Cerebrospinal fluid , circulation, lumbar puncture, disease, pathophysiology from Nelson Textbook of Pediatrics

1. CEREBROSPINAL FLUID
CIRCULATION, LUMBAR PUNCTURE,ANALYSIS
PRESENTER
Dr. Sunil D Mulgund
MODERATOR
Dr. Rohit

2. TOPICS:
• FUNCTION
• SECRETION
• CIRCULATION
• CSF PRESSURE
• LUMBAR PUNCTURE- INDICATION/CONTRAINDICATION
• CSF ANALYSIS

3. 3D representation of CSF distribution in brain

4. Cerebrospinal fluid (CSF) is a clear, plasma-like fluid (an ultrafiltrate of plasma) that
encloses the central nervous system (CNS). It occupies the central spinal canal, the
ventricular system, and the subarachnoid space.
FUNCTIONS:
CSF performs vital functions including: Support; Shock absorber; Homeostasis;
Nutrition; Immune function.
1.Support - The CSF supports the weight of the brain and suspends it in neutral
buoyancy Hence, the entire brain density is cushioned, protecting it from
crushing into the bony cranium.
2.Shock absorber - It protects the brain from damage during head trauma.
Otherwise, even minor head bopping will result in severe brain injury.

5. 3. Homeostasis - The biochemical constituents and volume of the CSF play vital
cerebral homeostatic roles:
 Maintains stable intrinsic CNS temperature.
 Biochemical constituents and electrolytes maintain the osmotic pressure
responsible for normal CSF pressure which is essential to maintaining normal
cerebral perfusion.
 Biochemical waste products diffuse into the CSF and are removed as CSF is
resorbed through arachnoid granulations into venous circulation, a small
percentage of CSF also drains into lymphatic circulation.
• 4. Nutrition - The CSF contains glucose, proteins, lipids, and electrolytes,
providing essential CNS nutrition.
• 5. Immune function - The CSF contains immunoglobulins and mononuclear
cells.

6. SECRETIONS:
CSF is predominantly secreted by the choroid plexus with other sources
(ependymal lining of ventricles, cells of piamater).
Choroid Plexus:- a network of blood vessels in each ventricle of the brain,
producing the cerebrospinal fluid.
Ependymal cells:-, type of neuronal support cell (neuroglia) that forms the
epithelial lining of the ventricles (cavities) in the brain
and the central canal of the spinal cord. Ependymal cells
also give rise to the epithelial layer that surrounds the
choroid plexus.

7. Ependymal cells:
• In the ventricles ependymal cells possess tiny hairlike structures called cilia on their
surfaces facing the open space of the cavities they line
• The layer of ependymal-derived cells surrounding the blood vessels of the choroid
plexus functions mainly to produce CSF. This is accomplished through the selective
uptake of water and certain other molecules from the blood into the cells. The
substances are then transported across the cells and are secreted into the lateral
ventricles in the form of CSF.
• The ependymal cells in the ventricles are loosely joined together by special
intercellular adhesion sites called desmosomes, which enable the cells to form a
nearly continuous epithelial sheet over the surface of the ventricles and spinal canal.
Because the junctions between the ependymal cells are loose, CSF is able to diffuse
from the ventricles into the central nervous system. The cells surrounding the
choroid plexus are connected by tight junctions, which prevent the leakage of
substances and fluids from the blood vessels into the CSF. This protects against the
unregulated entry of potentially harmful substances into the ventricles and
ultimately the central nervous system.

9. In H&E staining ependymal cells resemble cuboidal and columnar epithelia. They
have a small oval nucleus with dense chromatin.

10. • The epithelial cells of the choroid plexuses secrete cerebrospinal fluid (CSF), by a
process which involves the transport of Na+, Cl- and HCO3
- from the blood to the
ventricles of the brain.
• The unidirectional transport of ions is achieved due to the polarity of the epithelium,
i.e. the ion transport proteins in the blood-facing (basolateral) membrane are different
to those in the ventricular (apical) membrane. The movement of ions creates an
osmotic gradient which drives the secretion of H2 O.
• The CSF is constantly produced, and in humans the total volume is replaced about four
times each day. Thus, the total amount of CSF produced in 24 h is about 600 ml .

