SAEVA Congress 2018 Proceedings | 12-15 February 2018 | ATKV Goudini Spa
A right-handed person should stand on the horse’s right side and rest
wrist of the right hand on the dorsal midline of the horse cranial to
selected site, and holding the stilette in place, advance the needle along
median plane toward the LS space. The average depth to reach
subarachnoid space in a 450 kg horse is approximately 5 inches, and
diameter of the LS space approximately 1.0 inch.
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Advancement of the needle is usually without much resistance. Penetration
of the lumbo-sacral interarcuate ligament (ligamentum flavum) is usually felt
as a sudden loss of a slightly increased resistance, and the dura mater and
arachnoid may be penetrated at the same time; otherwise, these membranes
will be penetrated by advancing the needle a few millimeters, and this is
usually accompanied by some local response by the horse as described. If
CSF is not obtained, the needle can be advanced to the floor of the vertebral
canal and then withdrawn with slow rotation of the needle a millimeter or less
at a time. In this situation, the needle passes through the dorsal dura mater
and subarachnoid space and conus medullaris, then through the ventral
subarachnoid space and dura mater. It is imperative that the hand holding the
hub of the spinal needle rests firmly on the horse whenever the needle is held
or manipulated, and the stilette must always be in place during advancement
of the needle.
At each stage when the stilette is withdrawn to determine if the subarachnoid
space is entered, several different efforts should be made to obtain CSF
before the stilette is replaced and the needle advanced or withdrawn. First,
Queckenstedt’s maneuver can be performed by an assistant, occluding both
jugular veins to increase intra-cranial, and thus intra-spinal pressure. The
needle can be rotated up to 180° to stop any of the meninges or nerve roots
from lying across and occluding the bevel of the needle point. Finally, a small
(5 ml) syringe can be applied to the needle hub and gentle suction pressure
intermittently applied. (A heavy syringe tends to force the needle down further
and continuous strong suction pressure tends to also promote hemorrhage
and often occludes the needle with meninges or cauda equina.) With
movement of the horse during collection, the jugular veins can still be readily
occluded and CSF can often be aspirated from within the hub of the needle
without connecting the syringe to it, thus reducing the chance of dislodging
the needle from the subarachnoid space or initiating hemorrhage.
B. Imaging
1. Radiography.
2. Myelography.
3. Computerized tomography.
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