Case Study- Cerebrospinal Fluid

Question 1

A clear colorl ess CSF was obta i n ed by l umbar puncture from a 2 -yea r-old ch ild who is l ethargic and has fever.
A cell count on the undiluted specimen revealed 860 WBCs and 60 RBCs in 9 mm2 o f t h e hemocytometer. Figure 12 -25 represents the Wright-stained cytoce ntrifuged prepa ration of this CSF.

1. What are the cell counts?
2. Approximate the differential count.
3. What else can be observed on the Wright stain?
4. Which organism is most likely the causative agent, Neisseria meningitidis or Streptococcus pneumoniae? Why?

Answer 1

1. What are the cell counts?
   WBCs = 956 mm3
   ; RBCs = 67 mm3
2. Approximate the differential count.
   90% neutrophils, 10% lymphocytes
3. What else can be observed on the Wright stain?
   Cocci-shaped bacteria.
4. Which organism is most likely the causative agent, Neisseria meningitidis or Streptococcus pneumoniae? Why?

Determining genus and species of bacteria cannot be made on Wright stain. A Gram stain is needed for the initial identification of gram positive or negative, followed by culture and sensitivity.

Question 2

An elderly man fe ll in his home and was
b ought to the emergency department when discove red by a caregiver. How long ago he had fa llen is u n clear. Three tubes of CSF were col l ected and are displayed in
Figure 12 -26. A Wright stained cytocentrifuged preparation of this CSF is shown in Figure 12-27.

1. Explain how these results indicate a traumatic tap, fresh hemorrhage, or old hemorrhage.
2. What chemical analysis helps differentiate between CNS hemorrhage and traumatic tap?

Answer 2

1. Explain how these results indicate a traumatic tap, fresh hemorrhage, or old hemorrhage.

The presence of xanthochromia in each of the three specimen tubes rules out a traumatic tap. A traumatic tap would show pink to red coloration in the first tube collected with decreasing intensity of color
in subsequent tubes. In addition, xanthochromia indicates that hemoglobin has had time to oxidize. Therefore, the hemorrhage is probably not fresh.
The hemorrhage, and perhaps the fall, occurred approximately 1 to 2 days back as indicated by the presence of erythrophagocytosis on the Wright stain
smear. Furthermore, red blood cells are still present in the specimen and there are no siderophages seen, suggesting that the hemorrhage did not occur any
longer than a few days ago. See Table 12-2.

2. What chemical analysis helps differentiate between CNS hemorrhage and traumatic tap?

Testing for the presence of D-dimers can help
distinguish between CNS hemorrhage and traumatic tap. If D-dimers are not present, then the appearance of RBCs in the CSF is probably due to a traumatic tap.

Question 3

Observe the i mages from this case (Figs.12-28
and 12 -29).
1. Suggest a possible cause for the observations made.

Answer 3

1. Suggest a possible cause for the observations made.

The tubes of CSF in Figure 12-28 show decreasing amounts of red color. This disappearance of color as
CSF collection progress is suggestive of a traumatic tap. The nucleated red blood cells in Figure 12-29 confirm the occurrence of traumatic tap with nicking of a vertebrae.

Question 4

A patient comes into the emergency department with otorrhea .

1. Explain how to determine if the fluid is CSF.

Answer 4

1. Explain how to determine if the fluid is CSF.

The presence of tau transferrin band on protein electrophoresis of the fluid from the ear confirms that the fluid is primarily from the CNS.