Sinusitis, sinus headaches, sinus infections, sinus polyps…a plethora of words associated with an assortment of problems. Sometimes patients present complaining, “I have sinus,” as if the mere presence of the sinuses themselves is an abnormality.
What do we mean by the
term sinus? In medical lingo, a sinus is a space or
chamber with an opening into it, allowing for entrance and/or exit of things
such as fluids, secretions, air, etc. In
the ENT world, the term usually refers to the paranasal sinuses, where para- means “next to,” and as such, we are
referring to the sinuses around the nose.
These sinuses are spaces within the bones of the skull that empty or
drain into the nose. I’ll
interchangeable use both paranasal sinuses or just plain sinuses, but for this
purpose they terms are synonymous.
Some people presenting
with sinus-related problems sometimes plainly state, “Why don’t you just remove
my sinuses?” The confusion here is the
sinuses are not an actual physical entity or organ amendable to removal, but
really the lack thereof. As mentioned
above, the paranasal sinuses are the actual spaces, spaces developed within
bone and lined with mucosa—pink tissue that lines most of the orifices and
cavities inside the body. On the other
hand, some people don’t fully develop sinuses, where a sinus may actually be
absent, prompting concern that the lack of a sinus would cause a problem. On the contrary, lacking a sinus is a
benefit—it’s one less sinus cavity that can cause problems. And no—we cannot rid you of your sinuses by
filling them with something such as concrete.
Some of the sinuses are
present at birth, while others develop later as the child grows to
adulthood. Sinuses are very small in
young children relative to the size of their head and face. As the child ages, the face tends to grow at
a faster rate than the cranium (the part of the head enclosing the brain) and
likewise the sinus spaces increase in volume with facial growth.
Functions of The Paranasal
Sinuses
So, what purpose do the
paranasal sinuses serve? Several
hypotheses exist (as with many things in medicine there are no certainties):
1. Provides lightness to facial bones and
head. In other words, the air-filled
spaces of the sinuses serve to lessen the weight of the head. Imagine going through life dragging your face
on the ground. You’d never find a mate
and propagate the species. Besides, your
neck would cramp big-time, and your heavy head would certainly be a literal “pain
in the neck” (one of the rare certainties in medicine).
2. Creates buttresses that protect the brain
from injury. This is an interesting
hypothesis. The face will fracture in
rather predictable patterns depending on the nature of the injury. The facial bones are attached to the cranium
(the part of the skull that encases the brain) via structures called buttresses. These buttresses are partially formed by the
presence of the sinuses. With
significant facial injury enough to cause fractures (breaks in the bone) these
fractures tend to occur along these buttresses which act to dissipate forces
away from the cranium and brain, acting like a shock absorber, so to
speak. Although facial fractures are no
picnic and can require extensive surgery, many patients survive and can lead
quality lives, as compared to those suffering brain injury where mortality
(death) and morbidity (decreased quality of life) are more frequent and more
significant. In children, where the face
and sinuses are relatively small compared to the cranium, facial injuries are
less common but head or brain injuries are more common for the same type of injury. The adult, with a relatively larger face, has
better shock-absorptive protection.
3. Humidifies and warms inspired air before it
hits the lungs. As you already know, you
need the nose to breath in air. You can
do this only through the mouth, but this is difficult to do; try plugging both
sides of your nose and go out for a run or brisk walk or any other activity;
it’s very cumbersome and uncomfortable to do.
The tissue lining the nose and sinuses moisturizes and warms the air
before it hits your throat, trachea and ultimately your lungs. In other words, the air is conditioned prior
to entering the lungs. Unconditioned air
irritates the tissues of the trachea and lungs causing unpleasant things as
pain, coughing and difficulty breathing.
4. Provides a first-line of defense for entry
into the nose. The sinuses, along with
the rest of the inside of the nose, are lined with mucosa, much of which is
ciliated. Cilia are microscopic hair-like projections on the mucosal cells,
which move secretions and any foreign particles in the secretion. The cells also produce mucous which creates
the moisture within the nose and sinus cavities. It’s the presence of mucous that traps
potential disease-causing substances and the action of the cilia to propel those
substances out that creates a first line of defense to such a portal into the
body.
Air also circulates
through the sinuses to aid this function (think of increase surface area to
contact potential foreign invaders). In
addition, there are also immunologic cells in the mucosa that produce antibodies
as well as cells that serve to devour any foreign threat (such as bacteria,
viruses or fungi).
