Pharyngeal pouches
Contents
Synonyms:
Pharyngeal diverticula, Zenker's diverticulum, Pharyngo oesophageal diverticula.
Definition:
Pharyngeal pouches are mainly acquired and rarely congenital diverticula in and around the pharynx and oesophagus. These diverticula are nothing but circumscribed pouches caused by a protrusion of mucosa through a preexisting weakness / opening in the muscle layers of pharynx / oesophagus.
This is in contrast to the congenital diverticula like Meckel's diverticula where in the diverticula is covered by all the muscle layers of the wall of the viscous.
These pharyngo oesophageal diverticula may be single of multiple. It could be sited laterally or posteriorly. Majority of them arise above the level of cricopharyngeus muscle, rarely some of them may arise at the level of oesophagus.
Inferior constrictor:
is the most important muscle in the understanding the pathophysiology of pharyngeal diverticula. This muscle is described in two parts: Thyropharyngeus and cricopharyngeus respectively. The thyropharyngeus muscle arises from an oblique line on the thyroid ala, and a fibrous arch between the thryoid and cricoid cartilages. Its upper fibers overlaps the superior and middle constrictors, and the lower fibers lie edge to edge with the cricopharyngeus muscle. There is a potential space between the middle and inferior constrictors, lying over the pyriform fossa. This space is bounded anteriorly by the thyrohyoid muscle. This space is pierced by neurovascular bundle of the third arch.
Killian's dehiscence:
Is the junction between thyropharyngeus and cricopharyngeus muscles. This is a potentially weak area not supported by other constrictor muscles. The cricopharyngeus muscle is thicker and bulkier than the thyropharyneal component of inferior constrictor. The pressure generated by the constriction of cricopharyngeus muscle is sufficient to cause prolapse of mucosal lining through this potentially weak area.
The following are the weak spots around pharynx and oesophagus:
Lateral:
1. Above the superior constrictor
2. Between the superior and middle constrictors
3. Between the middle and inferior constrictors
4. Below cricopharyngeus - Killian-Jamieson's area
Posterior:
1. Laimer-Hackermann's area
2. Killian's dehiscence
Classification of pharyngeal diverticula:
Lateral:
1. Congenital
2. Acquired:
a. Normal bulges
b. Traumatic
c. Raised intrapharyngeal pressures (Pharyngoceles)
Posterior:
1. congenital
2. Acquired:
a. Traumatic
b. Intrapharyngo-oesophageal pressure
c. Posterior pharyngeal pulsion diverticulum (Zenker's diverticulum)
History:
The first pharyngeal pouch was described by Ludlow in 1769, when he performed autopsy on a patient who had dysphagia throughout his life. Wheeler performed the first documented surgical excision of pharyngeal pouch. Dohlman first performed endoscopic removal of pharyngeal pouch.
Etiopathology of pharyngeal diverticula:
Is still not clear. A lot of it has been attributed to the cricopharyngeal muscular contractions. Wouters and Van Overbeek proposed that an anatomical predisposition to a large Killian's dehiscence, which lies between the propulsive oblique fibres of the thyropharyngeus and the horizontal fibres of the cricopharyngeus, which have a sphincteric action, plays a prominent part in mucosal herniation.
Cook et al using videoradiography and manometry found intrabolus pressures were greater in patients with a diverticulum compared with an age matched healthy population and concluded that a disorder of diminished upper oesophageal opening was the cause.
Histologically it has been demonstrated that the cricopharyngeus muscle fibres are gradually replaced by fibro adipose tissue in these patients.
Congenital lateral pharyngeal diverticula:
Is a very rare entity, with only a few cases reported. These diverticula have been attributed to remnants of branchial cleft. These diverticula communicates internally, and usually found to be associated with second cleft commonly.
These patients commonly present with swelling over left side of neck since the ultimobranchial body growth is diminished or absent on the right side. These patients presented within two decades of life. These patients present with tender fluctuant swelling in the anterior triangle of neck. The patient may also have mild fever, with dysphagia.
Plain radiographs of neck usually show air inside the diverticulum. These diverticula can be better demonstrated by the use of contrast swallow using high density barium. Surgery must be performed once the acute episode has been treated with a course of antibiotic.
Acquired lateral pharyngeal diverticula:
Normal bulges: Small lateral pharyngeal bulges can be seen either arising in the pyriform fossa, or more rarely from the tonsillar fossa. This could become evident while performing a modified valsalva manuver. These normal lateral bulges are more common in elderly, probably due to reduced muscle tone, and loss of elasticity of the tissues. These bulges are usually bilateral and asymptomatic, and hence are thought to be normal variants.
Radiologically contrast studies demonstrate these bulges as smooth hemispherical prominences arising from either the tonsillary fossa or pyriform fossa, hence they are termed as pharygneal ears. They enlarge in size during performance of modified valsalve manuver.
Traumatic:
It has been reported by Atkins, that a certain group of criminals in central and north india had self inflicted diverticula where they hid stolen valuables. These diverticula have been produced by repetitive attempts to introduce a lead mass (size of a pigeons egg) in to the tonsillar fossa creating a diverticula. This diverticulum probably lies between the superior and middle constrictor muscles.
Raised intrapharyngeal pressure (Pharyngoceles): These large sometimes symptomatic diverticula arises from the precursor pharyngeal ears. This is due to repetitive increase in intrapharyngeal pressure. Loss of muscular tone due to ageing could also play a role. These diverticulae protrude through areas of weakness in the lateral pharyngeal wall and develop into pouches known as pharyngoceles. Men are commonly affected than women.
