IMAGING OF PARANASAL SINUSES

Dr. Archana Koshy

SINONASAL PHYSIOLOGY The normal secretions produced by the sinuses are cleared by the cilia

lining the mucosa .

These drain the secretions towards the natural sinus ostia .

FRONTAL SINUSES – drain into the frontoethmoidal recess through the

anterior ethmoid air cells into the anterior frontal recess of the middle

meatus.

ANTERIOR ETHMOID – drain into the anterior aspects of the hiatus

semilunaris .

MIDDLE ETHMOID – Through the ethmoid bulla , the posterior ethmoids

drain into the superior meatus .

MAXILLARY SINUS – drains via the infundibulum into the ostium .

SPHENOID SINUS – into the sphenoethmoid recess posterior to the superior

meatus .

Nasal StructuresThe nasal septum is a midline structure composed of both bone and cartilagenous

tissue. Its deviation can cause partial obstruction in the nasal cavities unilaterally or

on both sides depending on its shape.

The lateral nasal wall has three projections superior, middle and inferior

turbinates.

These structures divide the nasal cavity into three air passages the superior,

middle and inferior meatus.

The inferior turbinate is the lower most projections arising from the lateral nasal

bone and extending into the nasal cavity and running posteriorly toward the

nasopharynx.

The middle turbinate lies above the inferior turbinates. Anterosuperiorly, the

middle turbinate attaches to the skull base just lateral to the cribriform plate. In its

middle third it turns coronally and laterally to insert on the lamina papyracea and

posteriorly to the

roof of ethmoidal complex .

The basal lamella is the portion of the middle turbinate where it attaches to the

ethmoid

Coronal CT image showing nasal

structure. Middle turbinate (white

arrow) and lamina papyracea (black

arrow)

Coronal CT at the level of OMC showing

uncinate process

(black arrow), agar nasi cells (short

white arrow) and frontal recess(white

long arrow)

Coronal section showing anterior draining pathway including frontal

recess (white arrow), maxillary ostium (thin black arrow), infundibulum

(thick black arrow), middle meatus (short black arrow) and maxillary

sinus (star)

THE OSTEOMEATAL COMPLEX

• Region where the frontal ,anterior and middle ethmoid and maxillary sinuses

drain .

• Includes the fronto ethmoidal recess , uncinate process , hiatus semilunaris ,

ethmoid bulla , the maxillary infundibulum and ostium and the ethmoid

infundibulum .

• Disease at the OMC is the major cause of recurrent acute/chronic sinusitis .

Frontal sinuses.

FRONTAL RECESS

The frontal recess is an hourglass like narrowing between the frontal sinus and the anterior middle meatus through which the frontal sinus drains

The frontal recesses are the narrowest anterior air channels and are common sites of inflammation. Their obstruction subsequently results in loss of ventilation and mucociliaryclearance of the frontal sinus

SPHENOID SINUS

Sphenoid sinus develops in the body of the sphenoid sinus and drains via a sinus ostium into spheno ethmoid recess.

The degree of pneumatisation is variable and may extend into greater and lesser wing of sphenoid and pterygoid plates.

There are many important structures in relation to sphenoid sinus like vidian canal, optic nerve and foramen rotundum.

Ethmoid air cells

Thin walled air cavities in the lateral masses of the ethmoid

bone. Varies from 3 – 18 in number.

Clinically divided into anterior ethmoidal air cells & posterior

ethmoidal air cells, by basal lamella (lateral attachment of

middle turbinate to lamina papyracea)

Anterior drain into- Middle meatus.

Posterior- sup.meatus & spenethmoidal recess.

ANATOMICAL VARIANTS

PARADOXIC CURVATURE

Normally, the convexity of the middle turbinate bone is directed medially, toward the nasal septum.

When paradoxically curved, the convexity of the bone is directed laterally toward the lateral sinus wall.

The inferior edge of the middle turbinate may assume various shapes, which may narrow and/or obstruct the nasal cavity, infundibulum, and middle meatus.

Concha Bullosa It is an aerated turbinate, most often the

middle turbinate.

When the pneumatization involves the

bulbous segment of the middle turbinate, the

term concha bullosa applies.

