Tuesday, December 28, 2010

Parapharyngeal Space Abscess: Causes, Features, Treatment, Complications

Anatomy: Parapharyngeal space is pyramidal in shape with its base
at the base of skull and its apex at the hyoid bone.
Relations:
Medial: Buccopharyngeal fascia covering the constrictor
muscles .
Posterior: Prevertebral fascia covering prevertebral
muscles and transverse processes of cervical
vertebrae.
Lateral: Medial pterygoid muscle, mandible and deep
surface of parotid gland.
Styloid process and the muscles attached to it divide
the parapharyngeal space into anterior and posterior
compartments. Anterior compartment is related to tonsillar
fossa medially and medial pterygoid muscle laterally.
Posterior compartment is related to posterior part of lateral
pharyngeal wall medially and parotid gland laterally.
Through the posterior compartment pass the carotid
artery, jugular vein, IXth, Xth, XIth, XIIth cranial nerves
and sympathetic trunk.
It also contains upper deep cervical nodes.
Parapharyngeal space communicates with other
spaces, viz. retropharyngeal, submandibular, parotid,
carotid and visceral.

Aetiology:
Infection of parapharyngeal space can occur from:
1. Pharynx. Acute and chronic infections of tonsil and
adenoid, bursting of peritonsillar abscess.
2. Teeth. Dental infection usually comes from the lower
last molar tooth.
3. Ear. Bezold's abscess, petrositis.
4. Other spaces. Infections of parotid , retropharyngeal
and submaxillary spaces.
5. External trauma. Penetrating injuries of neck, injection
of loc al anaesthetic for tonsillectomy or
mandibular nerve block.
Clinical Features
Clinical features depend on the compartment involved.
Anterior compartment infections produce a triad of
symptoms: (i) prolapse of tonsil and tonsillar fossa, (ii)
trismus (due to spasm of medial pterygoid muscle) and
(iii) external swelling behind the angle of jaw. There is
marked odynophagia associated with it.
Posterior compartment involvement produces (i) bulge
of pharynx behind the posterior pillar, (ii) paralysis of
CN IX, X, Xl, and XII and sympathetic chain, and (iii)
swelling of parotid region. There is minimal trismus or
tonsillar prolapse.
Fever, odynophagia, sore throat, torticollis (due to
spasm of prevertebral muscles) and signs of toxaemia are
common to both compartments.
Complications
1. Acute oedema of larynx with respiratory obstruction.
2. Thrombophlebitis of jugular vein with septicaemia.
3. Spread of infection to retropharyngeal space.

4. Spread of infection to mediastinum along the
carotid space.
5. Mycotic aneurysm of carotid artery from weakening
of its wall by purulent material. It may involve common
carotid or internal carotid artery.
6. Carotid blowout with massive haemorrhage .
Treatment
Systemic antibiotics. Intravenous antibiot ics may become
necessary to combat infection.

Drainage of abscess. This is usually done under
general anaesthesia. If the trismus is marked, preoperative
tracheostomy becomes mandatory. Abscess
is drained by a horizontal incision, made 2-3 cm below
the angle of mandible. Blunt dissection along the inner
surface of media l pterygoid muscle towards styloid
process is carried out and abscess evacuated . A drain
is inserted . Transoral drainage should never be done
due to danger of injury to great vessels which pass
through this space.

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