Hydrocephalus Q and A

 

1. My close friend has developed hydrocephalus due to a colloid cyst on her third ventricle. What are the risks involved, regarding shunts? How long are they good for? What does the patient need to be aware of to monitor him/her self?

 

Answer: The risks of shunting are as follows (in descending order of frequency): Malfunction - the risk in children is 30-40% within one year, 60% within 5 years, and 80-85% within 10-12 years. Malfunction would potentially require that the shunt be changed - this would require an operation. Infection in 5-10% of cases, and requires that the shunt be removed in most instances (and a temporary drainage tube inserted for several days), the patient treated with intravenous antibiotics for a period of time, and the shunt replaced thereafter. Bleeding (which can, in rare instances, be in the brain itself) - less than 1% chance Injury to the brain - mostly related to bleeding if it occurs, and is very rare.

 

Injury to the chest or abdominal organs: extremely rare, occurring much less than 1% of the time. Patients with colloid cysts may or may not require a shunt. If the problem is one of blockage within one ventricle - one ventricle not communicating with another - the patient may benefit from endoscopic surgery to create a pathway between the 'blocked' ventricle and the other ventricles, with or without a concomitant shunt. Your neurosurgeon can tell you more information about this. The most common symptoms of shunt malfunction are headache, loss of appetite, nausea and vomiting.

 

2.       My son doesn't have any of the ''normal'' causes of hydrocephalus. Is it possible to never know what caused this?

 

Answer: Hydrocephalus can be due to a wide variety of causes. Congenital causes (failure of the passageways to open, brain malformations, etc.), scar, infections, tumours, and a wide variety of other causes may be the source. However, in many cases, particularly when hydrocephalus was present prenatally, the cause cannot ever be known with certainty.

 

3.       What is the difference between hydrocephalus and pseudotumour cerebri?

 

Answer: Pseudotumour cerebri is a condition in which there is an increase in intracranial pressure (pressure in the head) with headaches, visual changes, and papilloedema (swelling of parts of the retina where the optic nerve (the seeing nerve) exits through the back of the eyeball. We think of pseudotumour as occurring in overweight young women, but there are a variety of causes including certain medications such as oral contraceptives or the overuse of Vitamins (particularly Vitamin A, which is a fat soluble Vitamin and not easily eliminated from the body if large amounts are taken); steroid withdrawal: chronic sinus or ear infections; congestive heart failure: following neck surgery; blockage of the veins in the neck or venous sinuses in the head (rare); certain hormone disorders; lupus (an autoimmune disorder); and a variety of other possible causes.

 

Some, such as Vitamin A overuse and steroid withdrawal, are proven, others are simply thought to be possible causes with little evidence to support them. Unlike hydrocephalus, the ventricles (the fluid filled spaces in the brain) are SMALL rather than ENLARGED as they are in hydrocephalus. However, many of the other features of pseudotumour are similar to hydrocephalus, and it appears that pseudotumour and hydrocephalus may share a common pathophysiological mechanism in that in both there appears to be some blockage to the elimination of spinal fluid from the brain. Whereas in hydrocephalus, there may be an accumulation within the ventricles, enlarging them like a balloon, in pseudotumour cerebri this fluid may instead accumulate in the extracellular space (the spaces around each individual cell of the brain) rather than the ventricles.

 

This 'oedema' or swelling because of increased fluid in the brain itself compresses the ventricles rather than expanding them. Other people have suggested that blood flow may increase in the brain, but this is questionable and studies are contradictory. Finally, some people think that there may be an increase in the venous pressure in the head, which may account for some, but not all, cases of pseudotumour. The treatment for pseudotumour is sort of like treatment for hydrocephalus. Certain drugs may help some patients to decrease spinal fluid production, but these all have some pretty serious side effects. If this doesn't work, a shunt may be performed like in hydrocephalus. Another way to treat pseudotumour, particularly if visual problems are present is to make a hole (or fenestration) in the sheath that surrounds the optic nerve (the nerve from the eye back to the brain that makes you see). This fenestration allows some of the spinal fluid to escape and appears to effectively treat particularly the visual symptoms and blindness that can occur with pseudotumour.

 

4.       My 15 year old son received a shunt to treat an arachnoid cyst. He is having constant headaches that cannot be relieved with pain medication. Is this a common recovery process? How long does it take to adjust to pressure changes?

 

Answer: Patients with arachnoid cysts may experience headaches for several weeks after treatment. There may be several causes that must be sorted out. The most common cause is that the patient is adjusting to the new pressure (so-called overdrainage headaches) because the shunt is now withdrawing the spinal fluid from the cyst. These headaches are usually worse when the patient sits or stands because the shunt 'siphons' the fluid out of the cyst to a greater degree when the patient is upright. Over a period of weeks this usually resolves; occasionally an anti-siphon device may need to be added to the shunt to treat this if it doesn't resolve on its own. However, since most patients resolve on their own, most neurosurgeons suggest a period of observation before undertaking this additional surgery.

 

The second potential cause of headaches may be that the shunt is blocked and may need to be replaced. A third cause may be that the shunt is infected. Other, much less common causes, are bleeding into the cyst or other parts of the head, or some other problem related to the cyst or to surgery. Usually the character and timing of the headaches suggest a cause; your neurosurgeon may indeed be right that the headaches will resolve on their own with time - if they are due to overdrainage. If they do not resolve, or are getting worse, you should ask your doctor about the possibility of shunt malfunction or infection. A CT scan is sometimes helpful in differentiating among some of these possibilities.

