Water on the Brain

Hydrocephalus was first decribed by Hippocrates, but it was not until the 20th century that effective treatments were devised. Some of the biggest strides were borne of desperation — they say necessity is the mother of invention, but today we recognize two fathers who worked on behalf of their ill children.

One father is machinist John Holter, working on behalf of his son Charles Case “Casey”, born on November 7, 1955. (already a week of great inventions — but don’t confuse Holter with the other medical inventor, Norman J. Holter, who designed a wearable heart monitor for analyzing infrequent cardiac arrhythmias outside the clinic.)
The other father is Roald Dahl, whose son Theo developed hydrocephalus at the age of four months, after his carriage was struck by a taxi in 1960. Dahl was the author of many treasured works, including Willy Wonka and the Chocolate Factory, and James and the Giant Peach.
From the article written by Richard Hayward and originally published in The Times Higher Education:

Casey’s initial treatment consisted of intermittent withdrawals of CSF using a long needle passed through the skin, through the brain and into the expanded ventricles. He then had two unsuccessful attempts to insert a ventricle-to-abdominal cavity system incorporating tubing made of polythene.
Luckily, where Casey was being looked after in Philadelphia, two surgeons–doctors Spitz and Nulsen–had already demonstrated that a ventricle-to-atrium diversion system could work if it contained an expensive and impractical valve that could control the direction of flow while maintaining an adequate intracranial pressure. They used a rather inflexible polythene tube passed through the jugular vein to the heart.
Holter set about designing a valve for his son that could be used in a ventricle-to-atrium shunt system, and which would be both biocompatible and much simpler to manufacture. But his researches were not progressing quickly enough, so he opted for the old ball-valve model. Unfortunately, the tube tip snagged one of the centres in the heart responsible for rhythm control and the boy suffered a cardiac arrest. The surgeons had to massage his heart back into action for 30 minutes. Ironically, Holter’s first valve was ready eight or nine days later, but Casey was not the first patient to try it.

In the process of designing a self-sealing material for his shunt, Holter invented Silastic, which also sees use today in heart valves and breast implants:

The valve system was based on a chance observation of Holter’s – that, when the nurses in the hospital punctured the plastic tubing of a patient’s intravenous drip, the slit in the tubing produced by the angle at which the needle had been introduced appeared to seal itself as the needle was withdrawn. Holter surmised that if the pressure of the fluid were raised, this sealing effect would be overcome and fluid would leak out. His valve had two slit valves. But it was in his choice of material that Holter made an even more lasting contribution to medical history.
During his researches, Holter learnt that silicone incorporated into rubber produced a compound that was strong, heat-resistant, flexible and did not excite a tissue reaction when implanted. He promoted its refinement to a grade suitable for medical use. It was patented and manufactured as Silastic, which is now used for all hydrocephalus shunt systems as well as devices such as heart valves and breast implants.

Over 100,000 shunts were implanted in the 1960’s alone. Among them, a shunt in the brain of Theo Dahl:

As for Theo, as Jeremy Treglown reports in his biography of Roald Dahl, his early treatment in the US for hydrocephalus had been with the type of valve developed by Holter. But it kept blocking, and every time it did so, the pressure of the water inside his head rose to dangerously high levels–high enough to threaten his eyesight–requiring an emergency operation.
The family lived in a state of constant fear.
In 1961, they moved back to England and Theo’s care was taken over by neurosurgeon Kenneth Till at Great Ormond Street Hospital in London. He identified the silicone rubber slit valves of the Holter valve as the cause of the trouble – they became too easily clogged with the debris that can accumulate in the hydrocephalic ventricles, particularly when (as in Theo’s case) there had been bleeding in the brain. He, Dahl and Stanley Wade, a hydraulic engineer friend of Dahl’s, set about designing a new valve.

Theo Dahl survived and is still alive today. Sadly, Holter’s child suffered additional complications:

In the Wade-Dahl-Till (WDT) valve, the mechanism took the form of two metal discs, one set in a restrictive housing at each end of a short length of silicone rubber tubing. Movement of fluid under pressure from above moved each disc to an open position, but any pressure from below pushed the discs back and prevented retrograde flow.
Like the Holter valve, the early prototypes and the first commercial models were assembled in a home workshop and had a rather Heath-Robinson look: the Silastic tubing was secured to the valve housing at each end by a strong tie–black silk in the case of the WDT. By 1962, the WDT valve was ready for implantation.
However, while Wade, Dahl and Till were working on their prototype, for reasons unknown, Theo’s hydrocephalus entered a state of arrest.
Casey’s hydrocephalus did not arrest. Instead, 14 months after he had received the second Holter valve ever implanted, his shunt blocked and the lower end had to be transposed from the heart down into the abdominal cavity. One further revision was needed when he died after an epileptic fit at the age of five.
Both Casey and Theo had fathers who were exceptional men and who, despite–or perhaps because of–their intense emotional involvement in their child’s care, had the courage to take a step back from their feelings and do something to help. For John Holter, there is no doubt that he helped launch a new era in the treatment of hydrocephalus. Today there are more than 40 different valve systems available, including variations on the original Holter valve–and the name itself is still in everyday use.

That’s all for this week. If you care to read more about Roald Dahl’s stories, the New Yorker has an excellent read. Otherwise, please have a safe and enjoyable weekend. And see you next week!