The Ventricles, Choroid Plexus, & Cerebrospinal

THE VENTRICLES, CHOROID PLEXUS, & CEREBROSPINAL FLUID

DEVELOPMENT • 3RD WOG – neural canal & central canal • 24 – 26 days closure of the anterior (rostral) & posterior (caudal) neuropores, respectively • Neural tube lined by differentiating neuroepithelial cells undergoing cell division that give rise to the ependymal cells lining the mature ventricular system & central canal

VESICLES

VESICLES & VENTRICULAR CAVITY

Pontine flexure

Cervical flexure

Cephalic flexure Telencephalic flexure

5 WEEKS OF GESTATION

6 WEEKS OF GESTATION

8.5 WEEKS OF GESTATION

FORAMEN OF MAGENDIE & DEVELOPMENT LUSCHKA

2nd & 3rd months of development

CHOROID DEVELOPMENT PLEXUS

- found in both lateral ventricles, III & IV ventricles - artery invaginate thru the tela choroidea giving rise to primordial choroid plexus inside the ventricular system; villi development - begins to secrete CSF by the end of 1st trimester

CHOROID DEVELOPMENT PLEXUS

- arteries involved in the development of choroid plexus: IV ventricle - branches of posterior inferior cerebellar artery (PICA) III ventricle - branches of medial posterior choroidal artery Lat. ventricle - branches of the lateral posterior choridal artery & the anterior

VENTRICLES

Body

Anterior horn

Atrium, lateral ventricle

A/R- corpus callosum M- septum pellucidum L/F- caudate nucleus

Posterior horn R- corpus callosum M- calcarine fissure

Interventricular Foramen (Monroe)

Cerebral Aqueduct (Sylvius) Fourth L- cerebellar ventricle peduncle

Third ventricle

R- thin ependyma L- thalami F- hypo- & subthalamus A- l. terminalis, Ant. Comm. Inferior

A-f. Monroe P- splenium R- corpus callosum M- septum pellucidum F- fornix,c.plexus, thalamus

F- rhomboid Foramen of fossa

horn

Magendie

Foramen of Luschka Central canal *The only openings between the ventricles of the brain and the subarachnoid space surrounding the brain are the foramina of Luschka & Magendie in the fourth ventricle

BOUNDARY THIRD VENTRICLE Anterior commissure

Tela choroidea (choroid plexus)

Lamina terminalis

Dorsal thalamus & Hypothalamus Suprapineal recess Posterior commissure

Supraoptic recess

Pineal recess Infundibular recess Optic chiasm Infundibulum

- Cerebral aqueduct of Sylvius or Iter - only 1.5 mm in diam. - contains no choroid plexus - surrounded by a sleeve of gray matter containing small neurons; known as periaqueductal gray or central gray

IV VENTRICLE

-Hemorrhage into the ventricles from ruptured aneurysm, AVM or HPN bleed -Mass lesion obstructing the flow of CSF producing hydrocephalus -Inflammation & infectious process -Congenital anomaly involving the Iter as in stenosis or atresia

(desmosomes)

- Tanycytes: transport substances between ventricles & the blood

EPENDYMOMA - 5% - 6% of all glial neoplasms; originates from the ependymal cells - majority (60%-75%) are located in the posterior fossa - most frequent found in children younger than 5 years of age - signs & symptoms depend on the location of the tumor - characteristic histologic feature is the perivascular rosettes - treatment primarily is surgery followed by focal irradiation

Choroid plexus: - extend from the inferior horn of the lateral ventricle into the atrium (glomus choroideum), along the floor of the body of the lateral ventricle, continues through the interventricular foramen, and attaches to the roof of the III ventricle - it is also found in the IV ventricle attaching to the caudal roof and extends laterally into the foramen of Luschka

(Zonulae occludentes)

Blood-CSF Barrier

BLOOD-BRAIN-BARRIER - A physiologic barrier to the movement of many substances into or out of the brain - endothelial cells of brain capillaries form a continuous lining membrane joined by numerous tight (occluding) junctions & have no intercellular pores or fenestrations - in turn are surrounded by the endfeet of astrocytes - Normal condition: BBB prohibits movement of high-molecular weight substances (proteins,

BLOOD CHOROID PLEXUS SUPPLY

• Blood supply to the choroid plexus is via the choroidal arteries and the posterior cerebellar arteries • CP in the inferior horn, atrium & body of the lateral ventricle is served by the ant. choroidal artery (br. of ICA) & the lateral posterior choroidal artery (br. of P2) • CP in the III ventricle is served by the medial posterior choroidal artery (br. Of P2) • CP in the IV ventricle is served by brs. of the posterior inferior cerebellar artery (PICA) • CP extending out into the foramen of Luschka into the SAS is served by anterior inferior cerebellar artery (AICA)

Choroid Plexus Tumors: - CP papillomas or carcinomas - common between birth and 10 years - occurs in the IV ventricle in 50%60% - signs & symptoms: increased ICP due to hydrocephalus - treatment is by surgery & for the malignant one is a combination of chemotherapy followed by surgery and a combination of chemotherapy & radiation

CEREBROSPINAL FLUID (CSF) - Normal CSF: pressure 70 – 200 mm H2O clear, colorless sugar 45-80 mg% (40%-60% of blood glucose)

protein 15 – 45 mg/dL total/diff. cell count 0-5/ml (leukocytes) average volume 120 ml in adult production 450-500 ml/day - produced by the choroid plexus & absorbed by arachnoid villi or pacchionian bodies found in the superior sagittal sinus back into the circulation

CSF Findings in Various CNS Disorders DISORDER

PRESSURE

APPEARANCE

GLUCOSE

PROTEIN

Acute Pyogenic

increased

cloudy/turbid

decreased

increased

Inc. PMNs

Chronic TB, Fungal, Part.Tx M

increased

Clear or cloudy

decreased

increased

inc. lymphos

Acute Viral

Normal or Mildly inc.

normal

Mildly increased

SAH increased Traumatic tap

normal

Clear, colorless Bloody, does not clot, super-natant xantho. Bloody, clots spontaneously, No xantho.

CELLS

Inc. lymphos Plenty of rbcs

normal

increased

normal

4 mg inc. per Same as 5000 peripheral count rbc

Hydrocephalus: - obstructive hydrocephalus - communicating hydrocephalus - hydrocephalus ex vacuo - normal pressure hydrocephalus (NPH)