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8 Lumbar Cerebrospinal Fluid Taps

Luis Gaitero

Introduction The contrast injection is more prone to deposit epidurally during a
Lumbar puncture (tap) is an essential component in the investiga- lumbar myelographic procedure.
tion of neurological disease. The technique is originally credited to
Quincke’s description from 1891 [1]. The main indications for lum-
bar puncture [2] are: Anatomical Considerations
1 obtain a sample of CSF for diagnostic purposes; The three layers of meninges covering the central nervous system
2 inject radiopaque contrast materials (myelography); (CNS) are the dura mater, arachnoid, and pia mater. The CSF is
3 administer therapeutic drugs (antibiotics, chemotherapeutics); contained in the subarachnoid space. Lumbar puncture is per-
4 measure CSF pressure; formed at the interarcuate space between L5 and L6 or on space
5 reduce CSF volume for therapeutic purposes (as in benign cranially (L4–L5) to minimize the risk of direct damage to the spi-
intracranial hypertension). nal cord by the needle while still gaining access to the subarachnoid
CSF collection and myelography are the most common indications space. At these locations, the spinal cord has tapered into the conus
in veterinary medicine. medullaris and is surrounded by the cauda equina, both of which
CSF analysis is valuable in the investigation of many neurological are less likely than the cord itself to be damaged by needle insertion.
disorders and samples can be collected from the cerebellomedullary The lumbar cistern, the fluid‐filled subarachnoid space extending
(atlanto‐occipital) or the lumbar cisterns. Although the CSF flows beyond the last segment of the spinal cord, rarely extends to the
rostrocaudally and caudorostrally, it does so in a predominantly lumbosacral junction in dogs, whereas in cats collection may be
rostrocaudal direction. To enhance the chances of detecting abnor- attempted at L6–L7 or even the lumbosacral space. However, con-
malities, collecting from a site caudal to the lesion is desirable. sidering the variation in the location of the spinal cord segments
Consequently, lumbar CSF collection would be highly indicated in relative to vertebrae between dogs of different sizes (with the
thoracic and lumbar lesions; indeed, a lumbar CSF sample could be relationship of spinal cord segment to vertebra being more cranial
recommended over a cerebellomedullary one in any spinal lesion in large dogs than in small breeds), L4–L5 puncture could be more
caudal to C1. The lumbar tap is technically more difficult and successful than L5–L6 in large dogs [4–6].
demanding than the cerebellomedullary one, provides smaller CSF Access to a caudal lumbar intervertebral space requires insertion
volumes, and is associated with a higher likelihood of iatrogenic of a spinal needle through skin, subcutaneous fascia, ligaments, and
blood contamination. As a result, obtaining a sample from both epaxial muscles. The dorsal paraspinal musculature can be divided
sites to enhance the chances of detecting abnormal CSF findings is into three longitudinal muscle masses formed by numerous over-
acceptable, performing the cerebellomedullary first to decrease the lapping fascicles: from lateral to medial, the iliocostalis system, the
risk of CSF blood contamination [3]. longissimus system, and the transversospinalis system [4]. The
Similarly, myelograms can be performed through a cerebel- transversospinalis system is the most medial and deepest epaxial
lomedullary or a lumbar puncture. Although a lumbar puncture muscle mass and consists of a number of different systems of
procedure is more challenging, lumbar myelography has multiple fascicles, which join one vertebra. In the caudal lumbar region, the
advantages over cerebellomedullary, mainly a lower risk of iatro- musculus multifidus pars lumborum and musculus interspinales
genic trauma and better image quality and lesion delineation, par- are the deepest muscles of this epaxial medial mass. The multifidus
ticularly in thoracic and lumbar compressive lesions as the contrast lumborum is a strong homogeneous muscle composed of numer-
can be forced forward under pressure around the compression site. ous individual portions that overlap in segments, extending from

Current Techniques in Canine and Feline Neurosurgery, First Edition. Edited by Andy Shores and Brigitte A. Brisson.
© 2017 John Wiley & Sons, Inc. Published 2017 by John Wiley & Sons, Inc.
Companion website: www.wiley.com/go/shores/neurosurgery

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