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 Nervous system The nervous system is a small and complex system that consists of an intricate network of neural cells (or neurons) and even more glial cells (for support and insulation). It is divided according to its anatomical components as well as its functional characteristics. The brain and spinal cord are referred to as the central nervous system, and the branches of nerves from these structures are referred to as the peripheral nervous system. General Structure of the 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 Ventricular System The ventricular system is an extension of the subarachnoid space into the brain consisting of a series of interconnecting spaces and channels. Four chambers are filled with cerebrospinal fluid (CSF): the paired lateral ventricles, the unpaired 3rd ventricle, and the unpaired 4th ventricle. Ventricular System. Obstruction of CSF can be:
  • Proximal
    • 3rd ventricle
    • Aqueduct
  • Distal
    • 4th ventricle 
    • Foramen magnum

Congenital versus acquired

• Congenital
  • CNS malformations
    • Myelomeningocele
    • Chiari II malformation
    • Dandy-Walker malformation
    • Encephalocele
    • Aqueductal stenosis
  • Infections
    • Intrauterine infections
    • Rubella Rubella Rubella (also known as German measles or three-day measles) is caused by a single-stranded, positive-sense RNA virus of the Togaviridae family. Rubella only infects humans and spreads prenatally via vertical transmission or postnatally via droplet contact. Congenital rubella is associated with a classic triad of symptoms: cataracts, cardiac defects, and deafness. Infection in children and adults may be mild and present with constitutional symptoms along with a viral exanthem. Rubella Virus, cytomegalovirus Cytomegalovirus CMV is a ubiquitous double-stranded DNA virus belonging to the Herpesviridae family. CMV infections can be transmitted in bodily fluids, such as blood, saliva, urine, semen, and breast milk. The initial infection is usually asymptomatic in the immunocompetent host, or it can present with symptoms of mononucleosis. Cytomegalovirus (CMV), toxoplasmosis Toxoplasmosis Toxoplasmosis is an infectious disease caused by Toxoplasma gondii, an obligate intracellular protozoan parasite. Felines are the definitive host, but transmission to humans can occur through contact with cat feces or the consumption of contaminated foods. The clinical presentation and complications depend on the host's immune status. Toxoplasma/Toxoplasmosis, Zika Zika Zika virus belongs to the genus Flavivirus and is primarily transmitted by Aedes aegypti mosquitoes, but can also be transmitted sexually and transplacentally. Although most infected patients are asymptomatic, some may present with low-grade fever, pruritic rash, and conjunctivitis. Zika Virus Infection virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology: Overview, enterovirus
  • Intraventricular hemorrhage: associated with prematurity
  • Medication during pregnancy Pregnancy Pregnancy is the time period between fertilization of an oocyte and delivery of a fetus approximately 9 months later. The 1st sign of pregnancy is typically a missed menstrual period, after which, pregnancy should be confirmed clinically based on a positive β-hCG test (typically a qualitative urine test) and pelvic ultrasound. Pregnancy: Diagnosis, Maternal Physiology, and Routine Care: isotretinoin, misoprostol, metronidazole, antidepressants 
  • Genetics Genetics Genetics is the study of genes and their functions and behaviors. Basic Terms of Genetics 
• Acquired
  • Hemorrhage (intraventricular or subarachnoid)
  • Infections: meningitis Meningitis Meningitis is inflammation of the meninges, the protective membranes of the brain, and spinal cord. The causes of meningitis are varied, with the most common being bacterial or viral infection. The classic presentation of meningitis is a triad of fever, altered mental status, and nuchal rigidity. Meningitis 
  • CNS tumors

Pathophysiology

Normal CSF production

• CSF is produced in the choroid plexus of the ventricles → circulates through the ventricular system Ventricular System The ventricular system is an extension of the subarachnoid space into the brain consisting of a series of interconnecting spaces and channels. Four chambers are filled with cerebrospinal fluid (CSF): the paired lateral ventricles, the unpaired 3rd ventricle, and the unpaired 4th ventricle. 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 Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body's defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation.
• Subarachnoid villi inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body's defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation results in CSF accumulation causing:
  • Distension of the ventricular system Ventricular System The ventricular system is an extension of the subarachnoid space into the brain consisting of a series of interconnecting spaces and channels. Four chambers are filled with cerebrospinal fluid (CSF): the paired lateral ventricles, the unpaired 3rd ventricle, and the unpaired 4th ventricle. Ventricular System (ventricular dilation)
  • Increased intracranial pressure Increased Intracranial Pressure Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP) ( ICP ICP Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP))

