Head – Paranasal Sinuses, Nasal Cavity & Vestibulocochlear

PARANASAL SINUSES & NASAL CAVITY

Discuss the anatomy of the frontal sinus (15 marks).

DESCRIPTION

• Paired, often asymmetrical air cells within frontal bone
• Irregular median septum
• Perpendicular (frontal) and horizontal (orbital) parts
• Hourglass-shaped ostium

 BOUNDARIES

• • Anterior – anterior cortical table of frontal bone
  • Posterior – posterior cortical table of frontal bone

RELATIONS

• • Anterior – superciliary arch + skin of forehead
  • Posterior – anterior cranial fossa (frontal lobe)
  • Inferior – orbit

DRAINAGE

• • Into middle meatus via frontal recess
  • Size dictated by
    • Agger nasi (anterior)
    • Bulla ethmoidalis (posterior)
    • Uncinate process & middle turbinate (medial/lateral)

ARTERY

• supraorbital, supratrochlear, anterior ethmoidal artery

VEIN

• diploeic veins + superior ophthalmic vein

NERVE

• supraorbital + supratrochlear nerve

LYMPH

• submandibular (level II)

VARIANTS

• Insertion of uncinate process dictates drainage pathway
  • Uncinate attachment to skull base (medial variant) leads to Frontal Sinus draining into superior portion of ethmoidal infundibulum
  • Uncinate attachment to middle turbinate (medial variant) causes frontal sinus to drain into the ethmoidal infundibulum
  • Uncinate attachment to lamina papyracea (located laterally) causes the frontal sinus to drain into the superior aspect of the middle
  • Medial to uncinate process (separate to infundibulum – type I-III)
  • Lateral to uncinate process (into infundibulum – type IV-VI)
• Bulla frontalis (anterior ethmoid cells communicate with frontal sinus)
• Division by metopic suture
• Hypoplasia / aplasia