Hi;
Yes, TBIs can present with all sorts of symptoms, since the injury is often diffuse and a nice "bang" to the head causes acceleration and deceleration damage. However, if the ataxia is a fairly recent problem (actually, how long after the accident was he diagnosed?) and is getting worse, this might need specialist, i.e. Neurologist assessment. It could be caused by a degenerative process - now this is going to make you really happy isn't it ...

TBI Rehab is a specialist area within Physio and not many of us have received additional training to provide the adequate treatment/ education. If your Physio support is unsatisfactory, would you be able to contact the Specialist Rehab Centre and ask for alternative support/ suggestions? Or are they able to review your partner and set up a plan for him?

Generally, ataxia is rather difficult to treat. I am unaware of what current research suggests. Here's my take:
Some patients do well with passive guidance for the desired movements; some work well when the joints are approximated (="pushed"), as in working against resistance or in a situation where e.g. the hand is fixed on a surface, rather then asking the patient to do a "free movement in space". The principle here is also to do task orientated and purposeful movements, i.e. aiming for a specific goal. In my experience, most ataxic patients lack trunk control = you need a firm trunk to be able to control arm movements. So that's worth looking at.

Hope you understand what I am talking about.
Good on you for caring so much,
best of luck,
Fyzzio