Sinuses - Anatomy/Pathology/Reporting Flashcards
Drainage groups for sinuses
What are included in anterior and posterior group?
Anterior - anterior ethmoid cells, frontal and maxillary sinus. Drainage to middle meatus.
Posterior - sphenoid and posterior ethmoidal. Drain into superior meatus
When to image?
Acute sinusitis < 4 weeks is a clinical diagnosis and generally doesnt require imaging. Unless complications.
- Confirm disease
- Evaluate extend of disease
- FESS workup
-To look for anatomic variants
- Rule out other pathology
CT is best modality for inflammatory disease.
For complications and rule out tumour and look at orbital involvement - MRI
Use of plain film usually not appropriate.
5 patterns of rhinosinusitis?
Look for different blockages according to area once you see pattern.
- Sphenoethmoid (blockage sphenoethmoid recess or superior turbinate)
- Infundibular pattern (opacification of one of both maxillary sinuses with blocked infundibulum)
- Osteomeatal pattern - obstructionin region of hiatus semilunaris. (The frontal, maxillary, anterior, and middle ethmoidal sinuses all drain into the hiatus semilunaris of the middle meatus. Any mechanical block in this region causes inflammation of the above-mentioned sinuses).
- Nasal polyposis
- Sporadic pattern
mucosal thickening
retention cysts
antrochoanal polyp
silent sinus syndrome
odontogenic sinusitis
mucocele
It drainage pathways are blocked this can cause sinusitis.
Anatomy
What is hiatus semilunaris?
Hiatus semilunaris is a semicircular shaped opening located on the lateral wall of the nasal cavity.
It is a component of the ostiomeatal complex and **serves as the opening for the frontal and maxillary sinuses and the anterior ethmoid air cells. **
It is inferior to the ethmoid bulla and the uncinate process forms its anterior border.
Anatomy
Where is basal lamella?
How to find?
The basal lamella, also known as basal lamella of the middle turbinate, is an osseous lamella that separates the anterior from the posterior ethmoid sinuses
Tip to find - follow up posterior part of middle turbinate.
What is normal mucosal thickening?
Which sinuses is it abnormal?
Normal limits:
maxillary sinus: ≤ 4mm
ethmoid air cells: ≤ 2 mm
frontal sinus: 0 mm
sphenoid sinus: 0 mm
If you see thickening in frontal and sphenoid sinus, this is always abnormal and usually symptomatic.
Are mucous retention cysts of any concern?
None unless causing obstruction.
Features of a mucocele
Where sinus cavity is fully opacified and there is continuing mucus production but obstruction of drainage.
- Sinus expansion
- Bone remodelling
Can be high or low T2 signal depending on protein content.
If enhancement is present, it is only in the peripohery.
High density within a sinus - what could this represent?
Calcification in sinus - what to think of ?
High denisty - chronic sinusitis or fungus. Inspissated secretions can also do this.
Calcification - can be seen in mycetoma or odontogenic material.
FESS
What is the aim of it?
To restore drainage pathways.
Common targets are osteomeatal complex and frontal recess.
Pre-FESS CTs are now mandatory to reduce risk of complications.
Aim of pre FESS CT?
To look for anatomical variants and reduce risk of a surgical complication.
Use CLOSE mnemonic to comment on important areas.
Cribriform plate
Lamina papyracea
Onodi cells
Sphenoid pneumatisation
Ethmoidal artery (anterior)
CLOSE
Cribriform plate
- Lateral lamella depth - The deeper the olfactory fossa (lateral lamella) the higher risk of injury and CSF leak.
- Fovea ethmoidalis position should be horzontal.
CLOSE
Lamina papyracea
Check for previous or current trauma as risk of orbital infection.
Check for adherent unicinate process
CLOSE
Onodi cell
These are posterior most extension of ethmoidal air cells above sphenoid sinus.
Close relationship to the optic nerve and ICA - therefore important to mention!! Sinusitis and tumours can involve here and then optic nerve.
A mimic can be a sphenoid sinus recess (left side in picture).
Normal sphenoid sinus
- no horizontal septum
- no air cells above sphenoid sinus
Onodi cell
- horizontal septum on coronal between sphenoid and onodi cell
- optic nerve canal can be dehiscient
-
CLOSE
Sphenoid pneumatization
This be an operative risk of there is excessive pneumatization
Pneumatization of the sphenoid sinus can extend laterally to include the pterygoid plate and the greater wing or lesser wings of the sphenoid sinus.
Look at pneumatisation in relation to the sella.
Look for dehiscience of:
- vidian canal
- V2
- carotid canal
CLOSE
Ethmoidal artery
The anterior ethmoidal artery (AEA) is a branch of the ophthalmic artery. In endoscopic sinus surgery, it is usually identified in its location as it crosses the fovea ethmoidalis from posterolateral to anteriomedial, posterior to the bulla ethmoidalis, between the second and third lamellae.
What are Haller cells?
WHere are supraorbital air cells?
Where are they?
These are infraorbital ethmoidal air cells
Located at the inferomedial orbit.
Can become infected.
Mention in pre-FESS report.
Supraorbital air cells
Are in position as expected. Can be mistaken for frontal sinus.
What is Choanal atresia?
What is clinical presentation?
Crying/breathing etc
Choanal atresia, the most common congenital abnormality of the nasal cavity, is thought to result from failure of rupture of the oronasal membrane during the sixth week of fetal life.
It consists of obstruction of the posterior opening of the nasal cavity, which is mixed bony-membranous in approximately 70% of cases and pure bony atresia in 30% of cases.
Choanal atresia can be unilateral (in 50% to 60% of cases) or bilateral, and it is more common in girls (the female : male ratio is 2 : 1).
