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90 Section I: Diagnostics and Planning

positioned in the subarachnoid space but no fluid can be
obtained, this suggests that the space is blocked at a higher level
(as in acute intervertebral disc extrusions) or that the lumbar
cistern is infiltrated by a spinal lesion or adhesive arachnoiditis.
5 Meningitis, discospondylitis, epidural abscess: caused by poor sterile
technique.
6 Others (not reported in small animals):
• Iatrogenic intraspinal epidermoid cyst [8,9].
• Headache: common in humans, occurring in approxi-
mately 10–15% of patients after lumbar puncture [14].
Difficult to demonstrate in animals. The risk is reduced by
using the smallest caliber possible of nontraumatic spinal
needle [10,11].

Indications for Lumbar CSF Analysis
CSF evaluation is a crucial component of the neurological diagnos-
tic plan, particularly when an inflammatory CNS condition is sus- Figure 8.6 Cerebrospinal fluid (dog): neutrophilic pleocytosis showing
pected. CSF is routinely assessed for physical properties (color, numerous degenerated neutrophils and microorganisms consistent with a
clarity), total and differential nucleated cell count and cytology, and diagnosis of bacterial meningitis.
total protein concentration; normal general reference ranges are
provided in Table 8.1. An extensive revision on CSF sample analy-
sis, interpretation, and abnormal findings is beyond the scope of
this chapter and the reader is referred to more specific sources in
the veterinary literature [17,18].
CSF analysis (Table 8.1) is especially useful in diagnosing CNS
inflammatory diseases (meningitis, encephalitis, myelitis), as it
often reveals an increased inflammatory cell count and protein
concentration (Figures 8.6, 8.7 and 8.8). However, although CSF
analysis provides valuable data since abnormalities in CSF cytol-
ogy and protein are relatively sensitive indicators of CNS disease,
these are mostly nonspecific and the clinician should be careful not
over‐interpreting the findings. CSF analysis helps to narrow the
differential diagnosis and rule out some conditions but must be
interpreted cautiously in the context of the specific case signal-
ment, history, clinical signs, and neuroimaging. The main indica-
tions for collection of a lumbar CSF sample for analytical purposes
are as follows.
1 Thoracolumbar myelopathies: particularly to identify and charac- Figure 8.7 Cerebrospinal fluid (dog): neutrophilic pleocytosis with
terize inflammatory/infectious conditions (myelitis, meningitis, predominance of mature nondegenerated neutrophils consistent with a
meningomyelitis). diagnosis of steroid‐responsive meningitis arteritis.
2 CSF collection prior to myelography: contrast agents are low‐
grade leptomeningeal irritants and change the characteristics
of the CSF producing mild inflammation [19]; thus a fluid
sample must be collected before injection of contrast if CSF
evaluation is required later. A study in normal dogs showed
that CSF nucleated cell count returned to normal range within

Table 8.1 Normal lumbar CSF values in dogs.
Physical characteristics (clarity, color, viscosity): clear, colorless, same viscosity as
water
Total cell count
Red blood cells: 0/μL
White cells: 0–3/μL
Lymphocytes: 60–70% (small, well differentiated)
Monocytes: 30–40%
Differential cell count and cytology
Occasional neutrophils, eosinophils (<2%)
Choroid plexus and ependymal cells, squamous cells, chondrocytes,
hematopoietic cells: rare
Total protein: <45 mg/dL Figure 8.8 Cerebrospinal fluid (dog): mixed cell pleocytosis with a predom-
inant population of mononuclear monocytes and lymphocytes consistent
Source: Data from Vernau et al. [17] and Wamsley and Alleman [18]. with granulomatous meningoencephalomyelitis.