Complications and malfunctions of shunt systems

Sadly, much of my inspiration for blogs on hydrocephalus come about because of a bad situation that occurs either to me or one of my friends with hydrocephalus. This is one of those occasions. Early Monday morning, one of my friends passed away after tubing from his shunt broke and came into contact with his brain stem. You might wonder how such a thing could happen. So named because of its stem-like appearance, the brain stem is where the base of the brain attaches to the spinal cord. (WebMD, 2016) it's main job is to control the flow of messages between the brain and the rest of the body; it is also controls basic body functions such as breathing, heart rate, and blood pressure.

What can go wrong?

Hydrocephalus is treated by surgically implanting a shunt into the patient's brain, however, complications can develop or the shunt can malfunction. Interestingly, in pediatric patients, there is a fifty percent (50%) shunt failure rate after only two (2) years. The exact cause for this is unclear.

Shunt malfunction

A partial or complete blockage of the shunt system is know as a shunt malfunction. (Hydrocephalus Association, 2014) When this occurs, cerebrospinal fluid builds up and causes symptoms similar to those seen with untreated hydrocephalus.

The blockage is caused by a build-up of blood cells, tissue, or bacteria and occur anywhere system. Both the proximal catheter (which is implanted in the brain) as well as the distal catheter (which can be implanted either in the ventricle of the heart, the peritoneal cavity of the abdomen, or, rarely, in the spine) can be blocked. These blockages originate in either the choroid plexus or the ventricles of the brain. Generally speaking, in adult hydrocephalus patient's, blockages occur with greater frequency in the distal catheter.

Generally, a shunt system is durable, however, components of the system (pictured below) can become disengaged or fractured as the result of normal wear -- particularly in children due to their growth spurts. Also, although rare, a valve can fail due to a mechanical malfunction.

Shunt infection

A shunt infection usually occurs as a result of the person's own bacterial organisms and isn't caused by be exposed to someone who is sick. The most common bacterium to cause an infection is Staphlococcus epidermis. which is normally present on a person's skin as well as in the hair follicles and in the sweat glands. This type of infection is typically seen one (1) to three (3) months after shunt implant surgery, but can occur up to six (6) months later. In persons with a ventriculoperitoneal (VP) shunt is a shunt infection that occurs secondarily to an abdominal infection. Lastly, in persons treated with a ventriculoatrial shunt (which empties into the right ventricle of the heart) a generalized infection can occur.

Other shunt complications

Over drainage causes the ventricles to decrease in size and become slit-like (see: What is slit ventricle syndrome (SVS)?) due to the brain and meninges pulling away from the skull. SVS is most common in young adults who have been shunted since early childhood. A telltale symptom of SVS is severe intermittent headache that improves when the person is laying down.

Under drainage does the exact opposite and causes the ventricles to swell. When this occurs, the shunt might not be able to relieve the hydrocephalus symptoms. In order to restore a balanced flow of CSF, it might be necessary to implant a new shunt with a more accurate pressure valve. If the person has a shunt with programmable valves, the balance of flow can be restored by resetting the opening pressure.

 Subdural hematoma (pictured at left) occurs when a broken blood vessel in the meninges becomes trapped between the skull and the brain. It is seen most commonly in adults with Normal pressure hydrocephalus (NPH) and requires surgical intervention to correct it.

Multiloculated hydrocephalus is located (isolated) CSF compartment in the ventricular system that is enlarged and not in communication with the normal ventricle. It can be the result of trauma at birth, neonatal intraventricular hemorrhage, Ventriculitis, over drainage, or other conditions. This complication might be difficult to identify because it is typically seen in infants and children who might be neurologically compromised. Treatment involves surgery to implant ventricular catheters, Craniotomy and fenestration (opening) of the intraventricular loculations. (John Hopkins Medical, N.D.)

Seizures can sometimes occur in people (both adults and children) with hydrocephalus. Medical research has shown there is NO CORRELATION (emphasis added) between the site a shunt implant (or the number of revisions a person has) and a increased risk of developing seizures. The one possible exception to this involves children who have significant cognitive delays or motor disabilities are at higher risk (italic emphasis added) are more likely to experience seizures compared to children without similar delays or disabilities. Research has also shown that seizures aren't likely to occur at the time a shunt malfunctions, and the more likely explanation for the occurrence of a seizure disorder is related to an associated malformation of the cerebral cortex.

