- Y6 Neurology > Hydrocephalus > Flashcards

Hydrocephalus Flashcards

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1
Q

Where is CSF produced? Which space does is it occupy? How much usually circulates?

A
  • 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
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2
Q

Where is CSF absorbed?

A

Arachnoid granulations

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3
Q

Describe the ventricles of the brain.

A

Cerebral aqueduct connects the third and fourth ventricles

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4
Q

Where does CSF circulate in order?

A
  • 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
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5
Q

What are the types of hydrocephalus?

A
  • Communicating
  • Non-communicating
  • Normal pressure
  • Hydrocephalus ex vacuo
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6
Q

What is communicating hydrocephalus?

A

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)
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7
Q

What is non-communicating hydrocephalus?

A

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
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8
Q

What is normal pressure hydrocephalus?

A

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

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9
Q

What is hydrocephalus ex vacuo?

A

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

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10
Q

What are the causes of congenital hydrocephalus?

A

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
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11
Q

What are the causes of acquired hydrocephalus?

A

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
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12
Q

What are the causes of NPH(non-obstructive hydrocephalus)?

A

NPH causes

  • Idiopathic in most - probably due to deficiency of arachnoid granulations
  • SAH
  • Head trauma
  • Meningitis
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13
Q

What are the signs and symptoms associated with hydrocephalus in infants?

A

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
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14
Q

What are the signs and symptoms of hydrocephalus in children?

A

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
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15
Q

What are the signs and symptoms of hydrocephalus in adults?

A

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
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16
Q

What is the triad of symptoms in normal pressure hydrocephalus?

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A

Dementia

Incontinence

Disturbed gait

= “wet, wacky and wobbly” or “weird walking water”

Hakim’s triad

17
Q

What are the signs of NPH on examination?

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A

Signs:

  • N muscle strength, N sensation
  • Reflexes increased
  • Positive Babinski
  • Imbalance/inability to stand
  • Frontal release signs such as sucking/grasping reflexes in late stages
18
Q

What investigations would you do for hydrocephalus?

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A

Bloods - none necessary

Imaging:

  • CT - 1st line to assess ventricles
  • MRI - better for more details; e.g. Chiari malformation, cerebellar or periaqueductal tumours. Better imaging of posterior fossa than CT. Features of hydrocephalus on CT/MRI include:
    • Temporal horns greater then 2mm and clearly visible (usually not visible)
    • Evans ratio - ratio of widest part frontal horn to max biparietal diameter greater than 30%
    • Ballooning of frontal horns of lateral and third ventricles (“Mickey mouse ventricles”)
  • LP - diagnostic and therapeutic*, done after CT/MRI, may show improvement in symptoms after 40-50mL of CSF is withdrawn.

Other:

  • Radionucleotide cisternography - can be done in NPH to assess if a shunt would be useful
19
Q

How is hydrocephalus managed?

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A

Surgical:

  • Repeat LPs
  • EVD - External ventricular drain - used in acute, severe hydrocephalus, inserted into the right ventricle and drains into a bag at the bedside
  • VPS - ventriculoperitoneal shunting - long-term CSF diversion technique that drains CSF into peritoneum
20
Q

Which type of hydrocephalus must LP not be done in?

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A

Obstructive - because the difference of cranial and spinal pressures induced by drainage of CSF will cause brain herniation

21
Q

What is the prognosis with hydrocephalus?

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A

Shunting is lifelong but it’s not known whether it improves life expectancy (in NPH)

22
Q

What are the complications of NPH?

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A
  • Stroke - common post-op
  • Subdural haematoma
  • Bleeding
  • Shunt infection
  • Vascular disease and cognitive impairment
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