16
Central Nervous System
Demyelinating Diseases
The cellular components in CSF from patients with demyelinat-
ing diseases are variable, depending on the specific diagnosis
and the phase and extent of the disease. In multiple sclerosis, for
example, the cell counts and constitution may be normal dur-
ing quiescent phases of the disease. Immunophenotyping of the
lymphocyte populations generally reveals T-cell predominance,
with mature T cells expressing either the helper or suppressor
phenotype.22 Some observers have described a decreased sup-
pressor/helper cell ratio in both CSF and peripheral blood of
patients with multiple sclerosis during exacerbation owing to
an absolute decline in the number of suppressor cells.23,24 Other
studies, however, have failed to demonstrate differences in sup-
pressor/helper cell ratios between CSF from patients with mul-
tiple sclerosis and patients with other CNS disorders, such as
Guillain-Barre syndrome and CNS infections.25 Rarely, in acute,
rapidly progressive cases other cell types including polymorpho-
nuclear leukocytes and macrophages may be seen.
In most cases of Guillain-Barre syndrome, the CSF is acel-
lular, but when inflammatory cells are present, a lymphocytic
response predominates. The clinical picture is similar to that
of viral meningoencephalitis, with a polyclonal lymphocytic
population with T-cell predominance. For the other diseases in
which demyelination is a component, the nature and extent of
cellular elements in CSF reflect the nature of the infiltrate within
the parenchyma of the brain and spinal cord.
Vascular Disorders
The two general categories of vascular disorders that occur in the
CNS are hemorrhage and infarction, and both processes may
be reflected in the CSF. In cases of pure hemorrhage due to a
ruptured aneurysm, bleeding vascular malformation, or intra-
cerebral hemorrhage with rupture into the SAS, the appearance
of blood in the CSF is followed within hours by the appear-
ance of macrophages that rapidly begin engulfing the erythro-
cytes. Within several days, degeneration of the red blood cells
to hemosiderin produces the characteristic hemosiderin-laden
macrophages associated with this process (Fig.
16.5). This
sequence of events is a general response to the presence of blood
in CSF and is irrespective of the etiology of the bleeding. For
example, blood introduced into CSF during lumbar puncture or
a traumatic tap elicits an identical reaction.
Key features of hemorrhage
• Red blood cells;
• Macrophages engulfing erythrocytes; and
• Hemosiderin-laden macrophages.
Cerebral infarction frequently produces a secondary inflam-
matory response in CSF. Whether cells appear in CSF is a func-
tion of the size of the infarct and its proximity to the surface of
the brain or spinal cord. The type of cellular reaction is related
to the stage and character of the infarct and in general reflects
the histologic appearance of the intraparenchymal lesion. In the
early stages, polymorphonuclear leukocytes, sometimes with a
hemorrhagic component, are seen. This picture rapidly shifts to
a predominantly macrophage response in which fragments of
degenerated myelin fill the cytoplasm of the cells. At this stage,
the fluid may be extremely hypercellular and can be confused
Fig. 16.5 Hemosiderin-laden macrophage in cerebrospinal fluid from a
patient with subarachnoid hemorrhage (Papanicolaou x HP).
with a neoplasm if the observer does not consider the possibility
of a destructive lesion.
Key features of cerebral infarction
• Polymorphonuclear leukocytes with hemorrhage
(early stage); and
• Macrophages with fragments of degenerated myelin
(later stage).
Trauma
Cellular infiltrates in the CSF of victims of CNS trauma are
indistinguishable from the cells seen in subarachnoid hemor-
rhage and destructive lesions of other etiologies. Thus, red blood
cells and macrophages containing hemosiderin or myelin debris
are the most common manifestations of trauma in CSF. Patients
with sinus and basilar skull fractures with tears in the menin-
ges are at risk for developing leakage of sinus contents into the
SAS. The CSF in this setting contains a marked acute inflamma-
tory reaction. Bacteria and other elements, such as fragments of
Candida
and ciliated respiratory epithelial cells from the sinus
lining, may also be seen.26
Key features of trauma
• Red blood cells; and
• Macrophages containing hemosiderin or myelin
debris.
Reactions to Intraventricular Shunts
Highly cellular samples of CSF containing reactive ependy-
mal cells, epithelioid cells, and multinucleated giant cells
are
occasionally
obtained through
intraventricular shunts
(Fig. 16.6).27 They may be associated with a history of a mal-
functioning shunt and in some cases have been correlated with
a histologically documented granulomatous process occluding
the shunt tip. Recognition that this type of reaction may be asso-
ciated with a malfunctioning shunt is important in aiding the
surgeon in deciding whether a shunt revision is necessary. In
addition, awareness of this presentation avoids confusing this
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