11. CSF
CIRCULATION

13. Cerebrospinal Fluid Pressure
• The normal pressure in the cerebrospinal fluid system when one is lying in a horizontal
position averages 130 mm of water (10 mm Hg), although this may be as low as 65 mm
of water or as high as 195 mm of water even in the normal healthy person.
• The normal rate of cerebrospinal fluid formation remains nearly constant, so changes in
fluid
• Arachnoidal villi function like “valves” that allow cerebro-spinal fluid and its contents to
flow readily into the blood of the venous sinuses while not allowing blood to flow back-
ward in the opposite direction. Normally, this valve action of the villi allows cerebrospinal
fluid to begin to flow into the blood when cerebrospinal fluid pressure is about 1.5 mm
Hg greater than the pressure of the blood in the venous sinuses. Then, if the
cerebrospinal fluid pressure rises still higher, the valves open more widely. Under normal
conditions, the cerebrospinal fluid pressure almost never rises more than a few
millimeters of mercury higher than the pressure in the cerbral venous sinuses.
Conversely, in disease states, the villi sometimes become blocked by large particulate
matter, by fibrosis, or by excesses of blood cells that have leaked into the cerebrospinal
fluid in brain diseases. Such blockage can cause high cerebrospinal fluid pressure, as
follows.

14. • A large brain tumor elevates the cerebrospinal fluid pressure by
decreasing reabsorption of the cerebrospinal fluid back into the
blood.As a result, the cerebrospinal fluid pressure can rise to as much
as 500 mm of water (37 mm Hg) or about four times normal.
• The cerebrospinal fluid pressure also rises considerably when
hemorrhage or infection occurs in the cranial vault. In both these
conditions, large numbers of red and/or white blood cells suddenly
appear in the cerebrospinal fluid and can cause serious blockage of
the small absorption channels through the arachnoidal villi.
• This also sometimes elevates the cerebrospinal fluid pressure to 400
to 600 mm of water (about four times normal). Some babies are born
with high cerebrospinal fluid pressure. This is often caused by
abnormally high resistance to fluid reabsorption through the
arachnoidal villi, resulting either from too few arachnoidal villi or from
villi with abnormal absorptive properties.(Hydrocephalus)

15. • High Cerebrospinal Fluid Pressure Causes Edema of the Optic Disc—Papilledema.
Anatomically, the dura of the brain extends as a sheath around the optic nerve
and then connects with the sclera of the eye. When the pressure rises in the
cerebrospinal fluid system, it also rises inside the optic nerve sheath. The retinal
artery and vein pierce this sheath a few millimeters behind the eye and then pass
along with the optic nerve fibers into the eye itself. Therefore, high cerebrospinal
fluid pressure pushes fluid first into the optic nerve sheath and then along the
spaces between the optic nerve fibers to the interior of the eyeball;

16. Hydrocephalus
• Hydrocephalus means excess water in the cranial vault. This condition is frequently
divided into communicating hydrocephalus and noncommunicating hydrocephalus. In
communicating hydrocephalus fluid flows readily from the ventricular system into the
subarachnoid space, whereas in noncommunicating hydrocephalus fluid flow out of one
or more of the ventricles is blocked.
• Usually the noncommunicating type of hydrocephalus is caused by a block in the
aqueduct of Sylvius, resulting from atresia (closure) before birth
• As fluid is formed by the choroid plexuses in the two lateral and the third ventricles, the
volumes of these three ventricles increase greatly. This flattens the brain into a thin shell
against the skull. In neonates, the increased pressure also causes the whole head to swell
because the skull bones have not yet fused.
• The communicating type of hydrocephalus is usually caused by blockage of fluid flow in
the subarachnoid spaces around the basal regions of the brain or by blockage of the
arachnoidal villi where the fluid is normally absorbed into the venous sinuses. Fluid
therefore collects both on the outside of the brain and to a lesser extent inside the
ventricles. This will also cause the head to swell tremendously if it occurs in infancy when
the skull is still pliable and can be stretched, and it can damage the brain at any age.

17. Lumbar Puncture:
The procedure of taking fluid from the spine in the lower back through a hollow
needle, usually done for diagnostic purposes.
• A lumbar puncture (LP) should only be performed after a thorough neurological
examination and once all contraindications have been considered.
• Careful preparation, adequate analgesia and an experienced assistant are critical
• LP is performed at or below the L4 level
• The conus medullaris finishes near L3 at birth, but at L1-2 by adulthood
• The decision to perform LP should generally be discussed with a senior clinician
• It is preferable to obtain a CSF specimen prior to antibiotic administration; however,
antibiotics must not be unduly delayed in a child with signs of meningitis or sepsis
• In a child with fever and purpura, in whom meningococcal infection is suspected,
LP may not change the management and may cause deterioration
• In term infants, the seated position has been shown to be the best tolerated and to
also have the best chance of obtaining CSF.

