three C.T. membranes that cover spinal cord and brain.

consists of: pia mater and arachnoid and dura mater (pachymeninx)

• delicate
• highly vascular 
• covers surface of brain and spinal cord 
• connected to arachnoid by trabeculae

forms:

denticulate ligaments

filum terminale  

two lateral flatteend bands of pial tissue

adheres with dura mater w/ 21 attachments 

nonneural band of tissue 

condensation of pia mater

extends from conus medullaris to end of dural sac and fuses with it

Arachnoid 

• delicate
• non-vascular C.T.
• b/w dura and pia

forms:

a. arachnoid granulations/arachnoid villi

b. subarachnoid space  

• outer layer of meninges 
• dense C.T.

forms:

a. falx cerebri

b. tentorium cerebelli

c. diaphragma sellae

d. dural sinuses

vagal nerve

upper spinal nerve

• b/w cerebral hemispheres in long. cerebral fissures
• contains: superior and inferior sagittal sinuses b/w its two layers 

• separates: posterior cranial fossa from middle cranial fossa
• separates: temporal and occipital lobes from cerebellum and infratentorial brainstem

contains:

a. tentorial incisure

notch through which brainstem passes 

present in tentorium cerebelli

• roof of hypophyseal fossa
• contains: aperture through which hypophyseal stalk (infundibulum) passes

• Spinal Epidural Space
• Cranial Epidural Space
• Subdural Space
• Subarachnoid Space
• Subarachnoid Cisterns

a. Cerebellopontine angle cistern

b. Cerebrellomedullary cistern (cisterna magna)

c. Ambient cistern

d. Superior cistern

• b/w dura and vertebral periosteum
• contains:

a. loose areolar tissure

b. venous plexuses 

c. lymphatics

• injected w/ local anethetic to produce paravertebral nerve block

• potential space b/w periosteal and meningeal layers of dura
• contains:

a. meningeal a.
b. meningeal v. 

a. space b/w dura and arachnoid

b. intracranially transmits superior cerebral v. to venous lacunae of superior sagittal sinus

c. lateration of these "bridging veins" → subdural hemorrhage (hematoma)

• b/w pia and arachnoid
• contains: CSF
• surrounds entire brain + spinal cord
• entends below conus medullaris → S2--lumbar cistern

• dilations of subarachnoid space
• contains CSF
• named after structures over which they lie, i.e. pontine, chiasmatic, and interpeduncular cistersn
• 4 types:

a. cerebellopontine angle cistern

b. cerebellomedullary cistern (cisterna magna)

c. ambient cistern

d. superior cistern

• receives CSF from 4th ventricle via lateral foramina of Luschka 
• contains: facial nerve (CN VII) + vestibulocochlear n. (CN VIII)

• in midline b/w cerebellum and medulla
• receives CSF from 4th ventricle via median formaen of Magendie
• tapped for CSF (suboccipital tap)

• interconnects superior and interpenduncular cisterns
• contains: trochlear nerve (CN IV)

• overlies midbrain tectum

• benign
• slow-growing 
• well-demarcated tumors
• arise from meningotheal arachnoid cells
• 20%--primary intracranial tumors
• 25%--spinal tumors
• most frequently found in: anterior cranial fossa (parasagittal 25%, convexity 20%, basal 40%)
• histologically characterized by: whorling pattern and calcified psammoma bodies
• enlarge slowly
• create cavity in adjacent brain
• occurence: adult (20-60 yrs)
• most often in women (60%)

• lined by ependyma
• contain: choroid plexus, which produces CSF @ rate of 500 ml/day
• communicate w/ subarachnoid space via 3 foramina in 4th ventricle
• consists of: 4 fluid-filled communicating cavities w/in brain 

• two ventricles
• located w/in cerebral hemispheres
• communicate w/ 3rd ventricle via interventricular foramina of Monro
• consists of 5 parts:

a. frontal (anterior) horn

b. body

c. temporal (inferior) horn

d. occipital (posterior) horn

e. trigone (atrium) 

• w/in frontal lobe
• lateral walls are formed by head of caudate nucleus
• lacks choroid plexus 

• w/in medial portion of frontal and parietal lobes
• contains choroid plexus
• communicates via interventricular foramen of Monro w/ 3rd ventricle

• w/in medial part of temporal lobe
• has choroid plexus

• w/in parietal and occipital lobe
• lacks choroid plexus 

• @ the junction of body, occipital horn, and temporal horn of lateral ventricle
• contains: glomus 

• found w/in trigone
• large tuft of choroid plexus
• calcified in adults 
• visible on x-ray films and computed tomography (CT)

• slitlike vertical midline cavity of diencephalon
• communicated w/ lateral ventricles via interventricular foramina of Monro + 4th ventricle via cerebral aqueduct
• contains: pair of choroid plexuses in its roof 

• w/in midbrain
• connects 3rd ventricle w/ 4th ventricle
• lacks choroid plexus
• blockage → hydrocephalus (aqueductal stenosis)

