Frontal Sinus:
• Most clinically significant sinus in ox
• Complex system (not simple cavity)
• Cornual diverticulum: Extends into horn core (opened during dehorning = infection risk)
• Nuchal and postorbital diverticula
• Divided by oblique septum into rostral (minor) and caudal (major)
• Poor drainage (complex meatus communication)

Maxillary Sinus:
• Within maxilla, lacrimal, zygomatic bones
• Communicates with nasal cavity via high nasomaxillary opening (gravity drainage difficult)
• Communicates with palatine and lacrimal sinuses

The Paranasal Sinuses

The bovine skull is heavily pneumatized. The sinuses are diverticula of the nasal cavity lined with mucous membrane.

A. The Frontal Sinus (Sinus frontalis)

The most clinically significant sinus in the ox. It is not a simple cavity but a complex system of intercommunicating compartments.

Boundaries: Extends from the rostral third of the orbit to the nuchal crest, and laterally into the horn core.

Diverticula:

• Cornual Diverticulum: Extends into the process of the horn. Clinical Note: Dehorning in adult cattle opens this sinus, creating a direct portal for infection (frontal sinusitis).
• Nuchal Diverticulum: Extends caudally into the nuchal region.
• Postorbital Diverticulum: Located behind the orbit.

Compartmentalization: It is divided into a Rostral Frontal Sinus (minor) and a Caudal Frontal Sinus (major) by an oblique septum. The caudal sinus communicates with the nasal cavity.

Drainage: Drains intricately into the ethmoid meatus. Drainage is poor due to the complex anatomy.

B. The Maxillary Sinus (Sinus maxillaris)

Located within the maxilla, lacrimal, and zygomatic bones.

Boundaries: Anteriorly by the facial tuberosity; posteriorly by the bulla lacrimalis.

Communication: Communicates with the nasal cavity via the Nasomaxillary Opening (high in location, making natural drainage difficult). It also communicates with the palatine and lacrimal sinuses.

C. Surgical Trephination Points

Frontal Sinus: To drain the caudal frontal sinus, a trephine hole is placed approximately 2cm from the midline on a line connecting the centers of the orbits. Alternatively, post-dehorning drainage occurs through the horn stump.

Maxillary Sinus: Trephination is performed dorsal to the facial tuberosity, avoiding the nasolacrimal duct and the infraorbital nerve.