Paediatric Neurosurgery

Series 1. Posterior Fossa Tumour

This is an enhanced MRI of a child with a common posterior fossa tumour, a medulloblastoma. Although malignant, the cure rate in low risk patients can be as high as 70%. Total surgical removal is mandatory if one wants to be in the low risk category.

Series 2. Focal Brainstem Glioma

Brainstem gliomas are primary brain tumours that arise from a part of the brain called the brainstem. It is arguably the most vital part of the brain in that it is the relay station for all messages that travel between the brain proper and the spinal cord. It also contains the centre that controls breathing, swallowing, eye movement, facial expression, and many more important functions. Previously, tumours in this region were all considered "inoperable". Now, most paediatric neurosurgeons realise that to lump all brainstem tumours together under the one heading is inaccurate. For more information on brainstem tumours, please go to our FAQ page.

This particular boy had a focal brainstem glioma that had caused symptoms for many years.

What is hydrocephalus?

Hydrocephalus (H) is a condition that results in an excessive amount of cerebrospinal fluid (CSF) within the brain. The body normally produces approx. 500 mls of this clear fluid daily. Of course, it needs to reabsorb the same amount. If there is an obstruction to the natural flow of fluid or if there is an inability to absorb the fluid then the fluid accumulates within the ventricles (cavities within the brain substance) and sometimes the spaces around the brain ("communicating" H). The fluid may result in raised pressure, but this is not necessary to make the diagnosis. H may not require any treatment. This is called "arrested" or "compensated" H. The indications for treatment are:

1. If there is evidence of raised intracranial pressure. In a child with an open fontanelle (soft spot on the top of the head that remains open until approx. 18 months of age), the pressure can be readily palpated. In a child in whom the fontanelle is closed, the clinician depends on symptoms and signs. In a child who is unable to communicate, the symptoms are anorexia, irritability, vomiting and eventually drowsiness and death. The signs are papilloedema (swollen optic nerve seen with an ophthalmoscope), dilated scalp veins, split sutures (joints in the skull), sun-setting of the eyes and a head circumference that is crossing the percentile lines. In a child who can communicate, the symptoms are headache, nausea, double vision and tiredness. Sometimes intracranial hypertension can cause slow and insidious deterioration resulting in subtle changes such as a drop in school performance, failure to thrive and thinning of the skull.

2. If there is progressive enlargement of the ventricles as seen on serial CT scans, ultrasounds or MRI scans

What is the treatment?

1. Treat the cause:
Sometimes the blockage is due to a tumour. Removing the tumour will invariably relieve the H. If it is due to infection, treating the meningitis with antibiotics may not necessarily prevent H. If it is due to bleeding, especially in the premature infant, only 50% will require permanent treatment of their H.

2. Endoscopic third ventriculostomy (ETV):
This is an internal "bypass" procedure. When the H is secondary to a congenital or acquired obstruction within the ventricles (usually at the level of the aqueduct) an endoscope may be passed through a tiny burr hole at the top of the head and, under direct vision, manipulated into the third ventricle where a hole is then made in the floor of this cavity, resulting in the fluid bypassing the obstruction.

3. Shunt:
Sometimes the brain can't absorb the fluid, even if the obstruction is bypassed. This is called a communicating H and requires the CSF to be diverted elsewhere either temporarily (external ventricular drainage) or permanently (shunt). The shunt is made of Silastic so as not to evoke a bad "rejection" reaction from the body. It is tunnelled under the skin and placed in a cavity that can absorb fluid. This is usually the abdomen but may also be the chest (in older patients), the gall bladder (when the abdomen and chest are unsuitable) and even directly into the blood system (entering through a vein in the neck or head). Shunts are not perfect. They can fracture, block, get infected, overdrain and underdrain. Over 50% of shunts will need to be revised within the first year of being inserted!

What is the prognosis?
Patients can live perfectly normal lives with treated H. They can have normal IQs and physical abilities. Unfortunately, if H is not treated early enough or if complications occur from either the condition itself or the treatment, patients can suffer neurological problems such as blindness, lower IQs, "strokes" etc. Even when H is treated with a shunt or an ETV, some people can die. This mortality rate is still 1% per year in well developed countries (Australia and USA)