Incapacitated Child Tax Credit

Hi,
I wonder is anyone out there in the same position. I claim incapacitated child tax credit for my
disabled child. She is permanently incapacitated. My question is does this tax credit run until the child is 18 or 21? my child will be 18 this year and I'm wondering will I lose this tax credit?
The conditons on revenue.ie seem a bit vague.
from the website::
Conditions to Qualify
In order to qualify the child must:

• be under 18 years of age and permanently incapacitated either physically or mentally, or
• if over 18 years of age at the commencement of the tax year and is permanently incapacitated either physically or mentally from maintaining himself or herself and had become so permanently incapacitated before reaching 21 years ,or
• had become so permanently incapacitated after reaching 21 years, but while he or she has been in receipt of full-time education at any university, college, school or other educational establishment, or while training full-time for a trade or profession for a minimum of two years, or
• is any child for whom the claimant has custody of and maintains at his or her own expense and who is permanently incapacitated.

Does anyone out there still avail of this tax credit after their child has turned 18?
For instance, Is there an extension if the child is still in School?
Any help much appreciated.

Part 4 of the conditions to qualify for incapacitated child allowance does not specify any age, so you still qualify for the allowance once the criteria in the last paragraph apply to your situation; in other words, you can continue to claim incapacitated child allowance if you have custody of the child, you maintain him/her at your own expense, and they are permanently incapacitated. There is no age restriction on this criteria, i.e. they are still your child if they are 40 yrs of age and you are 65.

Thank you very Much!