Herniation

Abnormal protrusion of tissue through an opening. For example, a intervertebral disk (one situated between the vertebral bodies) can protrude and impinge on a nerve root.

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Protrusion of an anatomic structure ( e.g., intervertebral disk) from its normal anatomic position.

- caudal transtentorial h. displacement of medial temporal structures through the incisura, with or without rostrocaudal brainstem shift. SYN: uncal h..

- cingulate h. displacement of the cingulate gyrus beneath the falx.

- contained disk h. herniated disk material that remains covered by a thin layer of posterior annulus fibrosus or posterior longitudinal ligament; a disk protrusion is an example of a contained disk h..

- disk h. extension of disk material beyond the posterior annulus fibrosus and posterior longitudinal ligament and into the spinal canal.

- foraminal h. displacement of cerebellar tonsils through the foramen magnum.

- noncontained disk h. herniated disk material that comes directly in contact with the anterior epidural space through a complete defect in the posterior annulus fibrosus and posterior longitudinal ligament; of two main types: (1) extrusions, herniated material that is in continuity with the disk space, but extends completely into the epidural space and (2) sequestered, material that has lost continuity with the disk space and becomes a free fragment in the epidural space.

- rostral transtentorial h. displacement of anterior cerebellar structures through the incisura, with or without caudorostral brainstem shift.

- sphenoidal h. displacement of ventral frontal lobar tissue over the sphenoid ridge.

- subfalcial h. h. beneath the falx cerebri; usually of the cingulate gyrus.

- tonsillar h. h. of the cerebellar tonsils through the foramen magnum.

- transtentorial h. h. into the incisura, either from above (rostral transtentorial h.) or below (caudal transtentorial h.).

- uncal h. SYN: caudal transtentorial h..

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her·ni·a·tion .hər-nē-'ā-shən n

1) the act or process of herniating

2) HERNIA

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her·ni·a·tion (hur″ne-aґshən) the abnormal protrusion of an organ or other body structure through a defect or natural opening in a covering, membrane, muscle, or bone. See also hernia.