Congenital Aqueductal Stenosis (Hydrocephalus)

Congenital diseases are present by birth. Congenital aqueductal stenosis (Hydrocephalus) is the blockage in the cerebrospinal fluid flow in the ventricular system of the brain. Sylvius aqueduct (fluid-filled canal) shrinks, so the flow of CSF disturbs/is blocked.

Introduction

Hydrocephalus is a disease in which cerebrospinal fluid (CSF) accumulates in the brain. It may increase pressure inside the skull. The stenosis of the aqueduct is a narrowing or compression of the aqueduct of the brain that restricts the flowing of CSF in the tubular system of the brain.

Disturbance in the aqueduct can lead to hydrocephalus, it leads to congenital and/or obstructive hydrocephalus. The aqueduct of Sylvius is a slender channel, about 15 mm in range, that connects the third and the fourth ventricle. It is present in the dorsal midbrain, encircled by the periaqueductal gray matter.

The area of the pathway of cerebrospinal fluid is 0.5mm2 in children and in adults 0.8mm2. Narrowing of aqueducts is responsible for causing hydrocephalus in children (6–66%) and in adults (5–49%). During the early stages of development, the closure of the neural tube is the larger portion of the neural tube.  It becomes an adult during fetal development due to the thickening of nuclear masses and the fiber tract of mesencephalon.  

What are types of hydrocephalus

These are the following classes of this disease.

  • Congenital hydrocephalus
  • Compensated hydrocephalus
  • Acquired hydrocephalus
  • Normal pressure hydrocephalus

Congenital hydrocephalus

This condition is a baby born, caused by environmental and genetic factors during early development stages. The diagnosis of hydrocephalus is done by ultrasound before a child’s birth. It is caused due to the diffusion of cerebrospinal fluid in brain cavities. The males affected with this disease may have bent thumbs and are intellectually disabled.

Compensated hydrocephalus

It is the type of hydrocephalus that could be present at birth and may be treated during the first few months of childhood, but it remains for many years but its symptoms do not reveal for many years.

It is also observed in older people which is caused due to loss in brain volume due to aging or may be caused by a disorder that shrinks the brain cells.

Acquired hydrocephalus

It may be caused after birth due to problems in the nervous system such as nerve damage or problems of the central nervous system. It is acquired after birth due to tumors, the Head injury which blocks the absorption of cerebrospinal fluid in the brain.

 It can be acquired at any stage of life. It may affect 1 out of 1000 newborns. Its symptoms in older children may include blur vision or double vision, headache and memory loss, etc. It can be treated by eliminating the causes of symptoms such as tumor removal by surgery or by inserting a shunt.

Normal-pressure hydrocephalus

It is the form of communicating hydrocephalus. It is the condition in the older adults in which the cavities of the brain become large in size and the pressure of fluid does not increase within ventricles. The only way for it to be diagnosed is the continuous readings of intraventricular pressure. It may cause a disturbance in urinary flow and abnormal functioning of the lower limb.

Obstructive hydrocephalus

It is commonly caused due to aqueductal stenosis. There is a channel that connects the ventricles of the brain and it passes from the midbrain. And if there is a problem in the flow of cerebrospinal fluid then it leads to the obstructive hydrocephalus.

What are causes of hydrocephalus

The common causes are

  1. Tumor compression
  2. Narrowing of the aqueduct
  3. Septum formation
  4. Gliosis
  5. Forking

Tumor compression

In the midbrain region, a tumor grows which blocks the passage of CSF. Tumor forms in the pineal region of the midbrain and present at the level of the aqueduct of Sylvius. As the size of a tumor increases, it blocks the flow or movement of cerebrospinal fluid.

Narrowing of the aqueduct

The tube of the aqueduct is sometimes narrowed which causes disturbance in the CSF passage. It can be affected by birth and it may cause congenital aqueduct stenosis. Abnormal development can cause the folding of a neural plate and results in the narrowing of the neural tube from birth.

Septum formation

The membrane of the glial cell develops across the way and damages the flow of CSF. This membrane normally forms at the lower portion of the aqueduct to cause pressure to the cells of the upper part. This exerts pressure on the upper part of the aqueduct due to the excess flow of cerebrospinal fluid.

Gliosis

In this condition, the aqueduct is half/partially blocked. Gliosis is also caused by many other diseases of the central nervous system. To overcome the partial blockage of the aqueduct, increase the flowing rate of cerebrospinal fluid into the normal range. 

This phenomenon increases the pressure in the third ventricle and this results in increasing the velocity of cerebrospinal fluid. This causes stress in the aqueduct and damages the epithelial cells and results in gliosis and an increase in the size of glial cells.

  • Stenosis of aqueduct
  • Defect in neural tube
  • Arachnoid cysts
  • Dandy-walker syndrome
  • Chiari malformation

What are Causes of acquired hydrocephalus

What are Symptoms of acquired hydrocephalus

  • Headache
  • Cognitive difficulty
  • Consciousness
  • Tremors
  • Deformation of midbrain

Headache

This disorder may cause headaches in adults and children. This may happen in the early morning while waking up and may start at night time. The headache is resulting in the patient due to the increase in intracranial pressure. Sometimes it causes thunderclap headaches. It occurs due to the disturbed flow of cerebrospinal fluid.

