Epidemiology
Incidence
- Highest in Latin America (316 per 100,000 births) and Africa (145 per 100,000 births)
- Lowest in United States and Canada (68 per 100,000 births)
- Higher incidence in low- and middle-income countries due to:
- High crude birth rates
- High prevalence of neglected tropical diseases (NTDs)
Risk factors
- Central nervous system (CNS) infections
- Low birth weight (< 1,500 g)
- Prematurity
- Diabetes in mother
- Family history of hydrocephalus
Classification
There are different ways to characterize hydrocephalus, each of which can help physicians better understand the underlying cause and determine the appropriate treatment.
Communicating versus non-communicating
- Communicating (non-obstructive): caused by impaired absorption (most common) or excess production of cerebrospinal fluid (CSF)
- Non-communicating (obstructive): caused by a structural blockage of CSF flow in the ventricular system. Obstruction of CSF can be:
- Proximal
- 3rd ventricle
- Aqueduct
- Distal
- 4th ventricle
- Foramen magnum
- Proximal
Congenital versus acquired
- Congenital
- CNS malformations
- Myelomeningocele
- Chiari II malformation
- Dandy-Walker malformation
- Encephalocele
- Aqueductal stenosis
- Infections
- Intrauterine infections
- Rubella, cytomegalovirus (CMV), toxoplasmosis, Zika virus, enterovirus
- Intraventricular hemorrhage: associated with prematurity
- Medication during pregnancy: isotretinoin, misoprostol, metronidazole, antidepressants
- Genetics
- CNS malformations
- Acquired
- Hemorrhage (intraventricular or subarachnoid)
- Infections: meningitis
- CNS tumors
Pathophysiology
Normal CSF production
- CSF is produced in the choroid plexus of the ventricles → circulates through the ventricular system → 4th ventricle → subarachnoid space → absorbed by arachnoid villi (located in the subarachnoid space) → venous sinuses + systemic circulation
- Normal volume of CSF: 150 ml (reached by 5 years of age)
Acquired hydrocephalus
- Most commonly hemorrhage as a result of prematurity
- Most common defect: resorption of CSF
- Impaired CSF absorption most often occurs due to subarachnoid villi inflammation.
- Subarachnoid villi inflammation results in CSF accumulation causing:
- Distension of the ventricular system (ventricular dilation)
- Increased intracranial pressure (ICP)
An infant with normal intracranial pressure (left), and a child with hydrocephalus (right)
Image: “Hydrocephalus CDC” by CDC. License: Public Domain
Normal CSF production: CSF is produced in the choroid plexus of the ventricles → circulates through the ventricular system → 4th ventricle → subarachnoid space → absorbed by arachnoid villi (located in the subarachnoid space) → venous sinuses + systemic circulation
Image: “CFS_Circulation” by OpenStax. License: CC BY 4.0
Clinical Presentation
Symptoms
- Neonates and infants:
- Irritability
- Vomiting
- Poor feeding
- Seizures
- Children:
- Failure to thrive
- Behavioral changes → altered mental status
- Developmental delays
- Severe headache
- Persistent nausea and vomiting
- Drowsiness
- Abnormal gait
Physical examination
- Neonates:
- Tense or bulging fontanelles
- Frontal bossing
- Papilledema
- Irritability
- Vomiting
- Infants:
- “Setting sun” sign: upward gaze paresis, eyes appear driven down (early symptom, seen in 40% of obstructive hydrocephalus)
- Serial head circumference measurements > 98th percentile
- Nuchal rigidity
- Papilledema
- Children:
- “Setting sun” sign
- Cognitive deterioration
- Imbalance and gait disturbances
- Urinary incontinence
- Papilledema
Photo of a child with hydrocephalus and a noticeable “setting sun” sign
Image: “Sunset sign” by Louis Fischer. License: Public DomainDiagnosis
- Confirmed by neuroimaging with ventriculomegaly and evidence of increased intracranial pressure
- Newborns/young infants → ultrasound is preferred
- Older infants/children → computed tomography (CT) of the head or magnetic resonance imaging (MRI)
- Can be prenatally diagnosed by detecting congenital malformations (antenatal ultrasound)
- Use caution with lumbar puncture and CSF analysis
- Contraindicated in space-occupying lesions and obstructive hydrocephalus due to high risk of herniation
- Limit use to clinical suspicion of infection
Non-enhanced brain computed tomography scan of a 7-month-old boy with a history of pneumococcal meningitis. Axial image shows significant non-obstructive hydrocephalus resulting in compression of cerebral parenchyma. There are hypodensities involving the periventricular regions and the frontal lobes bilaterally with associated cystic encephalomalacia, especially on the right.
