Hydrocephalus; Causes, Symptoms, Diagnosis, Treatment

Anatomy? of Hydrocephalus

Types of Hydrocephalus

The cause of hydrocephalus is not known with certainty and is probably multifactorial?. It may be caused by impaired cerebrospinal fluid (CSF) flow, reabsorption, or excessive CSF production.

• Obstruction to CSF flow  – hinders the free passage of cerebrospinal fluid through the ventricular system and subarachnoid space (e.g., stenosis of the cerebral aqueduct or obstruction of the interventricular foramina) secondary to tumors, hemorrhages, infections or congenital malformations) and can cause increases in central nervous system pressure.
• Hydrocephalus – can also be caused by overproduction of cerebrospinal fluid (relative obstruction) (e.g., Choroid plexus papilloma, villous hypertrophy).
• Bilateral? ureteric obstruction – is a rare, but reported, cause of hydrocephalus.
• Congenital hydrocephalus  – means the condition is present at birth, caused by a complex interaction of genetic? and environmental factors during fetal development. Congenital hydrocephalus is now often diagnosed before birth through routine ultrasound?.
• Compensated hydrocephalus –  is hydrocephalus that is diagnosed in adulthood, but may have existed since birth. It can still be considered congenital.
• Hydrocephalus ex – vacuo –This type occurs after stroke, traumatic brain injury, or degenerative diseases. As brain tissue shrinks, the ventricles of the brain become larger.
• Acquired hydrocephalus –  develops after birth as a result of neurological conditions such as head trauma, brain tumor, cyst, intraventricular hemorrhage or infection? of the central nervous system.
• Normal pressure hydrocephalus occurs in older adults when the ventricles of the brain are enlarged, but there is little or no increase in the pressure within the ventricles. Sometimes the cause of NPH is known – but most often it is idiopathic?, which means the cause is not known.
• Communicating – Communicating hydrocephalus, also known as non-obstructive hydrocephalus, is caused by impaired cerebrospinal fluid reabsorption in the absence of any CSF-flow obstruction between the ventricles and subarachnoid space. It has been theorized that this is due to functional impairment of the arachnoidal granulations (also called arachnoid granulations or Pacchioni’s granulations), which are located along the superior sagittal sinus and is the site of cerebrospinal fluid reabsorption back into the venous system. Various neurologic conditions may result in communicating hydrocephalus, including subarachnoid/intraventricular hemorrhage, meningitis? and congenital absence of arachnoid villi. Scarring and fibrosis? of the subarachnoid space following infectious, inflammatory, or hemorrhagic events can also prevent resorption of CSF, causing diffuse ventricular dilatation.

Non-communicating – Non-communicating hydrocephalus, or obstructive hydrocephalus, is caused by a CSF-flow obstruction.

• Foramen of Monro obstruction – may lead to dilation of one or, if large enough (e.g., in colloid cyst), both lateral ventricles.
• The aqueduct of Sylvius – normally narrow to begin with, may be obstructed by a number of genetically or acquired lesions (e.g., atresia, ependymitis, hemorrhage, tumor?) and lead to dilation of both lateral ventricles as well as the third ventricle.
• Fourth ventricle obstruction – will lead to dilatation of the aqueduct as well as the lateral and third ventricles (e.g., Chiari malformation).
• The foramina of Luschka and foramen of Magendie – may be obstructed due to congenital malformation (e.g., Dandy-Walker malformation).

Others

• Normal pressure hydrocephalus (NPH)  – is a particular form of chronic? communicating hydrocephalus, characterized by enlarged cerebral ventricles, with only intermittently elevated cerebrospinal fluid pressure. Characteristic triad of symptoms are; dementia, apraxic gait and urinary incontinence. The diagnosis? of NPH can be established only with the help of continuous intraventricular pressure recordings (over 24 hours or even longer), since more often than not instant measurements yield normal pressure values.
• Hydrocephalus ex vacuo  – also refers to an enlargement of cerebral ventricles and subarachnoid spaces, and is usually due to brain atrophy? (as it occurs in dementias), post-traumatic brain injuries and even in some psychiatric disorders, such as schizophrenia. As opposed to 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.