Abdominal complications can also occur in patient's with hydrocephalus who are treated with a shunt. This is due to the fact the distal catheter of a ventriculoperitoneal (VP) shunt is placed in  the peritoneal cavity of the abdomen. Although complications associated with a VP shunt aren't less in frequency (when compared to a ventriculoatrial [VA] shunt), they tend to be less severe and have a lower mortality rate. These complications can include: peritoneal pseudocysts, loss of the distal catheter, bowel perforations, and hernias.

What is congenital aqueductal stenosis and hydrocephalus? (Part 2)

How is it diagnosed?

A diagnosis of hydrocephalus resulting from congenital stenosis of the aqueduct of Sylvius is typically suspected based on the presence of characteristic signs and symptoms (found in a physical exam) and/or imaging of the brain. Evidence of a mutation in the L1CAM gene can be used to confirm the diagnosis

How is it treated?

The treatment of HSAS is dependent on the signs and symptoms presented by each individual. For example, in persons with hydrocephalus, treatment involves brain surgery to implant a shunt. If it causes the child to have intellectual disabilities, a combination of early intervention and enrollment in special education classes might be recommended.

BIBLIOGRAPHY

National Institutes of Health (N.D.) Hydrocephalus due to congenital stenosis of aqueduct of Sylvius. Retrieved on February 7, 2018 from https://rarediseases.info.nih.gov/diseases/434/hydrocephalus-due-to-congenital-stenosis-of-aqueduct-of-sylvius

National Institutes of Health (2018). L 1 syndrome. Retrieved on February 7, 2018 from https://ghr.nlm.nih.gov/condition/l1-syndrome.

Online Mendelian inheritance in men (OMIM) (ND). MASA syndrome. Retrieved on February 7, 2018 from http://www.omim.org/entry/303350.

What is congenital aqueductal stenosis and hydrocephalus? (Part 1)

In yesterday's blog - as well as a blog I wrote last year - I touched on aqueductal stenosis. Today, I want to look at congenital aqueductal stenosis and how it causes hydrocephalus. This is a condition that is "near and dear" to me because I found out back in October that I suffer from the condition. Most likely, according to the neurosurgeon, that is what caused my hydrocephalus.

What is hydrocephalus due to congenital aqueductal stenosis (HSAS)?

Hydrocephalus due to congenital aqueductal stenosis (HSAS) is a form of L1 syndrome -- a group of conditions that primarily affects the nervous system and occurs almost exclusively in males. They (L1 syndrome disorders) can vary in severity and include, from most severe to least severe, x-linked hydrocephalus with aqueductual stenosis (HSAS), Spastic paraplegia 1, and x-linked complicated corpus callosum agenesis.

HSAS is an acronym for the characteristic features of the condition: a buildup of cerebrospinal fluid (CSF) in the brain (hydrocephalus) which is often present from birth, muscle stiffness or spasticity, adducted thumbs (meaning they are permanently bent inward toward the palms), and a narrowing (stenosis) of the aqueduct of Sylvius.

How is HSAS passed from parent to child?

HSAS is inherited in an X-linked recessive manner. This means the responsible gene is located on the X chromosome -- one of two sex chromosomes; the other sex chromosome is the Y chromosome. Females have two (2) X chromosomes in each cell while the male has an X chromosome and a Y chromosome in each cell.

One of the female's X chromosomes is "turned off" meaning all of the genes on that chromosome are inactive. If a female has a change (mutation) in the gene on one of their X chromosomes, she is considered to be a carrier but will not exhibit the symptom(s) associated with the mutation. In those rare cases, where the female does experience symptoms, they are generally milder than those experienced by the males. In contrast, a male has only one (1) X chromosome, so, if he inherits a mutation on that chromosome, he will be symptomatic.