Cognitive difficulty

It varies according to stages of the disorder. This symptom is mostly found in children who correspond with age. In this case, the child may be unable to spike and also unable to control movements. It may affect short- and long-term memory. Emotional imbalance is another symptom of cognitive difficulty. It also includes a lack of imbalance in posture.

Consciousness

It deteriorates the level of consciousness of patients and leads to coma/death.

Tremors

This is also another symptom but tremors are not common. It includes shaking of voice, uncontrollable shaking of the body for a short time.

Deformation of midbrain

Deformation of the midbrain is also another sign of stenosis. The CSF puts pressure on bones which cause deformation.

Other symptoms of hydrocephalus include.

  • Neck pain
  • Feeling sick
  • Sleepiness and can progress to coma
  • Change on mental conditions such as confusion
  • Blurred vision
  • Lost balance
  • Affected person can’t control his bladders
  • Abnormalities in eye movement
  • Paralysis of upward gaze
  • Abnormal pupil

Complications

This is usually caused by blockage of CSF in ventricles and space over the brain. It also occurs due to overflow or overproduction of cerebrospinal fluid or some other complications such as injury to brain cells and infections.

Due to overproduction of cerebrospinal fluid, the compression arises in the brain and causes neurological symptoms. These symptoms arise earlier in adults but in children or newborns, it may arise with the delay because their skull bone takes some time to fuse and the children having this condition have large heads and the other symptom is gazing downward continuously. The compression of the brain may cause many serious complications.

What is Diagnosis of hydrocephalus

  •  Magnetic Resolution Imaging (MRI)
  • CT scan
  •  Phase-contrast MRI
  •  Ultrasonography 

MRI imaging

MRI is beneficial to diagnose the abnormalities related to CSF flow. But also tells about the measures followed before surgery. It helps in managing the flow of CSF flow. This is a method of detecting abnormalities. It can visualize the entire length of the aqueduct to detect tumors, deformation, or any other cause.

CT scan

This is another technique to visualize the internal parts of the body without incision. A scan of the brain is performed to detect the flow of CSF in the aqueduct. It was used after shunt treatment to analyze the ventricle size. It provides more details than standard X-rays and can be a lifesaving tool by diagnosing hydrocephalus. The wavelength of the CT scan is 100 to 500 times greater than X-ray. Some patients cannot have CT scans due to some medical issues. CT scan is not common for children.

Phase-contrast MRI

This is an advanced technique than MRI to analyze the CSF flow in the ventricular system. In this technique, multiple images are taken in one cycle to determine the obstruction in CSF flow.

Ultrasonography

This technique is also used to diagnose the disease. It is used as initial techniques to diagnose the disorder because it is a simple and low-risk procedure. It may detect the hydrocephalus before the baby’s birth during the routine prenatal examination.

Parental testing

To test the parents the MRI, CT scan, and some other genetic testing is one to check the possibility of disease.

What is Treatment of hydrocephalus

The main purpose of all treatment methods is to open the blocked aqueduct and allow the continuous flow of CSF to reduce the pressure.

  • Surgical removal
  • Extracranial shunt
  • Endoscopic third ventriculostomy

Surgical removal

The surgery is performed to remove the tumors to normalize the CSF flow.

 Complications of surgery

Surgery causes many complications. Shunt stops the flow of cerebrospinal fluid and poorly regulates the fluid; it may cause many infections and mechanical problems. It may also cause internal bleeding. 

Extracranial shunt

This is also called cerebral shunts. This is mostly used in hydrocephalus patients. In this technique, a catheter is used to remove fluid to reduce pressure. There are various types of shunts according to the type of catheter or place of insertion of the catheter.

There are many problems linked with this treatment method such as it may cause over draining and under draining of cerebrospinal fluid. Over draining occurs when the pressure is too low.

Shunt complications

It may cause shunt malfunctioning, shunt failure, and shunt infection. The shunt can stop working if it disconnects. Due to disconnection cerebrospinal fluid again starts to accumulate and results in many problems. The rate of shunt failure is high, in 30% of people it is placed well during the first surgery and the rest of the people conduct many surgeries in their lifetime.

Infections due to shunt placement

These types of infections appear after some days or after months of surgery. These infections are common after shunt placement. The chances of these infections are 4-13% for every person that has gone through surgery.

Complications

It may cause brain damage but if the disease progresses by the time that damage could be permanent. It may cause learning procedures, speech problems, short term memory, and babies having this disorder. They cannot pay attention to some work and study. It may cause sensational problems such as epilepsy. It can cause severe effects on the physical coordination of different parts of the body. It may also affect the vision of the affected person.

 Other treatments

Some patients such as children may need some extra treatment depending on the severity and stages of the disorder. A care team for additional treatment may includes

Neurologist, provider of mental health, social worker, teacher of special education, occupational therapist and therapist, etc.

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