The document provides an overview of the anatomy and radiological examination of the paranasal sinuses. It discusses the key functions of the sinuses and describes the anatomical features and development of the four main paired sinuses: ethmoid, maxillary, frontal, and sphenoid sinuses. Important anatomical structures like the osteomeatal complex are also explained. High-resolution computed tomography is described as the preferred technique for detailed examination of the sinus anatomy and configuration.

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Paranasal Sinuses:
Radiological Anatomy
Dr. Hazem Abu Zeid Youset
December 2006

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What are the sinuses?
The sinuses are chambers in the bones of
the face and skull that are normally lined
with a thin mucosa. They communicate
with the nasal cavity via narrow openings.
Air and mucus enter and exit to and from
the sinuses through these openings.

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Function of Paranasal Sinuses
Humidifying and warming inspired air
Regulation of intranasal pressure
Increasing surface area for olfaction
Lightening the skull
Resonance
Absorbing shock
Contribute to facial growth

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OVERVIEW
Each patient's sinus anatomy has a unique
configuration, and it is vital that this is well
delineated for surgery to be successful.
The four paired paranasal sinuses are the
ethmoid, maxillary, frontal, and sphenoid
sinuses. These are named after the cranial
bones in which they are located. The sinuses
normally contain air

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TECHNIQUES OF SINUS
EXAMINATION
(1)PLAIN RADIOGRAPHY.
(2)HRCT.
(3)MRI.
(4)US.

7. WATERS VIEW
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HRCT
Prerequisites
High tube voltage kVp
High mAs
Thin slice
Pitch 1:1
Reconstruction bone algorithm

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THE ETHMOID AIR CELLS
The ethmoid sinuses are the sinuses "between the eyes." They are
typically fully developed by age 12. They are like a honeycomb,
consisting of multiple small sinus (usually 12-15 on each side) that
are separated by thin bony septa cells that together form the ethmoid
sinus.
At birth, usually three or four ethmoid cells are present. However, they
are difficult to recognize on x-rays until the infant reaches about six
months of age. Only the ethmoid and maxillary sinuses are
significantly developed enough at birth to be clinically significant.
(Significant growth of the sphenoid and frontal sinuses are rarely
seen until three years of age.)
The lateral or sidewall of the ethmoid sinus is called the "lamina
papyracea,"

10. 10 Pediatric Sinuses

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The upper border of the ethmoid sinus is called
the fovea ethmoidalis, or "ethmoid roof." The
fovea ethmoidalis is a part of the skull base and
separates the ethmoid sinus from the brain.
Medially along the roof of the ethmoid sinus is
the thinner bone of the cribriform plate that
separates the nasal cavity from the brain. The
cribriform plate tends to lie 2-3mm lower than
the fovea ethmoidalis.

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13. The ethmoid sinus can be thought of as
having two distinct groups of sinus cells.
The anterior group drains into a space
called the middle meatus, and the posterior
group drains into a space called the
superior meatus. The anterior and posterior
ethmoid cells are divided by a plate of
bone called the "basal lamella" or "ground
lamella."
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The anterior ethmoid cells can be further sub-divided
into
a) frontal recess cells, the most anterior and superior
communicates with the frontal sinus
b) Haller cells, on the lateral wall of the inf.
c) agger nasi cells, “anterimost” immediately
anterior and superior to the insertion of the middle
turbinates
d) bulla cells, is the largest and most constant air cell
of the anterior ethmoid complex “above and
posterior to the infundibulum”
e) conchal cells. pneumatization of the middle
turbinate.

15. The ethmoid infundibulum represents a cleft or
space through which a number of the sinuses (the
frontal, maxillary, and anterior ethmoid) drain.
Therefore, it is an important "major intersection."
The boundaries of this space are formed anteriorly
by the uncinate process, laterally by the lamina
papyracea, and in the back posteriorly by the
ethmoid bulla. The ethmoid infundibulum opens into
the middle meatus .
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The posteriort ethmoid air cells are larger but have a
smaller total area than the anterior cells.
Behind the ground lamella of the MT
Onodi cells “the most posterior cell” superolateral to
the sphenoid sinus.

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21. The maxillary sinuses
Pea sized and fluid filled at birth, it undergoes two rapid
growth spurts. The first is between birth and age three
years and the second is between age seven and 18. The
sinus becomes adult size by adolescence.
The drainage pathway or ostium of the maxillary sinus is
located in the superior and anterior part of the medial wall
of the maxillary sinus. Through this ostium the maxillary
sinus communicates with the nose. Specifically, mucus
drains from the maxillary sinus into the infundibulum in
the middle meatus and out into the nose.
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22. The roof of the maxillary sinus is also the floor of the
orbit. The floor of the maxillary sinus is formed by the
maxillary bone; specifically, a part called the "alveolar
process." The roots of the first and second molar teeth and
the second bicuspid teeth often project through the floor of
the maxillary sinus, where they are covered only by the
thin mucus membrane within the sinus.
The anterior or front wall of the maxillary sinus separates
the sinus from the cheek skin, while the posterior or back
wall separates the sinus from a space filled with blood
vessels and nerves. The upper part of this space is called
the infratemporal fossa, and the lower part is called the
pterygomaxillary space.
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25. The frontal sinuses
They are not clinically perceptible at birth. The frontal
sinuses can rarely be demonstrated on plain x-ray before
two years of age. Growth of the frontal sinuses is typically
complete by about age 20. About 5% of the population fails
to develop one or both frontal sinuses.
The frontal sinus has anterior and posterior bony walls. The
front wall separates the sinus from the forehead soft tissue
and skin. The back wall separates the sinus from the brain.
The front wall is approximately twice as thick as the back
wall.
The frontal sinus is usually divided into two sides by a very
thin bony divider. The mucus from the frontal sinus drains
out a small channel called the frontal recess, into the
infundibulum, then into the upper part of the middle
meatus, and out into the nose.
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27. The sphenoid sinus
The sphenoid sinus is not perceptible at birth. Further significant growth
does not begin until a child is three years of age. Pneumatization and
growth usually becomes rapid after seven years and reaches adult size
by 12-15 years.
The left and right sphenoid sinuses are separated by a thin bony
partition. The sphenoid sinuses are usually asymmetric. The sphenoid
sinus drains into the nose through the sphenoid ostium into a space
called the sphenoethmoid recess, and out into the nose.
Several important structures occupy positions in relationship to the
sphenoid sinus. Importantly, the optic nerve and pituitary gland are
above the sphenoid, and the pons is just behind the sphenoid. The
internal carotid arteries are just to the side of the sphenoid sinus. The
cavernous sinus is also found to the side of the sphenoid sinus.
In half of the population, the internal carotid artery forms a visible
indentation in the side wall of the sphenoid sinus. The bony wall is not
always complete, so great care must be taken when performing
sphenoid surgery.
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The osteomeatal complex
The "grand central station" of the sinuses is the
osteomeatal complex -- the most important sinus
opening. Any process that causes blockage in this
sensitive area can occlude the other sinuses that drain
into the osteomeatal complex.
The OMC is bounded medially by the middle
turbinate, posteriorly and superiorly by the basal
lamella, and laterally by the lamina papyracea.
Inferiorly and anteriorly the OMC is open. This
anatomic region therefore includes the anterior
ethmoid sinus, ethmoid bulla, frontal recess, uncinate
process, infundibulum, hiatus semilunaris, and middle
meatus.

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Thank you