Diabetes Insipidus as a Sequel to a Gunshot Wound of the Head

Weird Science AND Classic Science!  The Fridays continue! (unfortunately, I am working without Picasa right now due to the tragic death of my hard drive, so this post will be sadly without pictures.)

Classic Science this definitely is, as well as a truly textbook case.  Even better, it reminds me of Phineas Gage!  What can I say, I’ve got a thing for blows to the head (which might be why I like Mo’s blog so much, it is not only cool enough to hit you like a brick, he’s got articles on trepanation, people driving nails into their skulls, and other awesome stuff).  And it’s great, diabetes (which I would love to study if I could start my life over) AND traumatic brain injury!  *sings* These are a few of my favorite things…

“Diabetes insipidus as a sequel to a gunshot wound of the head” Graham, EA, Annals of Surgery, 1917.

It’s a short and pretty easy case study.  A 46 year old man was brought in having suffered a self-inflicted gunshot wound to the head (apparently he suffered it 14 hours BEFORE he was brought in, which is pretty impressive).  Following the gunshot, he was extremely mentally disturbed, but it’s possible he was mentally unstable prior to the wound, and that mental instability may have induced the suicide attempt. 

No matter what, it was an ugly wound to the right temporal region (think holding the gun to the right side of the head), with the bullet ending up subcutaneously in the left front (so the kick from the gun angled thebullt forward).  This means it crossed through most of his brain, and severed both of the optic nerves at the level of the optic chiasm.  For the first three days, the patient appeared to recover normally, although due to the bullet’s path, he was completely blind. 

But on the fourth day, he began to PEE.  And pee.  And pee.  It was so bad that they couldn’t even collect it all, he would urinate in the bed before they could even get him to a toilet.  He was voiding 4.5-5.5 liters per day, and drinking copiously to retain any fluid at all.   It never seemed to stop, even after he was discharged (to a mental hospital, unfortunately he remained severely unstable for the rest of his life).  The doctor diagnosed it as diabetes insipidus.

I’ll pause a minute here to clarify diabetes.  There’s diabetes mellitus (the kind caused by problems with insulin-secreting beta cells in the pancreatic islet.  I’ve been planning to post on this, but it’ll have to wait a bit), and then there’s diabetes insipidus, which is caused by anti-diuretic hormone (ADH or vasopression), and has nothing whatsoever to do with insulin.  Why are they both called diabetes?  Because the word diabetes does not actually refer to blood sugar or ADH.  Diabetes is of greek origin, and refers to the passing of urine.  The symptom that both of these disorders have in common is that people with diabetes insipidus and diabetes mellitus both pee a LOT.  People with diabetes mellitus pee because they have too much sugar in their blood, the kidneys clear the sugar, and water follows.  People with diabetes insipidus pee because of a lack of ADH.

Anti-diuretic hormone is a hormone secreted by the posterior pituitary gland, or neurohypophysis (neuro: controlled by neurons, hypophysis: Greek for “to grow beneath” because it hangs beneath the brain).  It’s actually made in the supraoptic nuclei of the hypothalamus, and transferred via neurons in the pituitary stalk to the posterior pituitary, where it is released into the bloodstream.  And what does it do?  It increases the permeability of the collecting duct of the kidney.  This means that when ADH is present, your collecting duct reabsorbs more water back into the body, rather than letting it go to the bladder as urine, so you have a decreased volume of urine.  The name anti-diuretic hormone highlights this, since diuretics are things that make you pee, so an anti-diruetic would be something that does the opposite. 

This also means that, when there is no ADH present, your body doesn’t collect water from the kidney, and the volume of your urine will increase.  A LOT.  Up to 8 liters/day, in fact.  Sound familiar?

So how does a man with a gunshot wound to the head stop ADH from getting to his kidneys?  The bullet, we know severed the optic chiasm.  The hypothalamus and pituitary are located below the optic chiasm.  The doctor who published the case study surmised that either the bullet severed the pituitary stalk directly, or the swelling from the trauma cut off the hypothalamus from the pituitary by putting pressure on the pituitary stalk.  With no communication between the hypothalamus and the pituitary, no ADH could be released into the blood stream, and without ADH, the patient just couldn’t stop going. 

This paper isn’t really in any way defining in the world of neuroendocrinology, but it makes an elegant case study of the connections between the brain and diabetes insipidus, a condition that people were still puzzling out in 1917.  And it became a classic case study, though modern case studies often use a car accident as an example of something that can sever the pituitary stalk, rather than a bullet to the head. 

And the weird Friday lesson learned here is:  if you are going to shoot yourself in the head, don’t miss.  You might get diabetes insipidus. 
Graham, E.A. (1917). DIABETES INSIPIDUS AS A SEQUEL TO A GUNSHOT WOUND OF THE HEAD. Annals of Surgery, 66(5), 529-531.

And I can’t leave without noticing this AWESOME song:  The closing credits song for “Portal”.  I have never actually played Portal, but I love this song.   It’s got science!  And cake!  And being locked inside, endlessly trying to get data, and yet somehow still wanting to do it, is totally the life of a grad student. 

“But there’s no sense crying over every mistake, you just keep on trying ’til you run out of cake…”