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 Table of Contents  
Year : 2021  |  Volume : 33  |  Issue : 2  |  Page : 226-229

Pneumosinus dilatans: A rare case report and review of literature

Department of Oral Medicine and Radiology, Thai Moogambigai Dental College and Hospital, Chennai, Tamil Nadu, India

Date of Submission01-Dec-2020
Date of Decision12-May-2021
Date of Acceptance02-Jun-2021
Date of Web Publication23-Jun-2021

Correspondence Address:
Dr. V R Nithya
Department of Oral Medicine and Radiology, Thai Moogambigai Dental College and Hospital, Golden George Nagar, Chennai - 107, Tamil Nadu
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jiaomr.jiaomr_253_20

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Pneumosinus dilatans is a rare entity that is documented only by a few reports. It is an abnormal expansion of the aerated frontal sinus, with sinus walls of normal thickness. The bone expansion is focal. A case was reported in our dental college; a 28-year-old male complaining of prominence on his forehead and it has an unknown cause and no functional problems. Computed tomography shows extension pneumatization and expansion of frontal sinus, which is extended from one side of the skull to the other side. It is benign and found to be asymptomatic. No evidence of pathological changes and no bone destruction seen. We discuss this case of etiology, clinical features, and radiological features.

Keywords: Frontal sinus, pneumocele, pneumosinus dilatans

How to cite this article:
Ramani P, Nithya V R, SreeDevi J, Vinod Kumar A C. Pneumosinus dilatans: A rare case report and review of literature. J Indian Acad Oral Med Radiol 2021;33:226-9

How to cite this URL:
Ramani P, Nithya V R, SreeDevi J, Vinod Kumar A C. Pneumosinus dilatans: A rare case report and review of literature. J Indian Acad Oral Med Radiol [serial online] 2021 [cited 2022 Oct 3];33:226-9. Available from: https://www.jiaomr.in/text.asp?2021/33/2/226/319070

   Introduction Top

Pneumosinus dilatans (PSD) is an idiopathic expansion of paranasal sinuses (PNS) containing air without any muscle mass.[1] Involvement of frontal sinus is common but might affect all PNS.[2] PSD is usually a benign and asymptomatic disease of unknown etiology with no evidence of bone destruction or pathological changes of the underlying mucosa. The condition was first described by Mayes in 1898 but was named pneumatocele and Benjamins assigned the name PSD in 1918;[3] he also described the difference between PSD and a pneumatocoele.

Afroze (2017) was the first who coined the term “Deer Horn Sinus” for PSD frontalis (PDF) because, on coronal computed tomography (CT) images, PDF may give an appearance of deer horn.

Urken et al[4] classified paranasal sinus PSD into three categories according to clinical symptoms, radiologic enlargement, and thinning of the sinus walls. In order of increasing severity, the classifications were hypersinus, PSD, and pneumocele. Classification is summarized in [Table 1].
Table 1: Urken et al. (1987) classification on Pneumosinus dilatans

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The average dimensions of the frontal sinus in the literature are 17 mm deep, 27 mm wide, 28 mm high (Paul et al., 1994).[5] Pneumonization of the frontal sinus or increase in the dimension leads to expansion of the sinus wall causing PSD.[6] PSD often is an incidental radiologic finding and is mostly diagnosed by the recognition of the frontal deformity.[7] The usual complaints are local pain, headache, frontal paraesthesia or sensory deficit, olfactory loss, and ophthalmic disturbances. X-rays, clinical findings, and hormonal examinations differentiate PSD from acromegaly and exostosis.[3] PSD is described either as an isolated form or in association with other diseases, such as arachnoid cyst, cerebral hemiatrophia, meningioma, and Klippel–Trenaunay–Weber syndrome.

   Case Report Top

A 28-year-old male patient presented with a history of gradual onset of swelling on the center of his forehead for the past 6 years. The swelling was progressively increasing in size with no history of headache, fever, rhinitis, sinus symptoms, or allergies. No previous history of upper respiratory infections or head injury was present.

Clinical Description

On extraoral examination, a single diffuse swelling measuring around 6 cm mediolaterally and 4 cm superoinferiorly was present on the forehead extending mediolaterally from midpoint of right supraorbital margin to midpoint of left supraorbital margin. The [Figure 1] surface of the swelling was smooth with no secondary changes. On palpation, the swelling was non-tender and bony hard consistency.
Figure 1: Extraoral photograph showing swelling of frontal bone

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Diagnostic Assessment

Routine blood investigations were within normal limits. Growth hormone and serum alkaline phosphatase levels were assessed to rule out endocrine and metabolic disorders and were found to be within normal limits.