**Bilateral choanal atresia presents with severe immediate onset of respiratory distress in the newborn, because infants are obligate nasal breathers. Symptoms are aggravated by feeding and relieved by crying. The inability to pass a nasogastric tube in a neonate with well-aerated lungs suggests the diagnosis. **
Bilateral ass with CHARGE
Approach to reporting CT Sinuses
CLOSE Summary
What is silent sinus syndrome?
What is cause?
Represents maxillary sinus atelectasis, resulting in painless enophthalmos, hypoglobus and facial asymmetry.
Presents in 3rd to 5th decade.
Chronic occlusion of the maxillary sinus ostium/ostia results in gradual resorption of the air. Subsequently, negative pressure is generated within the sinus 3. This, in turn, results in gradual inward bowing of all four of the maxillary walls: roof (orbital floor), medial, posterolateral and anterior walls. Orbital volume increases with resultant enophthalmos and variable flattening of the malar eminence 1.
CT
The sinus is fully formed but fully opacified and reduced in volume with inward bowing of all four walls. This manifests as:
- inferior bowing of the roof (orbital floor): - -
- increased orbital volume and enophthalmos
- lateral bowing of the medial wall
- lateral displacement of the middle and inferior turbinate
- posterior bowing of the anterior wall
- flattening of the malar eminence
- anteromedial bowing of the posterolateral wall
The uncinate process is usually superiorly and laterally displaced, in direct contact with the inferomedial wall of the orbit, and the ostiomeatal complex is occluded 1.
Reporting Summary - what we need to look at?
5 things
- Extent of nasal cavity and sinus opacification.
- Opacification of sinus drainage pathways
- Anatomical variants - nasal
- Critical variants - depth of lamella, sphenoid cells.
- Soft tissues of the brain, neck and orbits
Reporting:
Sinus opacification
Where?
- What?
Mucosal thickening
Opacification and density
Mass and traps - Effect? - Bone erosion, sclerosis, expansion
Reporting:
Talk about drainage pathways
- Osteomeatal complex
- Frontal recess
- Sphenoethmoidal recess
Reporting:
Nasal cavity anatomical variants
Mention nasal septum deviation if present (may need to do septoplasty)
If big turbinate - this may need removed in order to perform surgery.
Reporting:
Critical variants - ethmoid roof
Mention type
Important for surgeon to know this when doing ethmoidectomy
Reporting:
Position of anterior ethmoidal artery
Look for V shaped indentation on coronal
Normal position is superomedial orbit
If it sits a bit lower then there is a risk of injury during ethmoidectomy
Checklist for reporting Rhinosinusitis
Acute - air fluid levels and frothy secretions.
Chronic - look for hyperostosis.
Be aware masses such as SCC (can look like polyposis but look out for bony erosion)
**
Summary of sinus pathologies
Features of inverted papilloma
how to differentiate from antrochoanal polyp?
Inverted papilloma
3 types:
- inverted
- oncocytic
- exophytic
Typucally arise in middle meatus.
- soft tissue density
- extends into a sinus or ethmoid air cells
- will have a focal hyperostosis in 95 of cases (usually denotes the origin)
- cerebreform enhancement
Antrochoanal polyp is usually fluid density. Can extend from sinus or nasal cavity to choana.
Recurrence can be common due to imcomplete resection.
Fungal sinusitis
Simple vs invasive
What are features of invasive?
Fungal sinusitis is usually hyperdense on CT. Calcifiation is also a characteristic finding.
Reporting:
Masses in nasal cavity
What imaging technique can be used?
Secretions and inflammatory mucosa will be T2 hyerintense
Tumour will be iso/hypointense
Staging of nasal masses
T3 vs T4
What is considered T4?
Uncinate process can have different shapes
Which are the most important for the surgeon?
- Relation to the orbit and antral outflow (ethmoid infundibulum)
- Superior attachment of the uncinate process (frontal recess)
What is Agar nasi?
Where is it?
(Supra bulla cell below)
Supra agar cell
Most anterior ethmoid air cell.
Posterior to this is ethmoidal bulla.
If agar nasi is large, can obstruct drainage of frontal sinus through ‘frontal sinus drainage pathway’.
There can be extra cells above agar nasi than can also limit drainage.
Identify accessory sinus ostium
Where are they usually?
Where do antrochoanal polyps extend out through?
Through accessory sinus ostium
Role of MR in inflammatory and infectiive sinonasal disorders
What to look for in nasal angiofibroma?
Expansion of sphenopalatine foramen and erosion of the medial pterygoid plate
Summary of sinonasal tumours
Sinonasal SCC
Most common sinonasal malignancy (27.8-92%!) approx. 60-70%
Usually antrum (60-73%) and nasal cavity (20-30%), 10-15% ethmoid, 1% sphenoid and frontal
6-7th decade
Nickel exposure
Main imaging aim to assess submucosal extent
Local recurrence usual cause of treatment failure (20-50% first year)
Nodal involvement 15% (Antral SCC mainly)
Adenocarcinoma
10-20% sinonasal tumours
Predilection ethmoid (and superior nasal cavity)
Risk factors: wood dust
Emerging Renal cell-like adenocarcinoma)
Olfactory Neuroblastoma
Rare All age groups (was bimodal) but peak 40-50 yrs
Initial unilateral nasal vault mass
Highest % of retropharyngeal nodal involvement
Later extension intracranial/orbit
Recurrence may occur many years after initial treatment
Kadish staging
Rhabdomyosarcoma
Expansile destructive antral mass with extension into:
Orbit(through periosteum)
Nasal cavity
Maxillary alveolus
Pre antral
PPF
Infratemporal fossa
Chondrosarcoma
Peripheral enhancement. Enhancement of septae. High T2 signal.
Look for chondroic calcs on CT.