Absence of the Aqueduct of of Sylvius

Introduction

Yesterday afternoon I checked in with one of my Facebook hydrocephalus support group and the question came up whether it is possible for the aqueduct of Sylvius can be completely absent from the brain. After some early morning research, the answer to that question is "no". Let me explain what it does and you will better understand why this is the case.

The aqueduct of Sylvius serves as the communicator between the third and fourth ventricles of the brain. Located just above the hypothalamus (pictured at left) in the mid-brain, the Aqueduct of sylvius measures 15 to 18 millimeters long by 1 to 2 millimeters in diameter and is shaped like the neck of a swan. It contains the nuclei of the third and fourth cranial nerves.

What can go wrong?

In 1935, Lysholm suggested that a kink in the aqueduct of Sylvius was considered pathogonomic of space occupying lesions of the posterior fossa. Three years later, in 1938, Hyndman wrote about four (4) cases where tumors were located either in or pressing on the cerebellar vermis causing a kinked aqueduct of Sylvius. This was later reenforced by another researcher who hypothesized that a kink could be a variation of the normal. Below is a case study that seems to agree with that finding.

Case study # 1
While hospitalized for an unrelated issue, a 70 year-old man presented with the clinical triad of dementia, gait instability, and urinary incontinence. A radionuclide cisternagram strongly pointed to normal pressure hydrocephalus since the test demonstrated entrance of the nuclide into the ventricles with no flow over the cerebral convexities. pneumoencephalography indicated a kinked aqueduct, however, there was no displacement of the fourth ventricle. It also showed gross enlargement of the lateral ventricles.

Case study # 2
A 16 year-old boy presented with headache, double vision, nausea, and vomiting. Examination discovered bilateral papiledema (swelling of the optic nerve) accompanied by paresis of the upward gaze. (Just as an FYI, papiledema and paresis of the upward gaze are also characteristic symptoms in hydrocephalus patients -- especially those, such as myself who are unshunted.) A radiograph of the skull identified a Calcified pineal gland and a pneumoencephalagram indicated a kink in his Aqueduct of Sylvius. Based on these findings - and the lack of displacement of the fourth ventricle (which would be indicative of a tumor), he was diagnosed with Pinealoma -- a type of tumor that develops on the pineal gland.

Conclusion

Modern day research has disproved Lysholm's hypothesis that a kink in the aqueduct of Sylvius is pathognomonic - meaning that it is indicative - of space occupying lesions of the posterior fossa. It is now evident that a kink can also occur in persons with other cranial abnormalities such as those pointed out in the case studies cited above.

What are the different types of shunts and how do they work?

Introduction

Yesterday I was working on a blog for my Facebook hydrocephalus support group and one of the group admins (adminstrators) to write a blog discussing the different types of shunts -- here it is. Let's start by looking at the different types of shunts, their pathway, their inflow location, and their drainage location.

Shunt pathway              Type      inflow location      Outflow location

Ventriculo-peritoneal    VP           Ventricle (brain)     Peritoneal cavity
Ventriculo-atrial             VA           Ventricle (brain)     Right atrium of the heart
Ventriculo-pleural          VPL         Ventricle (brain)    Pleural cavity
Lumbo-peritoneal          LP            Lumbar spine        Peritoneal cavity

Now that I have probably confused you, let me see if I can make the "Inflow location" and "outflow location" make sense. The inflow catheter of the shunt system (also referred to as the proximal end) is the location where the Cerebropspinal fluid (CSF) is introduced into the shunt system. The outflow catheter of the shunt system (also referred to as the distal end) is the location that the CSF empties into to be reabsorbed by the body.

How does a shunt system work?

Also known as a "CSF diversion device", shunts have been used for 68 years (the first one was successfully implanted in 1949) to divert CSF from the ventricles within either the brain or subarachnoid space(s) to another part of the body where it can be reabsorbed. Implantation of a shunt creates an alternate pathway for the CSF which is constantly produced within the brain and usually (italics added for emphasis) restores the balance between CSF production, flow, and absorption when one (or more) of these functions becomes impaired. There are valves within the shunt's pathway that act as "on-off switches" when the Differential pressure (DP) - the pressure difference across the valve - exceeds the valve's opening pressure.