Causes of Hydrocephalus

• Aqueductal stenosis? – The most common cause of congenital hydrocephalus is an obstruction called aqueductal stenosis. This occurs when the long, narrow passageway between the third and fourth ventricles (the aqueduct of Sylvius) is narrowed or blocked, perhaps because of infection, hemorrhage, or a tumor. Fluid accumulates “upstream” from the obstruction, producing hydrocephalus.
• Poor absorption. Less common is a problem with the mechanisms that enable the blood vessels to absorb cerebrospinal fluid. This is often related to inflammation? of brain tissues from disease or injury.
• Overproduction. Rarely, cerebrospinal fluid is created more quickly than it can be absorbed.
• Neural tube defect – Another common cause of hydrocephalus is a neural tube defect (NTD). An open NTD, where the spinal cord? is exposed at birth and is often leaking CSF, is called a myelomeningocele, and is often referred to as spina bifida. This kind of NTD usually leads to the Chiari II malformation, which causes part of the cerebellum and the fourth ventricle to push downward through the opening at the base of the skull into the spinal cord area, blocking CSF flow out of the fourth ventricle and causing hydrocephalus.
• Arachnoid cysts – Congenital hydrocephalus can also be caused by arachnoid cysts, which may occur anywhere in the brain. In children, they’re often located at the back of the brain (posterior fossa) and in the area of the third ventricle. These cysts are filled with CSF and lined with the arachnoid membrane, one of the three meningeal coverings. Some arachnoid cysts are self-contained, while others are connected with the ventricles or the subarachnoid space. The fluid trapped by the cysts may block the CSF pathways, causing hydrocephalus.
• Dandy-Walker syndrome? – In Dandy-Walker syndrome, another cause of congenital hydrocephalus, the fourth ventricle becomes enlarged because its outlets are partly or completely closed and part of the cerebellum fails to develop. Dandy-Walker syndrome may also be associated with abnormal development in other parts of the brain and sometimes leads to aqueductal stenosis. In some instances, two shunts are placed in the child’s ventricles — one in the lateral ventricle and another in the fourth ventricle to manage the hydrocephalus.
• Chiari malformation – There are two types of Chiari malformation. Both types occur in the bottom of the brain stem where the brain and spinal cord join. The lowest portion of the brain is displaced and is lower than normal pushing down into the spinal column.
• Intraventricular hemorrhage – An intraventricular hemorrhage, which most frequently affects premature newborns, may cause an acquired form of hydrocephalus. When small blood vessels alongside the ventricular lining rupture, blood may block or scar the ventricles or plug the arachnoid villi, which allow CSF to be absorbed. When the CSF can’t be absorbed, hydrocephalus results.
• Meningitis – Meningitis is an inflammation of the membranes of the brain and spinal cord. Caused by a bacterial? or (less frequently) viral infection, meningitis can scar the delicate membranes called meninges that line the CSF pathway. An acquired form of hydrocephalus may develop if this scarring obstructs the flow of CSF as it passes through the narrow ventricles or over the surfaces of the brain in the subarachnoid space.
• Head injury – A head injury can damage the brain’s tissues, nerves, or blood vessels. Blood from ruptured vessels may enter the CSF pathway, causing inflammation. Sites of CSF absorption might then be blocked by scarred membranes – meninges – or by blood cells. The CSF flow is restricted, and hydrocephalus develops.
• Brain tumors – In children, brain tumors most commonly occur in the back of the brain which is referred to as the posterior fossa. As a tumor grows, it may fill or compress the fourth ventricle, blocking the flow of CSF and causing hydrocephalus. A tumor somewhere else in the brain might also block or compress the ventricular system.
• Brain hemorrhage – bleeding inside the brain.
• Brain lesions – areas of injury or disease within the brain. There are many possible causes, including injury, infection, exposure to certain chemicals, or problems with the immune system.
• Meningitis – inflammation of the membranes of the brain or spinal cord.
• Stroke – a condition where a blood clot or ruptured artery or blood vessel interrupts blood flow to an area of the brain.

Symptoms of Hydrocephalus

 Early symptoms may also include

• Eyes that appear to gaze downward;
• Irritability;
• Seizures;
• Separated sutures;
• Sleepiness;
• Vomiting.

