Frontal sinus

The frontal sinuses are the paranasal sinuses within the frontal bone. They are lined with mucosa and are most often two in number.

The frontal sinus has two chambers, one on each side, and they are almost always asymmetrical. Each sinus extends superior to the medial end of the eyebrow and back into the orbital portion of the frontal bone. However, three or more chambers may be present in ~10% (range 1.5%-21%). It is divided by thin bony intrasinus septa, usually off-midline and rarely dehiscent.

The orbit and anterior cranial fossa form important relations to these sinuses.

Drainage from the frontal sinus tends to be more variable than the other paranasal sinuses and there is inconsistent terminology used in its anatomic description 3. In general, the frontal sinus outflow tract consists of a narrowing at the lower medial corner of the sinus (frontal infundibulum), where an ostium (opening) is demarcated by a small ridge of bone at anterior sinus wall. Inferior to the ostium, drainage continues along a narrow passage known as the frontal recess 4 or superior compartment of the frontal sinus drainage pathway 3. At this point, variable anatomy frontal/ethmoidal bone junction leads to two main variations:

The frontal sinus is supplied by the supratrochlear, anterior ethmoidal, and supraorbital arteries, all of which are branches of the ophthalmic artery.

Venous drainage is via the superior ophthalmic veins.

Lymph drainage of the frontal sinus is into the submandibular nodes compared to the overlying skin which drains to the pre-auricular groups of nodes.

  • may be absent (i.e. aplasia) or underdeveloped (i.e. hypoplasia): unilateral (4%) or bilateral (5%)
  • may be large: extending through zygomatic processes, orbital bones, and into the squamae

They develop from anterosuperior pneumatisation of the frontal recess into the frontal bone. Development begins late in intrauterine life or may start after birth (from one to twenty years), initially in the vertical segment. Pneumatisation develops from 1-12 years old.

Head and neck anatomy
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Article information

rID: 7037
System: Head & Neck
Section: Anatomy
Tag: refs, sinus
Synonyms or Alternate Spellings:
  • Frontal sinuses

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Cases and figures

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    Figure 1: in red on annotated CT
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    Case 1: normal sinuses on CT
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    Case 2: aplastic frontal sinues
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