If only the attachment portion of the middle

turbinate is pneumatized, and the

pneumatisation does not extend into the

bulbous segment, it is known as a lamellar

concha.

Concha bullosa (arrow) causing partial

obstruction of the middle meatus. Note left

DNS

AGGER NASI AIR CELL

Its an ethmoturbinalremnant present in nearly all patients.

Located anterior to the vertical attachment of the middle turbinate to the skull base.

The degree of ANC pneumatization varies and has a significant effect on both the size of the frontal sinus ostium and the shape of the recess.

HALLER CELL

These are ethmoid air cells located

anterior to the ethmoid bulla, along the

orbital floor, adjacent to the natural

ostium of the maxillary sinus, which

may cause mucociliary drainage

obstruction, predisposing to the

development of sinusitis.

Coronal CT image showing Haller cells

(white arrows) along the roof of the

maxillary sinus medially, causing

narrowing of the infundibulum (black

arrow)

Sphenoethmoid cell (Onodi cell)

This is formed by lateral and

posterior pneumatization of the most

posterior ethmoid cells over the

sphenoid sinus.

The presence of Onodi cells

increases the chance that the optic

nerve and / or carotid artery would

be exposed in the pneumatized cell.

Coronal CT at the level of sphenoid

sinus (asterix), showing Onodi cells

lying superior to the sphenoid sinuses

and in close relation to optic nerves

(black arrows)

Accessory maxillary ostia

Accessory maxillary ostia are generally solitary, but occasionally may be multiple.

Such variation may be congenital or secondary to sinusal diseases.

Possible mechanisms involved in the development of such variation include:

main ostium obstruction, maxillary sinusitis or anatomical/pathological factors in the middle meatus, resulting in rupture of membranous areas.

VARIATIONS OF THE OPTIC NERVE The optic nerve, carotid arteries, and vidian nerve develop prior to

the paranasal sinuses, and are responsible for the congenital

variations in the walls of the sphenoid sinus.

Delano, et al., categorized the various relationships between the

optic nerve and posterior paranasal sinuses into four groups.

Type I: The most common type, it occurs in 76% of patients. Here,

the nerve courses immediately adjacent to the sphenoid sinus,

without indentation of the wall or contact with the posterior ethmoid

air cellThe nerve is seen to course

immediately adjacent to the

sphenoid sinus, without

contact with the posterior

ethmoid air cell

Type II: The nerve courses adjacent to the sphenoid sinus,

causing an indentation of the sinus wall, but without contact with the

posterior ethmoid air cell

Type III: The nerve courses through the sphenoid

sinus with at least 50% of the nerve being surrounded

by air

Type IV: The nerve course lies immediately adjacent

to the sphenoid and posterior ethmoid sinus

KEROS CLASSIFICATION Method of classifying the depth of the olfactory fossa.

In adults, the olfactory recess is a variable depression in the cribriform plate. It contains olfactory nerves and a small artery.

The depth of the olfactory fossa is determined by the height of the lateral lamella of the cribriform plate.

Keros in 1962, classified the depth into three categories.

Type 1: 1-3 mm (26.3% of population)

Type 2: 4-7mm (73.3% of population)

Type 3: 8-16mm (0.5% of population)

The type 3 essentially exposes more of the very thin cribriform plate to potential damage from trauma, tumour erosion, csf erosion (in benign intracranial hypertension) and local nasal surgery or orbital decompression.

Thin bone in the skull base, especially the cribriform plate, is susceptible to erosion, encephalomeningocoele herniation and csf leaks

Imaging modalities

X RAY

CT

MRI

X ray – Water’s view & caldwell view.

CT – gold standard. Coronal & axial sections.

MRI is predominantly used for pre and post operative

management of naso sinus malignancy.

The chief disadvantage of MRI is its inability to show the bony

details of the sinuses, as both air and bone give no signal.

PARIETOACANTHIAL PROJECTION:

WATERS VIEW

Extend neck, placing chin and nose against table/upright Bucky surface.

Head is adjusted so as to bring the orbito meatal line to a 45 degree angle to the casette holder.