Clinical Presentation

Symptoms

• Neonates and infants:
  • Irritability
  • Vomiting
  • Poor feeding
  • Seizures Seizures A seizure is abnormal electrical activity of the neurons in the cerebral cortex that can manifest in numerous ways depending on the region of the brain affected. Seizures consist of a sudden imbalance that occurs between the excitatory and inhibitory signals in cortical neurons, creating a net excitation. The 2 major classes of seizures are focal and generalized. Seizures
• Children:
  • Failure to thrive Failure to Thrive Failure to thrive (FTT), or faltering growth, describes suboptimal weight gain and growth in children. The majority of cases are due to inadequate caloric intake; however, genetic, infectious, and oncological etiologies are also common. 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 Urinary incontinence Urinary incontinence (UI) is involuntary loss of bladder control or unintentional voiding, which represents a hygienic or social problem to the patient. Urinary incontinence is a symptom, a sign, and a disorder. The 5 types of UI include stress, urge, mixed, overflow, and functional. Urinary Incontinence
  • Papilledema

Diagnosis

• 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

Management

Any patient with hydrocephalus and symptoms of ICP ICP Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (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 ICP Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (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 ICP Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (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 ICP Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP)
    • Due to the risk of infection and unclear benefit, serial LPs are no longer commonly performed.
• 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

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 Developmental milestones Developmental milestones are the skills or abilities that most children are able to perform when they reach a certain age. Understanding the appropriate milestones and at what age they are reached helps clinicians identify symptoms of delayed development. Developmental milestones are divided into 5 important domains: gross motor, fine motor, language, social, and cognitive. Developmental Milestones and Normal Growth

Shunt placement

• Shunt infection (following 5%–15% of procedures)
  • May progress to meningitis Meningitis Meningitis is inflammation of the meninges, the protective membranes of the brain, and spinal cord. The causes of meningitis are varied, with the most common being bacterial or viral infection. The classic presentation of meningitis is a triad of fever, altered mental status, and nuchal rigidity. Meningitis
  • May require shunt removal for treatment
• Shunt failure: obstruction of shunt 
• Overdrainage
• Seizures Seizures A seizure is abnormal electrical activity of the neurons in the cerebral cortex that can manifest in numerous ways depending on the region of the brain affected. Seizures consist of a sudden imbalance that occurs between the excitatory and inhibitory signals in cortical neurons, creating a net excitation. The 2 major classes of seizures are focal and generalized. Seizures
• Subdural hematoma: traumatic injury to the vascular system during stent insertion
• Abdominal complications: ascites Ascites Ascites is the pathologic accumulation of fluid within the peritoneal cavity that occurs due to an osmotic and/or hydrostatic pressure imbalance secondary to portal hypertension (cirrhosis, heart failure) or non-portal hypertension (hypoalbuminemia, malignancy, infection). 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 ICP Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP) is not elevated.
• Normal pressure hydrocephalus Normal Pressure Hydrocephalus Normal pressure hydrocephalus (NPH) is a neurodegenerative disorder characterized by the triad of gait abnormalities, dementia, and urinary urgency or incontinence. Normal pressure hydrocephalus can be either idiopathic or secondary to intraventricular or subarachnoid hemorrhage. Normal Pressure Hydrocephalus ( NPH NPH Normal pressure hydrocephalus (NPH) is a neurodegenerative disorder characterized by the triad of gait abnormalities, dementia, and urinary urgency or incontinence. Normal pressure hydrocephalus can be either idiopathic or secondary to intraventricular or subarachnoid hemorrhage. Normal Pressure Hydrocephalus): enlargement of ventricles without detectable elevations in ICP ICP Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (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.”)