We present a rare case of infratentorial mastoid trepanation, by drilling, from medieval Croatia. An artifi cial antemortal
opening was found in a male skeleton from the 11th century cemetery Zvonimirovo. It was placed roughly at the
intersection of the Frankfurt’s plane and the midline of the right mastoid. The right posterior parietal of the deceased
also exhibited a callus-like formation consistent with the linear cranial fracture. Our aim was to investigate by computed
tomography (CT) a possible presence of otopathology – a chronic middle ear infection – MEI/mastoiditis or cholesteatoma.
On the other hand, both standard radiography and CT were employed in a cranial fracture diagnostic agreement. The
generated CT scans confi rmed the presence of an artifi cial hole running into a well defi ned trepanne canal connected with
the antrum. The presence of otopathology was not established. The radiography and CT substantiated the presence of a
linear posterior parietal discontinuity – without displacement, in front of the right lambdoid suture. From the medical
point of view, it would be unusual to perform infratentorial – mastoid trepanation for reasons of treating supratentorial
trauma, i.e. possible posttraumatic acute subdural hematoma (PTASDH). However, since there was a lack of CT evidence
of osteolysis in ME, there is a possibility of medieval trepanation procedure performed for reasons of posttraumatic treatment.
To our best knowledge, usually, ancient trepanations described in Croatian bioarchaeology and all over the world
are supratentorial and do not always reveal such sophisticated surgical techniques
