Alexander Monro & Trepanation

“Alexander Monro secundus” by James Heath (1757–1834)– Wellcome Images. Licensed under Public Domain via Commons

Alexander Monro (1733-1817) was a Scottish physician and following in the footsteps of his father became a lecturer at Edinburgh University and held the Chair of Anatomy. He lectured mainly in anatomy and surgery for 41 years from 1759 to 1800 and several volumes of lecture notes taken by some of his students survive in the Manchester Medical Manuscripts Collection. They give a good insight into the 18th century perspective of how the human body was constructed and how it operated. In addition to this he gives quite detailed instructions to his students on the surgical procedures required to treat some common ailments and how best to perform them. One such procedure he alights upon in his 1770-1771 lectures is trepanning; the process of drilling a hole in the skull to relieve pressure.

There is archaeological evidence to suggest that people have been performing this procedure for many hundreds of years and it is probably more commonly associated with the medieval period. Nevertheless it was still a key part of medical education in the late 18th and early 19th centuries and on 13th April 1771 Monro described the process of trepanning in the case of a fracture to the skull causing the oppression of the brain to his students thus:

“I first take away only the skin & leave the proper pericranium and cellular membrane on it. I then make room for the saw: this is made quite circular. We in general avoid the large venous canals – & if possible the sutures, or the frontal sinuses. But if the fracture be over any of these with depression, we certainly had better operate over these than leave to nature or trepan at a distance. … In these cases we do the operation quite cautiously, or perhaps not cut the bone quite through but break its inner table.

A pretty large saw is better than a small one, especially where the depression is great, for this supersedes repeated operations. To let out matter we choose the most dependable part, but if there be a depression with fracture we have no choice but to lay the saw on the sound part & part of the fracture along the suture. It would be dangerous to trepan the depression.

We must be careful of saving as much as possible of the extracted periosteum on account of the bone requiring nourishment from it. This we do by carefully scraping the periosteum.

18th Century Trepanation Instruments. Anagoria – Own work. Licensed under CC BY 3.0 via Commons 

The Trephine is the cross instrument & in preference to the Trepan according to Mr Sharp. But the Trepan is preferable to it on account of its ease, expedience and safety, were surgeons sufficiently accustomed to the trepan.

We ought never to cut out the bone altogether & bring it along with the instrument, but try from time to time to see if it vacillates, & when the bone is nearly through we should break it out. For there is danger of tearing the dura mater, as I have just now you see, which Mr Sharp would say was rightfully done. To break it off I take two levators & break it out, & the edge will be as equal as if cut through. The levator is more simple and easy to break the bone with than forceps.

If there be matter fluctuating within we open the dura mater with a common lancet & this is in cross incisions, to let out matter better.”

He goes on with more detail about the use of levators and the raising of depressed bone but it is quite clear that this would be a highly dangerous operation, particularly at a time when there was no general anaesthetic and surgery had such a high mortality rate. Monro unfortunately does not offer us any indication as to the levels of success in terms of survival he has had with this procedure.

The Mr Sharp he refers to is most likely Samuel Sharp (1709-1778) a London based surgeon who ceased lecturing in 1757 and practicing in 1765. The clear disagreements Monro has with his methods are possibly indicative of the changes in procedure in a very short time or the simple fact that there wasn’t a clearly defined and accepted way of performing certain surgical techniques; medicine was still very much an evolving practice with much experimentation.

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