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Palatine tonsil

The palatine tonsils are paired lymphoid structures located in the oropharyngeal tonsillar fossa, between the anterior and posterior tonsillar pillars. They are part of Waldeyer’s ring and play a key role in immune defense against inhaled or ingested pathogens. Knowledge of their anatomy, function, and imaging characteristics is crucial for radiologists, ENT specialists, and surgeons, especially for evaluating infections, hypertrophy, or neoplasms.

Synonyms

  • Tonsilla palatina

  • Oropharyngeal tonsil

  • Paired lymphoid tonsils

  • Tonsillar fossa lymphoid tissue

Function

  • Provides immune surveillance for inhaled and ingested pathogens

  • Initiates local immune responses via lymphoid follicles

  • Produces lymphocytes and antibodies (IgA)

  • Acts as the first line of defense in Waldeyer’s ring

MRI Appearance

T1-weighted images:

  • The palatine tonsil appears as a soft tissue structure of intermediate signal intensity, slightly darker than surrounding fat.

  • Surrounded by hyperintense parapharyngeal fat, which enhances anatomical delineation.

  • Internal tonsillar crypts may appear as small linear or punctate areas of low signal.

  • Pathology such as tumors, abscesses, or hypertrophy may appear hypo- to isointense, with enhancement after contrast administration.

T2-weighted images:

  • Tonsils demonstrate intermediate signal, while fluid or edema within crypts or surrounding tissue appears hyperintense.

  • Useful for detecting infection, inflammation, or neoplastic changes.

  • Internal crypts and tonsillar sulci may appear as hyperintense foci due to secretions or fluid.

STIR (Short Tau Inversion Recovery):

  • Fat suppression highlights edema or inflammatory changes.

  • Normal tonsils remain intermediate signal, while infected or neoplastic tonsils appear hyperintense.

  • Particularly valuable for identifying subtle abscesses or early tonsillar tumors.

CT Appearance

  • On non-contrast CT, the palatine tonsil appears as a soft tissue density structure within the tonsillar fossa.

  • Surrounded by air in the oropharyngeal lumen, which appears hypodense (black), providing natural contrast to delineate the tonsil margins.

  • The tonsillar crypts may occasionally appear as small hypodense areas within the tonsil.

  • Pathological conditions such as tonsillitis, abscess, hypertrophy, or tumors are detected as areas of increased soft tissue density within the normally uniform tonsillar tissue.

  • CT is particularly useful for assessing peritonsillar space involvement, abscess formation, airway compromise, or calcifications.

MRI images

Palatine Tonsil axial image -img-00000-00000