Hydrocephalus Flashcards
Where is CSF produced? Which space does is it occupy? How much usually circulates?
- Ependymal cells in the choroid plexus of the lateral ventricles. third and fourth ventricles
- Occupies the subarachnoid space and the ventricular system around and inside the brain and spinal cord
- There is 125-150mL at any one time and 500mL is generated each day
Where is CSF absorbed?
Arachnoid granulations
Describe the ventricles of the brain.
Cerebral aqueduct connects the third and fourth ventricles
Where does CSF circulate in order?
- Produced mostly in two lateral ventricles
- CSF passes through the interventricular foramen of Monro to the third ventricle
- Then through the cerebral aqueduct to the fourth ventricle
- From the fourth ventricle the CSF can pass to the subarachnoid space through 4 openings: central canal of spinal cord, median aperture, two lateral apertures
What are the types of hydrocephalus?
- Communicating
- Non-communicating
- Normal pressure
- Hydrocephalus ex vacuo
What is communicating hydrocephalus?
NON-OBSTRUCTIVE hydrocephalus = when there is full communication between the ventricles and subarachnoid space
Causes:
- defective absorption of CSF (most often e.g. in meningitism, intracranial haemorrhage where there is damage to arachnoid granulations)
- overproduction of CSF (rarely)
- venous drainage insufficiency (occasionally)
What is non-communicating hydrocephalus?
OBSTRUCTIVE hydrocephalus = CSF flow is obstructed within the ventricular system or in its outlets to the arachnoid space
Causes:
- Intraventricular or extraventricular mass-occupying lesions that disrupt ventricular anatomy.
- Obstruction:
- Interventricular foramen
- Cerebral aqueduct
- Fourth ventricle
- Lateral/median aperture
- Obstruction:
What is normal pressure hydrocephalus?
A special type of chronic non-obstructive hydrocephalus with enlarged cerebral ventricles and only intermittently elevated raised ICP.
Diagnosis only established if intraventricular pressure is continuously measured over 24hrs
What is hydrocephalus ex vacuo?
Enlargement of cerebral ventricles and subarachnoid spaces, and is usually due to brain atrophy (occurs in dementias), post traumatic brain injuries, psychiatric disorders (e.g. schizophrenia)
Unlike hydrocephalus, this is a compensatory enlargement of the CSF-spaces in response to brain parenchyma loss; it is not the result of increased CSF pressure
What are the causes of congenital hydrocephalus?
Can be divided into CONGENITAL and ACQUIRED.
Congenital (in children and infants)
- Brainstem malformation –> cerebral aqueduct stenosis (10% of newborns with hydrocephalus )
- Dandy-Walker malformation (2-4% of newborns)
- Arnold-Chiari malformation (type 1 and 2)
- Bickers-Adams syndrome - X linked
- Congenital toxoplasmosis
- Arachnoid cysts
- Neural tube defects e.g. spina bifida - 80-90% will develop hydrocephalus
What are the causes of acquired hydrocephalus?
Acquired causes (in children and infants)
- SOLs - 20%
- Haemorrhage
- Infection e.g. toxoplasmosis
- Increased venous sinus pressure
- Iatrogenic - hypervitaminosis A
- Idiopathic
Acquired causes (in adults)
- Subarachnoid haemorrhage (33%) - blocks arachnoid villi
- Idiopathic
- Head injury
- Tumours
- Prior posterior fossa surgery
- Congenital aqueductal stenosis
- Meningitis
What are the causes of NPH(non-obstructive hydrocephalus)?
NPH causes
- Idiopathic in most - probably due to deficiency of arachnoid granulations
- SAH
- Head trauma
- Meningitis
What are the signs and symptoms associated with hydrocephalus in infants?
Signs:
- Fontanelle (soft spot) bulges
- Large head circumference - at or above the 98th percentile for age
- Dilated scalp veins: The scalp is thin and shiny with easily visible veins.
- Downward gaze - “setting sun sign” due to ocular globes deviated down and lids retracted, sclera visible above iris
- Separated sutures
- Increased limb tone: Spasticity preferentially affects the lower limbs. The cause is stretching of the periventricular pyramidal tract fibers by hydrocephalus.
Symptoms:
- Irritability
- Seizures
- Sleepiness
- Vomiting and poor feeding
What are the signs and symptoms of hydrocephalus in children?
Symptoms:
- Slowing mental capacity
- Headache (morning)
- Neck pain (= tonsillar herniation)
- Vomiting
- Blurred vision and double vision (papilloedema)
- Stunted growth and sexual maturation
- Spasticity causing difficulty walking
- Drowsiness
Signs:
- Papilloedema
- Failure of upward gaze
- Macewen signs - “cracked pot” sound on percussion of head
- Unsteady gait
- Large head
- Unilateral or bilateral 6th nerve palsy due to high ICP
What are the signs and symptoms of hydrocephalus in adults?
Symptoms:
- Cognitive deterioration
- Headaches (morning then continuous)
- Neck pain
- Nausea+Vomiting
- Blurred and double vision - “graying out” episodes (optic nerve compromise) and horizontal diplopia (6th nerve palsy) respectively
- Difficulty walking
- Drowsiness
- Incontinence (urinary first then faecal) - destruction of frontal lobes)
Signs:
- Papilloedema
- Failure of upward gaze and accommodation (= pressure on tectal plate)
- Unsteady gait
- Large head
- Unilateral or bilateral 6th nerve palsy
- Coma
