Seminar in Otorhinolaryngology

Deep neck space infections

M. J. Porter and C. A. van Hasselt

Abstract

Deep neck space infections occur within the potential compartments of the neck between thefascial layers. The commonest causes are acute tonsillitis, foreign bodies or dental disease. Thepatients usually complain of pain and swelling of the neck and, unless treated, the condition canrapidly deteriorate to cause asphyxiation. The treatment is initially by high dose intravenousantibiotics, usually penicillin and metronidazole. If the airway is in danger, a tracheostomyshould be performed. When the infection progresses to abscess formation, then external surgicaldrainage will be required.

Keywords: Abscess; Neck space

Introduction

Infections of the deep spaces of the head and neck areuncommon in the modern antibiotic era. However,they appear to be encountered frequently in the FarEast.1 The main factors responsible for this are thegenerally poor level of dental hygiene and the fre-quent ingestion of foreign bodies, especially fishbones.2 These infections still pose a serious threat tolife so that prompt diagnosis and appropriate treat-ment are necessary.

Anatomy

There are many potential 'spaces' in the head andneck and the subject can be made unnecessarily com-plicated by their enumeration. It is important to realizethat most of these spaces communicate with theparapharyngeal space which should be regarded asthe key to understanding the anatomy and pathologyof these infections.3

The neck contains superficial and deep fascial layers.The superficial fascia envelopes the platysma muscle.The deep fascia is divided into three layers (Fig. I).

Division of Otorhinolaryngology, Department of Surgery, The ChineseUniversity of Hong Kong, Prince of Wales Hospital, Sha Tin, Hong KongM.J. Porter, MA, FRCSC. A. van Hasselt, FCS (SA) M Med (Otol)Correspondence to: Dr C. A. van Hasselt

1. The investing layer of deep fascia is attached tothe mandible above, to the hyoid bone andinferiorly to the clavicle. It splits to enclose thesternomastoid and trapezius muscles. It also givesa covering to the submandibular gland.

2. The middle or visceral layer of fascia encircles thepharynx, larynx, thyroid and oesophagus. Thecarotid sheath, which surrounds the carotid ar-teries, internal jugular vein and vagus nerve, isderived from the visceral layer.

3. The prevertebral layer of deep fascia lies on thesurface of the prevertebral muscles and attachesto the spinous processes of the cervical vertebrae.

The major potential spaces lie between these fasciallayers as follows:

a. The parapharyngeal space (also known as lateralpharyngeal or pharyngomaxillary space) is a largepotential space which has the shape of an in-verted pyramid and lies lateral to the visceralfascia from the base of skull down to the level ofthe hyoid. It is limited inferiorly by the attachmentof the fascia covering the submandibular gland tothe digastric and stylohyoid muscles. It containsthe carotid sheath, lymphatic and cranial nervesIX, X, XI and XII.4

b. The retropharyngeal space lies between the vis-ceral fascial layer and the prevertebral fasciallayer. This potential space extends from the skullbase down into the posterior mediastinum.

Porter & van Hasselt: Deep neck space infections

Prevertebral Fascia

Carotid Sheath

Jugular Vein

Vagus NerveHypoglossal NerveCarotid ArteryParotid Gland

Mandible

Visceral Fascia

Tonsil

Tongue

1 Retropharyngeal Space

2 Parapharyngeal Space

Fig. 1. Anatomical cross section of the neck at the level of the tonsil.

c. The submandibular space is bounded by the floorof the mouth and the superficial fascial layerpassing from the mandible to the hyoid. It is di-vided into a sublingual space (above) andsubmaxillary space (below) by the mylohyoidmuscle.

Other potential spaces described include the su-perficial and deep temporal spaces, the parotid space,the masseter and buccal spaces, the canine space andthe pterygomandibular space.5

It should be remembered that paratonsillar ab-scesses (Quinsies) are still sometimes encounteredafter an episode of acute tonsillitis. These abscesseslie between the visceral layer of fascia and the tonsiland may coexist with an abscess in any of the deepneck spaces.

Aetiology

orIn the pre-antibiotic era, tonsillitispharyngolaryngitis were the usual causes of deepneck space infections.6 Although these are still a cause,other conditions are now responsible for at least halfof the cases seen in Hong Kong. Dental pathology is acommon aetiology7 and may take the form of gum

disease, dental caries or apical abscess. Two impor-tant clinical points should be made:

1. The dental condition responsible may not besymptomatic.

2. Infection may start spreading immediately afterdental treatment aimed at removing a focus ofdisease, e.g. extraction.8

In Hong Kong, the accidental ingestion of fish andanimal bones is a common occurrence. These maylacerate or lodge in the pharynx or oesophagus. At-tempts at removal may also result in lacerations andfurther damage. A breach in the mucosa offers accessfor organisms and consequent spread of infection.Such a patient would experience pain after swallow-ing the bone, find that the pain eased after 24 hours,but then re-emerged as cellulitis and abscess forma-tion became established.