18. Anatomical landmarks
• The spinal cord typically terminates at the level of L1 vertebral body in an adult and
slightly lower in a child. Below that level there are only spinal nerve roots traveling
within the lumbar cistern to reach their respective intervertebral foramina from where
they exit the dural sack. Because of their resemblance of a horse’s tail, this nerve bundle
is referred to as cauda equina. The distal tip of the spinal cord gives rise to filum
terminale, a fibrous structure that travels among the spinal nerve roots to finally attach
to the dorsum of the coccyx, anchoring the spinal cord and the dural sac distally. As a
general anatomical rule, the line drawn between the posterior iliac crests often
corresponds closely to the level of L3—L4. The interspace is selected after palpation of
the spinous processes at each lumbar level.
• The spinal cord in neonates extends further down the spinal canal than in older children.
Lumbar punctures should be performed at or below the L4 level. The L4 landmark is as in
older children - the line of the top of the iliac crests.

21. • Position the infant in the lateral position with trunk well flexed by the assistant holding the shoulders and legs
forward but with the neck extended and legs at a 90 degree angle to the hips - at the edge of the cot. Ensure
infant's back is parallel to the cot, with hips and shoulders vertical to the cot (not rotated).
• Some degree of flexion of the spine is helpful since it opens up the interspinous spaces and also stretches the skin
over the processes, allowing better definition of landmarks. It is not necessary to flex the neck with compromise of
the airway and increase in cerebral venous pressure. Infants may not tolerate the procedure well. This is usually
because of excessive flexion of the infant.
• Alternatively, term infants may be placed in a seated position on the edge of the table, with trunk flexed forwards,
stabilised from the front by the assistant. The infant's shoulders and hips are held in order to maintain vertical
alignment of the hips and shoulders during the procedure. This has been shown to be the best tolerated and to
also have the best chance of obtaining CSF.
• Regardless of theposition chosen, it is important to make sure that the patient’s shoulders and hips are straight to
prevent rotating the spine.

24. • A topical anesthetic (e.g. EMLA cream) can be applied 30 to 60 minutes before performing the puncture to
minimize pain on penetration.
• The subarachnoid space must be entered below the level of spinal cord termination. Any of the interspaces
between L3-L4 and L5-S1 can be used for the lumbar puncture in kids. Whether the lateral decubitus or sitting
position is chosen, the spine should be flexed maximally to increase spacing between spinous
processes. Extensive neck flexion, however, should be avoided to minimize a chance of respiratory
compromise. Make sure the hips and shoulders are aligned and that the back is perpendicular to the bed
surface.
• The procedure should be performed using sterile technique. The patient’s back should be carefully prepared
and draped using provided disinfecting solution and drapes. Orient yourself anatomically and find the L4
spinous process at the level of iliac crests (as described above). Palpate a suitable interspace distal to this level.
Infiltrate 2% Lidocaine subcutaneously (without epinephrine to prevent cord infarction should it be introduced
into the cord by accident) with a fine needle. A field block can be applied injecting into and on either side of the
interspinous ligaments. This anesthetizes not just the skin, but also the interspinous ligaments, muscles, and the
periosteum.
• Once the patient is properly positioned, the area sterilized and draped and adequate anesthesia of the area
achieved, the spinal needle can be introduced. Identify the two spinal processes in between which the needle
will be introduced, penetrate the skin and slowly advance the tip of the needle at about 10 degrees cephalad
(i.e. toward the patient’s umbilicus). Following penetration of skin, resistance will be encountered as the tip of
the needle passes through interspinous ligaments. Remember to frequently stop advancing the needle and
check for the presence of CSF by removing the stylet. You may feel a characteristic “pop” indicating entrance
into the subarachnoid space. If the needle is no longer progressing and resistance encountered, it is likely that
you have hit bone. Withdraw the needle leaving the tip in, recheck the landmarks and slowly progress the
needle again.
• You should attempt to measure the opening pressure using the manometer by attaching it via a stopcock to the
spinal needle. Normal opening pressure is 7 to 15 cm H2O. Always make sure to hold the spinal needle
securely between your thumb and index finger and brace your hand against the patient’s back, especially when
putting in or removing anything from it.

25. LP KIT:
• Spinal needle with a stylet (20 gauge or 22 gauge needle), 3-4 CSF
collection vials, sterile drape, manometer with three-way valve, local
anesthetic, syringes with needles (typically 18-gauge to draw up
anesthetic and 25-gauge to inject into the skin), disinfecting solution
(0.5% chlorhexidine/70% alcohol), sterile gloves, mask with face
shield and surgical cap.