Symptoms of congenital hydrocephalus (present at birth):

• breathing difficulties
• arm and leg muscles may be stiff and prone to contractions
• some developmental stages may be delayed, such as sitting up or crawling
• the fontanel, the soft spot on the top of the head, is tense and bulges outward
• irritability, drowsiness, or both
• unwillingness to bend or move the neck or head
• poor feeding
• the head seems larger than it should be
• the scalp is thin and shiny and there may be visible veins on the scalp
• pupils of the eyes may be close to the bottom of the eyelid, sometimes known as “the setting sun”
• there may be a high-pitched cry
• possible seizures
• possible vomiting

Symptoms of acquired hydrocephalus, which develops after birth, are

• rarely, bowel incontinence
• confusion, disorientation, or both
• drowsiness and lethargy
• headaches
• irritability, which may get worse
• lack of appetite
• nausea
• central nervous system infections such as meningitis, especially in babies
• bleeding in the brain during or shortly after delivery, especially in babies born prematurely
• injuries that occur before, during, or after delivery
• head trauma
• central nervous system tumors
• personality changes
• problems with eyesight, such as blurred or double vision
• seizures or fits
• urinary incontinence
• vomiting
• walking difficulties, especially in adults

Symptoms of normal pressure hydrocephalus. Signs and symptoms may take many months or years to develop.

• Changes in gait – The person may feel as if they are frozen on the spot when taking their first step to start walking. They may appear to shuffle rather than walk.
• Normal thinking process slows down – The person may respond to questions more slowly than normal, there may be delayed reactions to situations. The individual’s ability to process information slows down.
• Urinary incontinence – This usually comes after changes in gait.

Symptoms that may occur in older children can include

• Brief, shrill, high-pitched cry;
• Changes in personality, memory, or the ability to reason or think;
• Changes in facial appearance and eye spacing;
• Crossed eyes or uncontrolled eye movements;
• Difficulty feeding;
• Excessive sleepiness;
• Headache;
• Irritability, poor temper control;
• Loss of bladder control (urinary incontinence);
• Loss of coordination and trouble walking;
• Muscle spasticity (spasm);
• Slow growth (child 0–5 years);
• Slow or restricted movement;
• Vomiting.

Older children

• short, high-pitched cries
• personality changes
• changes in facial structure
• crossed eyes
• headaches
• muscle spasms
• delayed growth
• trouble eating
• extreme sleepiness
• irritability
• loss of coordination
• loss of bladder control
• larger than normal head
• trouble staying awake or waking up
• vomiting or nausea
• seizures
• problems concentrating

Young and middle-aged adults

• chronic headaches
• loss of coordination
• difficulty walking
• bladder problems
• vision problems
• poor memory
• difficulty concentrating

Diagnosis of Hydrocephalus

Examination in infants may reveal the following findings:

• Head enlargement (head circumference ≥98th percentile for age), especially crossing percentiles on the growth chart
• Dysjunction/splaying of sutures
• Dilated scalp veins
• Tense/bulging fontanelle
• Setting-sun sign – Characteristic of increased intracranial pressure (ICP); downward deviation of the ocular globes, retracted upper lids, visible white sclerae above irises
• Increased limb tone (spasticity preferentially affecting the lower limbs)

Children and adults may demonstrate the following findings on physical examination

• Papilledema (optic nerve swelling) – although this does not develop acutely
• Failure of upward gaze – Due to pressure on the tectal plate through the suprapineal recess; the limitation of upward gaze is of supranuclear origin
• Unsteady gait
• Large head
• Unilateral or bilateral sixth nerve palsy (secondary to increased ICP)
• Children may also exhibit the Macewen sign, in which a “cracked pot” sound is noted on percussion of the head.

Patients with NPH may exhibit the following findings on examination

• Normal muscle strength – no sensory loss
• Increased reflexes and Babinski response in one or both feet – Search for vascular risk factors (causing associated brain microangiopathy or vascular Parkinsonism), which are common in NPH patients
• Variable difficulty in walking – May have mild imbalance to inability to walk or to stand; the classic gait impairment consists of short steps, wide base, externally rotated feet, and lack of festination (hastening of cadence with progressively shortening stride length, a hallmark of the gait impairment of Parkinson disease)
• Frontal release signs (in late stages) – Appearance of sucking and grasping reflexes

Testing of Hydrocephalus

No specific blood tests are recommended in the workup for hydrocephalus. However, consider genetic testing and counseling when X-linked hydrocephalus is suspected, and evaluate the CSF in posthemorrhagic and postmeningitic hydrocephalus for protein concentration and to exclude residual infection.Obtain electroencephalography in patients with seizures.

