Cerebrospinal Fluid

The median aperture (“Foramen of Magendie”) drains CSF from the fourth ventricle into the cisterna magna. Cisterna magna occupies the interval between inferior surface of cerebellum and posterior aspect of medulla oblongata.

The two lateral apertures (foramina of Luschka), one on the left and one on the right, are the primary routes for drainage of cerebrospinal fluid from the fourth ventricle into the cerebellopontine angle cistern. The foramen on axial images is posterior to the pons and anterior to the caudal cerebellum.

The two interventricular foramens, or foramens of Monro, are apertures between the column of the fornix and the anterior end of the thalamus. The two lateral ventricles communicate with the third ventricle through these foramens and drainage of CSF occurs.

Lumbar CSF pressure is normally 70–180 mm H2O. Up to pressures well above this range, the rate of CSF formation is independent of intraventricular pressure. However, absorption is proportional to the pressure. At a pressure of 112 mm H2O, which is the average normal CSF pressure, filtration and absorption are equal. Below a pressure of approximately 68 mm H2O, absorption stops. 

• Large amounts of fluid accumulate when the capacity for CSF reabsorption is decreased (external hydrocephalus, communicating hydrocephalus). 
• Fluid also accumulates proximal to the block and distends the ventricles when the foramens of Luschka and Magendie are blocked or there is obstruction within the ventricular system (internal hydrocephalus, noncommunicating hydrocephalus).

Rate of CSF formation normally remains constant and is independent of CSF pressure. CSF absorption by arachnoid villi is proportionate to CSF pressure.
  Ref: Barrett K.E., Barman S.M., Boitano S., Brooks H.L. (2012). Chapter 33. Circulation through Special Regions. In K.E. Barrett, S.M. Barman, S. Boitano, H.L. Brooks (Eds), Ganong’s Review of Medical Physiology, 24e.

A i.e. I, II, VII, VIII 

A, C, & B i.e. Specific gravity is 1.003 – 1.0008, Total volume of CSF is 150 ml , & Daily production is 550 ml/day

A i.e. 70-180 mm CSF

C i.e. Epidural space

A i.e. 0.3 – 0.35 ml/minute

A i.e. Choroid plexus

C i.e 150 ml

B i.e. 6 – 12 mmHg

B i.e. 0.6 to 0.8

B i.e. Rate of CSF absorption

C i.e. Formed by arachnoid villi

C i.e. 7.33

CSF sugar is 2/3 of plasma sugarQ. So CSF/plasma glucose ratio is -. 0.6667. CSF pH is 7.33Q (less than plasma pH 7.4) and its pressure is maintained by its absorption at arachnoid villQ.

Hyperthyroidism cause decreased whereas, hypothyroidism/myxoedema is associated with increased CSF protein.

Regulation of CSF pressure by arachnid villi

– Rate of CSF formation is nearly constant, so it is seldom a factor in pressure control.

– Whereas, arachnoid villi function like valves that allow CSF to flow readily into blood in venous sinuses while not allowing blood to flow backward in opposite direction

– CSF flow begins when its pressure is 1.5 mmHg higher than the pressure of blood in venous sinuses.

The valve opens more widely, when this pressure difference is higher, which in normal conditions never allows CSF pressure to rise more than few mm Hg higher than cerebral venous sinus pressure.

– Absorption is proportional to pressure. At a pressure of 112 mm H₂0, which is average normal CSF pressure, filteration & absorption are equal. Below a pressure of 68 mm H₂0, absorption stops.

B i.e. Rate of CSF absorption

Answer is B (2/3 of plasma glucose):

Answer is None (May be associated with all of the above)

‘Diagnostic Nuclear Medicine’ by Sandler, Coleman & Patton (Lippincott-Williams) 4^th (2003)/ 838;

Arachnoid and piamater

CSF

• It is a clear colorless bodily fluid produced in the choroid plexus of the brain
• It occupies the subarachnoid space (the space between the arachnoid mater and the pia mater) and the ventricular system around and inside the brain and spinal cord.
• It constitutes the content of the ventricles, cisterns, and sulci of the brain, as well as the central canal of the spinal cord.

Ans. 4°C

Ans. is ‘b’ i.e., Beta-2 transferrin

Ans. is ‘a’ i.e., 100-150 ml

The major source of CSF is the choroidal plexus of all 4 ventricles, mainly in two lateral ventricles.

Other sources of CSF are ependymal cells of the ventricles and the brain itself, via perivascular spaces.

The total volume of CSF in an adult is about 125-150 ml.

The rate of formation of CSF is about 500-550 ml/day. Thus the CSF is replaced 3-4 times every day.