Other causes of deep neck space infections4, 9, 10

include:

— salivary gland calculus or sialectasis— oral trauma— endotracheal intubation— rigid oesophagoscopy— congenital cysts.

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Complications

Spontaneous rupture of the abscess can occur throughthe skin surface or alternatively into the mouth orpharynx. This may cause aspiration of pus and fatalchest infection.12

An abscess and the surrounding oedema behavesas a space occupying lesion which can rapidly lead toairway obstruction and asphyxiation. This is espe-cially true of infections of the submandibular space.Here, because of the firm attachment of the superficiallayer of fascia to the mandible and hyoid, the tongueis pushed backwards into the airway. Intubation un-der these circumstances is difficult and hazardousbecause of the distorted anatomy. Indeed, on at-tempting intubation in the young child with aretropharyngeal abscess, there is a danger of ruptur-ing the abscess and aspiration of the pus.

The jugular vein may become thrombosed and sendoff septic emboli which in turn may result in bacterialendocarditis, glomerulonephritis, septic arthritis orlung abscess.13 The wall of the carotid artery maynecrose leading to fatal haemorrhage. Should intraoralbleeding from the internal carotid artery occur, ligationof the common carotid artery is recommended.14

Spread of infection from the neck into the chest canoccur either along the carotid sheath into the superiormediastinum or via the prevertebral space into theposterior mediastinum. This can result in the seriouscomplications of mediastinitis and empyema.15, 16

Presentation

It will be apparent from the above that there aremany possible antecedents to a deep neck space in-fection. The patient may give a history of a recentepisode of acute tonsillitis or upper respiratory tractinfection. An episode of difficulty swallowing a bonemay be recalled. A history of dental pain or recentdental surgery can be important.

The features specific to the infection, however, in-clude pain in the mouth, throat or neck, fever, neckstiffness and trismus (due to irritation of the pterygoids).There is usually a visible swelling around the angle ofthe jaw although this may not be apparent in a purelyretropharyngeal space infection. Neurological defectscan occur due to involvement of the cranial nerves IX,X, XI and XII within the parapharyngeal space and aHorner's syndrome may be present. The progression ofthe infective process causes difficulty with swallowingand airway obstruction, a sign which indicates im-pending disaster. If the condition spreads to themediastinum, then increasing dyspnoea and chest painbecome evident.14 In children, the diagnosis of a purelyretropharyngeal abscess can be difficult to confirm asthe symptoms are non-specific.

Investigations

Routine haematology shows a raised white cell countand erythrocyte sedimentation rate (ESR). The bio-chemical profile is usually normal. Blood culturesshould be sent to identify the organisms and theirantibiotic sensitivity.

A lateral neck x-ray is useful in the diagnosis of aretropharyngeal'space infection as judged by the ex-pansion of the prevertebral soft tissue shadow (Fig.2). In both the normal adult and child, the distancefrom the body of C2 to the pharynx is between 2 and7 mm (average 3.5). At C6 the distance is between 5and 14 mm (average 7.9) for children and between 9and 22 mm (average 14) for adults.17 (It must be notedthat in children the figure is dependent on the positionof the neck, being greater when the neck is flexed).Other features seen on plain films are air in the softtissues and loss of the normal cervical lordosis.

Both computed tomography and ultrasound maydemonstrate an abscess cavity (Fig. 3). The diagnosticfeatures are those of a low density mass with airvisible in the centre, an enhancing rim and surround-ing oedema.18, 19 Total reliance on these investigationsis dangerous and the authors have experience of bothfalse positive and false negative scans.