Image: “Nonenhanced brain computed tomography scan” by Division of Neurology, Department of Pediatrics and Adolescent Medicine, American University of Beirut Medical Center, P.O. Box 11-0236, Riad El Solh, Beirut 1107 2020, Lebanon. License: CC BY 3.0
Sagittal T1-weighted MRI demonstrating obstructive hydrocephalus due to congenital aqueductal stenosis.
Image: “Obstructive hydrocephalus” by Division of Neurosurgery, Faculty of Medicine, King Abdulaziz University, PO Box 80215, Jeddah, 21589, Saudi Arabia. License: CC BY 2.0
MRI of head showing supratentorial non-communicating hydrocephalus (a, b) and slightly hypoplastic corpus callosum (c).
Image: “Magnetic Resonance of head” by Laboratorio de Inmunología y Biología Molecular, Doctorado en Biotecnología, Facultad de Ciencias Químico Biológicas, Universidad Autónoma de Sinaloa, Culiacán, Sinaloa, México. License: CC BY 2.0
Management
Any patient with hydrocephalus and symptoms of ICP requires intervention. The method used to relieve the pressure and the speed at which it is deployed is based on the severity of the patient’s ICP.
- Acutely symptomatic patients with life-threatening hydrocephalus:
- Extra ventricular drain (EVD): transcranial catheter connected to an external closed reservoir
- Can be placed rapidly and emergently
- Collects CSF to relieve pressure
- Allows serial measurement of ICP and serial CSF sampling
- Diuretics: may be acutely effective in select cases but do not have a long-term role
- Acetazolamide: decreases CSF production at the level of the choroid plexus by inhibiting carbonic anhydrase activity
- Furosemide: similar effect as acetazolamide, but not as potent and not usually used alone
- Lumbar puncture (LP):
- Used for diagnostic sampling of CSF, can also be used to reduce CSF volume and thus ICP
- Due to the risk of infection and unclear benefit, serial LPs are no longer commonly performed.
- Extra ventricular drain (EVD): transcranial catheter connected to an external closed reservoir
- Symptomatic but clinically stable or nonprogressive hydrocephalus patients:
- More intensive surgery is often tolerated.
- CSF shunting: ventriculoperitoneal or ventriculopleural shunt
- Catheter draining CSF to spaces in the body with high surface area and high capillary concentration where it can be safely reabsorbed
- Risks: infection and clogging of the catheters
- Endoscopic 3rd ventriculostomy: creating a passageway (or ostomy) in the bottom of the 3rd ventricle allowing CSF to drain into the subarachnoid space
- Asymptomatic, clinically stable patients:
- May be followed clinically
- Serial head circumference measurement
- Developmental screening
- Frequent head ultrasound
A diagram of a ventriculoperitoneal shunt in a baby
Image by Lecturio.Complications
Disease progression
- Herniation of the cerebral parenchyma
- Visual problems secondary to compression of the optic nerve
- Gait changes
- Death
- Cognitive dysfunction and loss of developmental milestones
Shunt placement
- Shunt infection (following 5%–15% of procedures)
- May progress to meningitis
- May require shunt removal for treatment
- Shunt failure: obstruction of shunt
- Overdrainage
- Seizures
- Subdural hematoma: traumatic injury to the vascular system during stent insertion
- Abdominal complications: ascites and an increase in intra-abdominal pressure
Mnemonic
“Don’t pump the shunt unless you’re stuck.”: The shunt pump should be accessed as little as possible.
Differential Diagnosis
The differential diagnosis of hydrocephalus includes:
- Reduction in brain volume: occurs due to cerebral atrophy or other brain malformations. Unlike hydrocephalus, ICP is not elevated.
- Normal pressure hydrocephalus (NPH): enlargement of ventricles without detectable elevations in ICP. Occurs most commonly in adults > 60 years old. Symptoms include a triad of urinary incontinence, ataxia, and cognitive dysfunction (i.e., “wet, wobbly, and wacky.”)
References
- Kahle, K. T., M.D., Kulkarni, A. V., M.D., Limbrick, D. D., M.D., & Warf, B. C., Dr. (2016). Hydrocephalus in children. Lancet, The, 387(10020), 788–799. doi:http://dx.doi.org/10.1016/S0140-6736(15)60694-8
- Blázquez, M., & Zarranz, J. J. (2018). Síndrome meníngeo. edema cerebral. hipertensión intracraneal. hidrocefalias. hipotensión intracraneal. In J. J. Zarranz (Ed.), Neurología (pp. 219–233). https://www.clinicalkey.es/#!/content/3-s2.0-B978849113071000012X
- Sato, O., Yamguchi, T., Kittaka, M., & Toyama, H. (2001). Hydrocephalus and epilepsy. Child’s nervous system: ChNS: official journal of the International Society for Pediatric Neurosurgery, 17(1–2), 76–86. DOI:10.1007/s003810000381
- Tully, H. and Dobyns, W. (2014). Infantile hydrocephalus: a review of epidemiology, classification and causes. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4334358/
