Hydrocephalus

Basics

Description

  • Increased volume of cerebrospinal fluid (CSF) in the cerebral ventricles
  • Subtypes include nonobstructive or “communicating” and obstructive or “noncommunicating”
    • Communicating hydrocephalus: overproduction or impaired reabsorption of CSF (ventricles still “communicate”)
    • Noncommunicating hydrocephalus: Flow of CSF blocked along 1 or more of the passages connecting the ventricles (ventricles do not “communicate”)
  • Obstructive hydrocephalus is the most common form:
    • Obstruction is present within the ventricular system or in the subarachnoid space
    • Acute obstructive hydrocephalus is usually secondary to CSF shunt blockage, subarachnoid hemorrhage (SAH), or traumatic brain injury (TBI) causing rapid rise in intracranial pressure (ICP), herniation, permanent cerebral damage, or death
    • Chronic obstructive hydrocephalus is usually due to the presence of a mass, such as an ependymoma
  • Nonobstructive hydrocephalus causes subacute symptoms and is a potentially treatable form of dementia:
    • Normal pressure hydrocephalus (NPH) is believed to result from cerebral atrophy and increased CSF in the cranial vault without an increase in ICP
    • Posttraumatic hydrocephalus occurs after TBI which causes dysregulation of CSF production and absorption

Etiology

  • Obstructive hydrocephalus from blockage at:
    • Aqueduct of Sylvius (most common, both lateral ventricles and 3rd ventricle dilated, 4th ventricle is spared):
      • Aqueductal stenosis can be congenital or acquired (postmeningitis, tumor, SAH, idiopathic)
    • Foramen of Monro (lateral ventricles dilated, usually bilateral but may be unilateral)
    • Foramina of Luschka and Magendie (4th ventricle blocked followed by 3rd and lateral ventricles)
    • Subarachnoid space around brainstem as sequelae of infection or SAH resulting in dilation of entire ventricular system
  • Nonobstructive hydrocephalus:
    • Normal pressure:
      • Increased intracranial volume of CSF without intracranial hypertension
      • Increased ventricular size on CT
      • Sometimes called “chronic hydrocephalus”
      • Usually occurs due to inadequate CNS absorption
    • Hypersecretory:
      • Overproduction of CSF usually from choroid plexus papilloma

Pediatric Considerations

Congenital hydrocephalus owing to:

  • Neonatal hemorrhage
  • Congenital malformations
  • Postmeningitis:
    • Subarachnoid scarring around brainstem

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