Prognostication, Predictions and Percentages

A little over a week ago I was diagnosed as a case of a Chronic Subdural Hematoma possibly due to a fall I had playing football a month earlier.

Typically, the fall causes a tear in a small blood vessel between the brain and the dura (one of the protective layers between the skull and the brain) resulting in a slow leakage of blood in the subdural space. The fall is often relatively innocuous with no initial symptoms. The bleeding continues slowly and it is only later, (in my case 2 – 3 weeks later) that symptoms arise due to the pressure of a now significantly large blood collection pressing on and displacing the brain.

The immediate treatment is to surgically drain the blood, relieve the pressure and allow the brain to expand back. This is done by drilling one or two small holes in the skull (burr holes) and evacuating the clot.

The surgery was performed and, as of now, I feel fine.

Great! The big question is what are the chances of a recurrence?

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“What is the probability of a cure?” This is one of the foremost questions on the mind of every patient who has a serious disease.

Some are too scared to even ask it. And those that do muster the courage to mouth the question will cower in fear at the possibility of an unfavorable response.

Most would storm heaven to be told that they were absolutely cured and the possibility of a recurrence was nil.

But can anyone, short of God, give such an opinion with certainty? On any issue, for that matter let alone a serious disease?

On crossing the street, for instance, can anyone say that it can be done with absolute, cent-percent safety? Even, for that matter, other simple, day-to-day activities like climbing the stairs, or taking an elevator, or going for a drive…

‘What are my chances of a cure?’ It’s a question that, as an oncologist, I’m asked regularly.

A number of factors need to be considered when replying to such a question.

Firstly, factors involving the disease itself. Medical Textbooks and statistical studies have extensively categorized and sub-categorized most illnesses based on all known variables. It is on the foundation of this data, coupled with the personal experience of the treating physician, that the probable course a disease will take is prognosticated.

But any physician worth his salt, will tell you that predicting the outcome of a disease is far from being an accurate science.

Take breast cancer for instance.  A low risk cancer would be one where the tumor is small in size, pathologically low grade (i.e. shows features of a low level of aggression when viewed under the microscope), does not involve the lymph nodes, and has a favorable hormonal receptor status. With appropriate treatment the majority of these patients would be cured of their disease.

However a few of these early cancers, contrary to expectation, will behave aggressively and recur. On the other hand, patients who have advanced disease, and who’ve be told in no uncertain terms that they are incurable, have, on occasion, been known to outlive the very physician that made the prediction!

The emotional state of the patient is another factor to consider when offering an opinion on the probable outcome of a disease. This is a person who is not only fighting to come to terms with the illness, but is also very likely to be bang in the middle of some form of aggressive and morbid therapy.

On one hand the physician needs to be as honest as possible, (as often, decisions on therapeutic options may be based on predicted future outcomes). On the other hand most physicians would like to temper their response to this very sensitive query, not wanting to increase the anguish of an already stressed individual.

The bottom line here is that opinions on predicted outcomes are at best generalizations, even when delivered by highly experienced professionals with unlimited access to the latest medical statistical data.

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It’s now 2 weeks since my surgery. Though I feel fine, even the tiniest throb in the head makes me wonder: Is this the beginning of a recurrent bleed?!

The only way to know for sure is a CT angiography of the brain that I’ve been advised to perform a month after my surgery, which is 2 weeks from now.  

Medical literature (freely available these days on the internet) puts the chance of a recurrent bleed in a chronic subdural hematoma anywhere from 5% to 30%.

When asked for his opinion on my chances of a re-bleed, my neurosurgeon put the probability of it occurring in me at less than 10%. Though this brought a bit of a gasp from my wife, (who was hoping to hear that I was absolutely, 100% cured), I knew that he was telling us that the prognosis was good.

On what did he base this optimistic judgment?  Was it something in my case history or the pre-operative CT scan or the intra-operative findings or even my uneventful post-operative recovery? Or perhaps it was a combination of all of these that suggested that the likelihood of a recurrence, in my particular case, was closer to 5% than 30%.

Or, maybe, besides being a gifted surgeon and clinician, just maybe, he was simply being a good human being, and, sensing our anxiety, opted to give me a more upbeat prognosis.

I guess only time will tell.