Hydrocephalus
Describe the CSF path with diagram.
- Cerebrospinal fluid is produced in the lateral, thrid and fourth ventricles by the choroid plexus.
- CSF travels from the lateral ventricles through the intrventricular foramina to the third ventricle through the cerebral aqueduct to the fourth ventricle.
- CSF then leaves the ventricular system at the fourth ventricle through the midline foramina of Magendie and the paired lateral foramina of Luschka.
- The CSF enters the subaracnoid spaces where it circulates and bathes the surface of the brain.
- The CSF leaves the subarachnoid space and enters the venous sinuses by unidirectional valves called arachnoid villi.
What is hydrocephalus?
- Hydrocephalus is defined as an increase in the volume of CSF within the ventricular system.
What are the types of hydrocephalus?
- Obstructive
- Communicating hydrocephalus
What are the characteristics of obstructive hydrocephalus ?
- Obstructive hydrocephalus is also called noncommunicating or intraventricular obstructive hydrocephalus.
- The block of CSF flow occurs within the ventricular system or at the foramina that exit the fourth ventricle in obstructive hydrocephalus, and the ventricular system enlarges proximal to the obstruction.
- An example of this is aqueductal stenosis.
What are the consuquences to obstructive hydrocephalus in children?
- Obstructive hydrocephalus results in increased intracranial pressure, which results in increased head circumference by widening of the sutures, in an attempt to decrease the pressure.
- The increased pressure also results in tense fontanelles.
- One measurement of head circumference is not an adequate investigation of hydrocephalus, rather the head circumference must be measured over time.
- Features of hydrocephalus include emesis (especially in the morning), decline in cognitive ability, headaches, papilloedema, ataxia, and defect in upward gaze.
What are the characteristics of communicating hydrocephalus?
- The obstruction in communicating hydrocephalus occurs at the basal cisterns or at the surfaces of the cerebral hemispheres.
- An example is scarring at the arachnoid villi.
- Features of communicating hydrocephalus are like those of obstructive hydrocephalus.
What imaging procedures are useful in evaluating children suspected to have hydrocephalus?
How do you distinguish obstructive from communicating hydrocephalus by imaging studies?
Case 1:
A 2 month old infant is brought to the pediatrician because of irritability for 2 weeks. His parents complain that he cries constantly and that his cry is high pitched. His parents also complain that he has vomited each morning for the past 3 days. The family brought him in only 1 week ago with complaints of irritability with constipation. The pediatrician noticed that his head circumference has been growing more rapidly than his height and weight. The patient also has a tense anterior fontanelle. The infant is also noted to have papilloedema and difficulty with upward gaze.
Q:
A:
Case 2:
A case of communicating hydrocephalus with imaging studies.
Hydrocephalus Obstructive
Clinical:
F-54 with delayed milestones, S/P occipital decompression of Chiari malformation, with progressive gait ataxia, adduction paresis of eyes, nystagmus and dementia
CT scans without contrast show enlargement of lateral and third ventricles, but not the fourth ventricle, due to aqueductal stenosis. The posterior fossa is distorted due to a congenital Chiari malformation and previous surgery.