My sources:

Hydrocephalus Association (shunt fact sheet)
Neuropathology: an illustrative interactive course

Recovery after VP shunt implant surgery (part 2)

Yesterday, we looked at placement and recovery following ventriculo-peritoneal surgery. Today, we will look at recovery once the patient gets home and potential complications that can occur.

Recovery at home

After surgery, the patient may experience tenderness in their neck or belly since these are both incision sites. Overall, shunt implant surgery is VERY safe procedure, however, complications can occur both during the procedure and during the recovery period. These include: 1) Infection either in the brain or in the shunt itself; 2) Bleeding inside the brain; 3) Damage to brain tissue; or 4) Edema (swelling) of the brain.

Additionally, in rare cases, patients might experience fever (>36.0 celsius), headache, abdominal pain, fatigue, or a spike in blood pressure (or experiencing symptoms similar to before the shunt was implanted) are indications of either an infection, shunt malfunction, or shunt failure. THESE ARE POTENTIALLY LIFE-THREATENING -- NOTIFY YOUR DOCTOR OR PROCEED TO THE NEAREST EMERGENCY DEPARTMENT.

What is the prognosis for implant patients?

Shunting is successful in reducing intracranial pressure (ICP) in most patients. One drawback to the shunting process is the fact that it generally (italics added) has to be replaced after several years -- particularly in small children. For infants, the anticipated life of a shunt is two (2) years. After age two and in adults with a shunt, this increases to eight (8) or more years. (I have a friend whose shunt is 37 years-old). Shunt systems require frequent monitoring to prevent: 1) Mechanical failure; 2) Obstruction; or 3) Infection.

My sources:

What is a vetriculoperitoneal shunt? (Healthline.com)

Recovery after VP shunt implant surgery (part 1)

Some background . . .

A few minutes ago on one of my Facebook hydrocephalus support groups, we had a mom ask about recovery after shunt implant surgery. Her infant son was several days post surgery and, while his incision was healing well, the group was concerned about abnormal swelling around the incision site. Being the group's resident "egg-head" (pun intended) I sprang into action to find the answers to her questions. This blog is the results of my research.

What is a VP shunt?

A ventriculo-peritoneal (VP) shunt is used to remove excess cerebrospinal fluid (CSF) from the skull of patients suffering from Hydrocephalus. It is so named because the distal end of the shunt is placed in the peritoneal cavity of the abdomen where it empties and the CSF is reabsorbed by the body.

How is the implant done?

Surgical implant of a VP shunt requires the neurosurgeon to make one (1) burr (drill) hole and  two (2) incisions: a hole is drilled (burred) using a surgical drill behind the patient's ear to place the proximal end of the shunt into the affected ventricle of the patient's brain, one incision is made into the neck to aid in the placement of the tubing into the chest / abdomen area; and one incision is made in the patient's abdomen to receive the distal end of the shunt. Barring any unforeseen complications, the procedure usually takes about (italics added) 1.5 hours.

Are there risks associated with shunt implant surgery?

Simply put, as with any surgical procedure, there are risk involved. Generally, however, the benefits of shunt implant surgery out-weigh the risks. In addition to breathing issues, possible reaction to medication(s), and bleeding or blood clots, shunt implant surgery carries several unique risks: 1) Bleeding from the brain or blood clot(s); 2) Swelling of the brain; 3) Development of bowel perforation (a hole) following the surgery; 4) Leakage of CSF fluid under the skin; 5) Infection of the shunt, brain, or in the abdomen; 6) Damage to brain tissue; or 7) Seizures.

In order to prevent potential complications (and to facilitate faster healing) the patient might (italics added) be required to lie flat for the first 24-hours after the surgery. The duration of the post-operative hospital stay is dependent on why the shunt was originally needed. For example, a shunt being placed to try congenital hydrocephalus might not require as long of a hospital stay as one for a shunt placed to treat Acquired hydrocephalus which is caused by a traumatic brain injury (TBI) or an infection. The health care team will carefully monitor the situation.

My sources:

1) Ventriculo-peritoneal shunting           (Medine.com)
2) What is a vetriculoperitoneal shunt? (Healthline.com)