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Head and Neck Biochemistry > CSF > Flashcards

CSF Flashcards

1
Q

What is the total volume of CSF?

A

150ml

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2
Q

What is the daily production of CSF?

A

550ml

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3
Q

What is the turnover for CSF?

A

> 3.5 times

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4
Q

What is CSF and where is it made?

A

plasma controlled ultra-filtrate produced by the choroid plexus of the 4th & lateral ventricles & around blood vessels
> It is in direct communication & it is actually same as brain ECF

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5
Q

What is the function of CSF?

A
  1. provide mechanical support
  2. cushioning for the brain & spinal cord
  3. transport biological waste
  4. optimises environment for neuronal function
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6
Q

What forms the blood brain barrier?

A

Tight junctions between the epithelial cells of the capillaries & those of the colloid plexus

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7
Q

What is the function of the blood brain barrier?

A
  • prevent free movement of large & hydrophilic molecules between plasma & CSF & facilitating movement of essential molecules like glucose
    > Fat soluble molecules cross the barriers freely
    > HCO3 and H uses carbonic anhydrase in the choroid plexus to allow their passage & regeneration as carbon dioxide and water
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8
Q

What factors affect blood brain barrier permeability?

A
  1. Inflammation
  2. Immaturity
  3. Toxins
  4. Neovascularity (trauma, tumor)
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9
Q

Describe the course of cerebral spinal fluid?

A

circulates from brain tissue & choroid plexus into the ventricles, subarachnoid space, via the lateral and medial foramina of lushka & Magendie, and arachnoid villi

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10
Q

What is a lumbar puncture?

A

when a needle is inserted into the spinal canal to collect CSF for diagnostic testing
> stringently aseptic
> tube 1- glucose
> tube 2 - chloride, protein, IgG
Note: CSF in ventricles has lower protein than in the lumbar region

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11
Q

What are the contraindications for a lumbar puncture?

A
  1. Raised intracranial pressure
  2. Infection at site
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12
Q

CSF analysis aids in the diagnosis of?

A

Subarachnoid hemorrhage
Meningitis
Demyelinating disease
Malignancy
Head injury

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13
Q

What clinical findings distinguish bacterial from viral menigitis?

A

lactate
Lactate > 3.9mmol/l = bacterial
Lactate < 2.8mmol/l = viral

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14
Q

Explain the presence of LDH in CSF?

A

LDH is normally present in CSF : <40u/L in adults or <70u/L
- differentiates traumatic tap from hemorrhage because fresh traumatic taps do not elevate LDH

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15
Q

What is a traumatic tap and how do you distinguish it?

A

occurs if the needle inadvertently has entered an epidural vein during insertion during LP
> a yellowish tinge to the CSF fluid = xanthrochromia

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16
Q

Describe glucose in CSF?

A
  • Enters CSF by passive diffusion or active transport
  • roughly two-thirds of plasma glucose
  • Normal fasting CSF glucose is 2.2-3.9 mmol/L
17
Q

Describe chloride in CSF?

A
  • Important for TB meningitis diagnosis
  • normal range is 116mmol/l - 130mmol/l
  • Cl < 100mmol/l is diagnostic
18
Q

Describe protein in CSF?

A
  • Spinal fluid is an ultrafiltrate of plasma lacking HMW proteins
    e.g Alpha-2 macroglobulin, IgM
  • protein concentration of CSF is less than 1% of plasma
    > slightly higher in babies due to peremeable BBB
19
Q

Describe a subarachnoid hemorrhage in CSF?

A

red cells are a diagnostic feature
- RBCs that have been in the CSF for >4 hrs cause yellow staining of the CSF called Xanthochromia
> indicates previous bleeding
- 2-4 hrs : RBCs lyse & release oxyhemoglobin ( pink to orange color change)
- At 12hrs : Hb metabolized to bilirubin, levels peak at 36 hrs & persist to weeks

20
Q

Name other causes of xanthochromia?

A
  1. High CSF protein (>1.5g/L)
  2. elevated serum bilirubin
  3. Meningeal melanoma
  4. Hypercaroteinemia
  5. Rifampicin therapy
  6. Previous traumatic tap
21
Q

Explain the diagnostic evidence of demyelinating disorders in CSF?

A
  1. elevated levels of basic myelin protein (BMP) from breakdown of myelin sheath with high CSF protein levels from immunoglobulins
    = DDs release BMP into the CSF
    > Can be used to diagnose MS even in the absence of oligoclonal bands
    Note: MBP is usually < 1.5ng/ml
  2. The IgG synthesis rate or the IgG/Albumin index is also used for diagnosis
    - measure the levels of both IgG and albumin
    Note : MS is associated with increased IgG synthesis rate
  3. Oligoclonal bands seen also in lymphoma, chronic lymphocytic leukaemia, malignancies, chronic active hepatitis, rheumatoid arthritis
22
Q

What is the protein index?

A
  1. assesses amount of intrathecal protein synthesis due to inflammation or other pathology
  2. assesses permeability of BBB in relation to increased thecal protein synthesis
    > Albumin is the reference protein
    > Normal CSF albumin/Serum albumin ratio is less than 9
    > CSF IgG index is 0.3 to 0.8
    > Greater indicates increased intrathecal synthesis
    Note: IgG index = IgGcsf/IgGserum divided by ALBcsf/ALBserum
23
Q

Describe possible errors in metabolism that could affect CSF?

A
  1. Glycine encephalopathy(Non ketotic hyperglycinemia) - Increased glycine synthesis
  2. Respiratory chain disorders - Increased CSF lactate and pyruvate
  3. 3-phosphoglycerate dehydrogenase deficiency - low CSF serine
  4. Organic acidemias - increased lactate

Head and Neck Biochemistry (1 decks)

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