Microbiology

As techniques for anaerobic culture have improved,it has become apparent that most infections are pre-dominantly anaerobic or mixed, a pure aerobic culturebeing uncommon. The oral flora or the organismscommonly responsible for acute tonsillitis are usuallycultured. We have noted a high incidence ofStreptococcus milleri in the infections encountered atthe Prince of Wales Hospital. Other organisms oftenfound are the anaerobic Streptococci or Peptostreptococci,Bacteroides melaginensis and Fusobacterium. The aero-bic organism is most commonly a Streptococcus. B.fragilis and Staphylococcus aureus are noticeably absentfrom culture.11

Treatment

Antibiotics should be administered intravenouslywhen there is clinical evidence of spreading infectionin the neck, bearing in mind the likely sensitivity ofthe responsible organisms until a specimen has beencultured. As a first line of treatment, penicillin in dosesup to 20 megaunits a day should be administeredtogether with metronidazole. In cases of penicillin al-lergy, clindamycin is a good alternative. Theaminglycosides are not normally indicated. Resistanceof B. melaninogensis is uncommon but reported in up

Fig, 2, Lateral x-ray of neck showing widening of theprevertebral soft tissues, a gas shadow (upper arrow)and a foreign body (lower arrow).

to 20% of isolates in the United States.19 This should beremembered if the infection fails to resolve as ex-pected. Definitive therapy will be determined by theantibiotic sensitivity of organisms cultured from ma-terial obtained from aspiration or surgical drainage.

In cases where respiratory obstruction threatens,securing an airway becomes the priority. Intubationrequires the expertise of a skilled anaesthetist andmay not always be successful. A tracheostomy, beingthe only alternative, may equally be difficult and haz-ardous to perform.

The need for surgical drainage requires carefulclinical judgement. Many infections are seen at thestage of cellulitis before an abscess cavity and frankpus have formed and it may be difficult to decidehow long to continue with conservative managementor when to abandon it in favour of surgery. If thehistory is short and the patient well, then at least 24hours of antibiotic therapy should be administeredbefore surgical drainage is considered. The patient'sgeneral clinical condition and. airway require closemonitoring. The clinical features to be observed arethe degree of pain, dysphagia and the amount of

Fig, 3.ity (arrow) in the prevertebr

swel l ing in the neck. A persistent temperature,leucocytosis and tachycardia would suggest abscessformation. The patient should also be followed withserial lateral neck x-ravs, ultrasound and CT scans.Failure to respond to antibiotics alone is an indicationfor drainage. If the history is of a swelling progress-ing over several days, then it is likely that pus willhave formed. The finding of pus on needle aspirationor definite radiological evidence of abscess lo.rmaf.ionare both indications far immediate drainage. Somecases have been successfully treated by CT-guidedneedle aspiration alone.20, 21

Surgical approaches

Unilateral submandibular space infections andparapharyngeal space infections are approached asCor submandibular gland excision (Fig. 4, 1), continu-ing by blunt dissection in front of the carotid sheath.This route leads all the way up to the skull base,"

Retropharyngeal space infections may require dif-ferent approaches depending upon the clinicalcircumstances. In infants, it is usually due tosuppurative lymphadenitis and peroral incision isideal. In earlier times, it used to be recommended thatthis be performed in the head down position withoutanaesthesia for fear of rupturing the abscess withsubsequent aspiration of pus. With the availability ofmodern paediatric anaesthesia, initial intubation ispreferable.23 In the adult, the retropharyngeal space isbest approached via an incision anterior to the middlethird of sternomastoid muscle, retracting the carotidsheath posteriorly (Fig. 4, 2). If the abscess is high inthe neck, it can be approached behind thesternomastoid, retracting the carotid sheathanteriorly.24 if the infection is thought to be due totuberculosis of the cervical spine, aspiration ratherthan external drainage of the pus is required.

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Fig. 4. Diagram to illustrate the incisions used to drainneck abscesses.

An infection of the submandibular space is oftenbilateral and requires a midline horizontal incision(Fig. 4, 3). Ludwig's angina is a necrotising cellulitisin this compartment, in which abscess formation canoccur but is unusual. Intravenous antibiotics are thefirst line of treatment. The condition can progress torespiratory obstruction in as little as 12 hours andtracheostomy is indicated if there is any doubt aboutthe safety of the airway. If the infection fails to re-spond or pus can be demonstrated, then the spaceshould be explored surgically. In Patterson's series of20 cases, seven needed airway support of which fourrequired a tracheostomy. Of the nine cases explored,pus was present in fewer than half.8

Masseter spaces are drained into the mouth andtemporal spaces from above the zygoma (Fig. 4, 4).

In conclusion, deep neck space infections consti-tute an emergency which requires prompt admissionto hospital, immediate parenteral antibiotics andvigilant clinical attention. Progression may be rapidresulting in extension of the infection to the chest orairway obstruction. Surgical drainage is often requiredto prevent the occurrence of these life-threateningcomplications.

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