Tonsillar herniation

Last revised by Travis Fahrenhorst-Jones ◉ on 3 May 2023

Citation, DOI, disclosures and article data

Citation:

Hacking C, Fahrenhorst-Jones T, Silverstone L, et al. Tonsillar herniation. Reference article, Radiopaedia.org (Accessed on 02 Jun 2023) https://doi.org/10.53347/rID-37113

DOI:

https://doi.org/10.53347/rID-37113

Permalink:

https://radiopaedia.org/articles/37113

rID:

37113

Article created:

26 May 2015, Craig Hacking ◉ ◈

Disclosures:

At the time the article was created Craig Hacking had no recorded disclosures.

View Craig Hacking's current disclosures

Last revised:

3 May 2023, Travis Fahrenhorst-Jones ◉

Disclosures:

At the time the article was last revised Travis Fahrenhorst-Jones had no financial relationships to ineligible companies to disclose.

View Travis Fahrenhorst-Jones's current disclosures

Revisions:

19 times, by 15 contributors - see full revision history and disclosures

Systems:

Central Nervous System

Sections:

Gamuts

Tags:

herniation, brain herniation, midline shift

Synonyms:

Tonsillar herniations
Coning

Tonsillar herniation is a type of brain herniation characterized by the inferior descent of the cerebellar tonsils below the foramen magnum >3 mm ⁵. Clinically, the presence of tonsillar herniation is often called coning.

The terminology of caudally displaced tonsils is discussed in the article on cerebellar tonsillar ectopia.

Pathology

It is a secondary sign of markedly raised intracranial pressure. The skull is a rigid structure and an increase in volume of the contents is matched by a corresponding decrease in CSF volume, intravascular blood volume and/or brain herniation; see Monro-Kellie hypothesis. Common causes of raised intracranial pressure are tumor, hemorrhage, edema, stroke or abscess. Tonsillar descent is often a preterminal event as the brainstem is compressed against the clivus, affecting the vital life-sustaining functions of the pons and medulla, such as the respiratory and cardiac centers.

Radiographic features

Tonsillar herniation is seen on CT and MRI as effacement of the CSF cisterns surrounding the brainstem and as inferior descent of the cerebellar tonsils below the level of the foramen magnum.

Obstructive supratentorial hydrocephalus may result from fourth ventricle compression.