I discuss issues pertaining to the practice of neuropathology -- including nervous system tumors, neuroanatomy, neurodegenerative disease, muscle and nerve disorders, ophthalmologic pathology, neuro trivia, neuropathology gossip, job listings and anything else that might be of interest to a blue-collar neuropathologist.
Thursday, November 13, 2008
Whither the Illusory Cowdry B Inclusion of Polio?
In a recent post about poliomyelitis, the illustrious Dr. John Donahue of BrownUniversity (pictured) correctly pointed out that I did not mention the presence of Cowdry B inclusions in my histological description of the disease. Having never seen polio under the microscope, I went looking in textbooks and on the web for a photomicrograph of a polio-related Cowdry B inclusion. Failing in my search, I turned to the esteemed Dr. Tom Smith of the University of Massachusetts to see if he had such a picture. With his permission, I quote Dr. Smith’s email to me:
“I have the same problem you and everyone else seems to have -- I've never seen one myself and cannot find any photos of one either in my own file or anywhere in books or on the web. I remember reading a description a long time ago - I think it might have been from the old AFIP neuropath teaching slide set - that they were supposed to be small eosinophilic (?) nuclear inclusions that were sometimes seen in neurons in poliomyelitis. I don't remember actually seeing them in the slide in that teaching set. From the description, I had the impression they might have resembled Marinesco bodies or maybe even normal but prominent nucleoli... or perhaps those small inclusions seen in some neurodegenerative dementias. They don't seem to be as 'specific' as Cowdry A inclusions and perhaps they don't even exist? Frankly I think Cowdry B inclusions have reached the point where they should be relegated to the trashbin of neuropathology.” (Emphasis added.)
I recently photographed a Marinesco body (see picture, arrow points to the eosinophilic body) within the
nucleus (outlined) of a pigmented neuron in the substantia nigra.
Could the Cowdry B inclusion be an elaborate hoax perpetrated upon us by Dr. E.V. Cowdry when he first described Cowdry type A and type B inclusions in 1934? Dr. Smith’s response:
“Well, I doubt that it was a hoax but I think some of those folks were quite prone to seeing things that just the passage of time (and new information) has proved to be ‘not real’. Another case in point - how many Alzheimer type 1 astrocytes have you
I then wrote back to the individual who got me started on this hunt for the illusory Cowdry B in the first place: John E Donahue, MD. Here’s what Dr. Donahue had to say about the issue:
“I think these descriptions are very old and go back to the day where everything was described visually, without knowing etiology. (Remember, there are eight structures of Scherer from the original 1938 article, only three of which are really relevant anymore, and maybe even the gliosarcoma being a tertiary structure may be going the way of the dinosaur since I've heard recently that the gliosarcoma arises from a single precursor cell)…”
Fuller and Goodman, in Practical Review of Neuropathology (Lippincott, 2001), define a Cowdry B purely on morphological grounds -- with no implication as to the cause (polio or otherwise) -- as being small, eosinophilic, intranuclear inclusions with no halo and causing no nuclear effacement. I quote page 20: “[T]he quotidian Marinesco bodies that are routinely observed in the neurons of the pigmented brainstem nuclei are sterling examples of the Cowdry type B beau ideal.”
Perhaps the Marinesco body, rather than a “sterling example”, may in fact be the only example of a Cowdry B inclusion! Come to think of it, I think I’ll offer a $10 reward for anyone who can send me a photomicrograph of a polio-related Cowdry B inclusion. Email me the photo at firstname.lastname@example.org
I hope you have better luck finding one than I did!