The Ventricular System and Cerebrospinal Fluid (CSF)

Reminder of Tube Shape of Early CNS – easy to see it is a fluid filled tube (not so easy to see in adult brain)

Side & Frontal Views of Ventricles

Lateral Ventricles in the Hemispheres

Lateral Ventricles From Above

n These are the canals of the cerebral hemispheres or telencephalon

3^rd Ventricle in Diencephalon

Interventricular foramen links lateral ventricles to 3^rd ventricle

Sagittal Section Thru vertically oriented 3^rd Vent. On midline of diencephalon

n Connects to skinny cerebral aqueduct, the canal of the midbrain

4^th Ventricle in the Hindbrain

Choroid plexus located in ventricles continuously produces CSF, replacing the ~125-150 ml several times/day

Circulation of CSF

Arachnoid Granulations Allow CSF Re-absorption into dural sinus blood

Meningitis (inflammation of meninges)

n Can be caused by bacteria, virus, fungus, or reaction to chemicals/drugs

n Headache, fever, stiff neck, irritability, photophobia, nausea, possible seizures or altered mental state, rash

n Bacterial meningitis can progress very rapidly and is a medical emergency (up to10% death rate). Several different common bacteria – if they gain access to the CNS – can cause it (Haemophilus influenzae B (Hib), Streptococcus pneumoniae, Neisseria meningitidis (the cause of the meningococcal meningitis in the news)

Meningitis continued

n Inflammation/swelling can lead to lasting deficits in 20-30% (impaired hearing, vision or movement, retardation, epilepsy, hydrocephalus), especially in neonatal cases or if treatment is delayed

n Viral meningitis is generally less serious

n Meningitis more common in young and adults with special risk factors.

Tests

n CT scan can show swollen meninges

n Lumbar puncture (spinal tap) to identify infection

n Kernig’s sign

n Brudzinki’s sign

n Bacterial meningitis treated with antibiotics

n Now vaccines for 2 varieties available: Hib and Meningococcal (Menimmune for Neisseria strains A,C,Y)) No vaccine for for the strain B most often striking

Meningococcal Vaccination

Spinal
Meninges

n Spinal cord ends at the top of the L2 vertebra.

Needle Enters Via Intervertebral foramen

Needle Enters Subarachnoid Space

Epidural Anesthesia

Spinal or Intrathecal Anesthesia

(into subarachnoid spac

Hydrocephalus

n Excessive CSF (enlarged ventricles)

• Noncommunicating hydrocephalus – an obstruction prevents flow of CSF thru ventricles

• Communicating hydrocephalus – CSF not reabsorbed normally

• Rarely a tumor may cause excess production

n In an infant, the head can expand, but in adult intracranial pressure (ICP) rises.

Enlarged Ventricles

Enlarged Skull (bones not yet fused in infants)

Implanted Shunt to Drain CSF

3rd Venticulostomy

Normal Pressure Hydrocephalus

n Occurs in older (60+) individuals

n Show 3 symptoms:

• Dementia

• Gait (walking) problems (hesitation, slowness)

• Incontinence

n Scan shows enlarged ventricles but CSF pressure is now in normal range

n Symptoms improve with shunting/removal of some CSF

n ……………………………………………………

n Sometimes ventricles enlarge because of loss of adjacent brain tissue (e.g. in Huntington’s, schizophrenia) rather than a CSF problem

Some Other CNS Infections

n Viral

• Rabies

• Creutzfeld-Jakob Disease

• Encephalitis

n Fungal (most often Candida albicans)

• Usually in immune-compromised individuals

Infections continued

n Parasitic Infections

• Neurosyphilis

• Lyme Disease (from ticks)

• Brucellosis (from cattle)