Brief Answer:
reason is not clear from these documents..

Detailed Answer:
Hello XXXXXX, Welcome back to HCM..

I've gone through your query and reviewed the complete hospital case-summary of the patient enclosed in the other query..

Now SDH (acute or sub-acute) is mostly due to trauma only.. however there are certain contributory factors to it, which also play a major role i.e. age-related brain atrophy, alteration in vessel wall's structure(mostly age related fragility) , drug induced(certain blood-thinners) , some hereditary and other bleeding disorders, rarely even without any of these(known as spontaneous)..

Even though in one of the column of the summary , it was mentioned as "un-witnessed fall", still it's not possible to comment on the exact nature of the incidence without any direct witness or any direct evidence of trauma to head..however it should be noted that, though not definitely but at this age, even mildest form of head injury can give rise to this kind of condition..

Hope this'll clear your doubt, let me know if you need any further clarifications..

Take Care
Kind Regards

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