Imaging studies of Hydrocephalus

The following imaging studies may be used to evaluate patients with suspected hydrocephalus

• Computed tomography (CT) scanning – To assess size of ventricles and other structures
• Magnetic resonance imaging (MRI) – To assess for Chiari malformation or cerebellar or periaqueductal tumors
• Ultrasonography through anterior fontanelle in infants – To assess for subependymal and intraventricular hemorrhage; to follow infants for possible progressive hydrocephalus
• Skull radiography – To detect erosion of sella turcica, or “beaten copper cranium” (or “beaten silver cranium”)—the latter can also be seen in craniosynostosis; (after shunt insertion) to confirm correct positioning of installed hardware
• MRI cine – To measure CSF stroke volume (SV) in the cerebral aqueduct; however, such measurements don’t appear to be useful in predicting response to shunting
• Diffusion tensor imaging (DTI) – To detect differences in fractional anisotropy and mean diffusivity of the brain parenchyma surrounding the ventricles; allows recognition of microstructural changes in periventricular white matter region that may be too subtle on conventional MRI
• Radionuclide cisternography (in NPH) – To assess the prognosis with regard to possible shunting—however, due to its poor sensitivity in predicting shunt response when the ventricular to total intracranial activity (V/T) ratio is less than 32%, this test is no longer commonly used

Treatment of Hydrocephalus

Procedures to draw off fluid

The following are possible procedures

• A spinal tap – may be done if the opening between your baby’s ventricle and spinal cord is partially blocked. The blockage is often due to an intraventricular hemorrhage. The healthcare provider may also do a spinal tap if your baby’s body is making too much CSF. Your healthcare provider inserts a small needle into your baby’s back, into the fluid-filled space surrounding the spinal cord. Some CSF is drawn out with this needle. This may relieve some of the pressure on the ventricle, allowing the rest of the fluid to drain.
• A ventricular tap – may be done if the opening between the ventricle and spinal cord is completely blocked. The healthcare provider places a device similar to a rubber stopper into your baby’s skull. This allows access to the ventricle. A healthcare provider can then draw fluid out of the ventricle with a needle. This may be done as a temporary solution while waiting for the blockage to go away.
• A ventricular peritoneal (VP) shunt – is a tube that your healthcare provider places inside your baby’s brain. The tube is connected to a catheter (thin, flexible tube) that is tunneled through the body to the stomach. The shunt draws fluid off the brain. The fluid then travels through the catheter and drains into the stomach, where it is soaked up by the body. The shunt and catheter are enclosed under the skin. They can’t be seen from the outside. They’re permanent, but will need to be replaced as the baby grows.

Surgery of Hydrocephalus

• Ventriculoperitoneal (VP) –  shunt (most common)
• Ventriculoatrial – (VA) shunt (or “vascular shunt”)
• Lumboperitoneal shunt – Only used for communicating hydrocephalus, CSF fistula, or pseudotumor cerebri)
• Torkildsen shunt (rarely) – Effective only in acquired obstructive hydrocephalus (ventriculocisternostomy)
• Ventriculopleural shunt (second-line therapy)  Used if other shunt types contraindicated

Rapid-onset hydrocephalus with ICP is an emergency. The following procedures can be done, depending on each specific case:

• Ventricular tap in infants
• Open ventricular drainage in children and adults (EVD, external ventricular drain)
• Lumbar puncture (LP) in posthemorrhagic and postmeningitic hydrocephalus
• VP or VA shunt

Repeat LPs can be performed for cases of hydrocephalus after intraventricular hemorrhage (which can resolve spontaneously). If reabsorption does not resume when the CSF protein content is less than 100 mg/dL, spontaneous resorption is unlikely to occur. LPs can be performed only in cases of communicating hydrocephalus.

Alternatives to shunting include the following

• Choroid plexectomy or choroid plexus coagulation
• Opening of a stenosed aqueduct
• Endoscopic fenestration of the floor of the third ventricle (however, contraindicated in communicating hydrocephalus)

A care team for children may include a

• Pediatrician or physiatrist, who oversees the treatment plan and medical care
• Pediatric neurologist, who specializes in the diagnosis and treatment of neurological disorders in children
• Occupational therapist, who specializes in therapy to develop everyday skills
• Developmental therapist, who specializes in therapy to help your child develop age-appropriate behaviors, social skills and interpersonal skills
• Mental health provider, such as a psychologist or psychiatrist
• Social worker, who assists the family with accessing services and planning for transitions in care
• Special education teacher, who addresses learning disabilities, determines educational needs and identifies appropriate educational resources

References