Lateral skull view radiograph revealed bulging of the anterior table without any evidence of bony erosion. Computed tomography (CT) scan of facial bones showed extensive pneumatization, measuring 18.3 mm superoinferiorly in the coronal section and 35.6 mm in the axial section with an expansion of the frontal sinus, which extended from one side of the skull to the other end. Axial views showed expansion of frontal sinus where the anterior table of frontal sinus was pushed forward without any bony erosion [Figure 2] and [Figure 3].
Figure 2: Coronal section and Axial section of CT scan showing expansion of frontal sinus

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Figure 3: Midsagittal section of CT scan showing expansion of frontal sinus

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Diagnostic nasal endoscopy did not reveal any intranasal abnormality. The ophthalmological assessment was also within normal limits.

Based on the clinical and radiological findings, a working diagnosis of PSD was made.

The differential diagnosis for PD, both clinical and radiological [Table 2], is the osteoma and pneumocele with an enlarged aerated paranasal sinus with thinned bony walls.[8]
Table 2: Clinical and radiological differential diagnosis

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Therapeutic Intervention

As the patient was asymptomatic, he was not willing for treatment for the condition.

Follow Up and Outcome

The patient is asked to report after 6 months for review or before that if any symptoms precede.

   Discussion Top

The case of PSD, its etiology, and pathogenesis are still a matter of discussion. In normal subjects, it was found that there is a wide variation in the degree of pneumatization of the sinuses. Overgrowth may occur in acromegalic subjects or cases of agenesis of a cerebral hemisphere. The etiology of PSD is poorly understood as may be evident from the many mechanisms that have been proposed by various authors and it is still under discussion. Most authors attribute it to a ball-valve action secondary to either redundant mucosa or a minor inflammatory process with a consequent rise in pressure within the sinus by Dhillon and Williams.[9] Benedikt et al.[10] also suggested that spontaneous drainage of a mucoele must be the causative agent in a case of air-filled expansion of the ethmoid sinus, whereas many others think that the hormonal influence of osteoblastic activity contributes to the ingrowth and expansion of the sinus. We found that PD of the frontal sinus is the most commonly involved sinus. In doing so, we came across 15 cases of PD involving the frontal sinus, not including our own. In addition, attention was given to patient age, and pediatric cases proved to be rare even among those with PD [Table 3]. There are much more hypotheses that have been proposed to explain the pathogenesis of PSD. Benjamin in the year 1918 who described a rare case of abnormal dilatation of the frontal sinus containing only air. Lombardi in 1967 reported 51 cases and described its predilection as most regularly in the frontal sinuses followed by the sphenoid, maxillary, and ethmoidal sinuses.[11] PSD is characterized by idiopathic progressive expansion of one or more PNS beyond normal margins without evidence of mucous membrane changes.[12] The expansion may involve the sinus completely or only a part of the sinus will be involved. Alterations of growth and sex hormone levels have also been implicated in PSD. Such alterations result in a disturbance in the osteoblastic activity, leading to excessive bone growth and abnormal sinus pneumatization and expansion. Overgrowth may occur in acromegalic subjects under the impact of general growth factors or as a compensatory phenomenon in cases of agenesis of the cerebral hemisphere. Prott[13] suggested that enlargement of the sinus could have been secondary to an increased intrasinus pressure. The increase in the intrasinus pressure is caused by an efferent duct obstruction. These changes caused by probable valve obstruction of the frontal sinus resulted in optic nerve compression, so endoscopic restoration of nasoantral communication resulted in a full recovery. The patient usually has complaints of slowly changing facial contours and dull pain in the enlarged region and local pressure and diplopia. It should be differentiated from hyperpneumatized sinus and pneumocele.[8] Congenital abnormality has been proposed as a possible mechanism leading to unchecked development and growth of sinus and the meninges cells that lead to PSD and associated tumors. PSD is diagnosed with a CT scan and MRI. The criteria for diagnosis of PSD are enlargement of an air cell or the complete sinus and the presence of air alone in the walls of the sinus. It is a benign condition and many methods of repair of the cosmetic defect have been described.
Table 3: Case reports of PD of paranasal sinus

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   Conclusion Top

PSD is an extremely rare condition, which causes facial deformity as it is caused by gross enlargement of apparently paranasal sinus filled with air with unclear etiology. Correction can be done by surgical intervention only if the aesthetic point of concern. But recurrence after surgical repair is unlikely.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