Position the median saggital plane is perpendicular to the midline of grid or table/upright bucky surface.

Ensure that no rotation or tilt exists.

Centering is done at acanthion.

CALDWELL

Place patient's nose and forehead against upright Bucky or table with neck extended to elevate the OML 15° from horizontal. A radiolucent support between forehead and upright Bucky or table may be used to maintain this position.(alternate method if Bucky can be tilted 15°.)

Align MSP perpendicular to midline of grid or upright Bucky surface.

Centering is done at nasion, ensuring no rotation.

1

PARIETOACANTHIAL TRANSORAL

PROJECTION: OPEN MOUTH WATERS METHOD

CT procedures and techniques

CT is currently the modality of choice in the evaluation of

the paranasal sinuses and adjacent structures.

Its ability to optimally display bone, soft tissue, and air

provides an accurate depiction of both the anatomy and

the extent of disease in and around the paranasal sinuses.

In contrast to standard radiographs, CT clearly shows the

fine bony anatomy of the osteomeatal channels.

SCAN LIMITS :

From the ant margin of

frontal sinus to post

margin of sphenoid sinus

Coronal section procedure

Coronal scans are performed by hyperextension of the patients head and

angulation of the gantry

The patient should preferably be in the prone position with the chin resting on a

pad -KEEPS THE FREE FLUID OUT OF THE INFUNDIBULUM .

In patients unable to do the above, the HEAD HANGING position should be

acceptable .

The gantry should be angled perpendicular to the hard palate .

The ideal scan thickness is 3-5 mm to cover the anterior margin of the

frontal sinus to the posterior margin of the sphenoid sinus .

The radiation dose is kept to the minimu by use of low mA with peak kV of

120.

Images should be obtained at an intermediate setting of 2000-2500 HU

window width and 200-350 HU window level as this provides details of

bone and soft tissues on a single set of films .

PATHOLOGIES AFFECTING THE

PARANASAL SINUSES

1.INFLAMMATORY SINUS DISEASE

a) ACUTE SINUSITIS• Often due to secondary bacterial infection following an URTI of viral

origin or a local infection .

• The infection causes swelling of the mucosa which appears as an opaque rim around the periphery of the sinus .

• Accompanied by an outpouring of the mucus into the sinus cavity , causing an opaque sinus on plain X-ray* .

• Non specific sign ,although in most cases,denotes infection , a sinus filled with blood or new growth can give a similar appearance .

• In any doubts about the presence of fluid , a tilted view should be obtained – to confirm the presence of a fluid level .

Inflammatory sinus disease. Coronal CT image of Inflammatory mucosal disease

demonstrates maxillary (red arrows) and ethmoid (blue arrows) sinus mucosal

thickening, and osteomeatal unit opacification (white arrows).

COMPLICATIONS

1. Osteomyelitis –May follow empyema which may rarely lead to bone

involvement

-Results in loss of outline of the sinus wall followed by frank osteolysis and

bone sequestration.

2. Intracranial abscess- Spread of infection from the frontal or sphenoid

sinuses may result in an intracranial abscess

-CT/MRI will show the characteristic ring enhancement .

3. Orbital cellulitis – Commonly follows an ethmoiditis and may result in

abscess formation , situated outside the perioribita adjacent to the

infected sinus .

B) CHRONIC RHINOSINUSITIS

• Chronic inflammatory disease of the paranasal sinuses and nasal cavity

clinically represents recurrent acute sinusitis or a prolonged episode

that has failed to respond to conservative management .

• CT is the investigation of choice as this defines the degree and extent

of involvement of the paranasal sinuses

• Also provides the surgeon with a ‘roadmap’ of the anatomy before

surgery .

• FESS is usually the treatment for patients with chronic rhinosinusitis .

OSTEITIS. Axial CT image of chronic sinusitis indicated by left sphenoid

sinus mucosal thickening and debris with adjacent osseous wall

thickening (blue arrow). There is also scattered ethmoid air cell

opacification (white arrow)

IMAGING FOR FESS(SSCT)

• Particular attention is paid to the OMC , as most chronic rhinosinusitis is

associated with disease in the middle meatus .

