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Chapter 8: Lumbar Cerebrospinal Fluid Taps 89

A

B

C
Figure 8.5 (A) Lateral radiograph of caudal
spine. Substantial overlapping of bilateral
anatomical components (ribs, lumbar transverse
processes, wings of ilium) confirms proper
patient positioning. (B) Lateral radiograph
showing adequate spinal needle placement at L5–L6
and myelographic study. (C) Lateral radiograph
showing proper needle placement at L4–L5 and
myelography and previously inserted L5–L6 spinal
needle still in place.

and death. Increased intracranial pressure can be suspected when with high pressure, the media may enter the central canal and cause it
the patient shows progressive obtundation, papilledema, bilateral to dilate. The consequences can include paresis and extreme pain.
miosis, and/or decerebrate rigidity. When these clinical signs are A good evaluation of the potential risks and benefits from obtain-
observed, the puncture should not be performed until advanced ing a CSF sample for analysis by the clinician is vital. In the case of
imaging (CT or MRI) of the brain excludes the presence of large hemorrhagic diathesis or infected lumbar skin, if CSF analysis
space‐occupying lesions or findings associated with suspected proves to be essential for diagnostic and therapeutic purposes, the
increased intracranial pressure (cerebellar herniation, mass procedure can be attempted with efforts made to reverse the
effect, severe brain edema, severe hydrocephalus). There is no coagulopathy (if at all possible) and limit the chances of spreading
advantage of lumbar versus cerebellomedullary CSF collection in the skin infection.
terms of brain herniation risk. In humans, lumbar puncture has
been reported to cause herniation or impaction of the cord in Potential Complications of Lumbar CSF Tap
patients with spinal mass lesions [14]. 1 Brain herniation: sudden release of CSF pressure distally can
2 Elevated risk of anesthetic complications: CSF collection in small result in herniation.
animals requires general anesthesia in order to prevent move- 2 Spinal cord trauma: preexisting trauma to the area being tapped
ment. Although generally not recommended, lumbar puncture or ongoing thrombocytopenia or other clotting disorder could
may be attempted with heavy sedation and local anesthesia if the result in intraspinal hemorrhage.
patient presents an unacceptable anesthetic risk. 3 Iatrogenic hemorrhage: due to inadvertent trauma to the venous
3 Hemorrhagic diathesis: in patients with thrombocytopenia or sinuses, or dural or arachnoid vessels. Generally, this is of little
coagulopathies, or taking oral anticoagulants, there is a risk of consequence, although blood contamination can prevent ade-
iatrogenic CNS hemorrhage. quate CSF sample interpretation. However, occasionally exten-
4 Suspected active intracranial hemorrhage. sive spinal epidural, subdural, subarachnoid, intraspinal or even
5 Skin or soft tissue infection around the lumbar puncture site, intracranial bleeding may be induced [15,16].
because of the possibility of introducing infection into the 4 Failure to obtain CSF (“dry tap”): can result from the presence of
intrathecal compartment. spinal disease narrowing the interarcuate space (as in degenerative
6 Central canal dilation with myelography: if the end of the needle is joint disease). In these cases another attempt should be made in
placed in the central canal or if the contrast material is injected rapidly the interspace cranially or caudally. If the needle is adequately