On the face of it-that Beethoven's deafness was caused/contributed by" parental abuse" seems a bit odd! How could "parental abuse" be a contributing factor deafness?
Beethoven was abused by various family members, including receiving frequent blows aimed directly to his head and ears. These beatings are stated to have caused bleeding from the ears, severe tinnitus & vertigo (with nausea) and most likely also caused ruptured ear drums & damage to the cochlea (possibly similar to the injuries that Zebadee2010 here on AD suffered from his fall) .
In addition to trauma-related hearing loss (and tinnitus) many researchers/scholars have stated that medical documentation exists indicating that Beethoven likely had Otosclerosis as well as trauma-related-hearing loss.
For more information on Beethoven's live I'd suggest "Thayer's Life of Beethoven" as a reliable and respected work to start with - there are of course many other books/texts about Beethoven's life, health, music etc.
Are there any other persons this has happened to?
Yes.
Head trauma IS one of the three major causes of hearing loss (the others two being genetic and infection/disease/immune) and was much more common before the advent of highly mechanized factories, where people where doing the majority of building/construction/assembly etc by hand and before basic workplace safety regulations such as helmets/hardhats etc became mandatory. Falls and car accidents are the most "common" means of trauma-related-hearing loss (aside from blows to the head from fights including boxing, martial arts etc espeically when headgear is not worn.)
There thousands of documented cases where head trauma (falls, abuse, seizure disorder/epilepsy, "lesions/plaques" such as in MS etc) is stated to be the specific cause of one's hearing loss - ranging from minor to profound in degree & commonly accompanied by fluctuating tinnitus as well as balance issues (including vertigo). For specific cases of trauma induced hearing loss/deafness, past and present medical journals are an accessible & reliable source - many of which are available online (ie. university libraries) or via physical medical libraries or universities' sciences libraries.
Hope this helps
I have wondered if he had an excellent memory for sound akin to having photographic memory.
It's likely that Beethoven had especially accurate relative pitch (if not true "perfect pitch") as well as an eidetic memory for pitches (the sound of each note). It's not "common" exactly, but it's not "rare" either. I know a number of people (hearing, Hoh and LD) including myself who have played musical instruments from peri-lingual ages (3-4) who develop "near eidetic memories" for music or pitches (even if we don't have perfect pitch etc). My personal thought on this is that because we started playing musical instruments - learning pitches, intervals, patterns etc during a time that our language centre was developing, in many ways our brains see and "store" music as a language (not just sounds) along side English, ASL etc. Because our brain views music as a language we are able to "internalize" it in a nearly identical manner as we internalize English - complete with an "internal voice" (similar to the "voice" hearing, Hoh and LD people may hear "internally" when thinking words, reading, etc). In my case, my "internal music voice" not only functions like a 'built in music player' that lets me "play back" music and voices internally that sound IDENTICAL to listening aurally to the music, I also have what for all intends and purposes is an "internal orchestra" that allows me to CREATE original music or (with constant practice) "hear" music notation. One "quirk" of this is that it's NOT like memorization where I consciously would listen carefully to something so that I would be able to "play it back" internally at a later date (in fact I'm unable to do this) - instead it's a completely subconscious occurrence which I am only aware of once the "playback" happens, which could be weeks, months or years after the "internal recording" takes place!! For me "getting a tune stuck in my head" - means that I literally have a song PLAYING in my head on "loop", NOT that I'm internally humming a tune to myself. The sounds are SO real that it could almost be called an auditory hallucination (but it's not) - and there have been a number of times when I'm drifting off to sleep, dreaming or just starting to wake where I'll "hear" something and be woken only to discover that there isn't an external source for the sound at all!
I know a number of others who are like myself in this regard as well - in fact a number of my (former) fellow orchestra members also experience music/sound this way - EVEN though we are typically VERY visual conscious learners (I can't memorize things by listening to them - only by visual & or kinetic means). Personally - I think it's very likely that Beethoven experienced music in a similar way as myself & my orchestra-mates do ... which would allow him to continue to compose as he did ... espeically when combined with becoming intimately familiar with the vibrations associated with each pitch/note etc. For me vibration and sound are intimately and inextricably connected - to the point that if I feel a vibration my brain automatically generates a sound to accompany the vibration EVEN if there is no audible sound associated with that vibration