Page 334 - Clinical Anatomy

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The accessory nasal sinuses 319

2◊◊A fracture involving the sinus, severe enough to tear the dura and pia-
arachnoid, will place the subarachnoid space in communication with the
nasal cavity and C.S.F. may then be detected trickling through the nostril,
usually on the affected side (C.S.F. rhinorrhoea) although, as these sinuses
may communicate, a contralateral leak sometimes occurs.
3◊◊The neurosurgeon must take into account the considerable variations
in size and extent of the frontal sinus when proposing to turn down a
frontal skull flap; obviously, he will want to avoid opening the sinus
because of the risk of infection. He therefore consults the radiographs of the
patient’s skull preoperatively, which will clearly show the configuration of
the sinuses.

The maxillary sinus (antrum of Highmore)
(Fig. 226)

This is a pyramidal-shaped sinus occupying the cavity of the maxilla. Its
medial wall forms part of the lateral face of the nasal cavity and bears on it
the inferior concha. Above this concha is the opening, or ostium, of the max-
illary sinus into the middle meatus in the hiatus semilunaris (Fig. 225). This
opening, unfortunately, is inefficiently placed as an adequate drainage
point.
The infra-orbital nerve lies in a groove which bulges down into the roof
of the sinus, while its floor bears the impressions of the upper premolar and
molar roots. These roots are separated only by a thin layer of bone which
may, in fact, be deficient so that uncovered dental roots project into the
sinus. Note that the floor of the sinus, therefore, corresponds to the level of
the alveolus and not to the floor of the nasal cavity — it actually extends
about 0.5in (12mm) lower than the latter.

Clinical features

1◊◊The maxillary sinus, or antrum, may become infected either from the
nasal cavity or from caries of the upper molar teeth.
Antral puncture can be carried out using a trocar and cannula passed
through the nasal cavity in an outward and backward direction below the
inferior concha.
More adequate drainage may require removing a portion of the medial
wall of the sinus below the inferior concha or fenestrating the antrum in the
gingivolabial fold (Caldwell Luc operation). The old operation of draining
the antrum via an extracted upper molar tooth is now seldom, if ever,
performed.
2◊◊The numerous symptoms and signs which may be produced by a carci-
noma of the maxillary sinus are easily remembered anatomically.
(a) Medial invasion encroaches on the nasal cavity, producing
obstruction of the nares and epistaxis. Blockage of the nasolacrimal
duct in this wall may cause epiphorea (leakage of tears down the face).
(b) Invasion of the orbit displaces the globe and causes diplopia. If the