26. CSF PRESSURE:
Normal opening pressures are 90-120 mm H2O in newborns,
60-180 mm H2O in young children
12-120 mm H2O in older children and adults.
The 90th percentile in children has been reported to be 250 mm of H2O.
The most common cause of an elevated opening pressure is an agitated patient. Sedation and high body mass
index can also increase the opening pressure.

27. INDICATIONS:
Meningitis, encephalitis, and idiopathic intracranial hypertension (previously referred to as pseudotumor
cerebri), and it is often helpful in assessing subarachnoid hemorrhage; demyelinating,(multiple sclerosis,
Guillian barre syndrome) degenerative, and collagen vascular diseases, Tuberculoma, Neurocystecercosis.
CONTRAINDICATIONS:
Contraindications to performing a lumbar puncture include supected mass lesion of the brain, especially in the
posterior fossa or above the tentorium and causing shift of the midline; suspected mass lesion of the spinal
cord; symptoms and signs of impending cerebral herniation in a child with probable meningitis; critical illness
(on rareoccasions); skin infection at the site of the lumbar puncture; and thrombocytopenia with a platelet
count <20k ,If disc edema or focal findings suggest a mass lesion, a head CT should be obtained before
proceeding with lumbar puncture to prevent uncal or cerebellar herniation as the CSF is removed. In the
absence of these findings, routine head imaging is not warranted. The physician should also be alert to clinical
signs of impending herniation, including alterations in the respiratory pattern (e.g., hyperventilation; Cheyne-
Stokes respirations, ataxic respirations, respiratory arrest), abnormalities of pupil size and reactivity, loss of
brainstem reflexes, and decorticate or decerebrate posturing. If any of these signs are present or the child is so
ill that the lumbar puncture might induce cardiorespiratory arrest, blood cultures should be drawn and
supportive care, including antibiotics, should be initiated. Once the patient has stabilized, it may be possible to
perform a lumbar puncture safely.

29. Complications
• Postdural puncture headache (relatively common)
• Local back pain
• Infection
• Spinal hematoma
• Subarachnoid epidermal cyst
• Apnea
• Transient limp or pararesthesias
• Transient ocular palsy
• Cerebral herniation

30. CSF

31. CSF -WBC’S
• Normal CSF contains up to 5/mm3 white blood cells, and a newborn can have as many as 15/mm3.
Polymorphonuclear cells are always abnormal in a child, but 1-2/mm3 may be present in a normal neonate.
An elevated polymorphonuclear count suggests bacterial meningitis or the early phase of aseptic meningitis
(see Chapter 603). CSF lympho cytosis can be seen in aseptic, tuberculous, or fungal meningitis; demy
elinating diseases; brain or spinal cord tumor; immunologic disorders, including collagen vascular diseases;
and chemical irritation (following myelogram, intrathecal methotrexate).

32. CSF –RBC’S
• Normal CSF contains no red blood cells; thus, their presence indicates a traumatic
tap or a subarachnoid hemorrhage. Progressive clearing of the blood between
the first and last samples indicates a traumatic tap. Bloody CSF should be
centrifuged immediately. A clear supernatant is consistent with a bloody tap,
whereas xanthochromia (yellow color that results from the degradation of
hemoglobin) suggests a subarachnoid hemorrhage. Xanthochromia may be
absent in bleeds <12 hr old, particularly when laboratories rely on visual
inspection rather than spectroscopy. Xanthochromia can also occur in the setting
of hyperbilirubinemia, carotenemia, and markedly elevated CSF protein.

33. CSF - PROTIEN
The normal CSF protein is 10-40 mg/dL in a child and as high as 120 mg/dL in a neonate.
The CSF protein falls to the normal childhood range by 3 mo of age. The CSF protein may
be elevated in many processes, including infectious, immunologic, vascular, and
degenerative diseases, blockage of CSF flow, as well as tumors of the brain (primary CNS
tumors, systemic tumors metastatic to the CNS, infiltrative acute lymphoblastic leukemia)
and spinal cord. With a traumatic tap, the CSF protein is increased by approximately 1
mg/dL for every 1,000 red blood cells/mm3. Elevation of CSF immunoglobulin G, which
normally represents approximately 10% of the total protein, is observed in subacute
sclerosing panencephalitis, in postinfectious encephalomyelitis, and in some cases of
multiple sclerosis. If the diagnosis of multiple sclerosis is suspected, the CSF should be
tested for the presence of oligoclonal bands.