• The CT will show the extent of mucosal thickening and the number of

sinuses affected , and help confirm that the pathology is due to an

inflammatory process .

• CHRONIC DISEASE-will manifest with thickening and sclerosis of the

bones.

• Acute on chronic sinus secretions have a Ct density around 10-25 HU :

watery or mucoid density .

• Once the secretions have chronically thickened and concentrated , the Ct

density will rise to 60-80 HU .

• The MR appearance depends on the protein content of the secretion and

hence can be quite variable .

• MRI is reserved for difficult cases where there is a doubt about the

pathology on SSCT or to assess any intracranial involvement .

• SSCT helps the surgeon avoid the known hazards of endoscopic surgery .

• Shows the anatomical landmarks and the anatomical variants .

• FIVE distinct patterns in which chronic rhinosinusitis presents itself :

1. Infundibular pattern – Obstruction of the maxillary infundibulum resulting in isolated maxillary sinusitis

2. Osteomeatal pattern – Middle meatus obstruction resulting in ipsilateralsinusitis affecting the frontal , anterior and middle ethmoids and the maxillary antrum

3. Sphenoethmoidal recess pattern – Obstruction results in posterior ethmoid and sphenoid sinusitis

4. Sinonasal polyposis – Sinonasal polyps are evident with opacification of various sinuses .

5. Sporadic pattern- retention cysts,mucoceles and mild mucosal thickening without mucosal obstruction

SINONASAL POLYPOSIS • Soft tissue pedunculated masses of edematous hyperplastic upper

respiratory mucosa .

• Specific polysaccharide material within the ground substance attracts excess fluid and electrolytes .

• Commonest site – Ethmoids followed by maxillary antra and then the sphenoid sinus .

• Plain Xrays and SSCT confirm the presence of a polpoidal mass :

1) Widening of the infundibulum

2) Opacification of the sinuses

3) Thinning of the sinus walls, nasal and ethmoid septa

4) Bulging of the lamina papyracea –Displacement of the eyeballs and hypertelorism

Extensive nasal polyposis

(long white arrow) causing

obstruction of anterior

(short white arrow) and

posterior (black arrow)

drainage pathways causing

pansinusitis

Multiple polyps in the maxillary sinus (white arrow) and in the

sphenoid sinus (black arrow)

MUCOCELE

Defined as the end stage of a chronically obstructed sinus – an

obstructed , airless, mucoid filled expanded sinus .

Most commonly affected is the frontal ( 66%) ; Sphenoid mucocele is

rare .

On CT- Mucoid attenuation collection with remodelling of the wall

-The bone may be locally thinned or eroded

MRI is the optimum imaging modality – any intracranial or intraorbital

extension can be assessed before surgery .

Post contrast MRI typically shows peripheral enhancement of the

mucosa with no enhancement of the secretions .

• FRONTAL SINUS MUCOCELE

-Expansion of the sinus cavity with loss of the scalloped margin of the

normal sinus .

The sinus is more opaque than normal , due to secretions ,but may

appear more radio-dense if bone destruction is marked .

CT will show the full extent of the expansion and is usually enough to make

the diagnosis

MRI may be used to assess intracranial extension.

ETHMOID MUCOCELE

-Majority are found in the anterior ethmoid air cells

-Usually more obvious clinically as most present with a palpable mass at

the medial canthus .

SPHENOID MUCOCELE

-Has to be diagnosed and intervened early before vision is compromised

-Involvement of the optic nerve , cavernous sinus and oculomotor

nerve is common due to the proximity of these structures to the sinus .

CT/MRI –shows partially rounded expansion of the sinus .

Mucocele of the ethmoid sinus. Plain X-

ray Water’s view (A) shows an expanded

and opaque left ethmoid sinus.

Coronal non-contrast CT (B) shows the

expanded sinus containing soft tissue

densities. The wall of the sinus are

thickened but are intact

A left sided ethmoidal mucocele (A)

encroaching on the left orbit.

Left globe in proptosed.

T2W MR axial and coronal sections (B)

of the same patient showing

hyperintense fluid contents of the

mucocele

FUNGAL DISEASE

• Usually diagnosed when an apparent routine infection fails to respond to normal antibiotic treatment .

