Describe the endoscopic anatomy of the nose and the landmarks of safe sinus surgery.

Endoscopic Anatomy and Safe Landmarks

• Nasal endoscopy has transformed rhinology, and the anatomy is learned as a sequence of passes rather than as a static picture.
• Preparation — topical decongestant and anaesthetic (such as lignocaine with phenylephrine or cocaine).
• Instruments — a rigid 4 mm 0-degree scope for routine work, a 30 or 45 degree scope to look into the frontal recess and maxillary antrum, and a flexible scope in children and where the nose is very narrow
• The first pass — along the floor: the inferior turbinate and inferior meatus, the floor of the nose, back to the choana, the nasopharynx, the eustachian cushion, the fossa of rosenmuller and the adenoid. This pass is where nasopharyngeal carcinoma is found
• The second pass — the middle meatus: between the middle turbinate and the lateral wall, identifying the uncinate process, the ethmoid bulla, the hiatus semilunaris and any accessory ostium, polyp, pus or oedema. Pus in the middle meatus is the endoscopic hallmark of anterior sinus disease
• The third pass — the sphenoethmoidal recess: between the septum and the middle turbinate, upward and backward to the superior turbinate and the sphenoid ostium, and the olfactory cleft
• The landmarks that keep surgery safe, and each corresponds to a specific danger:
• The maxillary line — a curved eminence over the nasolacrimal duct, marking the anterior limit of dissection and warning of the lacrimal system
• The ground (basal) lamella of the middle turbinate — the boundary between anterior and posterior ethmoid cells, so the surgeon knows which compartment is being entered
• The lamina papyracea — the orbit laterally; periorbital fat appearing in the field means the orbit has been entered, and the eye should be palpated at intervals to detect a developing haematoma
• The skull base and the cribriform plate medially — the medial roof is thinnest, so dissection is kept lateral to the middle turbinate attachment
• The anterior ethmoidal artery, crossing the ethmoid roof, sometimes in a free mesentery below the skull base — and if divided it may retract into the orbit and cause a rapidly expanding haematoma that blinds
• The sphenoid ostium, located medially at about 7 cm and 30 degrees from the nasal sill, and identified low and medially, since going laterally risks the optic nerve and carotid