• b/w cerebellum and brainstem
• contains: pair of choroid plexus in caudal roof
• expresses CSF into subarachnoid space via two lateral foramina of Luschka and single medial foramen of Magendie 

• clear, colorless, acellular fluid
• found in: subarachnoid space + ventricles 

• produced by choroid plexus 
• rate: 500 ml/day
• total CSF volume = 140 ml

• supports and cushions CNS against concussive injury
• transports hormones + hormone-releasing factors
• removes metabolic waste products through absorption

• site of greatest absorption 

• flows from ventricles via 3 foramina of 4th ventricle → subarachnoid space and over the convexity of hemisphere → superior sagittal sinus → venous circulation

• no more than 5 lymphocytes/µl
• sterile--usually
• normal values

a. pH: 7.35

b. Specific gravity: 1.007

c. Glucose: 66% of plasma glucose

d. Total protein: < 45 mg/dl in lumbar cistern

• 80-180 mm of water (CSF) in lumbar subarachnoid space when pt is in a lateral recumbent (decubitus) position 

• dilation of cerebral ventricles
• caused by blockage of CSF pathways
• characterized by: excessive accumulation of CSF in cerebral ventricles or subarachnoid space

• noncommunicating hydrocephalus
• communicating
• normal-presure 
• hydrocephalus ex vacuo
• pseudotumor cerebri (benign intracranial hypertension)

• due to obstruction w/in ventricles
• i.e. congential aqueductal stenosis

• due to blockage w/in subarachnoid space 
• i.e. adhesions after meningitis

• CSF is not absorbed by arachnoid villi
• secondary to post-traumatic meningeal hemorrhage
• clinically characterized by: triad of progressive dementia, ataxic gait, urinary incontinence (wacky, wobbly, and wet)

• loss of cells in caudate nucleus 
• i.e. Huntington disease

• increased resistance to CSF outlfow @ arachnoid villi
• characterized by: 

a. papilledema w/o mass

b. elevated CSF pressure

c. deteriorating vision

• ventricles may be slit-like
• occurs in obese young women

• inflammation of pia-arachnoid of brain, spinal cord or both
• types:

a. bacterial (pyogenic)

b. viral (lymphocytic)

• common in children under 5 yrs (>70% of all cases)
• clinical characterization:

a. fever

b. headache

c. nuchal rigidity w/ kernig sign

• result in cranial n. palsies (CN III, IV, VI, VIII) and hydrocephalus

• newborn: <1 month

cause: group B streptococci (S. agalactiae) + E. coli

immunization against Haemophilus influenzae has significantly reduced this type of meningitis

• older infants and young children: 1 month- 9 yrs

frequent cause: S. pneumoniae + Neisseria meningitidis

• older adults: 

cause: S. pneumoniae

• numerous neutrophils
• decreased glucose level
• elevated protein level

• also known as: aspectic meningitis
• characterized by:

a. fever

b. headache

c. nuchal rigidity w/ Kernig sign

• Mumps virus
• Enteric cytopathic human orphan (ECHO) viruses
• Coxsackie virus
• Epstein-Barr
• Herpes simplex virus (type 2)

• numerous lymphocytes
• normal glucose
• normal to slightly increased protein

• transtentorial (uncal)
• transforminal (tonsillar)
• subfalcial

• chemosensitive zones
• monitor concentrations of circulating hormones in blood + CSF
• located in periphery of 3rd ventricle
• area prostrema--found in floor of 4th ventricle
• highly vascularized w/ fenestrated capillaries
• no blood-brain barrier (subcommissural organ--exception)
• includes:

a. organum vasculosum of lamina terminalis

b. median eminence of tuber cinereum

c. subfornical organ

d. subcommisural organ

e. pineal body

f. area postrema

• vascular outlet for LH releasing hormone + somatostatin

• contains neurons that release and inhibit hormones into hypophyseal portal system

• located on inferior surface of fornix @ level of interventircular foramen of Monro
• contains neurons that project to supraoptic nuclei + organum vasculosum
• central receptor site for angiotensin II

• below the posterior commisure @ junction of 3rd vent + cerebral aqueduct
• composed of:

a. specialized ependymal cells

b. glial elements

c. capillary bed--contains nonfenestrated endothelial cells

• contains: 

a. calcareous granules--in brain sand/acervulus

i. seen on x-ray film + C.T. 

ii. occur after 16 yrs of age

b. pinealocytes--epiphyseal cells 

i. highly vascular w/ fenestrated capillaries

• derived from: diencephalon
• innervated solely via postganglionic fibers from superior cervical ganglion of ANS
• synthesizes: serotonin + melatonin. 
• antigonadotrophic function
• pinealosomes--found in dorsal midbrain syndrome

• two small subependymal oval areas on either side of 4th ventricle rostral to obex
• contains modified neurons + astrocytes-like cells surrounded by fenestrated capillaries
• chemoreceptor zone--triggers vomiting in response to circulating emetic substances
• role in food intake + cardiovascular regulation