Page 291 - Clinical Anatomy

ECA5 7/18/06 6:50 PM Page 276

276 The head and neck

Clinical features

1◊◊Damage to the hypoglossal nerve is readily detected clinically by hemi-
atrophy of the tongue and deviation of the projected organ towards the
paralysed side.
2◊◊If the unconscious or deeply anaesthetized patient is laid on his back, the
posterior aspect of the tongue drops back to produce a laryngeal obstruction.
This can be prevented either by lying the patient on his side with the head
down (‘the tonsil position’), when the tongue flops forward with the weight
of gravity, or by pushing the mandible forwards by pressure on the angle of
the jaw on each side; this is effective because genioglossus, attached to the
symphysis menti, drags the tongue forward along with the lower jaw.
3◊◊Although lymphatics pierce the floor of the mouth (i.e. the mylohyoid
muscle) to reach the submental and submandibular lymph nodes, it is an
interesting fact that these tissues are not affected by lymphatic spread of
malignant cells (although they may be invaded by direct extension of
growth). It seems that the nodes are involved by lymphatic emboli and not
by a permeation of the lymphatic channels.
The bilateral lymphatic spread of growths of the posterior one-third of
the tongue is one factor contributing to the poor prognosis of tumours at
this site.

The floor of the mouth
The floor of the mouth is formed principally by the mylohyoid muscles.
These stretch as a diaphragm from their origin along the mylohyoid line on
the medial aspect of the body of the mandible on each side, to their inser-
tion along a median raphe and into the hyoid bone. They support the
tongue as a muscular sling (Fig. 200).
On the lower aspect of this diaphragm, on each side, are the anterior
belly of the digastric muscle, the superficial part of the submandibular
gland and the submandibular lymph nodes, all covered by deep fascia and
platysma.
Lying above mylohyoid are the tongue muscles, as a central mass, with
the sublingual salivary gland and the deep part of the submandibular gland
and its duct lying beneath the mucosa of the mouth floor on either side.

Clinical features

Ludwig’s angina is a cellulitis of the floor of the mouth, usually originating
from a carious molar tooth. The infection spreads above the mylohyoid;
oedema forces the tongue upwards and the mylohyoid itself is pushed
downwards so that there is swelling both below the chin and within the
mouth. There is considerable danger of spread of infection backwards with
oedema of the glottis and asphyxia.
Drainage is carried out by a deep incision below the mandible which
must divide the mylohyoid muscle.