The first otological surgery in a skull from the site of El Pendón (Reinoso, northern Spain)

Description of the skull and its pathologies

This article focuses on the discovery of a skull from the Dolmen of El Pendón in July 2018. Its chronostratigraphic context corresponds to the second phase of use of this megalith. The skull was lying on its right side with the face facing south, towards the entrance to the burial chamber (Fig. 3). He preserved a complete neurocranium, including the frontal, parietal and temporal bones, and the occipital bone without the basilar section. Of the facial bones, the nasal bone, the zygomatics and the lower region of the maxillary bone (without teeth or alveolar cavities except for the left first molar) remained. Additionally, root impressions were visible in the cortical surface of the frontal and parietal regions (Fig. S6 and Supplementary Video).

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Study skull found at the site of El Pendón. Superior: Frontal and lateral view of the skull (Photo: ÑFotógrafos Photography Study). Lower: Skull with mastoidectomy in situ as part of the megalithic ossuary.

Analysis indicates that it is a mesocephalic skull that belonged to a woman, who probably died at an advanced age. While obliteration of cranial sutures is consistent with a middle-aged individual – 35-50 years old, loss of all maxillary teeth long before death – given alveolar reabsorption of teeth and loss of bone density – suggests an age approaching the elderly. This statement is based on the general good oral health of the community whose remains are deposited in the dolmen. Therefore, the loss of all teeth in life means old people. The presence of aged individuals is confirmed by the documentation of fully ossified thyroid cartilages. This particular ossification is estimated to end at age 652.

The external auditory canal is widened on both sides in a postero-superior and inferior direction, connecting the mastoid cells and the tympanic cavity to the outside (Fig. 4). The edges are smooth and round; on the right side, its diameter is 12 mm, while on the left side it is 9 mm. No areas of bone fracture, fissure or callus are visible on either side. The inner surface of both cavities shows typical speculated bone formations, which reflect bone reabsorption changes common in inflammatory mastoid processes3.4. However, both cavities do not reflect any significant lack of mastoid pneumatization, which is common in people with inflammatory middle ear conditions in childhood.5, suggesting late onset of an underlying disease. It is important to emphasize that the bony wall separating the auditory canal from the mastoid—scutum-was preserved on both cavities (Fig. 4).

Figure 4
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CT scans and details of the two temporal bones of the skull under study and some samples from the comparative analysis. Upper: Details of the external auditory region on the right (a) and the left (b) temporal bones of the skull under study. Of note is the deterioration of the tympanic cavity in both temporal bones due to taphonomic processes. Middle: Current skull with mastoidectomy performed by students of the Faculty of Medicine of the University of Valladolid (vs) and example of an archaeological skull without any pathology used for comparative analysis (D). The red arrows indicate the external auditory canal. White arrows indicate bone erosion in the posterosuperior part of the external auditory canal due to mastoidectomy. The yellow arrows indicate the scutum– thin bone spur formed by the upper wall of the external auditory canal and the side wall of the tympanic cavity. *Mastoid process. Lower: Computed tomography (CT) scan of parasagittal sections at the level of the right middle ear (arrows point towards the middle ear) from the skull under study (and) and a current skull without pathology (F).

Signs of bone regeneration and remodeling are evident. Traces of mastoiditis or mastoid abscess found in paleopathological analyzes of ancient skulls show major osteolytic defects without signs of repair, which, in the absence of medication or adequate surgical drainage, often have a tragic end6. Nevertheless, the surface histological analysis shows that signs of bone remodeling are evident in the trepanation carried out on this skull, thus testifying to the survival of the individual. Remodeling fields are binary features exhibiting surfaces of formation or resorptionseven. In adulthood, this process is “secondary remodeling”, in which bone resorption and bone deposition occur at the same site, replacing old and damaged bone in a highly regulated cycle.8. In dry bones, we can detect four distinct surfaces: resorbable, characterized by osteoclasts and resorption gaps; depositary, characterized by osteoblasts; at rest – or neutral, characterized by cells exerting no bone activity and remodeling reversals, which are interfaces between the resorption and deposition fields9.