• Aspergillus fumigatus – most common

• The ethmoids and the maxilla antra are commonly involved. The frontal are rarely affected .

• The findings vary from non specific mucosal thickening without bone involvement to an opacified sinus with a central mycetoma with reactive new bone formation or even erosions .

• On CT- High density central mass separated by mucoid separations .

-Areas of calcification may be present .

-Calcifcation may be diffuse , nodular or linear

-Accompanied by bone expansion and bone destruction in the invasive form of the disease .

MRI- Signal hypointensity is the distinctive feature of aspergilloma

Due to the paramagnetic effect of heavy metals present in the fungal ball .

CT images coronal and axial showing diffuse nasal and sinus mucosal

thickening with hyperdensities (black arrows) causing expansion and blockage of

the sinuses.

On bone window, the ethmoid lamellae and sinus walls are remodelled and

eroded (white arrow)

Invasive fungal sinusitis: Axial T2WI (left) and T1WI (right)

images showing soft tissue in the frontal, ethmoid and

sphenoid

sinuses which is isointense on T1WI and hyperintense on

the T2WI

GRANULOMATOUS DISEASE

• Majority are infectious

• Include Tuberculosis , Syphilis, leprosy, rhinoscleroma and

actinomycosis .

• Non specific findings on imaging .

• Most of these start in the nasal cavity with soft tissue masses and

chronic non specific pan sinusitis .

• A diagnosis of granulomatous disease should be considered when

there is evidence of nasal septal mass with septal erosion on

imaging .

LEPROSY: DESTRUCTION OF THE NASAL BONES (ARROW) AND A

PERFORATED NASAL SEPTUM ARE CHARACTERISTIC CHANGES OF

LEPROMATOUS LEPROSY

RETENTION CYSTS

• Occur as a result of obstruction of the ducts of the mucosal glands .

• Usually small, have a well defined outline

• CT- Smooth , broad based soft tissue mass with a well defined

outline .

• MRI – Low intensity on T1 and bright on T2 but may appear bright on

T1 depending on the concentration of entrapped secretions .

TUMOURS OF THE PARANASAL SINUSES

• BENIGN TUMOURS

-OSTEOMA –

• Benign slow growing tumours containing mature compact or

cancellous bone .

• Occur most frequently in the frontal sinus, followed by ethmoid and

maxillary sinuses

• May block the drainage of a sinus resulting in recurrent infection

and/or mucocele .

• Large frontal osteomas can erode the inner table to the frontal bone

which may allow the infection to spread intracranially and

pneumocephalus will be seen .

• Posterior extension may lead to the compromise of the optic nerve .

• Plain film and CT – Well defined very dense lesion (if it contains mature

bone)

• Less ossified if it contains cancellous bone

Osteoma of the left frontal sinus.

Axial and coronal CT scans showing a dense bony lesion of the left sinus

occupying much of the sinus cavity leaving only a thin rim of air around it.

PAPILLOMA• The mucosal lining of the nose is derived from ectoderm and is called the

schneiderian membrane .

• Can give rise to three types of papillomas :

(a) FUNGIFORM – Arises from the nasal septum,usually anteriorly .

(b) INVERTED- Commonest usually originate

(c) CYLINDRICAL CELL from the lateral wall .

-Inverted papillomas – Characterestically arises from the lateral nasal wall

near the middle turbinate and extend into the sinuses ,usually involving the

maxillary and ethmoid sinuses .

SYMPTOMS – Nasal obstruction , epistaxis and anosmia .

INVERTED PAPILLOMA of

the right antrum and

ethmoids. Noncontrast CT

scan shows a hyperdense

soft tissue lesion in the

right

ethmoid and nasal cavity

extending into the right

antrum.

The middle turbinate is

destroyed and the septum

shows focal erosion.

The floor and medial wall of

the orbit is eroded at places

Imaging appearance can vary from a small nasal polypoid mass to

an expansile mass with remodelling of the nasal cavity

May extend into the sinuses with secondary obstructive sinusitis .