 

5.       Can climate change or altitude change cause headaches associated with hydrocephalus?

 

Answer: I know of no evidence that any changes in altitude or pressure will affect shunt function - if your shunt is indeed malfunctioning, it likely is simply a coincidence. Of course there are a variety of other causes of headaches, even in patients with hydrocephalus. For example, a change in altitude may cause a change in sinus pressure which could cause headaches. There may be many other causes of headaches. However, a shunt malfunction can obviously be a serious problem, and if your headaches continue, you must consult a neurosurgeon to evaluate your shunt to make certain that it is working properly.

 

6.       Can shunts move a little bit from the place it was? What are the statistics of happening this? Can you re-operate to do adjustments or to unclog the shunt? How do neurosurgeons decide where to place the valve?

 

Answer: Shunts malfunction in children at the rate of 30-40% within the first year, 60% within 5 years, and 85% within 10 years. Adults with hydrocephalus have lower shunt malfunction rates, for reasons that are unknown. Shunt malfunction usually is due to blockage of the catheter that is within the brain. Blockage is usually with either tissue, blood, or other stuff (talc from the surgeon's glove, particles, etc.) that gets into the lumen of the shunt tube. Less commonly, the shunt becomes disconnected, or the other end (the part in the abdomen in the case of a ventriculo-peritoneal shunt, or the veins or heart in the case of a ventriculo-atrial shunt). The least common cause of shunt malfunction in most series is that the valve itself malfunctions.

 

If you are within 6 months of shunt insertion, you also need to consider the possibility of a shunt infection (95% of shunt infections become manifest within 6 months of surgery). With a ventriculo-atrial shunt, fevers, chills, headaches, vomiting, and other signs of shunt blockage are the rule. I assume you are asking what places one can place the other end of the tubing (rather than the valve, which usually is placed under the scalp). There are a few preferred drainage sites for shunts. The most common these days is the peritoneum (the abdominal cavity). This is the preferred site because, although the frequency of complications is about the same as with atrial shunts, the severity of these complications is less with peritoneal shunts.

 

However, atrial shunts have been used by neurosurgeons since the 1950s and are still very popular, although they are being used less frequently at this time. A third site is the pleural space (the chest cavity outside of the lungs), which, although it sounds bad, is actually a very easy place to place a shunt. In times past, atrial shunts were the most commonly placed shunts. However, peritoneal shunts have become the most popular in many hospitals, and pleural shunts are becoming a second most favourite site with many paediatric neurosurgeons (for children older than 5 years), the atrial shunts now having fallen to 'third place' on the list of favourite sites. Finally, if there is no other site in which to put a shunt, the gall bladder is a distant fourth favourite site.

 

7.       Has there ever been a case where there has been a connection between a facial nerve injury and hydrocephalus?

 

Answer: I know of no association between hydrocephalus and facial nerve injury, or between hydrocephalus and facial pain per se. One thing you should be aware of is that the facial nerve (the 7th cranial nerve) controls muscle movements (the so-called muscles of facial expression), but isn't generally involved in facilitating facial sensation or facial pain. Facial pain can have a wide variety of causes including injury to facial structures (the jaw, the maxilla or other facial bones, etc.), sinuses, ears, teeth, and a wide variety of other structures. Facial pain may also be associated with injury to the trigeminal nerve (the 5th cranial nerve), which provides sensation to the face. If this nerve is injured as a result of a facial injury, chronic pain may result. A neurosurgeon or someone skilled in the evaluation of face pain should be able to sort out these issues and decide what is the source of your pain.

 

8.       Are shunts susceptible to flus, colds, infections, etc? Can drainage rates be affect mental facilities? What test and treatments treatments are available if the previous question is affirmative?

 

Answer: Shunt malfunction can be manifest in a variety of ways. The usual signs and symptoms headaches, nausea and vomiting - are obviously the most common, but some people (about 4-7% in most series) have a seizure as a manifestation of a shunt malfunction. Others can present with loss of their mental faculties, cognition, memory loss, or change in personality. A shunt usually works pretty steadily, although there are fluctuations depending upon your position (whether you are lying down or standing up), the type of shunt, and a number of other factors. Although I have heard from many people that 'shunts can malfunction or function differently in the face of an infection', this is anecdotal evidence, and I know of no scientific evidence that this is so. A shunt is evaluated by a CT scan to check the size of the ventricles. Most patients with shunt malfunction have an increase in size of their ventricles which confirms the shunt malfunction.

 

In addition, a series of X-rays (a shunt continuity study or shunt series) may be performed to assess whether the shunt has become broken or disconnected. Unfortunately, a minority of patients may have little or no change in the size of their ventricles despite signs and/or symptoms of shunt malfunction. If these tests are normal and there is still a clinical suspicion, the next step in evaluating the shunt is usually to perform a shunt tap to measure the pressure in the head. This is done by placing a small needle into the shunt under the skin and measuring the pressure directly. In most cases, a combination of these tests can identify or exclude a shunt malfunction. The last resort is to directly measure the pressure in the head by placing an intracranial pressure monitor (a small fibre optic catheter which is placed through a small drill hole in the skull and used to measure pressure for 1 or more days). However, this is fairly involved and is usually not necessary in most cases.

 

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