Meninges Ventricles and Cerebrospinal Fluid

I. MENINGES are three connective tissue membranes that surround the spinal coal and brain.

A. They consist of the pia mater, arachnoid, and dura mater.

1. The pia mater is a delicate, highly vascular layer of connective tissue. It closely covers t he surface of the brain and spinal cord.

2. The arachnoid is a delicate, nonvascular connective tissue membrane. It is located between the dura mater and the pia mater.

3. The dura mater is the outer layer of meninges. It consists of dense connective tissue.

B. Meningial spaces

1. The subarachnoid space (Figure 2-1) lies between the pia mater and the arachnoid. It terminates at the level of the second sacral vertebra. It contains the cerebrospinal fluid (CSF).

2. Subdural space a. In the cranium, the subdural space is traversed by "bridging" veins.

b. In the spinal cord, it is a clinically insignificant potential space.

3. Epidural space a. The cranial epidural space is a potential space. It contains the meningeal arteries and veins.

b. The spinal epidural space contains fatty areolar tissue, lymphatics, and venous plexuses. The epidural space may be injected with a local anesthetic to produce a paravertebral ("saddle") nerve block.

C. Meningial tumors

1. Meningiomas are benign, well-circumscribed, slow-growing tumors. They account for 15% of primary intracranial tumors and are more common in women than in men (3:2). Ninety percent of meningiomas are supratentorial.

2. Subdural and epidural hematomas a. Subdural hematoma is caused by laceration of the superior cerebral (bridging) veins.

b. Epidural hematoma is caused by laceration of the middle meningeal artery.

D. Trauma

E. Meningitis is inflammation of the pia-arachnoid area of the brain, the spinal cord, or both.

Superior sagittal sinus

Arachnoid granulation

Velum interpositum

Great cerebral vein of Galen

Interventricular foramen (of Monro)

Third ventricle Interpeduncular cistern Cerebral aqueduct Pontine cistern

Superior sagittal sinus

Meninges Ventricle

Subarachnoid space

Subdural space Epidural space

Central canal

Spinal cistern —

Conus medullans

- Filum terminale

Figure 2-1. The subarachnoid spaces and cisterns of the brain and spinal cord. Cerebrospinal fluid is produced in the choroid plexuses of the ventricles. It exits the fourth ventricle, circulates in the subarachnoid space, and enters the superior sagittal sinus through the arachnoid granulations. Note that the conus medullans terminates at L-l. The lumbar cistern ends at S-2. (Reprinted with permission from Noback CR, Strominger NL, Demarest R: The Human Nervous System, 4th cd. Baltimore, Williams Wilkins, 1991, p. 68.)

Superior cistern

Straight sinus in tentorium

Confluence of the sinuses

Fourth ventricle

Medial aperture Cerebellomedullary (magna) cistern

Subarachnoid space

Subdural space Epidural space

Central canal

Spinal cistern —

Conus medullans

- Filum terminale

Figure 2-1. The subarachnoid spaces and cisterns of the brain and spinal cord. Cerebrospinal fluid is produced in the choroid plexuses of the ventricles. It exits the fourth ventricle, circulates in the subarachnoid space, and enters the superior sagittal sinus through the arachnoid granulations. Note that the conus medullans terminates at L-l. The lumbar cistern ends at S-2. (Reprinted with permission from Noback CR, Strominger NL, Demarest R: The Human Nervous System, 4th cd. Baltimore, Williams Wilkins, 1991, p. 68.)

1. Bacterial meningitis is characterized clinically by fever, headache, nuchal rigidity, and Kernig's sign. (With the patient supine, the examiner flexes the patient s hip, but cannot extend the knee without causing pain. It is a sign of meningeal irritation.) [Remember: Kernig = knee.] More than 70% of cases occur in children younger than 5 years of age. The disease may cause cranial nerve palsies and hydrocephalus.

a. Common causes

(1) in newborns, bacterial meningitis is most frequently caused by Group B streptococci (vStrepiococcus agalactiae) and Escherichia coli.

(2) In older infants and young children, it is most frequently caused by Haemophilus influenzae.

(3) In young adults, it is most frequently caused by Neisseria meningitidis.

(4) In older adults, it is most frequently caused by Streptococcus pneumoniae.

b. CSF findings

(1) Numerous polymorphonuclear leukocytes

(2) Decreased glucose levels

(3) Increased protein levels

2. Viral meningitis is also known as aseptic meningitis. It is characterized clinically by fever, headache, nuchal rigidity, and Kernig's sign.

a. Common causes. Many viruses are associated with viral meningitis, including mumps, echovirus, Coxsackie virus, Epstein-Barr virus, and herpes simplex type 2.

b. CSF findings

(1) Numerous lymphocytes

(2) Normal glucose levels

(3) Moderately increased protein levels

Headache Happiness

Headache Happiness

Headache Happiness! Stop Your Headache BEFORE IT STARTS. How To Get Rid Of Your Headache BEFORE It Starts! The pain can be AGONIZING Headaches can stop you from doing all the things you love. Seeing friends, playing with the kids... even trying to watch your favorite television shows. And just think of how unwelcome headaches are while you're trying to work.

Get My Free Ebook


Responses

  • arianna
    Where is meninges located?
    5 years ago
  • paul
    What are meninges and cerebrospinal fluid?
    5 years ago
  • colin watt
    What meningial space contains spinal fluid?
    5 years ago

Post a comment