Going into brain surgery with your eyes open
How might keeping patients awake during surgery lead to the more successful removal of brain tumours? James Keidel, in his shortlisted entry for the 2011 Wellcome Trust Science Writing Prize, explains.
For all the amazing things we can feel though our brains, the brain itself is unable to feel anything at all. This is good news for Holly, as her surgeon delicately applies an electrode to the exposed surface of her brain. Until recently, patients with low-grade tumours like hers were not typically offered surgery as the risks were thought to outweigh the rewards. Although these tumours are invariably a death sentence, they are a slow one that lurks undetected for years, with no effect on the everyday behaviours we take for granted. The physician must therefore strike a balance between length and quality of life as even a successful tumour removal may damage healthy tissue and disrupt fundamental aspects of who we are, such as the ability to speak and be understood.
Now however, a number of neurosurgeons are taking an aggressive approach to this disease. Leading this movement is Hugues Duffau, Professor of Neurosurgery at the University Hospital Centre in Montpellier. Duffau has pioneered the use of ‘awake craniotomy’ for the removal of these tumours – surgery during which the skull is cut away and the brain exposed, while the patient remains fully conscious. Holly is awake throughout the operation and is assessed continuously, which is where the electrode comes in.
As Holly sits upright on the table, a psychologist shows her pictures of animals one-by-one. As she names the animals shown, Duffau periodically applies a small electrical current to her exposed brain. When this disrupts her ability to name the object, a small tag is placed on the brain’s surface, sparing this area if at all possible during the surgery. Throughout the operation, as the scalpel cuts deeper into the brain, this same procedure is repeated.
The end goal is the elusive balance between removing as much of the tumour as possible and ensuring that the surgery itself does not create new problems for the patient. Sometimes, the electrode touches parts of the brain that although obviously cancerous, still disrupts Holly’s ability to name the picture in front of her. When stimulated in one place, she may call a tiger a “biger” – in another she may call it a lion. In either case it is clear that these regions must be spared.
Yet beyond the benefits to individual patients, this work is fundamentally changing the way neuroscientists think about the mind. Much of what we know about how the brain functions comes from observing the sudden and often catastrophic damage caused by stroke. Stroke victims often suffer very specific deficits in one domain, such as language, while abilities such as vision and movement remain completely intact. These findings have led to a view of the adult brain as a set of regions specialising in one function only, be it understanding speech or facial recognition. Unsurprisingly then, when one of these areas is damaged the function is often lost permanently.
Although true in the case of stroke, for Holly it is quite the opposite. Her tumour is located in a region of the brain’s left frontal lobe called ‘Broca’s area’ – essential for language production. Damage to this area typically leaves the victim with so-called telegraphic speech – the inability to produce more than two- or three-word sentences like “boy…see…dog” – while leaving the power to understand what others say completely intact.
After Holly’s tumour is removed her speech will return in a matter of days or weeks. Within a few months she will be back to work. This leads to a clear paradox: why does a stroke in this area cause irreversible damage to speech, while a tumour that causes equivalent damage has almost no effect at all?
The answer, according to Duffau, lies in the concept of neuroplasticity. While infants have extremely ‘plastic’ brains that can adapt to almost anything that is thrown at them, things are much tougher for adults. Though we can learn new concepts like ‘iPad’ or ‘Twitter’, it is almost impossible to learn completely new skills. Nonetheless, Holly’s language remains unaffected even as her tumour slowly eats away at the very part of the brain considered indispensible for the ability to speak. Why this is possible is not only a question for researchers, but for anyone interested in how the brain works.
How long can Duffau’s patients maintain their quality of life? How will this work change how we understand the brain? These remain very open questions. What is clear is that a new horizon is in sight, both for neurosurgeons and for neuroscientists. The tools now exist, but how they are used will affect both how we are treated medically and how we view ourselves.
This is an edited version of James’s original essay. Views expressed are the author’s own.
Over the coming months, we’ll be publishing the shortlisted essays in this year’s inaugural competition.