The first time we encounter the writer and presenter Clemency Burton-Hill in this Arena documentary, she is in full, fluent, broadcasterly flow, promoting her new book on classical music, Year of Wonder. The next time we see her, she is struggling to spell her own name. The former clip is from 2017, the latter while Burton-Hill was recovering from the brain haemorrhage she suffered in January 2020 at 38 years old.

My Brain: After the Rupture covers the two years after Burton-Hill’s brain injury. She begins recording herself in her hospital bed, having clearly grasped the journalistic potential of documenting such a life-altering event. She tries to speak, but much of what she says is incomprehensible: she can remember most words, but has lost the ability to actually say them. Her terror and despair, however, is crystal clear. “I don’t know that this is going to be OK,” she eventually manages to utter, her voice wavering violently.

It isn’t OK. While Burton-Hill’s physical and verbal progress over the next two years seem astonishing from the outside, her emotional landscape – dominated by fury, impatience, anxiety and grief – suggests the psychological repercussions of her brain bleed are too profound to fully articulate. This is despite her absolute candour: her body, she says, is “frozen in neurological winter”. Rather than delving into the technicalities of Burton-Hill’s medical condition, this fascinating, raw and intimate documentary simply bears witness to a woman navigating the loss of her former self with bravery and superhuman determination.

That former self was defined by a love of music. Burton-Hill has lost sensation in the right side of her body, which means it’s initially impossible for her to play her beloved violin. She was an accomplished player and the instrument has long been an “ally and a friend”: we see her four-year-old self perform Bach’s Minuet 1; in home videos she’s air-violining on the sofa. She has spent her career extolling the virtues of classical music, so her inability to play is now the source of much frustration and sadness.

It’s a career Burton-Hill is extremely keen to return to. Before the haemorrhage she was working on a sequel to Year of Wonder; soon, she has painstakingly finished the book. It’s an incredible achievement – but as she goes through a proof with her editor, Burton-Hill is suddenly overwhelmed by agony. She is desperate to put the book behind her because she “can’t have bits of my former life taunting me”. Collaborating with her past self only highlights how much she has changed.

As the whole preschooler-playing-Bach thing suggests, Burton-Hill has always been a high-achieving perfectionist (she graduated with a double-first from Cambridge). Combine that with lifelong “crippling self-doubt” and you have someone for whom accomplishment and career success is hugely validating. Considering Burton-Hill’s catastrophic health issues, it’s telling that a throwaway remark by an insensitive doctor constitutes one of the film’s most brutal scenes. She was a writer and a musician, he implies. “So after the mourning stage, it’s figuring out: what can I do now that will fulfil me in a way that [those things] fulfilled me?” As Burton-Hill tears up, we realise she has just been robbed of something precious: her belief that she will one day excel at work in the way she once did.

Yet it’s the more generic elements of Burton-Hill’s life that are most moving to watch. In the early days, she’s tormented by the fact that she is too exhausted to play with her sons; later she is gutted by her eldest’s admission that he is forgetting what she was like before the rupture. While her family background is not particularly relatable on paper – her father is Humphrey Burton, host of 70s arts programme Aquarius (he also established the BBC’s Young Musician of the Year, which Burton-Hill presented in the 2010s) – its dynamics are universal. Burton was a largely absent father, his daughter has been craving his affection her whole life. One of the most emotional moments here has nothing to do with the brain bleed; instead, it involves her 90-year-old dad crying about his parental regrets.

The documentary concludes at the end of 2021, as Burton-Hill launches the second Another Year of Wonder book. Earlier, she explained the concept of a two-year recovery window after a brain haemorrhage, which is presumably why the film ends there. But it leaves you wondering how she’s coping, three years on. Has she continued to push herself career-wise or have her passions and priorities changed? Has she made peace with her new reality? I’d like to think Burton-Hill has held on to the admirably fierce mantra with which she approached her brain injury back then: no acceptance, just defiance.

• My Brain: After the Rupture aired on BBC Two and is on iPlayer now.