Dr . Nirajan Neupane

Development of CNS, meninges & CSF

1. Dura mater ( Dura: tough)

-Tough outer covering of brain & spinal cord

-Mesodermal in origin

- cranial dura : divided into Periosteal layer & meningial layer : Dural venous sinus in between

2. Arachnoid mater ( Arachnoid : spider-web like)

-Avascular , no nerves

3. Pia mater ( pia : soft)

-Firmly attached with the surface of brain and spinal cord and extends as filum terminals below conus medullaris upto coccyx

CSF

-Clear ,watery fluid isotonic with serum , pH 7.33

-Comparing with plasma , equal Na

Higher Cl , Mg

Lower K, Ca, HCO3, glucose(40-70mg/dL) , protein

-No RBC ,no neutrophils, lymphocytes: 0-4 / mm3, monocyte a few

-Volume :150 ml , although produced 500ml/day

Functions of CSF

• Buoyancy

• Cushion

• Exchange media

• Maintenance of ICP

( normal : 5- 15 mmHg)

• Hydrocephalus : excess volume or pressure of CSF ; leading to dilated ventricles

Lumber punctureUsed to inject anesthetic in the epidural space or to withdraw CSF from the subarachnoid space

• Spinal tap is typically performed at the L4-L5 interspace

• Goal of the lumber puncture is to obtain sample of CSF

without damaging spinal cord.

• i.e., To keep the cord alive , keep the needle between L4 and L5 ( Five)