frontal cavity 38 39
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|Comment:||Pneumosinus dilatans: A report of three new cases and their surgical management.|
|Publication:||Ear, Nose and Throat Journal|
|Article Type:||Brief Article|
|Date:||Jan 1, 2000|
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