Anatomy and Physiology
Waldeyer ring describes a circular structure of lymphoid tissue located in the nasopharynx and the oropharynx. It is formed by the two palatine tonsils, pharyngeal tonsils or adenoids, tubal or Gelach tonsils surrounding eustachian tube opening and lingual tonsils. The lymphoid tissue of Waldeyer tonsillar ring contains B-cell lymphocytes, T-cell lymphocytes, and a few mature plasma cells. This tissue is primarily involved in secretory immunity and regulates immunoglobulin production.
The cells are organized in lymphoid follicles similar to lymph nodes, but have specialized endothelium-covered channels that facilitate antigen uptake directly into the tissue. The independence of this system from lymphatic drainage is a unique advantage for antigen acquisition. The location of Waldeyer tonsillar ring and its design allow direct exposure of the immunologically active cells to foreign antigens entering the upper aerodigestive tract, which maximizes immunologic memory. These tissues are most active from the ages of 4–10 and tend to involute after puberty. After their involution, the secretory immune function of these tissues remains, but at a lower level.
The palatine tonsils are the largest component of the Waldeyer ring and are found in the lateral walls of the oropharynx. The tonsils are located within a tonsillar fossa formed by three pharyngeal muscles. The palatoglossus muscle forms the anterior tonsillar pillar, the palatopharyngeal muscle forms the posterior tonsillar pillar, and the base of the tonsillar fossa is formed by the pharyngeal constrictors, primarily the superior constrictor. The fibrous capsule of a tonsil is attached to the fascia of the pharyngeal muscles. The potential space between the tonsil and the pharyngeal muscles is a usual site of a peritonsillar abscess.
The glossopharyngeal nerve lies deep to the superior pharyngeal constrictor and supplies sensation to the tonsil through the tonsillar branch. The tympanic branch of glossopharyngeal nerve is responsible for a referred otalgia that is commonly present with tonsillar inflammation or following tonsillar surgery. The descending branches of the lesser palatine nerve are another sensory supply to the tonsil. The arterial blood supply is primarily based at the inferior pole, and the tonsillar branch of the dorsal lingual artery, the ascending branch of the palatine artery, and the tonsillar branch of the facial artery enter at this site. The superior pole receives its blood supply from the ascending pharyngeal artery and from the lesser palatine artery. Venous drainage occurs through a venous peritonsillar plexus that drains into the lingual and pharyngeal veins and feeds into the internal jugular vein. Lymphatic drainage is usually to the tonsillar lymph node behind the angle of the mandible, or to other jugulodigastric lymph nodes.
The tonsillar lymphoid tissue forms deep crypts that are lined with stratified antigen-processing squamous epithelium. These crypts maximize the exposure of tissue to surface antigens. They can also harbor debris and bacteria and become a source for infection, halitosis, and tonsilloliths.
The adenoids or pharyngeal tonsils and the lingual tonsils are not as well defined or specialized as the palatine tonsils. These structures consist of lymphoid tissue covered by a specialized, pseudostratified, ciliated columnar epithelium that forms redundant surface folds to maximize the surface area of the tissue. The adenoids are located over the surface of the superior and posterior wall of the nasopharynx, and have greatest growth in the first years of life.
Due to the confined space, adenoid hypertrophy can be a cause of upper airway obstruction in young children. By the age of 5, the adenoids start to regress and, with skull base growth, adenoid hypertrophy is rarely a problem thereafter. The blood supply to the adenoids includes numerous branches of the palate and pharynx. Venous drainage is to the pharyngeal plexus, and the lymphatics drain into the retropharyngeal and pharyngomaxillary lymph nodes.
Infections
The oropharynx and Waldeyer tonsillar ring are normally colonized by many species of aerobic and anaerobic bacteria, including staphylococcus, nonhemolytic streptococci, lactobacillus, bacteroides, and actinomyces. These organisms, and other pathogenic bacteria, viruses, fungi, and parasites, can cause infections of tonsillar and adenoid tissue. Oropharyngeal cultures obtained during the infection are not always useful in distinguishing the offending pathogen as they often yield multiple organisms, reflecting the normal flora of the oral mucosa.
Acute pharyngotonsillitis may be caused by viral or bacterial infection, viral etiology being the most common. It is often difficult to distinguish between the two causes based on clinical exam. Patients present with fever, malaise, odynophagia, and lymphadenitis. On a physical exam tonsillar enlargement, erythema, and exudate may be present.
Roughly half of cases of acute pharyngotonsillitis have a viral etiology. Patients commonly present with complaints of sore throat and dysphagia. Upon examination, there is often fever, tender cervical lymphadenopathy, tonsillar inflammation, and erythema with possible exudate. Common viral pathogens include adenovirus, rhinovirus, reovirus, respiratory syncytial virus (RSV), influenza, and parainfluenza viruses. Treatment for most viral infections is generally supportive. In some cases, patients develop a bacterial superinfection of tonsils that results in more severe symptoms. These patients benefit from systemic antibiotics.
Tonsillar infections with the Coxsackie virus result in herpangina, which presents as ulcerative vesicles over the tonsils, posterior pharynx, and palate. The disease commonly occurs in children under the age of 16. Such patients present with generalized symptoms of headache, high fever, anorexia, and odynophagia.
