Dr Ram’s Blog

8th January 2016

Dr Ram Kumar’s latest neuro-scientific venture

“Awesome!” William “Bill” S. Preston, Esq. 1989

That was how Bill Preston and Ted Logan described their excellent adventure in the historical docu-drama.

Being filled with awe is also how I would describe my latest neuro-scientific creative venture involving 3-D printing.

Specifically, together with the help from 3D Life Prints Ltd, I have managed to construct a 3-D printed skull recreating the very trajectory of the tamping rod that was explosively propelled through the skull vault of the 19th Century US railroad worker, Phineas P. Gage.

Alas poor Phineas, I knew him not

For those who don’t know, the penetrating traumatic brain injury to the left* frontal lobe that Phineas Gage sustained following his occupational mishap, and the gross changes in his social behaviour afterwards , was one of the key historical accounts in neuro rehabilitation and increased our understanding of brain function.

I had spotted a number of years ago the paper in PLOS One by Van Horn and colleagues which recreated the trajectory of this tamping rod and modelled the consequences of both the focal brain injury and the more dispersed white matter connectivity changes in brain networks.

But unfortunately, as with all 2-D pictures, it was insufficient to further my understanding. I prefer something more concrete, real and kinaesthetic which is why I like clinical examination and neuro anatomical dissections.

Below, in Figure 2, is one of the 2-D pictures attempting to convey the trajectory of the tamping rod as modelled by Van Horn and colleagues, based on Phineas Gage’s skull remains and contemporary descriptions of the incident.

Fig 2. Modelled trajectory of penetrating skull and brain injury of Phineas Gage, demonstrating left frontal lobe injury and involvement of white matter tracts.

So armed with the article by Van Horn et al, a detailed 3-D skull shape available in the public domain that I downloaded, and software to allow creation of 3-D model cylindrical rod (SketchUp), and some pure luck, I managed to construct a cylinder to represent the tamping rod, and then somehow I managed to orient it so as to pass through the skull (a royal pain on a 2-D screen, I can tell you) to simulate the trajectory in Figure 2. The result is shown in Figure 3.

Fig 3. My SketchUp reconstruction of skull and tamping rod, attempting to recapitulate Figure 2.

I saved this 3D image in various file formats and prayed that one of them would work when uploaded to online 3D printing services. First time round, the files did not seem to work properly to allow for 3-D printing. The shell structure formed by the skull was apparently not “closed”.

So my ambitions lay dormant for a while. Until I met up Michael Richard from 3D Life Prints, who are currently undertaking some work in the Innovation Hub at Alder Hey Children’s Hospital. Michael managed to sort out the needful: to get the shell structure closed sufficiently to allow a 3D print to be formed.

Before I knew it, I had my 3-D printed Phineas Gage-o-like skulls, replete with simulated tamping rod. The detail on these skulls are, to repeat myself from earlier, awesome. This is because the skulls have been printed up on a higher performance 3D printer than usually available from online companies. For example, the skulls have a clear nasal septum and teeth visible (zoom up Figure 4).

Fig 4. 3D Phineas Gage-o-like skulls with detailing.

The two skulls in Fig 4 are printed in a high density rigid plastic called ABS, with a soluble support which was melted off. My aim is to get Phineas Gage-o-like skulls printed in titanium, or stainless steel. Maybe to use as a prize, that I will award to myself for this piece of work.

I think I will get in touch with Van Horn and colleagues to see if there is some way I can go even further, and re-construct the actual skull bones and trajectory using the co-ordinates established in their paper, rather than my dead reckoning approach using a generic skull model.

Michael told me that in fact there are virtual reality visualisation methods with haptic interfaces that are coming along which would allow me to interactively explore 3D wireframe structures, rather than the 2D projections as in Van Horn’s publication. This would overcome the weakness of using real-world 3D printed models to explore internal brain (as opposed to external skull) injury, in which the details are all hidden well beneath the surface.

My feeling after going from the written page to holding a real object in my hands, is that 3-D printing or some other kinesthetic transformation of 2D pictures will aid medical education and training and help with discussion with non-professionals as well.

*Van Horn and colleagues calculated that Phineas Gage had focal injury to his left frontal lobe, rather than bilateral or right frontal lobe injury. However they do highlight that there was likely to have been wider white matter network dysfunction.