If the zebras are scaring you, send the Marines
Medical students are taught to be parsimonious with their diagnoses: to use Ockham’s Razor. The simpler of two explanations is more likely to be the accurate one. Although that seems to work backwards for conspiracy-theorists, it is an important logical principle for diagnosis.
One condition is more likely than two or more. A common condition is more likely than a rare one. This is summed up for medical students in the saying: ‘If you hear hoof-beats, think horses. Not zebras.’
Many doctors are afraid to diagnose rare, or multiple, conditions. One doctor gave a colorful flourish to describe this reticence as zebra retreat syndrome.1 To be fair, he also described doctors who take the opposite extreme. Like TV’s Dr. House, they order expensive tests for rare and less likely options too freely.
I had problems from an under-active pituitary gland: I do not remember a time without diabetes insipidus (DI). It was only diagnosed in my late teens.
DI has nothing to do with insulin. The more common diabetes that relates to insulin is diabetes mellitus. Both diabetes mellitus and DI cause excessive drinking and urination, but for completely different reasons.
I saw an endocrinologist when I was in high school. I had not had any big growth spurt. He found that my testosterone was low-normal. He offered testosterone replacement but said that it might limit my total height. I also had gynecomastia—male breast tissue—that was only detected years later. (it was a daring accessory for an all-male high-school!) My voice didn’t break, it just made a very slow, stately, meander from treble (boy soprano) down to my present tenor by my mid-twenties.
I only sent doctors back on the diagnostic trail by chance. In my Honors year at university, I accidentally banged my head and had a minor concussion. CT scans found no bleeding, but revealed some abnormalities in my pituitary and pituitary stalk.
My sister went into a flat panic about cancer. I was calmer, willing to find out what doctors said more specifically, and that proved wise.
Scans opened the way
After CT and MRI scans, my doctors went on a diagnostic safari for almost three years. They started with the more serious and more common options. Lymphoma? No. The neurologist said I would be sicker, or maybe dead.
More and more tests, and stranger and stranger options were eliminated. Could I have been near bats? My father was a keen caver, and he took me down a cave or two, so, yes. I think that was about histiocytosis x.
Do I have any Irish ancestry? Cerebral sarcoidosis is more common in Irish people.
The neurologist ruled out a liver biopsy. He said it was pretty rare, and he would not allow it to be carried out on his child.
Other tests also revealed that the abnormality, whatever it might have been, was growing; and it was pressing against my optic nerve. My field of vision was beginning to contract. That made a diagnosis a more pressing priority.
The doctors took their best option to diagnose it. I had a transsphenoidal biopsy. That is where a surgeon opens a pathway under the upper lip, and up the sphenoid sinus for a neurosurgeon to reach the base of the brain.
But my diagnosis was still evasive. Doctors could not agree. They sent my results to one of the top organizations for diagnosis globally: the Armed Forces Institute of Pathology in the United States (AFIP). They said that I had lymphocytic hypophysitis: a rare pituitary problem. I was only one of 300 recorded cases. It was then thought to have a pronounced gender-bias. Almost ten times more females than males had it.
I also found out years later that one of my Australian doctors said she thought I had the lymphocytic hypophysitis. That was a great example of a zebra retreat: she was correct, but the other doctors thought her idea was too wild. (A great thing for her CV- to have the US military back up her dissenting diagnosis.)
My hypophysitis was treated with radiosurgery. I had a course of focused, stereotactic radiotherapy. Stereotactic radiotherapy only affects specific points. I will have hormone deficiencies for the rest of my life. I have been on hormone replacement therapy since my teens.
MS was always there
The MRIs had also shown spots in my brain that looked a lot like MS lesions.
An eye test (visual evoked potentials), and then a cerebrospinal fluid sample seemed to rule MS out of the running. The spots—hyperintensities (that actually were MS lesions)—were ascribed to a psychiatric illness: perhaps bipolar disorder. I was medicated for some fifteen years as if I had bipolar disorder.
My cognitive problems became slowly worse. I earned first-class honors in history. I later did a graduate Law degree. That took me six years instead of three to complete.
The end of psychiatry
When I was twenty-nine years old, I moved in to live with my partner Tim. He doubted the psychiatric label. At the suggestion of a doctor friend of his, we slowly tapered down my various psychiatric medications. I did not go manic or get depressed. But I did become noticeably more present.
Tim had noticed my cognitive problems, too. After he broached the subject and I agreed that there was something wrong, we set up a review. Several sessions with a neuropsychologist established that my cognition was above my expected age average in some areas. My cognition in some other areas, however, was ‘frankly impaired’. Areas like space-form awareness, and short-term memory. Ouch!
Just a few days later I had my first, and so far only, obvious and undeniable MS relapse. I picked a good place for it, too! We were in an isolated mountain lodge. The walk out from the lodge to the car park normally takes forty minutes. That time it took me almost two hours. I was staggering, falling, and slurring my speech. I thought ‘No officer, I have not had any alcohol’.
Back home, a GP said it was probably just an infection.
Tim was not convinced it was just an infection, and took me to a hospital. I had another cerebrospinal fluid sample taken. That conclusively showed MS oligoclonal banding. To my great fortune, the duty neurologist at the hospital passed my case on to another neurologist whom she knew: an internationally renowned MS expert. He does the public health trifecta: he treats, he does research, and he teaches. He said, I not only definitely had MS, but it had been present for a long time: maybe 10 to 15 years.
MS can have physical, sensory and cognitive effects. Mine has had mostly cognitive, and partly sensory, rather than physical effects. The fact that my MS has been almost entirely cognitive in its effect helped its mislabeling as a psychiatric illness.
At last I have the right diagnoses, and a good group of doctors, and other professionals, so now my health has improved.
Despite the zebras.
Note
- Groopman, J. How doctors think, Houghton Mifflin, Boston and New York, 2008 (p126-7).
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About the Author
Michael Bradley was born in Sydney. He completed an Arts Degree, with Honours in History, and a Law Degree. He has not proceeded to admission as a lawyer, due to his MS. He now lives in Canberra with his partner, Tim, and the chocolate Burmese cat who just walked in and took over.