Sinus and Anterior Skull Base Flashcards
Esthesioneuroblastoma overview
rare, Olfactory mucosa tumor
AKA Olfactory neuroblastoma
Typically seen in adolescent or middle aged patients w/ mild epistaxis and nasal obstruction
Esthesioneuroblastoma imaging
- Best imaging: Enhanced MR with bone only CT
- Characteristics: Dumbbell-shaped mass with “waist” at cribriform plate
- Bone remodeling died with bone destruction, esp of cribriform
Esthesioneuroblastoma staging
- Kadish staging system good for prognosis
- A: limited to nasal cavity
- B: Nasal cavity+ paranasal sinuses
- C: Extends to skull base, intracranially, orbit
- D: cervical mets
Esthesioneuroblastoma general tx and recurrence/mets rate
- TX: Surg+ Chemo
- 5 yr survival: 75-77%
- Recurrence 30%
- Mets in 10-30%
Sinus mass DDX
Esthesioneuroblastoma
SCC
Sinonasal adenocarcinoma or minor salivary tumors
Sinonasal NHL
Sinonasal Melanoma (Intense on T1 MRI)
Sinonasal undifferentiated carcinoma
JNA in young men
Frontal Sinus normal variations
Absent 5%
Unilateral 15-20%
Frontal sinus pneumatizes from ethmoid with 4 Pits
Lots of variation
1st –> Agger nasi cell (most consistent, 98% have it)
2nd –> Front sinus
3rd and 4th–> Supraorbital cells
Kuhn and Bohler Classification
Drainage pattern of frontal sinus
1: Single frontal recess above agger nasi cell
2: tier of cells in frontal recess above agger nasi
3: Large cell pneumatizing from frontal recess into frontal sinus
4: cell totally isolated within frontal sinus
Frontal Recess anatomy
Middle turbinate is medial
Lamina papyracea is lateral
Posteriorly is bulla lamella (if this doesnt reach skull base, the recess may open into suprabullar recess)
Frontal process of maxilla is anterior
Weakest point of ethmoid bone
Lateral lamella of ethmoid
Frontal sinus drainage
- MC medially 80%
- Directly into Agger nasi (10%)
- Posteriorly (10%)
Maxillary Sinus Hypoplasia
Bolger et al
Import bc there’s an increase risk for surgical damage to orbit
3 types
I: Mild, elongated orbit, atrophic uncinate
II: Very small sinus
III: All bone, no sinus
Anterior ethmoid arteries
Always behind optic nerve
“Nipple sign” on CT coronals
Ethmoid Bulla
Most constant and largest anterior ethmoid cell
Projects inferomedially over hiatus semilunaris
MC drains into retrobulbar space but varies
Basal Lamellae
Where middle turb attaches to orbit
Separates anterior from posterior ethmoids
Haller cells
Infraorbital air cell
Can impinge on ostiomeatal complex blocking maxillary sinus drainage
Sphenoid Sinus safety
Axial scans tell you about carotid protection
If sphenoid septum attaches to carotid canal
Ostiomeatal complex 5 structures
- Maxillary ostium
- Infundibulum
- Ethmoidal bulla
- Uncinate process
- Hiatus semilunaris
Infundibulum
Uncinate is medial
Orbital plate of ethmoid id lateral
Common channel draining the ostia of the maxillary antra and anterior ethmoid air cells to the hiatus semilunaris
Often continuous with the frontonasal recess
Uncinate process
Arises from posteromedial aspect of nasolacrimal duct
Anterior boundary of hiatus semilunaris
Hiatus semilunaris
final drainage passage, b/t ethmoid bulla superiorly and free edge of uncinate process
Chordoma Imaging CT and MRI features
CT:
well circumscribed, destructive lytic lesion
irregular intratumoral calcifications
Moderate enhancement
Can have positive thumb sign (mass imprints on pons)
MRI
T2: Highly enhancing
T1 w/ contrast: honeycomb appearance
T1: Low intensity
Chordoma Pathophysiology and activity
Embryonic remnants of the primitive notochord (earliest fetal axial skeleton, extending from the Rathke’s pouch to the coccyx)
Extradural and result in local bone destruction
Locally aggressive, but uncommonly metastasise
30-35% of them are sphenoid-occipital
The rest are vertebral or sacrocoxygeal
Clival mass DDX
Chordoma chondrosarcoma of skull base plasmacytoma meningioma of skull base pituitary macroadenoma ecchordosis physaliphora
7 segments of the ICA
Mnemonic and segments
- Mnemonic: C’mon Please Learn Carotid Clinical Organizing Classification. Bouthillier classification
- C: cervical segment
- P: petrous segment
- L: lacerum segment
- C: cavernous segment
- C: clinoid segment
- O: ophthalmic segment
- C: communicating segment
Petrous Apex DDX
- asymmetrical marrow
- petrous apex cephalocoele
- petrous apicitis
- congenital cholesteatoma
- cholesterol granuloma: most common cystic appearing lesion
- mucocoele of petrous apex
- benign tumours
* meningioma
* schwannoma - malignant tumours
* skull base chondrosarcoma: MC solid lesion
* skull base chordoma: often midline but can involve the petrous apex
* plasmacytoma
* metastatic lesion - Langerhans cell histiocytosis
- aneurysm of terminal internal carotid artery
Petrous apex cephalocoele
rare form of cephalocoele centered typically in the posterolateral part of Meckel cave with variable extension into the petrous apex. They can be unilateral or bilateral (commoner)
Usually asymptomatic, but can p/w SNHL, trigem neuralgia
Petrous apicitis pathophys and S/s
Infection with involvement of bone at the very apex of the petrous temporal bone.
Usually 2/2 otomastoiditis
S/S:
- deep facial pain due to inflammation of the adjacent dura and trigeminal nerve in Meckel’s cave
- abducens nerve palsy (see Gradenigo syndrome) due to involvement of Dorello’s canal
Cholesterol Granuloma Overview
Middle ear granulation tissue which is particularly prone to bleeding, and is a frequent cause of a hemotympanum