Corpus trapezoideum

The trapezoid body , also trapezoidal body called, is in the lower brain stem on the border of the hindbrain to Mark Brain , in the caudal pons (bridge) is one it the white matter of the ventral pontine tegmentum ( tegmental pontine ). In some animals, such as cats, it forms a delicate transverse bulge on the ventral brain stem below the bridge.

Schematically a cross section through the hindbrain with 4th ventricle (13) at the level of VIII Nn vestibular (1) and cochlear (2) and the front (3) and rear (4) screw cores - are colored blue fiber trains of auditory pathway to olivary nucleus superior (upper olive, 7), mostly crossing in the corpus trapezoideum (trapezoidal body, 8) and ascending further as Lemniscus lateralis (10). The nuclei corporis trapezoidei (9) are embedded in the trapezoidal body.
Only half of the fibers crossing the midline ( raphe , 11) are shown; The tracts of the descending pyramidal tract (12) are shown in red .

The structure, which can already be seen with the naked eye, is caused by numerous transverse fiber strands, where most of the axons of 2nd neurons of the auditory pathway cross . Starting from the nucleus cochlearis anterior (anterior cochlear nucleus ), these fibers move to the opposite side and rise to the nucleus olivaris superior (upper olive nucleus), to the nucleus lemnisci lateralis (loop nuclei ) and above all to the colliculus inferior (lower hill), the lies in the roof of the midbrain ( tectum mesencephali ). These connections are part of the lemniscus lateralis , which also carries uncrossed fibers and those from the posterior cochlear nucleus ( nucleus cochlearis posterior ).

In the area of ​​the corpus trapezoideum, some core areas are grouped in which fibers are already switched to 3rd neurons of the auditory pathway, the

• Nuclei corporis trapezoidei , in humans we distinguish three on each side:
  • Nuclei anterior corporis trapezoidei
  • Nuclei lateralis corporis trapezoidei
  • Nuclei medialis corporis trapezoidei

At about the level of the corpus trapezoideum the VI. ( Nervus abducens ), VII. ( Nervus facialis ) and VIII. ( Nervus vestibulocochlearis ) cranial nerve to the brain surface.

Individual evidence

1. ↑ see Terminologia Anatomica (TA), p. 113 (A.14.1.05.315).
2. ↑ John Mendoza: Trapezoid Body . In: Encyclopedia of Clinical Neuropsychology . Springer New York, 2011, ISBN 978-0-387-79947-6 , p. 2549 (accessed January 3, 2019).
3. ↑ see Terminologia Anatomica (TA), p. 114 (A.14.1.05.421 to .424).