The bioccipital width can be used to evaluate the size of the ventricular system, which may be enlarged in hydrocephalus.
Examination: axial section of a head CT scan
A line is drawn perpendicular to the long axis of the skull at the maximum intracranial width of the occipital cranium.
Parameters:
(1) maximum width of the left occipital horn in cm along the line
(2) maximum width of the right occipital horn in cm along the line
(3) intracranial width along the same line in cm
bioccipital index =
= ((width of left occipital horn) + (width of right occipital horn)) / (intracranial width)
Interpretation:
• For a fetus > 32 weeks of gestation, the range is 0.12 to 0.28, with a mean of 0.17.
