What’s abnormal in this image? Here’s a hint. Here is an example
of normal. When evaluating for possible elevation in
intracranial pressure, it has been shown that optic nerve sheath
diameter (ONSD) measurements correlate with elevated
intracranial pressures.(1,2) The optic nerve attaches to the
globe posteriorly and is wrapped in a sheath that contains
cerebral spinal fluid. The optic nerve sheath is contiguous with
the dura mater and has a trabeculated arachnoid space through
which cerebrospinal fluid slowly percolates. ONSD Normal Ranges
|Normal Adults||< 5 mm| |Children >1 yr||< 4.5 mm| |Infants < 1
yr||<4 mm| The ONSD is measured 3 mm posterior to the globe for
both eyes. A position of 3 mm behind the globe is recommended
because the ultrasound contrast is greatest. It is best to
average two measurements of each eye. An average ONSD greater
than 5 mm is considered abnormal and elevated intracranial
pressure should be suspected. In severe cases of elevated ICP,
one can see an echolucent circle within the