Epstein–Barr Virus (EBV) belongs to the herpes family of viruses and causes acute pharyngitis as a part of infectious mononucleosis. In developed nations and regions of high socioeconomic status, primary infection by EBV occurs during the second and the third decade of life. This is not the case in developing countries where more young children are affected by the disease. EBV is transmitted orally, and manifests as fever, generalized malaise, lymphadenopathy, hepatosplenomegaly, and pharyngitis. The tonsils are severely enlarged, sometimes to the point of compromising the airway, and are covered with an extensive grayish-white exudate. When the virus is acquired at a younger age, symptoms are often less severe.
EBV preferentially infects and transforms human B lymphocytes. The incubation period is about 2–6 weeks, during which EBV induces a proliferation of infected B cells. This is followed by a cellular immune response, characterized by the appearance of “atypical” cytotoxic T lymphocytes in the blood. In immunosuppressed patients with inherited or acquired immunodeficiency, such as AIDS, X-linked lymphoproliferative disorder, and post-transplant immunosuppression, this T-lymphocyte response is limited, and uncontrolled proliferation of B cells may result in hyperplasia of lymphoid tissues. EBV is also associated with Hodgkin and non-Hodgkin lymphomas, Burkett lymphoma, nasopharyngeal carcinoma, and other lymphoproliferative disorders.
Diagnosis of acute infectious mononucleosis usually can be made upon clinical observation of absolute lymphocytosis, atypical lymphocytes in the peripheral smear, heterophile antibodies, and EBV-specific antibodies. Increased fluid intake, rest, and analgesics comprise primary treatment. In the case of progressive airway obstruction due to obstructive tonsillar swelling, a short course of systemic steroids can also help. Rarely, a nasopharyngeal airway, nasotracheal intubation, tonsillectomy, or tracheotomy might be required to secure the airway.
An acute retroviral syndrome is a manifestation of primary infection with the human immunodeficiency virus (HIV). Following 1–5 week incubation period, symptoms develop that include fever, nonexudative pharyngitis, lymphadenopathy, and systemic symptoms such as arthralgia, myalgia, and lethargy.
Group A beta-hemolytic streptococcus (GABHS) is the most common cause of acute bacterial pharyngotonsillitis in children. “Strep throat” is a very common disease among adolescents and children, with an incidence that peaks during the winter and spring months, and tends to be uncommon in children less than 3 years of age. Transmission generally occurs through droplet spread and the incubation period is about 2–5 days. Symptoms usually include fever, sore throat, cervical lymphadenopathy, dysphagia, and odynophagia. Physical examination typically reveals tonsillar and pharyngeal erythema with purulent exudate.
Throat culture with a blood agar plate (BAP) is the standard method for establishing the diagnosis of pharyngitis caused by group A streptococcus in children. Office-based rapid antigen-detection tests (RADT) are also available. These tests have excellent specificity; however, the sensitivity of these tests is lower when compared to BAP leading to recommendation to confirm negative RADT results with BAP culture. The definitive tests to determine GABHS infection is measuring serum titers of antistreptolysin O (ASO). Certain individuals, “carriers,” have positive throat cultures and remain asymptomatic.
Early diagnosis of GABHS pharyngitis and appropriate antimicrobial treatment is a standard of care to primarily prevent rheumatic fever. Although a number of drugs have shown promise in treating GABHS, a 10-day course of Penicillin V remains the treatment regimen of choice. Amoxicillin is commonly substituted for penicillin. Intramuscular benzathine penicillin G given as one dose is also an effective treatment and can be used when compliance with oral regimen is a concern. First-generation cephalosporins, macrolides, and climdamycin are alternatives for treatment of patients allergic to penicillin.
Most GABHS pharyngotonsillitis is benign and self-limited; however, the potential for nonsuppurative and suppurative complications exists. The emphasis on rapid diagnosis and the widespread use of antibiotics have markedly decreased the incidence of nonsuppurative complications. In contrast, suppurative complications of acute bacterial tonsillitis are still commonly encountered.
Scarlet fever occurs secondary to the endotoxin production by the bacteria during the episode of acute streptococcal pharyngotonsillitis. Clinical presentation includes erythematous rash, fever, lymphadenopathy, dysphagia, and erythematous tonsils and pharynx covered with a yellow membranous film. The tongue may become red, with desquamation of the papillae, often described as “strawberry tongue.”
Acute rheumatic fever usually occurs 1–4 weeks following pharyngotonsillitis caused by GABHS. Streptococcal infection results in production of cross-reactive antibodies to heart muscle, leading to subsequent endocarditis, myocarditis, or pericarditis. Once heart tissue damage occurs, little can be done to reverse the process.
Poststreptococcal glomerulonephritis typically occurs as an acute nephritic syndrome about 1–2 weeks after a pharyngotonsillar infection or skin infection with a GABHS. The pathogenic mechanism of the disease involves injury to the glomerulus by deposition of the immune complexes as well as circulating autoantibodies.
A clinical entity known as pediatric autoimmune neuropsychiatric disorder associated with group A streptococcal infection (PANDAS) has been described. PANDAS is associated with the abrupt onset of severe exacerbations of obsessive–compulsive type behaviors or tics in children following GABHS infection. The pathophysiology of this condition is thought to be similar to Sydenham chorea, in which antineuronal antibodies cross-react with regions in the basal ganglia, producing behavioral and motor disturbances.
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