An Eagle’s Skull

Our Human Remains Conservator was doing some work for our new Body Voyager galleries when she came across a skull which had an unusual feature. In this blog she explains what makes this feature so rare and tells us more about the condition that caused it.

Sometimes in a museum you find things you aren’t looking for. Today I was looking at a particular skull in relation to the trephination holes going through each of its temporal bones, which will be part of our new Body Voyager galleries.  As I looked at the skull, the thing that really stood out to me were its styloid processes.

A number of bones have styloid processes – the name comes from the Greek ‘stylos’, meaning pillar, and it’s a part of a bone that sticks out for muscles to attach to. The one we’re talking about is part of the temporal bone – the part of the skull that sits under the ear and holds the structures for hearing. It acts as a point of attachment for several ligaments and muscles associated with the tongue and larynx. For something that’s doing such an important job in relation to our speech it’s a very delicate thing, a slender rod pointing down near the bottom of the temporal bone. Most of our skull is very robust – it has to be, protecting the brain and doing all that chewing – but this protrusion is fragile and is easily snapped off once the flesh has gone, and so it is often missing on many skulls.

Skull with a normal styloid process, about 2.6cm in length

Sometimes the styloid process can be elongated, and this is what we can see fairly dramatically here. The styloid process is typically under 2.5cm, and in some people it can be entirely ensheathed within the temporal bone. It is considered elongated if it is over 3cm long. This is quite rare – it is seen in less than 4% of the population. The styloid processes in this skull are 3.7cm on the right side, and 3.4cm on the left – though the one on the left looks like a fragment may have broken off. However, it is not unusual to see styloid processes of different lengths – in fact, elongated styloid process is more typically seen on one side only.

Skull showing elongated temporal styloid processes

In less than 10% of those with elongated styloid process there is a condition called Eagle syndrome, whose symptoms classically include a mild but nagging pain in the jaw, throat, face or tongue, which is worse when swallowing or sticking out the tongue. It can sometimes feel like there is something stuck in the throat, or cause problems turning the head. This is because the length of the bone can irritate cranial nerves, several of which pass close to the bone, and can abrade against ligaments, interfering with movement. Occasionally it can compress the carotid artery, which may lead to headaches and visual disturbances, and possibly even a stroke.

We can see that this skull is quite unusual, not just for the length of the styloid processes themselves, but the fact that this can be seen on both sides. This raises an interesting question when considered alongside the two trephine holes that led me to this skull in the first place. Trephination – drilling holes into the skull – is one of the oldest surgical procedures, seen in human remains going back to Neolithic times. It has been done for a variety of reasons, ranging from letting out evil spirits, treatment for fractures, headaches and epilepsy, and towards the end of the nineteenth century to perform leucotomy and lobotomy for what was termed aberrant behaviour. The connection between the styloid process and the symptoms described was only made by and ENT specialist called W.W.Eagle in 1937  – long after our gentleman had died, at the age of 60. We do not have his clinical history to know whether he displayed the symptoms of Eagle syndrome, and we do not know why he had the symmetrical trephine holes in his temporal bones. Was this an attempt to treat Eagle syndrome? We will never know for certain, but looking at his skull with our current understanding of the condition makes us wonder about his life.

(Featured image via y Polygon data were generated by Database Center for Life Science(DBCLS)[2]. – Polygon data are from BodyParts3D[1], CC BY-SA 2.1 jp, https://commons.wikimedia.org/w/index.php?curid=33450177)

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