The nasal septum usually remains intact but may be remodelled with

bowing of the septum .

INVERTED PAPILLOMAS – usually multicentric .

ADENOMAS – may simulate a nasal polyp but are locally invasive

and local recurrence occurs if they re not completely excised .

NASAOPHARYNGEAL ANGIOFIBROMA

-Rare histologically benign but locally aggressive tumour .

-Highly vascular polypoid mass-usually in males (10-18)

-Almost all tumours originate from the posterior choanal tissue near the

pterygopalatine fossa and the sphenopalatine foramen .

-They fill the entire nasopharynx and frequently extend into the

pterygolpalatine fossa causing widening of the fossa and anterior bowing

of the posterior ipsilateral antral wall .

-Intracranial extension occurs uncommonly in 5-20%-----Superior orbital

fissure widening is seen as an indication .

ANGIOFIBROMA LATERAL X-RAY OF SKULL - showing anterior bowing

(small arrow) of the posterolateral wall of the maxillary sinus due to the

angiofibroma (open arrow)

Angiofibroma: Contrast enhanced axial CT sections show a well-defined

mass in the nasal cavity and in the pterygomaxillary fissure which is wide.

Posterolateral wall of the antrum is pushed anteriorly (Arrow).

Coronal sections shows widening of the pterygomaxillary fissure

• In addition , a soft tissue nasopharyngeal mass and opacification of the

sphenoid sinus may be seen .

• Cross sectional imaging may demonstrate an avidly enhancing mass .

• Multiple flow voids will be seen within the tumour on T1 and T2

weighted spin – echo sequences .

• The internal maxillary artery and the ascending pharyngeal artery are

the major feeding vessels which will be demonstrated on angiography

• Pre operative embolisation may be used to aid subsequent surgery .

ANGIOMATOUS POLYP

- Located in the nasal fossa and NOT the NASOPHARYNX , unlike the

nasopharyngeal angiofibroma .

- Does not extend into the pterygopalatine fossa or intracranially .

- The vascular supply of these lesions is less extensive than

angiofibromas .

- Does not enhance avidly following intravenous contrast and vascular

flow voids are not seen on MRI .

LYMPHOMAS

Forty-seven percent of non-Hodgkin’s lymphomas are found in the head and neck; 90 percent of these are in the cervical lymph nodes.

Though the nasopharyngeal region surrounded by the Waldeyer’s ring is a potential site of lymphoma, actual involvementof the sinonasal cavity is rare.

Lymphomas arising in the nose and PNS are of the non-Hodgkin’s type and are seen in cases of disseminated lymphoma.

Lesions may be mistaken for sinusitis, polyposis and granulomatous processes.

On CT and MR - bulky masses which show moderate enhancement.

The osseous changes include remodeling, expansion, erosion and infiltration of the sinus walls.

Primary lymphoma of the paranasal sinus is uncommon.

Mucosal thickening may be mild or in the form of a mass

MALIGNANT TUMOURS Plain radiographs are no longer recommended for screening for sinonasal

malignancy

Cross-sectional imaging is required to stage these tumours in order to visualisethe extent of tumour beyond the sinuses.

The areas of particular concern are the intraorbital cavity, pterygomaxillaryfossa, pterygopalatine fossa, infratemporal region and intracranial extension

CT acquisition is much faster with helical and multislice scanners , is sensitive to bone destruction and is more readily available.

Gadolinium-enhanced MRI is better than CT for the detection of intracranial and perineural tumour extension.

Nodal disease may be assessed by either CT or MRI.

Intravenous contrast enhancement allows identification of rim enhancement and central necrosis, which is often seen in squamous cell carcinoma.

Extracapsular spread of nodal disease is better assessed by CT than MRI.

Ideally scans should include the first and second oral draining nodes.

Tumours involving the maxillary antrum drain initially to the retropharyngeal nodes but level 2 (upper internal jugular) and level I (submandibular) groups may be involved and these should therefore be included within the scan.

Collimation should be 5 mm or less.

Direct coronal and axial scans should be obtained with both bone and soft-tissue algorithm.

On MRI a slice thickness of 4 mm or less should be used.

