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PubMed This is a summary of 21 peer-reviewed journal articles Updated
Otolaryngology · Chronic Sphenoid Sinusitis

The Path to a Precise Diagnosis

At a Glance

Isolated sphenoid sinusitis is difficult to diagnose with a standard physical exam. Doctors rely on nasal endoscopy to check for drainage, high-resolution CT scans to map bony anatomy and plan safe surgery, and MRIs to ensure the infection hasn't spread to nearby nerves or the brain.

Because isolated sphenoid sinusitis is rare and located deep within the head, it is rarely diagnosed by a simple physical exam. Diagnosis requires a “high index of suspicion”—meaning your medical team must actively look for it, even if you don’t have typical “sinus” symptoms like congestion or a runny nose [1][2]. The diagnostic journey typically involves three key steps.

1. Nasal Endoscopy: The First Look

A nasal endoscopy is a procedure where an ENT specialist uses a thin, flexible tube with a camera to look at the back of your nasal passages [2]. They are specifically looking at the sphenoethmoidal recess, which is the “drainage port” for the sphenoid sinus.

  • What they look for: Signs of infection like purulence (pus), polyps, or significant swelling (edema) [3][4].
  • A Note of Caution: Because the sphenoid sinus is so deep, it is possible for a nasal endoscopy to look normal even if there is an active infection trapped inside the sinus [2].

2. CT Scan: The Gold Standard for Anatomy

A high-resolution CT scan (Computed Tomography) is the most important tool for planning your treatment. It provides a detailed “road map” of the bones in your skull [5][6].

  • Bony Anatomy: CT is the best way to see Onodi cells (posterior ethmoid cells that grow over the sphenoid) and to check for bony dehiscence (natural gaps in the bone protecting your carotid artery or optic nerve) [7][8].
  • Identifying the Cause: CT can show calcified plaques (small white spots), which are a strong indicator of a fungal ball (mycetoma) [9][10].

Checklist for a Complete Radiology Report

For your evaluation to be considered “complete” and safe for surgical planning, the radiology report from your CT scan should systematically address the following landmarks [11][12]. You can use this checklist to review the report with your doctor:

  1. Optic Canal: Is there protrusion of the optic nerve into the sinus? [13]
  2. Internal Carotid Artery (ICA): Is the bone over the artery thin or missing (dehiscence)? [8]
  3. Onodi Cells: Are these posterior cells present? [7]
  4. Sinus Septa: Where do the internal walls of the sinus attach? (If they attach to the carotid artery wall, they must be handled with extreme care during surgery) [14].
  5. Sinus Expansion (Pneumatization Pattern): How expanded or “aired out” is the sinus? A widely expanded sinus means the blood vessels are more exposed, requiring a more cautious surgical approach [15][16].

3. MRI: Looking at the Nerves and Brain

While CT looks at the bone, an MRI (Magnetic Resonance Imaging) looks at the soft tissues, nerves, and brain [17][6]. An MRI is not always necessary, but it is explicitly required if your doctor suspects:

  • Intracranial Extension: If there is concern the infection is moving toward the brain or causing meningitis [18][19].
  • Cavernous Sinus Involvement: To check for life-threatening blood clots (thrombosis) in the major veins behind the eyes [17][18].
  • Neoplasms: To rule out tumors if a mass is seen on the CT scan [20][21].

Return to Main Page

Common questions in this guide

Why is a CT scan necessary for sphenoid sinusitis?
A high-resolution CT scan provides a detailed map of the bones in your skull. It is the best way to see the exact anatomy of your sphenoid sinus and identify indicators like a fungal ball before planning any treatment.
What are Onodi cells and why do they matter?
Onodi cells are posterior ethmoid air pockets that grow over the sphenoid sinus. Identifying them on a scan is critical for your doctor to plan a safe surgery and avoid injuring nearby important structures like the optic nerve.
Do I need an MRI to diagnose sphenoid sinusitis?
An MRI is not always required, but your doctor will order one if they suspect the infection is spreading toward your brain or major nerves. It helps visualize soft tissues and rule out serious complications like blood clots or meningitis.
Can a nasal endoscopy miss a sphenoid sinus infection?
Yes, because the sphenoid sinus is located very deep in the head, an endoscopy might look completely normal even if there is an active infection safely trapped inside the sinus cavity.
What does calcification in my sinus scan mean?
Calcified plaques are small white spots that appear on your CT scan. They are a strong indicator of a fungal ball, also known as a mycetoma, which requires a different treatment approach than a standard bacterial infection.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Based on my CT scan, do I have 'Onodi cells,' and how do they affect the way we treat this infection?
  2. 2.Is there evidence of 'calcification' in the sinus, which might suggest a fungal ball rather than a bacterial infection?
  3. 3.Do you see any signs that the infection or inflammation has spread toward the cavernous sinus or the brain?
  4. 4.Based on my symptoms and imaging, should I also have an MRI to look at the soft tissues and nerves?

