Trapezoid body

The trapezoid body or ventral acoustic stria is a structure in the pontine tegmentum formed by the crossing-over (decussation) of a portion of the efferent second-order fibers of the ventral cochlear nucleus (anterior cochlear nucleus). After decussating, some of these fibres proceed to ascend in the contralateral lateral lemniscus to reach and terminate in the dorsal nucleus of lateral lemniscus, and inferior colliculus.

The trapezoid body is part of the auditory pathway. It is one of three distinct decussating second-order efferent fiber pathways of the cochlear nuclei (the other two being the dorsal acoustic striae, and intermediate acoustic striae). Not all efferents of the cochlear nuclei decussate though; the partial decussation of the cochear nuclei afferents is thought to be functionally important for sound localization.

Anatomy
The trapezoid body is formed by horizontally-oriented, commissural fibers which are readily identifiable.

Projections
The fibres of the trapezoid body terminate (synapse) in the (contralateral):


 * medial nucleus of trapezoid body (which in turn projects third-order fibres to medial superior olivary nucleus),
 * medial superior olivary nucleus,
 * dorsal nucleus of lateral lemniscus,
 * inferior colliculus.

Relations
It is situated in (the caudal portion of ) the ventral pontine tegmentum at the level of the pontomedullary junction. It is situated immediately dorsal/posterior to the pontine nuclei, and ventral/anterior to the medial lemnisci.