34. CSF- GLUCOSE
The CSF glucose content is approximately 60% of the blood glucose in a healthy child. To prevent a
spuriously elevated blood:CSF glucose ratio in a case of suspected meningitis, it is advisable to collect
the blood glucose before the lumbar puncture when the child is relatively calm. Hypoglycorrhachia
is found in association with diffuse menin- geal disease, particularly bacterial and tubercular
meningitis. Wide- spread neoplastic involvement of the meninges, subarachnoid hemorrhage,
disorders involving the glucose transporter protein type 1, fungal meningitis, and, occasionally,
aseptic meningitis can produce low CSF glucose as well. A Gram stain of the CSF is essential if there is
a suspicion for bacte- rial meningitis; an acid-fast stain and India ink preparation can be used to
assess for tuberculous and fungal meningitis, respectively. CSF is then plated on different culture
media depending on the suspectedpathogen. When indicated by the clinical presentation, it can also
be helpful to assess for the presence of specific antigens (e.g., latex agglutination for Neisseria
meningitidis, Haemophilus influenzae type b, or Streptococcus pneumoniae) or to obtain antibody or
polymerase chain reaction studies (e.g., herpes simplex virus-1 and -2, West Nile virus,
enteroviruses). In noninfectious cases, levels of CSF metabolites, such as lactate, amino acids, and
enolase can provide clues to the underlying metabolic disease.

35. CSF - CULTURE
Cerebrospinal fluid (CSF) should be transported quickly to the laboratory and then
cytocentrifuged to concentrate organisms for microscopic examination. CSF is routinely
cultured on blood agar and chocolate agar, which support the growth of common pathogens
causing meningitis. If tuberculosis is suspected, cultures for mycobacteria should be
specifically requested. Culture of larger volumes of CSF (>5 mL) significantly improves yield
of mycobacteria. Historically, rapid antigen detection tests for bacterial pathogens such as
Haemophilus influenzae type b and Streptococcus pneumoniae were used to attempt to
detect organisms in CSF without the need for culture. These techniques have now been
proven to lack sensitivity and, in some cases, specificity. It has been demonstrated that a
cytospin Gram stain is as sensitive as bacterial antigen tests for detection of microorganisms
in CSF. In contrast, the cryptococcal antigen test can be useful when cryptococcal meningitis
is suspected. Historically, India Ink preparations were used to detect Cryptococcus in CSF, but
this method is insensitive compared to the antigen detection assay. In the postvaccine era,
the epidemiology of infectious meningitis is rapidly changing, and acute bacterial meningitis
is now a relatively infrequent event in North America. Many CSF infections are associated
with shunts or other hardware, and Propionibacterium and coagulase-negative staphylococci
are the organisms most frequently isolated from shunt infections. The laboratory should
include media to facilitate the growth of Propionibacterium in CSF specimens received from
neurosurgery patients.

36. CSF - CYTOLOGY
• Cerebrospinal fluid (CSF) cytology, i.e., the cytologic evaluation of its cellular composition, forms an
integral part of the neurologist's armamentarium. Total and differential cell counts provide important
first information across a spectrum of pathologic conditions involving the central nervous system and
its coverings. CSF samples require immediate processing, ideally within 1 hour from collection. Upon
centrifugation cytology is commonly assessed on May-Grunwald-Giemsa stains. Several additional
stains are available for the identification of infectious agents such as bacteria or fungi, or the further
specification of neoplastic cells by immunocytochemistry. The evaluation warrants familiarity with
cytologic characteristics of cells across normal and diseased states. In normal CSF, lymphocytes and
monocytes are encountered. A predominance of neutrophil granulocytes suggests bacterial meningitis
and prompts search for intracellular bacteria. In contrast, in viral and chronic infections lymphocytes
and monocytes prevail. Upon activation lymphocytes typically enlarge and eventually differentiate into
plasma cells. Similarly, monocytes differentiate into macrophages that clear cellular debris.
Macrophages that contain fragments of erythrocytes or hemoglobin degradation products are
referred to as erythro- or siderophages, both of which indicate prior subarachnoid hemorrhage.
Likewise, the detection of tumor cells is specific for neoplastic meningitis, although false-negative CSF
cytologies are frequent. In summary, detailed morphologic workup of CSF samples provides valuable
diagnostic information and is mandated in all cases with elevated cell count, computed tomography-
negative suspected subarachnoid hemorrhage, and neoplastic meningitis. In all cases it needs to be
interpreted in the clinical context and complements other clinical and laboratory findings.

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