questions 4

Cerebrospinal Fluid (CSF)

Topic updated on 03/27/17 11:10am

  • A 22-year-old male presents with altered mental status, fever, and headache. The patient is able to sluggishly answer questions. Passive flexion of the neck leads to spontaneous contraction of the hips. Pain is elicited when attempting to fully extend the knee while his hips are at a 90 degree angle. A skin finding is shown to the right.
  • Function
    • serves as a mechanical cushion for the CNS
      • protects the brain against concussive injury
    • removal of metabolites
      • CSF flow is one-way
    • hormone and hormone-releasing factor transportation
    • homeostasis
      • CSF pH affects ventilation and cerebral blood flow
  • Production
    • produced by the choroid plexus epithelial cells within ventricles
      • found in lateral, third, and fourth ventricles
    • reabsorbed into circulation by arachnoid granulations
      • enters dural venous sinuses
      • entire volume of CSF is recycled 2-3 times per 24 hours
  • Ventricular system communications
    • lateral ventricle → 3rd ventricle
      • via the interventricular foramen of Monro
    • 3rd ventricle → 4th ventricle
      • via the cerebral aqueduct (Aqueduct of Sylvius)
    • 4th ventricle → subarachnoid space via
      • foramina of Luschka (lateral)
      • foramina of Magendie (medial)
  • Compared to the serum:
    • ↓↓ protein
    • ↓ glucose
    • ↓ pH
    • K+, Ca2+, Mg2+
    • same Na+
Cerebrospinal Fluid Analysis
Test Normal Bacterial Viral Fungal/TB
Opening pressure
  • ≤ 20 cm H
  • normal or slightly ↑
  • Clear
  • Cloudy
  • Clear
  • Cloudy
Cell count
  • 0-5 cells/µL
  • ↑ (PMN)
  • ↑ (Lymphocytes)
  • ↑ (Lymphocytes)
  • < 45 mg/dL
  • Slighty ↑
CSF:Serum glucose
  • > 0.6
  • Normal
  • Hydrocephalus
    • dilated ventricles via several types
      • communicating
        • ↓ reabsorbtion of CSF
          • scarring of arachnoid granulations following meningitis
        • ↑ production of CSF (rare)
          • choroid plexus papilloma
      • noncommunicating/obstructive
        • obstructed flow of CSF 
          • stenosis at narrow point along ventricular system
            • e.g., at the cerebral aqueduct, foramen of Monro
          • Chiari II malformation
          • Dandy-Walker syndrome
      • normal pressure (NPH)
        • ↓ reabsorbtion of CSF with chronic dilation of ventricles and normal CSF pressure 
        • distortion of corona radiata produces triad of 
          • urinary incontinence
          • dementia
          • apraxic gait
          • "wet, wacky, wobbly"
        • imaging
          • enlarged ventricles on CT/MRI
        • treatment 
          • peritoneal shunt
      • ex vacuo
        • ↑ in CSF due to ↓ in brain size 
          • e.g., Alzheimer disease
        • ventricles appear large but CSF pressure is normal


Qbank (2 Questions)

(M1.NE.27) An 88-year-old man is brought to his primary care physician by his son. The patient has been in excellent health his entire life, but in the last few years appears to have grown steadily confused. He frequently calls his son about things that they have already discussed, forgets where he has placed his keys, and recently the patient's son noticed several unpaid bills on the patient's desk at home. The patient is upset at being "dragged" into see the physician and claims that everything is fine--he is just "getting older". A complete neurologic exam is normal except for significant difficulty with recall tasks. In the course of the medical work-up, you obtain a CT scan and see the findings in figure A. What is the most likely cause of this patient's CT findings? Topic Review Topic
FIGURES: A          

1. Blockage of the cerebral aqueduct
2. Cortical atrophy
3. Increased CSF production
4. Congenital malformation
5. Infection

(M1.NE.4671) A 75-year-old man is brought to a neurologist by his daughter. She says that her father has had several falls over the last six months. He has also begun having periodic urinary incontinence. She originally attributed these changes to 'old-age.' However, he has now started to become increasingly forgetful. She is concerned that he may have Alzheimer's disease and decided to bring him to the office for evaluation. Physical exam is notable for abnormal gait. Urinalysis is negative for nitrites and leukocyte esterase. CSF analysis shows: Opening pressure: 100 mm H20; Total protein: 20 mg/100mL; WBCs < 5/mm^3. MRI results are shown in Figure A. Which of the following is the most likely mechanism of his disease process? Topic Review Topic
FIGURES: A          

1. Bacterial infection
2. Viral infection
3. Beta-amyloid plaque deposition
4. Scarring of arachnoid granulations
5. Ventricular stenosis

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