Haritosh K Velankar
Lecturer in ENT, Rajawadi Hospital, Ghatkopar, Padmashri DY Patil Medical College, Mumbai 400 077.
Retropharyngeal abscess, is a commonly seen pathology secondary to acute infection of throat or chronic infections, like Tuberculous cervical spine and cervical lymph node tuberculosis. The infection can spread to the parapharyngeal area or posterior mediastinal area, as the retropharyngeal space communicates with it. Delay in diagnosis and treatment can lead to risk of complications like, spontaneous rupture of abscess leading to tracheobronchial aspiration or stridor due to laryngeal oedema. It is seen that factors which lead to retropharyngeal abscess are namely, reduced immunity, debility, HIV and improper or inadequate treatment.
INTRODUCTIONRetropharyngeal abscess is a pathology seen in two forms, acute retropharyngeal abscess, is commonly seen in children below 4-5 years. It is as a result of suppuration of retropharyngeal lymph nodes, secondary to infection in adenoid, nasopharynx, posterior pharyngeal wall, sinuses and tonsil, in adults, it may result as a direct infection due to some penetrating injury or foreign body.
Chronic retropharyngeal abscess, is usually seen in adults or slightly elder children. It is due to tuberculous infection of the cervical spine, as the pus directly spreads through the anterior longitudinal ligament. In children below 4-5 years it occurs due to tuberculous infection of the retropharyngeal lymph nodes secondary to tuberculosis of deep cervical nodes.
Retropharyngeal space, lies behind the pharynx between the buccopharyngeal fascia covering the constrictor muscle and the prevertebral fascia. It extends from the base of the skull of the bifurcation of trachea. Space is divided into two lateral compartments (space of Gillette) by a fibrous raphe. Each lateral space contains retropharyngeal nodes which usually disappear after 4-5 years of age. As the retropharyngeal space communicates with the parapharyngeal space and the posterior mediastinum, infection can spread to these areas. Prevertebral space lies between the vertebral bodies posteriorly and the prevertebral fascia anteriorly (Figs 1 and 2)
Fig 2 Anatomy of Retropharyngeal Space
Acute retropharyngeal abscess is usually seen in children less than 4-5 years of age. It is due to spread of infection from, nasopharynx, oropharynx, rarely from mastoid infection, as the pus might track down along the undersurface of the petrous bone. In adult, it is because of some penetrating injury, or foreign body piercing in the posterior pharyngeal wall. In adults, abscess due to naso-oropharyngeal infection is rare, because lymph node in the retropharyngeal space disappear, usually after the age of 4-5 years. Predisposing factors are namely, debility, exanthemata, decreased immunity, and nowadays very common in HIV.
The organisms found in the pus in acute cases are, staphylococcus aureus, streptococcus viridans, klebsiella pneumoniae, escherichia coli and heamophilus species.
The patient presents with, h/o fever, throat or nose infection, difficulty in swallowing, in case of abscess extending upto nasopharynx, there is nasal obstruction. In some advanced cases, there is restlessness, torticollis and stridor or croupy cough.
On examination, there is neck stiffness, tender cervical lymph nodes and a unilateral swelling seen in the posterior pharyngeal wall, with signs of acute inflammation.
Complication like sudden rupture of abscess leading to traecheobronchial aspiration or laryngeal oedema can take place.
Diagnosis is confirmed, as the WBC count shows leucocytosis with increase in neutrophil count, Xray neck lateral view, shows increase in the space between the vertebra and the air column with air shadow. CT scan can confirm the diagnosis.
Treatment is, incision and drainage of abscess done transorally, without anaesthesia, in a head low position to avoid aspiration. Anaesthesia is avoided as there is risk of aspiration during intubation due to injury to the pharyngeal wall. In case of a child, it is done after mummifying the child by wrapping it in a towel and keeping the head low. It is very important to have a good suction machine to suck out the pus after incising it. To be very safe pus can be first aspirated, to decrease the pressure in the abscess cavity, and then incised. Antibiotics are mandatory to take care of the infection. Steroids can be given in case of stridor or croup. Tracheostomy is done as a life saving procedure in case of severe laryngeal oedema.
Chronic retropharyngeal abscess is seen in two forms.
Lateral type - It occurs due to Kochs infection of the cervical lymph node spreading to retrophryngeal nodes and forming a cold abscess. It is only seen in children below age of 5 years. The swelling seen intra orally is classically seen on the sides, and not in the midline, as there is a central raphae. Swelling is fluctuant and with minimal signs of inflammation.
Central type - It is due to Potts tuberculous cervical spine, the abscess is present between the body of vertebra and the prevertebral fascia. It begins in the midline and then spreads to both sides. It can present at any age, with restricted movements of neck and pain at the back of neck. On oral examination there is a swelling in the midline, in the pharyngeal wall, is fluctuant and with less signs of inflammation.
Haemogram in both chronic forms shows in creased lymphocyte count, raised ESR and Mantoux test may be positive. X-ray lateral view of cervical spine will show caries of spine with increase in retropharyngeal space and air shadow in it. CT scan can be done to confirm it.
Treatment includes anti Kochs therapy, central retropharyngeal abscess is aspirated and drained in a head low position without anaesthesia to avoid aspiration of pus into the tracheobronchial tree. For lateral abscesses, under antibiotic and anti tubercular treatment cover, incision and drainage is done, by external incision in neck at the anterior or posterior border of sternocleidomastoid muscle.
Pott’s spine requires orthopaedic treatment (Fig. 3).
Recent literature indicates that incidence of acute retropharyngeal abscess is on the decline, due to availability of better antibiotics, used for upper respiratory infection. On the other hand incidence of chronic retropharyngeal abscess is on the increase in the Western countries due to ressurgence of tuberculosis secondary to HIV. It is seen that factors which lead to retropharyngeal abscess are namely, reduced immunity, debility, HIV and improper or inadequate treatment. Therefore, it should not be forgotten that most important tools in making early diagnosis are proper history and careful examination. A delay in the diagnosis and treatment can lead to increased risk of complications like, spontaneous rupture of abscess leading to tracheobronchial aspiration or stridor due to laryngeal oedema.
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