I'm not trying to dissuade you from ECT, but this is all info that I wish someone had told me before I made the decision (sorry it's so long). It's difficult to get this info since a lot of doc's aren't even aware. You have to really dig into the research to find out a lot of this info.

It's been 8 months since completing ECT & I'm still having these problems: slow cognitive processing, difficulty w/reading, sleep issues, decreased eye hand coordination & spatial ability, vision problems, difficulty w/cause & effect, distractibility/inattention, changes in hearing/ taste/smell, impulsivity, disinhibition, easily frustrated, mental fatigue, apathy, difficulty w/problem solving, language problems and anxiety

I had none of these symptoms before ECT & they say it's permanent.

This is not that uncommon. The FDA Advisory Committee on ECT (2011) gathered patient testimony & reported: reduced cognitive ability, difficulty learning/reading, unable to perform previous job skills, memory problems, brain damage, reduced quality of life, suicidality,worsening or onset of new psychiatric symptoms, loss of motor skills/coordination, damage to speech, sleep problems, visual/auditory problems, loss of creative ability, etc.
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The info about the 6 weeks can be found in several places. One of them is a research article "Effectiveness of ECT in Community Settings" (Sackheim et al 2004) It found that patients' ratings of depression significantly worsened at 4 weeks after the completion of ECT. The 4th week was the turning point of relapse. By the end of the follow-up period at 24 wks, 64.3% of patients had relapsed. They estimated that by the 10th day after ECT, patients had lost 40% of the improvements they’d gained during ECT. In the end, there were only 23.4% of the patients that responded to the ECT and did not relapse in the first 6 months.

The American Psychiatric Association Task Force Report (1990) notes that patients with pre-existing cognitive impairment are at greater risk of cognitive side effects during a course of ECT.

You might want to look up info on "cognitive reserve." It basically says that everyone starts out with a certain amount of brain capacity to protect them from old age, dementia, etc. So with TBI, you're already at risk for developing these things sooner. But then if you add any other kind of injury to the brain, the side effects are compounded more than what you'd expect from that head injury alone.