Sagittal T1-weighted fatsaturated scans after gadolinium enhancement may also be useful in assessing perineural and intracranial extension.

Squamous cell carcinomas show little contrast enhancement.

However, contrast administration is necessitated in CT evaluation of these tumors because it can help to differentiate

(1) Fluid from areas of necrosis

(2) involvement of normal structures from tumors especially in the orbit

(3) and to delineate intracranial extent of the tumor

Limitations of CT scan include:

1. Inability to distinguish between inspissated and retained secretions from tumors

2. Detect involvement of the periorbital structures especially the lamina papyracea and the adjacent structures

3. To differentiate soft tissues involvement by tumors versus swelling due to edema.

On MRI inflammatory tissue and retained secretions can be differentiated with some degree of confidence from tumors as the latter have a higher water content and thus appear to be of high intensity on T2WI and low intensity on T1WI

Coronal MRI images showing mass to be isointense on T2WI which enhances on post

contrast images (black arrow).

MR show extensive lesion with aggressive behavior infiltrating into the right

orbit, frontal sinuses and frontal bone diploe.

Also seen are intensely bright maxillary sinuses (short white arrow) on T2WI which

does not enhance suggestive of postobstructive changes.

Note normal thin mucosal enhancement of maxillary sinuses (long white arrow)

These tumours often present at an advanced stage.

The commonest tumour is squamous cell carcinoma, which accounts for

80% of all sinus malignancies.

Approximately 50-65% arise in the maxillary sinuses,10-25% in the

ethmoid sinuses and 15-30% in the nasal cavity.

Small tumours will mimic the appearances of chronic sinusitis and nasal

polyposis, thus many patients will be diagnosed at a late stage of their

disease.

The Primary tumour shows little if any enhancement on CT following

intravenous contrast.

On MRI, the tumours are of intermediate T, signal intensity and slightly

higher signal intensity on T,-weighted images.

Larger tumours may have areas of necrosis and haemorrhage

altering the signal intensities within them.

They also enhance slightly following intravenous gadolinium.

SQUAMOUS CELL CARCINOMA OF THE RIGHT MAXILLARY SINUS.

Noncontrast CT scan shows soft tissue mass of intermediate attenuation with

central necrosis filling the right antrum.

The lesion extends beyond the bony walls of the sinus, bone window setting show

extensive lytic destruction of the walls

Intestinal-type adenocarcinomas of the sinonasal cavities are

especially common in individuals with a previous exposure to

hardwood dust

The histology of the high-grade tumours resemble colonic and gastric

carcinomas.

In these patients metastatic disease from gastrointestinal primaries

should be ruled out before making the diagnosis, but this is a rare

occurrence.

MALIGNANT MELANOMAS Occur more commonly in the sinonasal cavities.

When they do occur, involvement of the nose is more common than the

sinus.

Local recurrence or metastatic disease within the first year is seen in up

to 65% of patients, metastases affecting the lungs, nodes, brain,

adrenal glands, liver and skin.

These tumours enhance more avidly than squamous cell carcinomas

on postcontrast scans.

Some lesions willexhibit high signal intensities on T,-weighted

sequences owing to the presence of haemorrhage and/or melanin.

OLFACTORY NEUROBLASTOMA Arises from the olfactory epithelium of the nasal cavity and is a tumour of

neural crest origin.

Epistaxis and nasal obstruction

The prognosis is related to the extent of disease at presentation.

These lesions are hypointense to brain on T,-weighted images and

hypertense to brain on T2 -weighted images.

Coronal and sagittal scans are usual to determine the relationship of the tumour to the cribriform plate and intracranial extension.

The tumours enhance with intravenous contrast on both CT and MRI.

Metastatic disease is seen in up to 38% of patients, with involvement of cervical lymph nodes, parotid glands, skin, lung, liver, eye, spinal cord and spinal

Olfactory neuroblastoma: Axial and coronal contrast enhanced CT section

showing a uniformly enhanced mass in the right nasal cavity extending from

the superior nasal fossa upto the inferior turbinate, the thinned out nasal

septum bulges to the left. There is erosion of the right fovea ethmoidalis and

the cribriform plate