Prof. Dr. Ahmet Özdoğan
ENT — General

Onodi Cells (Sphenoethmoidal Cells)

Onodi cells are the posteriormost ethmoid air cells pneumatising superolaterally beyond the sphenoid sinus face, present in 8–14% of the population; when present, the optic nerve courses through or immediately adjacent to the cell in 78% of cases, creating a critical risk in FESS.

Onodi Cells (Sphenoethmoidal Cells) is a concept in general ENT whose meaning becomes clear only when it is linked to examination findings. Onodi cells are the posteriormost ethmoid air cells pneumatising superolaterally beyond the sphenoid sinus face, present in 8–14% of the population; when present, the optic nerve courses through or immediately adjacent to the cell in 78% of cases, creating a critical risk in FESS. Age, symptom duration, comorbidities, earlier treatment and daily limitation can all change the interpretation. this topic assessment brings nasal-sinus symptoms, this term throat-tonsil context, the finding upper-airway impact and this entry sleep links into one ENT frame. In this the clinical point practice approach, the term explains which finding is being assessed and why it matters. The first clinical frame for the dictionary entry is to separate functional impact from safety concerns: Identified on sagittal CT as an air cell posterior to the expected sphenoid face; on axial CT alone it may be confused with the sphenoid sinus. This distinction prevents rushed treatment decisions.

In the first visit for this topic, the patient's goal and safety boundary are clarified. Duration, side, daily impact, response to medication or surgery and current reports are read together. this term review may combine ENT examination, this entry endoscopic assessment, the clinical point oral cavity-oropharynx inspection and the dictionary entry audiological testing when useful. this topic decisions record fever, this term pain-bleeding pattern, the finding hearing or nasal blockage, this entry sleep impact and the clinical point infection recurrence separately. Assessment of the dictionary entry looks for consistency between history and examination: Preoperative identification of Onodi cells is a standard-of-care and medicolegal expectation. If findings do not match, staged reassessment or a second opinion may be clearer than moving directly to a procedure. Laboratory work, audiology, endoscopy, ultrasound, CT, MRI or biopsy is requested only when it improves decision quality.

A this topic plan aims to reduce symptoms without adding unnecessary procedural burden. Mild stable findings are discussed as lower-urgency observation points, while progressive or structural changes are handled with more caution. the clinical point planning discusses medical treatment, the dictionary entry allergy control, this topic endoscopic procedures, this term adenoid-tonsil strategy or the finding airway surgery by indication. The goal in this entry is not to choose the most aggressive option, but to find the right step between safe observation and effective intervention. Options are ordered by comparing short-term relief with preservation of long-term function.

Monitoring for the clinical point compares previous examination, imaging, tests or operation notes with the current picture. the dictionary entry follow-up compares pain, this topic nasal openness, this term sleep quality, the dictionary entry hearing impact and this topic infection recurrence over time. When this term is explained, patient goals, medical necessity and realistic expectations meet on the same ground. Follow-up advice separates warning signs without creating panic; the finding follow-up with high fever, increasing pain, worsening blockage or recurrent infection deserves reassessment.

This this entry entry prepares patients and relatives but does not diagnose. Safer conclusions come from combining the complaint with examination findings, test results when needed, risk profile and a review plan.

Diagnosis

CT is mandatory. Onodi cell is identified on sagittal CT as an air cell posterior to the expected sphenoid face. Axial CT alone may lead to confusion with the sphenoid sinus. Optic canal dehiscence (4–8%) can be further evaluated with MRI when optic nerve compression is suspected. Types should be noted per Stammberger classification; optic nerve risk must be stated in the surgical informed consent.

Treatment

Surgery in the posterior ethmoid including an Onodi cell requires meticulous step-by-step dissection. Neuronavigation is at a standard recommendation level. The posterior-superior wall must not be penetrated without confirming optic nerve and carotid position. Only bipolar cautery should be used near the optic canal. Transfer to a tertiary centre should be considered for inexperienced surgeons.

Outcomes and Follow-up

Optic nerve injury during FESS is estimated at 0.03% overall; this rate increases dramatically without preoperative Onodi identification. Permanent blindness results from nerve transection or disruption of its blood supply. Preoperative Onodi identification is standard of care and a medicolegal expectation. Postoperative visual change is a surgical emergency requiring simultaneous ENT plus ophthalmology plus neurosurgery consultation.

When to Seek Care

When Onodi cells are identified on preoperative CT, the surgeon's informed consent process must be complete. Any visual change during FESS recovery constitutes a surgical emergency; the patient must be sent to the emergency department. When posterior ethmoid pathology is observed alongside CT findings showing optic canal proximity, referral to an experienced sinus surgeon is recommended.

Frequently asked questions

What is Onodi Cells (Sphenoethmoidal Cells)?
Onodi cells are the posteriormost ethmoid air cells pneumatising superolaterally beyond the sphenoid sinus face, present in 8–14% of the population; when present, the optic nerve courses through or immediately adjacent to the cell in 78% of cases, creating a critical risk in FESS. Onodi Cells (Sphenoethmoidal Cells) is a concept in general ENT whose meaning becomes clear only when it is linked to examination findings.
When is Onodi Cells (Sphenoethmoidal Cells) clinically important?
In the first visit for this topic, the patient's goal and safety boundary are clarified. It is assessed together with examination, endoscopy or imaging in nasal, throat, sinus and upper-airway complaints.
When is ENT assessment relevant for Onodi Cells (Sphenoethmoidal Cells)?
ENT assessment becomes relevant if symptoms last more than a few weeks, become one-sided or progressive, or are accompanied by breathing, swallowing, voice, hearing or neck-mass findings.
What information helps assessment of Onodi Cells (Sphenoethmoidal Cells)?
It is useful to note when symptoms started, which side is affected, previous operations or treatments, current medication, imaging and test reports, and the effect on daily life. It is assessed together with examination, endoscopy or imaging in nasal, throat, sinus and upper-airway complaints.

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References

This glossary entry is for informational purposes only and does not constitute medical advice. Consult a qualified specialist for diagnosis and treatment.

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