Our results show that bone resorption and rest are the only states of activity present on the intervention zone of the left ear (Supplementary Fig. S10). The resorption surface is identified for the presence of Howship lacunae and could be related to the replacement of damaged bone due to infection. In fact, no sign of pathological bone was found. The most plausible interpretation of these results is that after the intervention this woman survived, since resorption is in progress, but the pathological bone has been eliminated. In contrast, in the right ear, clearly visible areas of resorption along with an area of ​​bone deposition provide evidence that reversal of remodeling is taking place (Supplementary Fig. S11). The resorption phase lasts about two weeks. After this phase, the reversal lasts about 4 to 5 weeksten. Thus, the presence of a well-defined inversion line in this right ear means that this woman survived the procedure.

Differential diagnosis

The hypothesis proposed in this research is that the individual to whom the skull belonged was probably operated on on both ears, with an indefinite delay between the two operations. From the differences in bone remodeling between the two temporals, it appears that the intervention was first performed on the right ear, due to an auricular pathology alarming enough to require intervention, to which this prehistoric woman survived. Subsequently, the left ear would have been intervened; however, it is not possible to determine whether the two procedures were performed consecutively or whether several months or even several years have passed. This is therefore the first documented evidence of surgery on both temporal bones and, therefore, most likely the first known radical mastoidectomy in human history.

A well-documented disease in paleopathological studies of ancient skulls is cholesteatoma.11. A cholesteatoma is a destructive lesion of the temporal bone, which tends to expand and gradually erode adjacent structures, leading to hearing loss, vertigo and intracranial complications; he is treated surgically12. A rare type of cholesteatoma is congenital cholesteatoma, characterized by the presence of epithelial embryonic remains in the middle ear, usually associated with well pneumatized mastoids in young patients, where destruction of the tympanic cavity predominates.5. Acquired cholesteatomas are more common; they are associated with sclerotic or diploic mastoids, in which epithelial remains are introduced into the middle ear by perforation or tympanic intussusception. This tends to occur in the postero-upper quadrants, beginning with the initial erosion of the scutum or the bony wall of the atticus13. It is also known as cholesteatoma of the external auditory canal, which is usually unilateral and characterized by epithelial accumulation that may progress to extensive temporal bone erosion in patients with a history of injury or surgery. Its spontaneous appearance is quite rare14. Finally, malignant otitis externa, histiocytosis or tumors can lead to significant bone destruction. However, they are rarely bilateral and often result in the premature death of the individual.

Here, an acquired cholesteatoma of the middle ear must be excluded, because the scutum is present on both temporal bones. Other diseases, such as malignant otitis externa or temporal bone tumors are also ruled out a priori, as they are rarely bilateral and generally lead to premature death, for which the documented bone remodeling previously described on both temporal bones would be impossible. Finally, a bilateral congenital cholesteatoma or of the external auditory canal, both rare, can hardly be the cause of the mastoid affection found in the tympanic cavity which led to the performance of this pioneering surgery.

Surgical instruments

In addition to the macroscopically visible evidence mentioned above in the temporal bones, seven cut marks at the anterior edge of the surgical trephination made in the left ear were identified. They are parallel, short (2 to 4 mm) and linear with a clear triangular or “V” section. However, these marks are not visible on the right side, probably due to the bone remodeling process that was taking place (Fig. 5).

Figure 5
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Set of cut marks identified on the left temporal bone of the skull under study. Lateral view of the left side of the skull (a), detail of the left temporal bone with otological surgery (b), and magnified image of the cut marks located at the anterior edge of the surgical trephination performed in the left ear, next to the mastoid process (vs).

This discovery is further evidence that this is the first documented mastoidectomy to date. Given the pre-metallurgical chronology of the site, this surgical intervention had to be carried out with a lithic instrument. Several pieces were placed as funerary objects or ritual offerings next to the dead. The most important were flint tools from different sources, of which several typologies have been identified: simple and retouched blades of different sizes, geometric microliths and arrowheads of different shapes (Fig. 6).

Figure 6
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Selection of a set of flint lithic tools – blades, geometric microliths and arrowheads – from the El Pendón ossuary. In the line below are four lithic tools which have been subjected to “blind” analysis by a specialist in traceability and wear analysis (Supplementary text S3).

A blind tracing analysis was carried out on a set of lithic tools from the dolmen with the aim of identifying the possible technique or tool that made it possible to perform this particular surgery. One piece showed signs of use for butchering and had probably come into contact with bone material: a flint blade 31 mm long and 7 mm wide at its distal end, with simple direct retouch forming slight footprints (Fig. 6). Use-wear analysis revealed that after being extracted from the core, the blade was subjected to heating not exceeding 300/350°C, given the absence of fire cracks and other types of marks of heat treatment (Fig. S9 and Supplementary Text S3).