5. Provides resonance to the voice. The thinking here is the voice has tonal
qualities created by the airspaces of the sinuses, where sound resonates or
vibrates, providing a unique characteristic that possibly aids in the hearing
and understanding of human speech. Thus
the sinuses are important in human communication. Also the pleasant aspects of singing are a
large part due to nasal and sinus resonance.
Listen to someone singing with a cold and plugged nose and you get the
picture—it’s not as pleasing.
Anatomy
As with anything else in
the body—even with air-containing spaces such as the paranasal sinuses—problems
can arise. An abnormal problem arising
in the body is called disease. Before getting into diseases, a little primer
of sinus anatomy is required. Doctors
study anatomy first before studying pathology (disorders of tissues in the
body) and ultimately means to diagnosis and treating the disease affecting that
particular anatomic part.
There are 4 major
sinuses: frontal, ethmoid, maxillary and sphenoid sinuses. There is one of these sinuses on each the
face and skull that drain into the respective side of the nose. The frontal sinuses form above the eyes in
the forehead. The ethmoid sinuses are located just medial or in between the
eyes. The maxillary sinuses are located
below the eyes in the cheek areas, above the upper teeth. The sphenoid sinuses are contained in the
part of the skull base way in the back and empty through ostia in the very back
of the nose.
The best means to
demonstrate anatomy is with cross-sectional imaging, and I’ll use several computed tomography (CT) scans to
demonstrate this.
 |
| Figure 1 |
Imagine viewing
successive slices done in this manner, from front to back (or as we say in the
medical world, “from anterior to posterior”).
This is how we read and interpret CT images (Figure 2)
 |
| Figure 2 |
On CT images, black is
air, white is bone, and gray is soft tissue, fluid, mucous, pus, blood, polyps, tumor
or anything other than bone or air. You’ll notice there is some gray hue within
the bone of the hard palate: this is bone marrow (which in a sense is soft tissue). The CT in Figure
2 shows a large mucous retention cyst filling the left maxillary sinus. By convention, the patient’s right side of
the body (or face in this example) is on the left side of the image and the
patient’s left side is on the right of
the image. Imagine the patient whose
image you’re viewing is looking directly at you.
Inside the nose lateral
to the middle turbinate (between the middle turbinate and the side wall of the
nose next to the eye) is something called the ostiomeatal complex, where ostium
= opening, and meatal = pertaining to
the meatus. This is where the frontal,
ethmoid and maxillary sinuses drain.
Thus this is an important area where disease in this area or blockage
can affect all 3 of these sinuses. The
sphenoid sinuses drain via a separate ostium, way in the back of the nose. Figure
3 is a sagittal view through the face and head. Imaging slicing the head down the middle,
just a little to the left of the nasal septum and you’ll see the left side of
the nasal cavity (inside of the nose) and the sphenoid sinus, bisected in that
same plane (Figure 4).
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| Figure 3 |
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| Figure 4 |
The ethmoid sinuses have
multiple thin bone septations, creating multiple small chambers within that
sinus. These bone septations often are
removed during surgery to create a single-chambered ethmoid sinus, but that’s a
topic for another discussion on surgery.
Symptoms of Sinus
Problems, Sinusitis
Problems affecting the
ostiomeatal complex (OMC) can affect proper ventilation and drainage of the
frontal, ethmoid and maxillary sinuses.
This is the reason patients with sinusitis often have more than one
sinus involved.
Also remember there are
things around the sinuses themselves, as the sinuses are spaces encased in
bone. Outside the bone is muscle, soft
tissue and skin. Deep to the sinuses on
the other side of the skull base is the brain. Thus, pain over one or more
sinuses does not necessarily mean the source is the sinuses, as those other
areas can be affected as well.
Symptoms of sinus
problems: headaches, facial pain, pain around (periorbital) or behind the eyes
(retro-orbital), upper teeth pain, nasal congestion (stuffiness or difficulty
with nasal breathing), nasal discharge or drainage, decrease voice resonance
(giving the stuffy nose or hyponasal
quality to the voice) postnasal drainage, cough (especially when lying down or
sleeping), sometimes asthma.—bronchospasm, where the small tubes leading from
the trachea to the lungs spasm and become narrow, causing difficulty breathing
and wheezing (that fine, high pitched noise heard in the lungs usually when a
person affected with this exhales).
More on the
treatment—medical, home remedies and surgical—in future posts. One final note: do us all a favor and avoid
the urge to test the shock-absorptive properties of your facial bones by plunging
face-first onto a hard surface. Or head-butt your spouse; your face/head pain
will be the least of your troubles.
©Randall S. Fong, M.D.
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