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Radiology Quiz Case 1: Diagnosis FREE

Arch Otolaryngol Head Neck Surg. 2010;136(11):1142. doi:10.1001/archoto.2010.189-b.
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Diagnosis: Pneumosinus dilatans (PSD) of the sphenoid sinus

Although its precise definition has been disputed,1PSD is characterized by an abnormal dilation of an air-filled paranasal sinus2that expands beyond its normal anatomical boundaries without thinning of its bony walls.3The first reported case was described in 1918.2The frontal and sphenoid sinuses are most commonly involved,3but the maxillary sinuses, ethmoid air cells, and even a concha bullosa may be affected. The entire sinus or only a part of it may be involved.4The age at presentation varies, but PSD frequently occurs between the ages of 20 and 40 years, with a male predominance.5

Pneumosinus dilatans can be differentiated from a simple pneumocele by the integrity of its bony sinus walls. In a pneumocele, there is thinning of the surrounding bone, which is not seen in PSD.3However, some authors have used both terms interchangeably.3Pneumosinus dilatans should be included in the differential diagnosis of expansile processes of the paranasal tract.6

The pathogenesis of the abnormal sinus dilation is poorly understood.2,3Theories include abnormalities in bony remodeling secondary to neoplastic processes; 1-way-valve mechanism with increased intrasinus pressure2; developmental disorders in which the normal pneumatization process fails to stop7; gas-forming organisms; spontaneous drainage of a mucocele; hormonal factors; and disturbances of osteoblastic and osteoclastic activity.5Antral studies have demonstrated abnormally high pressure in PSD; however, the presence of normal ostia in some cases contradicts this theory.7Some authors believe that if an ostium is small enough to create air trapping, it should also cause problems with mucus drainage,7which is not seen in PSD. Furthermore, blockage of a paranasal sinus ostium will more likely result in negative pressures and effusion rather than expansion.8Chronic inflammatory changes are sometimes observed on histologic examination, as in this case, but are not seen uniformly.8The finding of chronic inflammation and the absence of the intersinus septum may suggest that the dilated sinus was the result of spontaneous drainage of a sphenoid mucocele, but the bilateral patent ostia do not support this theory.

Pneumosinus dilatans has been reported in patients with conditions such as von Recklinghausen disease, fibrous displasia, prolonged cerebrospinal fluid shunting, meningiomas, and arachoid cysts,5but these associations are from case reports and are most likely incidental. There is an even rarer variant of PSD, called pneumosinus dilatans multiplex, in which all the paranasal sinuses and mastoid air cells are involved.5

The expansion of the sinuses in PSD can cause both aesthetic and functional problems, and the symptoms of PSD are related to the site of expansion.5For example, PSD of the frontal sinuses generally presents as a slow change in the external frontal facial countours, pain, diplopia, or other pressure-related symptoms.4On the other hand, if the maxillary sinuses are involved, it may present with nasal obstruction and pain elicited by changes in atmospheric pressure.6

The treatment of PSD is based on patient symptoms, including cosmetic deformities.5If PSD is thought to be the result of pressure disequilibrium, osteotomy should be considered.6Many different treatment modalities have been proposed, including sinus puncture and open or endoscopic sinus surgery. Interestingly (and for unknown reasons), in most cases, the abnormal enlargement stops with surgical treatment.4

In conclusion, PSD is a rare disorder for which there is no consensus regarding pathogenesis or treatment. In this case, the radiographic findings showed that the PSD was an air-filled, expanded sinus without thinning of the sinus wall that occurred in a patient without previous sinus surgery.

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Submissions

Residents and fellows in otolaryngology are invited to submit quiz cases for this section and to write letters to the Archivescommenting on cases presented. Quiz cases should follow the patterns established. See Instructions for Authors (http://archotol.ama-assn.org/misc/ifora.dtl).

Material for CLINICALPROBLEMSOLVING: RADIOLOGYshould be submitted electronically via the online submission and review system at http://manuscripts.archoto.com.

