Quantitative anatomy of the fourth ventricle floor: a cadaveric morphometric study

Area of Science:

• Neurosurgery
• Neuroanatomy
• Microsurgery

Background:

• The fourth ventricle floor has critical surface landmarks overlying brainstem nuclei.
• Detailed morphometric data on these landmarks are limited, hindering microsurgical planning.

Purpose of the Study:

• To conduct a morphometric analysis of the fourth ventricle floor using cadaveric specimens.
• To emphasize dimensions, symmetry, and proportional relationships for surgical planning.

Main Methods:

• Analysis of 40 formalin-fixed adult human brainstems.
• Measurement of 16 anatomical parameters, including linear distances and qualitative observations of key landmarks.
• Calculation of anatomical ratios and comparison with prior cadaveric studies.

Main Results:

• Mean floor length: 33.58 mm, width: 20.0 mm.
• Facial colliculus divides floor into symmetrical ~43% rostral/caudal segments.
• Hypoglossal and vagal trigones occupy 25.44% and 12.69% of caudal floor length, respectively.
• Safe midline corridor is 30.59% of floor width.
• Significant asymmetry noted in lateral recess lengths and striae medullares bundle counts.
• Most measurements significantly differed from previous data (p < 0.001).

Conclusions:

• First quantitative definition of hypoglossal and vagal trigones.
• Clarifies topographic relationships of surgical corridors on the fourth ventricle floor.
• Provides normative data to enhance microsurgical planning and patient safety.