Questions For You

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Related questions

Do I Need a CT or MRI for Chronic Sphenoid Sinusitis?Is Sphenoid Sinusitis Often Misdiagnosed as Migraines?

References

References (21)
  1. 1

    Surgical treatment of isolated sphenoid sinusitis - A case series and review of literature.

    Villemure-Poliquin N, Nadeau S

    International journal of surgery case reports 2021; (79()):18-23 doi:10.1016/j.ijscr.2020.12.091.

    PMID: 33422847
  2. 2

    Evaluation and treatment of isolated sphenoid sinus diseases.

    Tang IP, Brand Y, Prepageran N

    Current opinion in otolaryngology & head and neck surgery 2016; (24(1)):43-9 doi:10.1097/MOO.0000000000000218.

    PMID: 26575516
  3. 3

    Isolated Fungal Sphenoid Sinusitis After Endonasal Transsphenoidal Approach.

    Chung HJ, Lee H, Oh J, Chang JH

    Ear, nose, & throat journal 2022; (101(6)):NP238-NP239 doi:10.1177/0145561320961205.

    PMID: 32965127
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    Series of isolated sphenoid disease: Often neglected but perilous.

    Yap HJ, Ramli RR, Yeoh ZX, Sachlin IS

    SAGE open medical case reports 2022; (10()):2050313X221097757 doi:10.1177/2050313X221097757.

    PMID: 35646372
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    Endoscopic Treatment of Isolated Sphenoid Sinus Disease in Children.

    Wang PP, Ge WT, Ni X, et al.

    Ear, nose, & throat journal 2019; (98(7)):425-430 doi:10.1177/0145561319841227.

    PMID: 31012343
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    Chronic Sphenoiditis With Deep Neck Space Extension: Case Report With Review of the Literature and Postulated Mechanisms for Extracranial Extension.

    Rossi IR, Levinson J, Kuan EC, Tajudeen BA

    Ear, nose, & throat journal 2024; (103(3)):151-155 doi:10.1177/0145561321989453.

    PMID: 33470832
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    Imaging Analysis of Onodi Cells on Cone-Beam Computed Tomography.

    Ali IK, Sansare K, Karjodkar F, Saalim M

    International archives of otorhinolaryngology 2020; (24(3)):e319-e322 doi:10.1055/s-0039-1698779.

    PMID: 32754243
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    Neurovascular structures in the lateral recess of the sphenoid sinus. A computed tomography evaluation.

    Treviño-Gonzalez JL, Santos-Santillana KM, Maldonado-Chapa F, Morales-Del Angel JA

    Neurocirugia 2023; (34(3)):105-111 doi:10.1016/j.neucie.2022.11.011.

    PMID: 36774255
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    Analysis of factors affecting diagnosis of unilateral isolated fungal sphenoid sinusitis.

    Wang Y, Chen X, Li D, et al.

    SAGE open medicine 2024; (12()):20503121241308694 doi:10.1177/20503121241308694.

    PMID: 39698144
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    Visual function loss in fungal sphenoid sinusitis: clinical characteristics and outcomes.

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    Scientific reports 2024; (14(1)):8649 doi:10.1038/s41598-024-59107-2.

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    Preoperative Computed Tomography Imaging of the Sphenoid Sinus: Striving Towards Safe Transsphenoidal Surgery.

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    Journal of neurological surgery. Part B, Skull base 2020; (81(3)):251-262 doi:10.1055/s-0039-1691831.

    PMID: 32499999
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    A Novel International Endoscopic Sphenoid Surgery Classification (IESSC): A Delphi Consensus.

    Albaharna H, Alrasheed A, AlQahtani A, et al.

    International forum of allergy & rhinology 2025; (15(8)):828-836 doi:10.1002/alr.23572.

    PMID: 40126454
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    Sphenoid Sinus Pneumatization Types and Correlation with Adjacent Neurovascular Structures Using Cone-Beam Computed Tomography.

    Tavakoli M, Jafari-Pozve N, Aryanezhad SS

    Indian journal of otolaryngology and head and neck surgery : official publication of the Association of Otolaryngologists of India 2023; (75(3)):2245-2250 doi:10.1007/s12070-023-03796-0.

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    Anatomical and Volumetric Analysis of the Sphenoid Sinus by Semiautomatic Segmentation of Cone Beam Computed Tomography.

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    The Journal of craniofacial surgery 2021; (32(3)):1166-1170 doi:10.1097/SCS.0000000000007209.

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    Sphenoid sinus pneumatization types, extensions and adjacent neurovascular structures: a systematic review with meta-analysis and meta-regression.

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    Evaluation of the relationship between sphenoid sinus morphology and area and volume by computed tomography.

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    [Cavernous sinus thrombosis as a rare cause of exophthalmos in childhood : A case report].

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    Diagnosis of Acute Isolated Sphenoid Sinusitis Based on a Positive Kernig Sign in a Pediatric Patient.

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This information is for educational purposes and does not replace professional medical advice. Always review your imaging and radiology reports directly with your ENT specialist.

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