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Neuroradiology Case of the Week
Case 489
April 2010
Daniel Hoi Shuen Tam, MD, and P-L Westesson, MD, PhD, DDS
Clinical
Presentation: Patient is a 27-year-old female who first presented five years ago with headache.
Imaging Findings: Initial CT (five years ago) showed a mass centered at planum sphenoidale. The differential considerations included fibrous dysplasia and osteoma. Biopsy of this mass a month later was consistent with osteoma. Two years later CT showed an increase in the size of this osteoma.
Three years from initial presentation an MRI of this osteoma demonstrated low to intermediate T1 signal and low T2 signal with slight heterogeneous contrast enhancement. This MR examination also demonstrated stable asymmetric narrowing of the optic canals bilaterally, right greater than left. In addition, the caliber of the intracanalicular portion of the right optic nerve is significantly smaller in comparison to the left, a finding which is similar on prior CT examinations.
Patient underwent decompression of the intracanalicular portion of the right optic nerve a year ago and 4 months later the left optic nerve as well as.
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Figure 1: Initial CT scout image shows a large lobulated, well-circumscribed density overlying the retroorbital region.
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| Figure 2: Initial maxillofacial and orbital CT image demonstrates a dense, lobulated mass centered at planum sphenoidale. |
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| Figure 3: Two years later CT shows an increase in the size of the osteoma. |
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Figure 4A: Three years from initial presentation an axial T2WI MR depicts the osteoma with low signal intensity. In addition, there is stable asymmetric narrowing of the optic canals bilaterally, right greater than left. The caliber of the intracanalicular portion of the right optic nerve is significantly smaller in comparison to the left, a finding which is similar on prior CT examinations. |
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| Figure 4B: In addition, post-contrast axial T1 MR demonstrates mild heterogeneous enhancement. |
Diagnosis: Osteoma centered at planum sphenoidale
Discussion:
Craniofacial osteomas are benign tumors of the skull base, often involving the paranasal sinuses. The frontal sinus is the most common site of involvement, followed by the ethmoid, maxillary, and sphenoid sinuses, respectively. The origin of these tumors has been ascribed to embryologic tissue maldevelopment, trauma, or infection. The growth rate of these tumors is very slow, and it may take many years for osteomas to become clinically apparent. The complications of osteoma growth are obstruction of sinus ostia, extension into adjacent bones and the intracranial cavity, and displacement of anatomic structures [1].
Surgical removal of these tumors is done if they extend beyond the boundaries of the sinus, continue to enlarge, are localized in the region adjacent to the nasofrontal duct, or if signs of chronic sinusitis are present and, regardless of size, in symptomatic tumors. Surgical approaches are divided into external, endoscopic drill-out, and combined endoscopic and external procedures [2].
Cases of isolated lesions of the sphenoid sinus are rare. For descriptive purposes, clinicians divide them into inflammatory and non-inflammatory with prevalence of the former. Symptoms of the sphenoid sinus disease are difficult to characterize, the most common of them being vague headache and visual disturbances.
In one series, 22 subjects were analyzed retrospectively. There were 5 patients with bacterial sinusitis, 6 with fungal sinusitis, 4 with allergic thickening of the mucous membrane with no evidence of bacterial or fungal infection, 2 with mucocele, 1 with sphenoid osteoma, 1 with inverted papilloma, 1 with a foreign body and 2 with cerebral fluid fistula.
Isolated lesions of the sphenoid sinus (even very rare tumors like those presented here) can in most cases be safely approached and removed endoscopically. Except for bilateral oculomotor nerve paralysis in one patient, this cohort’s postoperative course was uneventful. The patients noted improvement in all preoperative symptoms [3].
In another series, out of a group of 86 patients with osteomas in the bones of the skull and face, 21 patients were diagnosed with osteomas of the paranasal sinuses. The mean age of this cohort was 50 years, with a predominance of male subjects (2:1). Again, the frontal sinus was the most frequently involved (57%), followed by the maxillary, ethmoid and the sphenoid sinuses [4].
References:
- Namdar I, Edelstein DR, Huo J, Lazar A, Kimmelman CP, Soletic R. Management of osteomas of the paranasal sinuses. Am J Rhinol. 1998 Nov-Dec;12(6):393-8. PMID: 9883294 [PubMed]
- Strek P, Zagólski O, Skhadzien J, Kurzynski M, Dyduch G. Osteomas of the paranasal sinuses: surgical treatment options. Med Sci Monit. 2007 May;13(5):CR244-50. PMID: 17476198 [PubMed]
- Strek P, Zagólski O, Skhadzien J, et al. Endoscopic surgical treatment of patients with isolated sphenoid sinus disease. Otolaryngol Pol. 2007;61(3):254-9. Polish. PMID: 17847777 [PubMed]
- Gay Escoda C, Bescos Atín MS. Osteomas of the paranasal sinuses. Av Odontoestomatol. 1990 Dec;6(10):587-90, 592-4, 596-8. Review. Spanish. PMID: 2088358 [PubMed]
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