   References Top

Singh H, Ramakrishnan N, Sarin D. Pneumosinus dilatans. Med J Armed Forces India 2007;63:300-1.  Back to cited text no. 1
Ricci J. Pneumosinus dilatans: Over 100 years without an etiology. J Oral Maxillofac Surg 2017;75:1519-26.  Back to cited text no. 2
Khizer Hussain Afroze, BS Suresh, Subhash Lakshmiprabha., Pneumosinus Dilatans Frontalis- A Rare Anatomical Variation of Frontal Sinus, International Journal of Anatomy, Radiology and Surgery. 2017 Jul, Vol-6(3): AC01-AC02.  Back to cited text no. 3
Urken ML, Som PM, Lawson W, Edelstein D, Weber AL, Biller HF. Abnormally large frontal sinus. II. Nomenclature, pathology, and symptoms. Laryngoscope 1987;97:606-11.  Back to cited text no. 4
Stringer SP. The sinuses. Edited by Paul J. Donald, Jack L. Gluckman, and Dale H. Rice, Raven Press, New York, 1994, 687pp, $175.00.  Back to cited text no. 5
Alatar AA, AlSuliman YA, Alrajhi MS, Alfawwaz FS. Maxillary pneumosinus dilatans presenting with proptosis: A case report and review of the literature. Clin Med Insights Ear Nose Throat 2019;12:1179550618825149.  Back to cited text no. 6
Stretch J, Poole M. Pneumosinus dilatans as the aetiology of progressive bilateral blindness. Br J Plast Surg 1992;45:469-73.  Back to cited text no. 7
Giesbrandt J. Radiology Review Manual.  Back to cited text no. 8
Dhillon RS, Williams DC. Pneumosinus dilatans. J Laryngol Otol 1987;101:828-32.  Back to cited text no. 9
Benedikt RA, Brown DC, Roth MK. Spontaneous drainage of an ethmoidal mucocele: A possible cause of pneumosinus dilatans. Am J Neuroradiol 1991;12:729-31.  Back to cited text no. 10
Walker JL, Jones NS. Pneumosinus dilatans of the frontal sinuses: Two cases and a discussion of its aetiology. J Laryngol Otol 2002;116:382-5.  Back to cited text no. 11
Gardel J, Maduro M. An observation of pneumosinus dilatans [in French]. Ann Otolaryngol Chir Cervicofac 1965;82:619-21.  Back to cited text no. 12
Prott W. Pneumosinus dilatans der stirnholen. Laryngol Rhinol 1977;56:277-82.  Back to cited text no. 13
Harrison MS. Pneumosinus frontalis. J Laryngol Otol 1955;69:108-14.  Back to cited text no. 14
Adams WM, Jones RI, Chavda SI, Pahor AL, Taifa KT. Pneumosinus dilatans: a discussion of four cases and the possible aetiology. InPresented at the 16th Congress of the European Rhinologic Society in Ghent 1996 Sep 7.  Back to cited text no. 15
Appelt EA, Wilhelmi BJ, Warder DE, Blackwell SJ. A rare case of pneumosinus dilatans of the frontal sinus and review of the literature. Ann Plast Surg 1999;43:653-6.  Back to cited text no. 16
Klossek J, Dufour X, Toffel P, Fontanel JP. Pneumosinus dilatans: A report of three new cases and their surgical management. Ear Nose Throat J 2000;79:48-51.  Back to cited text no. 17
Dempf R, Wenzel U, Gundlach KKH. Pneumosinus dilatans frontalis: Two case reports. J Craniomaxillofac Surg 2005;33:130-4.  Back to cited text no. 18
Patel AC, Hammoudeh JA, Urata MM. Pneumosinus dilatans: A rare cause of frontal sinus expansion--Case report and review of literature. J Oral Maxillofac Surg 2008;66:2380-6.  Back to cited text no. 19
Galiè M, Consorti G, Clauser LC, Kawamoto HK. Craniofacial surgical strategies for the correction of pneumosinus dilatans frontalis. J Craniomaxillofac Surg 2013;41:28-33.  Back to cited text no. 20
Bouguila J, Ben Rejeb M, Omezzine M, Mani R, Khochtali H. Pneumosinus dilatans: Rare cause of slowly changing frontal contours. Aesthet Surg J 2015;35:NP47-53.  Back to cited text no. 21


  [Figure 1], [Figure 2], [Figure 3]

  [Table 1], [Table 2], [Table 3]


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