Meninges & Ventricular System

Question 1

Meninges

Answer 1

CNS protection ( central nervous system coverings)
- cover the brain and spinal cord
Location of the meninges varies

Question 2

3 main layers of Meninges

Answer 2

Dura Mater ( most outer layer)
- thick

Arachnoid membrane
- fluid filled subarachnoid space that contains cerebrospinal fluid

Pia mater
- Directly on the surface of the brain/spinal cord

Question 3

Meninges: Special Modifications

Answer 3

Falx Cerebri
Tentorium Cerebelli

Question 4

Falx Cerebri

Answer 4

Dural “partition” between the 2 cerebral hemispheres
Located: in the longitudinal fissure

Question 5

Tentorium Cerebelli

Answer 5

Partition between the cerebrum and the cerebellum
1. Osseous portion
- shelf of the bone from the occipital/parietal bones
2. Membranous Portion
- dura mater

Question 6

Cranial Cavity

Answer 6

Dura mater is adhered to the periosteum

Question 7

Vertebral Canal

Answer 7

Dura mater is NOT adhered to the periosteum

Question 8

Cerebrospinal Fluid Function (CSF)

Answer 8

Protection
Contains substances to alter neuronal activity
Removal of waste metabolites (sleep)
Administration of drugs or contrasts agents ( Intrathecal)
Clinical diagnostic tool

Question 9

CSF Production

Answer 9

Major source: (Choroid Plexus lateral, 3rd, 4th ventricles)
Minor sources: ependymal cells, arachnoid membrane

Rate of production independent of intracranial pressures
- important clinically

Diuretics can be used to decrease CSF production
- important consideration in certain neurological disorders

Question 10

CSF Regulation

Answer 10

Arachnoid Villi are the major regulators of CSF pressure
- CSF from subarachnoid space passes into venous circulation

Question 11

CSF Location

Answer 11

Picture

Question 12

Flow/ Pathway of CSF

Answer 12

Lateral ventricle
Third ventricle
Mesencephalic duct
Fourth ventricle
-> subarachnoid space and or central canal of spinal cord
From the subarachnoid space (drainage occurs)
->Arachnoid villus
Dorsal sagittal sinus
Veins

Question 13

Subarachnoid space

Question 14

Hydrocephalus

Answer 14

Excess accumulation of CSF in the brain or cranial cavity

Loss of parenchyma )CSF fills space)
- In utero viral infections, vascular insults, others

Obstruction to flow
- Acquired–> neoplasia, inflammatory, others

Question 15

CSF Characteristics

Answer 15

Clinical evaluation of CNS disease
- clear colorless fluid
- Protein levels (varies with species)
- WBS count (low), cell type present
- others

Question 16

CSF Collection

Answer 16

Under anesthesia

Question 17

CSF Collection Sites

Question 18

When is CSF tap is contraindicated

Answer 18

CSF tap is contraindicated if pressures suspected to be elevated