Page 1080 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Nervous system 1055

VetBooks.ir 10.13 3 There are many large veins at the AO site
so whole blood may appear in the hub of the
needle. If this is from contamination from
an extradural vein, the amount of blood will
decrease as more CSF is drawn. Use several
2-ml syringes to obtain serial aliquots, rather
than one larger syringe, and the one that is least
blood-contaminated should be submitted for
laboratory analysis. If haemorrhage is part of the
disease process, the amount of blood visible will
not decrease as CSF is withdrawn.

Fig. 10.13 Location for atlanto-occipital CSF If a sample of CSF is centrifuged and the super-
collection. natant is clear, the blood is contamination from the
collection procedure. If the supernatant is xantho-
chromic (yellow) this suggests that haemorrhage is
a challenge for ataxic horses, and so protocols for AO part of the disease process; the yellow colour is due
and C1:C2 cervical centesis, to obtain CSF in the to the products of haemoglobin breakdown from
standing horse under sedation and local anaesthe- erythrocytes.
sia, have been recently reported in small numbers of
horses. Collection of CSF should not be performed Lumbrosacral (LS) CSF collection
at cranial sites if increased intracranial pressure A CSF sample can be obtained from the subarachnoid
(e.g. a space-occupying lesion) is suspected because space at the LS articulation in the horse (Fig. 10.14).
the sudden release of CSF pressure on puncture of This can be performed with the horse restrained in
the subarachnoid space could result in cerebellar stocks and with the aid of local anaesthesia. Sedation
herniation and an exacerbation of neurological signs. can cause the horse to swing its weight onto one
A protocol for obtaining CSF from the AO site hindlimb, making the procedure more challenging,
in the recumbent horse under general anaesthesia is but is often necessary in excitable or unpredictable
described below: horses.

1 After sterile preparation of the skin, insert an
18–20 gauge 9-cm (3.5-inch) spinal needle, with 10.14
the bevel to one side, at the intersection of a
line drawn caudally in the dorsal plane from the
external occipital protuberance, and a line drawn
transversely across the cranial border of the
wings of the atlas.
2 The needle should be roughly parallel with the
ramus of the mandible. The needle should be
inserted steadily and the stylet removed to check
that CSF appears at the hub of the needle. Once
CSF appears at the needle hub do not push the
needle any further. A sterile syringe can be
attached to the hub of the needle and 1–2 ml Fig. 10.14 Lumbosacral CSF collection. The
CSF obtained. A loss of resistance or ‘pop’ is not clinician’s left hand is placed at the site for needle
reliably detected when the subarachnoid space is puncture and the fingers of the right hand are at
penetrated in the horse at the AO site. the right tuber sacrale.