Reprints are not available from the authors.

REFERENCES

Martin  AJJarosz  JMThomas  NW The strange association of pneumosinus dilatans and arachnoid cyst: case report and review of the literature. Acta Neurochir (Wien) 2001;143 (2) 197- 201
PubMed Link to Article
Benjamins  CE Pneumosinus frontal dilatans. Acta Otolaryngol 1918;1412- 422
PubMed Link to Article
Yazici  BErdogmus  BGuclu  EOzturk  O Pneumosinus dilatans of the ethmoid sinus presenting with exophthalmus: a case report and review of the literature. Dentomaxillofac Radiol 2007;36 (2) 105- 106
PubMed Link to Article
Acar  MYucel  ADegirmenci  BYilmaz  MDAlbayrak  R Pneumocele vs. pneumosinus dilatans: review of the literature with a case of frontal sinus pneumocele. Tohoku J Exp Med 2004;202 (4) 295- 297
PubMed Link to Article
Kiroglu  YKarabulut  NSabir  NAYagci  ABGakmak  VOzguler  U Pneumosinus dilatans and multiplex: report of three rare cases and review of the literature. Dentomaxillofac Radiol 2007;36 (5) 298- 303
PubMed Link to Article
Trimarchi  MLombardi  DTomenzoli  DFarina  DNicolai  P Pneumosinus dilatans of the maxillary sinus: a case report and review of the literature. Eur Arch Otorhinolaryngol 2003;260 (7) 386- 389
PubMed Link to Article
Suryanarayanan  RAbbott  G Pneumosinus dilatans: demonstrated by sinus expansion on serial sinus X-rays with discussion of possible aetiology. J Laryngol Otol 2007;121 (1) 96- 99
PubMed Link to Article
Walker  JLJones  NS Pneumosinus dilatans of the frontal sinuses: two cases and a discussion of its aetiology. J Laryngol Otol 2002;116 (5) 382- 385
PubMed Link to Article

Figures

Tables

References

Martin  AJJarosz  JMThomas  NW The strange association of pneumosinus dilatans and arachnoid cyst: case report and review of the literature. Acta Neurochir (Wien) 2001;143 (2) 197- 201
PubMed Link to Article
Benjamins  CE Pneumosinus frontal dilatans. Acta Otolaryngol 1918;1412- 422
PubMed Link to Article
Yazici  BErdogmus  BGuclu  EOzturk  O Pneumosinus dilatans of the ethmoid sinus presenting with exophthalmus: a case report and review of the literature. Dentomaxillofac Radiol 2007;36 (2) 105- 106
PubMed Link to Article
Acar  MYucel  ADegirmenci  BYilmaz  MDAlbayrak  R Pneumocele vs. pneumosinus dilatans: review of the literature with a case of frontal sinus pneumocele. Tohoku J Exp Med 2004;202 (4) 295- 297
PubMed Link to Article
Kiroglu  YKarabulut  NSabir  NAYagci  ABGakmak  VOzguler  U Pneumosinus dilatans and multiplex: report of three rare cases and review of the literature. Dentomaxillofac Radiol 2007;36 (5) 298- 303
PubMed Link to Article
Trimarchi  MLombardi  DTomenzoli  DFarina  DNicolai  P Pneumosinus dilatans of the maxillary sinus: a case report and review of the literature. Eur Arch Otorhinolaryngol 2003;260 (7) 386- 389
PubMed Link to Article
Suryanarayanan  RAbbott  G Pneumosinus dilatans: demonstrated by sinus expansion on serial sinus X-rays with discussion of possible aetiology. J Laryngol Otol 2007;121 (1) 96- 99
PubMed Link to Article
Walker  JLJones  NS Pneumosinus dilatans of the frontal sinuses: two cases and a discussion of its aetiology. J Laryngol Otol 2002;116 (5) 382- 385
PubMed Link to Article

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