Hi Emily!
A patient could experience the syndrome of the trephined without a sunken skull.
Here’s an exceprt from a 2021 article: “Furthermore, SoT is often associated with a sinking skin flap morphology, a radiologic [30] and clinical sign [47]. Although this association led to the development of new terminology for the syndrome (“sinking skin flap syndrome”), numerous findings in the literature indicate the existence of SoT in patients without sinking skin flap morphology[42].”
(https://pmc.ncbi.nlm.nih.gov/articles/PMC8976790/#:~:text=Introduction-,Syndrome%20of%20the%20trephined%20(SoT)%20is%20an%20underrecognized%20complication%20after,skin%20flap%20morphology%5B42%5D.)
It is recommended that patients be positioned in Trendelenburg to help alleviate symptoms as they await cranioplasty. Here’s a quote from another article in the Journal of Neurosurgery: “Syndrome of the trephined” or “syndrome of the sinking skin flap” is an unusual condition in patients with large skull defects, in which progressive neurological deterioration occurs in association with the scalp flap sinking into the defect. In our case both these features were promptly reversed and corrected by lowering the patient’s head, and subsequently by cranioplasty.”
(https://thejns.org/view/journals/j-neurosurg/111/4/article-p650.xml#:~:text=normal%20pressure%20hydrocephalus.-,%E2%80%9CSyndrome%20of%20the%20trephined%E2%80%9D%20or%20%E2%80%9Csyndrome%20of%20the%20sinking,head%2C%20and%20subsequently%20by%20cranioplasty.)
That first article also contains some information about the importance of prompt treatment, as the “window of opportunity” closes fairly quickly with less neurologic improvement with increased time to cranioplasty.