sinusitis
Meaning of sinusitis: Nearly every case starts as an ordinary cold, and the newer name rhinosinusitis records that the nose is inflamed too.
Definition of sinusitis
Sinusitis is inflammation of the lining of the paranasal sinuses, the air-filled spaces within the bones around the nose. Swelling blocks the narrow openings that drain each sinus, so mucus is trapped and facial pressure, a blocked nose, thick discharge and a dulled sense of smell follow. Most cases begin with a viral cold, and bacterial infection develops in only a small share.
Why does blockage matter so much?
Each sinus is a sealed pocket of air within bone, opening into the nose through a gap only a few millimeters across. A carpet of tiny hairs sweeps mucus steadily toward that gap and out. When the lining swells, from a cold or from allergy, the gap closes first because it is the narrowest point. Mucus then has nowhere to go. Pressure builds behind the block, the trapped fluid stops moving, and bacteria that would normally pass straight through find a still, warm pool to multiply in. Almost everything about the illness follows from that one narrow opening.
Which sinus produces which symptom?
| Sinus | Location | Where discomfort is felt |
|---|---|---|
| Maxillary | Within the cheekbones | Cheek and upper teeth |
| Frontal | Forehead above the eyes | Forehead, worse on bending |
| Ethmoid | Between the eyes | Between and behind the eyes |
| Sphenoid | Deep behind the nose | Back of the head and the neck |
The maxillary sinuses drain through an opening near their roof rather than their floor, so gravity works against them, which is part of why they are involved most often. Roots of the upper back teeth reach into that sinus, so dental infection can seed it and sinus pressure can be felt as toothache.
When is it more than a cold?
Viral inflammation of the sinuses accompanies most colds and settles as the cold settles. Two patterns suggest something further: symptoms persisting without improvement well beyond the span of a cold, and symptoms that improve and then clearly worsen again. Thick colored nasal discharge does not by itself separate viral from bacterial disease. The ethmoid sinuses are divided from the eye socket by a wall of bone thinner than a fingernail, and infection crossing it produces swelling, redness and pain on moving the eye, described as orbital cellulitis. Sinusitis lasting months, called chronic, behaves as a different problem, driven by persistent inflammation, nasal polyps or a structural narrowing rather than by ongoing infection.
Also known as
Used in a sentence
Imaging showed mucosal thickening consistent with chronic sinusitis.
Good to know
Thick colored discharge occurs in viral sinusitis as readily as in bacterial sinusitis, so appearance alone does not identify the cause. Swelling or redness around the eye, or pain on moving it, indicates spread beyond the sinus rather than a worse sinus infection.
Word origin
Where “sinusitis” comes from
From the Latin sinus, meaning a hollow, curve or bay, with the Greek suffix -itis, meaning inflammation.