What do you think is serial growth with small ANs?

[Keeping Up]

*** an attempt at a bit of math geekiness - I haven't done algebra in years! I think we have a few math folks here ***


Alright been having a bit of fun playing with volume formulas - obviously somewhat of a proxy.

So, to use my example - I have a tiny little AN at 5mm x 8mm.  With a sphere volume (or a prolate spheroid because it has a different radius - 4/3 x pie x r(2) x height - so 4/3 x 3.14 x (2.5mm x 2.5) x 4mm = 105mm(3)). 

I thought that a 25% growth would be somewhat extreme - but that actually only leaves me with a 5.4mm x 8.64mm AN - still really quite small, and really not that much growth.

So, what 'growth' do you think raises an eyebrow with small ANs.

FYI - a .5cm growth (ie. average growth at 6months - but typically for large ANs only, the small ones do typically grow slower) would imply a volume of 134.6 mm(3) or about 28% growth.

FYI (2) - .5cm growth on a 1.2cm x 1cm AN would imply a volume growth of about 14.5%

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Not sure if that made much sense, but it seems that a 5mm growth a 6 months (or 1 cm at one year) [the Americans must be amused by the whole metric system - a whole new ballgame - I am young(ish) and Canadian so metric is 2nd nature) - would be extreme for a small AN.

Just working it out in my head - will ask next week.  See if the doctor understands my math logic on volume growth.  Regardless, I have 5 months to go!

Ann

[Keeping Up]

Ooops - so '2nd nature' - I messed up - will need to come back and redo my calculations - an average growth I think is 1mm not 1cm.

will be back to recheck my notations!

[Larry]

Ann,

You can't apply a maths formula projecting growth patterns re mass for these things.

The key issue is how far into the brainstem has it grown. measuring the distance from the bone to the brain, mine is 18mm. the cut off for radiotherapy is 25mm.

My AN almost doubled in mass in 15months. My neurosurgeon told me of a case where the AN doubled in size (and mass) in 7 months precluding rasiotherapy treatment. this growth was incredible and unusual but nevertheless happenned.

The important things here, and i know I'm off the topic a bit' is the size and whether it is causing symptoms or not.

Laz

[HeadCase2]

Hi Ann,
  I share your engineering like approach to looking at the size of ANs.  Look for posts from the top directory that contain "Volume calculation" and you'll find a few topics like this, calulating the volume of an AN by modeling it as an elipsoid.  AN shape can be more complex than an elipsiod, but it's a useful approximation.  I also agree with Larry that location is very important, and what structures the AN tumor compromises.
  Most articles I've seen list the "average" growth of an AN to be around 2mm/year.  But from hanging out here on the forum we have to realize that the growth rate can be variable, even for the same individual over time.
Regards,
  Rob

[leapyrtwins]

Ann -

IMO the thing to keep in mind is that the words "average" and "normal" don't always apply to everyone.

My diagnostic MRI showed my AN was 1.5 cms, but when I had surgery approximately 6 weeks later, my neurosurgeon said it had "doubled"; my neurotologist said it had "almost doubled". 

Regardless of who was correct, my AN was obviously more than 1.5 cms when it was removed.  So, I either had very rapid growth or an MRI that had inaccurate measurements. 

I guess my point is, serial growth may or may not apply to you and your AN, which is why doctors recommend MRIs every six months to monitor growth.

Also, as Laz mentioned, sometimes treatment decisions are made based on the location of an AN and/or the problems it is causing.

BTW, as an American, I can tell you that I don't understand the metric system.  I didn't understand it back in grade school and I still didn't understand it 30-something years later when I tried to help my children decipher it last year in 6th grade 

Jan