Symptoms:
Entrapment of food inside the diverticula causes dysphagia, which could be intermittent. Sometimes there may be regurgitation of entraped food from the diverticula casuing foul taste and bad odor. Patients may also have nocturnal coughing and choking. If the mass enlarges enough to affect the larynx, voice changes can occur. Patients may also manifest with chronic pulmonary problems. The mass may lie anterior to the sternomastoid muscle. This mass is compressible, and on compression may empty its contents with a gurgling sound. This is known as Boyce sign. Indirect laryngoscopy may not reveal much. Sometimes a small slit may be seen close to the pyriform fossa.
Plain radiographs of neck may reveal the diverticula as a translucency lateral to the pyriform fossa. Videofluroscopic techniques using high density barium really clinches the diagnosis. The high density barium effectively coats the diverticula and is retained for a longer duration to make diagnosis reliable.
Posterior pouches:
Posterior pharyngeal diverticula are more common than lateral diverticula. Among the various types of posterior pharyngeal diverticula, the posterior pulsion diverticulum (Zenker's diverticulm) is more commonly encountered.
Congenital Posterior diverticula: These are very rare. This diverticulum arises from above the cricopharyngeus, and is lined by normal pharyngeal mucosa. The whole diverticula is covered with muscle differentiating it from an acquired pulsion diverticula.
Acquired posterior diverticula:
Traumatic posterior pharyngeal diverticulum: This is a very rare condition. The etiological factor is hypopharyngeal trauma, either from damage caused by obstertitian's finger during breech delivery, or due to blind passage of suction / endotracheal tubes. Initially, there may be reactive spasm of cricopharyngeal muscle causing dysphagia and drooling.
Diverticulum due to raised intrapharyngo-oesophageal pressure: This rare variety of posterior diverticulum protrudes through the Laimer-Hackermann area. It commonly occurs in old individuals probably due to weakness of supporting musculature.
Posterior pharyngeal pulsion (Zenker's) diverticulum:
Zenker called this pulsion diverticula. Earlier foreign body impaction was attributed as a cause of this diverticulum. Killian attributed spasmodic contraction of the circular fibers at the upper end of the esophagus.
Etiology:
Theories attributed to the formation of Zenker's diverticulum:
Negus theory: Tonic spasm of cricopharyngeus muscle
According to Negus Killian's dehiscence occur as a result of man assuming erect posture, causing the larynx and cricopharynx to move lower down into the neck resulting in other constrictors to lie obliquely. There is also a lack of posterolateral longitudinal muscles which are seen elsewhere in the alimentary tract. Criopharyngeal muscle spasm associated with the pharyngeal stippling peristalsis causes prolapse of the mucosa through the weak portion in the posterior portion of pharynx (Killian's dehiscence).
Dohlmann's theory: Lack of inhibitory stimuli to the cricopharyngeus muscle.
Dohlmann postulated that lack of inhibitory stimuli to the cricopharyngeus muscle causing increased intraluminal pressure in the pharynx causing prolapse of mucosa through killian's dehiscence.
Wilson's theory: Second swallow due to pharyngeal laxity.
In patients with posterior pharyngeal diverticulum, the pharynx was found to be large. A second swallow becomes necessary to completely empty the pharynx. This second swallow occurs against a closed circopharyngeal sphincter. The attendent increase in the intraluminal pressure causes the pharyngeal mucosa to prolapse through the killian's area.
Korkis theory: Neuromuscular inco-ordination and associated congenital weakness could cause this problem.
Stages of posterior pharyngeal diverticulum:
Stage I: Small mucosal protrusion (initial stage) Patients may have a sticky sensation in the throat.
Stage II: A definite pouch with oesophagus and hypopharynx still in line (intermediate stage) Regurgitation and gurgling sounds are common in these patients (Boyce sign).
Stage III: A large pouch with the hypopharynx in line with the neck of the diverticulum. The oesophagus inlet is pushed anteriorly. Patients in this stage have severe dysphagia.
Clinical features:
1. Difficulty in swallowing
2. Regurgitation of undigested food from the diverticulum
3. Weight loss
4. Halitosis
5. Hoarseness of voice
Radiography:
Plain radiographs of neck may show a triangular lucency in the prevertebral tissues, with the apex at the level of the cricoid cartilage. This is due to the presence of air in the upper part of the pouch. Contrast videofluoroscopy clinches the diagnosis.
Treatment:
1. Dilatation of cricopharyngeus
2. Diverticulectomy
3. Inversion
4. Diverticulopexy
Endoscopic:
1. Dohlmanns electocoagulation
2. Dohlmanns laser treatment
3. Stapling
Endoscopic diathermy:
Dohlmann's operation:
This procedure was first described by Mosher. The septum between the diverticulum and oesophagus is devided. Initially scissors was used to divide it. Since bleeding produced was enormous use of diathermy to divide the septum was resorted to. Major risk of this surgical procedure is the ever present danger of mediastinitis. In contrast to external approach this procedure can also be performed in elderly individuals. For this procedure a double beaked oesophagoscope is used. The larger beak is introduced into the oesophagus while the smaller beak is inserted into the diverticulum. The intervening septum is divided.
External surgical approach is resorted to in patients with stage III diverticulum. The diverticulum is exposed through a transverse skin incision in the neck. After excising the diverticulum the mucosa should be carefully approximated / stapeled.
