Hi Mitsuyo
I will try to answer some of your queries:
1) How far can the chemical travel? So, ESIs could remain local, correct? What else could affect the degree of spread? I had Epidural Anesthesia for child-birth three times. Before the first one, an anesthegiologist told me that I would need higher dose than usual due to the scar tissues caused by a previous lumber surgery. First labor ended up with a C-section with even higher dose of the drug and longer administration with additional Morphine injected via the same catheter for post-operative pain.
* amount of chemical administered? yes
* duration of such administration? yes
* number of such administration? yes
(2) Does the \"traveling\" or spread occur over time or in a very short period of time from the point of chemical insult? for oil-based myelogram dye there could be a fresh spread if the encapsulated droplets are disrupted e.g. by a fall; however, these days, most chemicals spread quickly once administered
(3) Can we assume that scarring will only spread as far as the chemical can reach? not necessarily
(4) Is scarring the beginning stage of Arachnoiditis? no, the first stage is an inflammatory response when the nerve roots swell; second stage, the scarring (fibrosis) begins; third stage the scar tissue sticks the nerve roots together and pulls them out around the dural sac, if severe the clumping may even obliterate the subarachnoid space, impeding CSF flow
(5) Is scarring itself different from arachnoiditis? in a way; what we are talking about most of the time with this forum is the severe form of arachnoiditis i.e. adhesive arachnoiditis; this is the clinically significant form. Asymptomatic arachnoiditis can be present without being a problem.
(6) If AA did indeed spread, would it show up on an MRI of different level/area? quite possibly
I had a fusion at L5-S1. I believe the Epidural Anesthesia was given at a higher level than that. My myelogram with CT showed clumping of several nerve roots at about L4.
(7) The same myelogram showed ventral extradural defects at L1-L2 through L4-L5. What does this mean? Is this a sign of existing scarring? it may reflect scar tissue inside and/or outside the dura, causing damage to the dura either distorting it or even compromising it's integrity
(8) I think there are two ways to \"see\" the progression of AA: progression of symptoms, which can be subjective and influenced by many factors, and progression of scarring, inflamation, clumping of nerve roots, etc, which can be seen in MRIs, etc. Can we assume that the latter progression can only be measured by comparing MRIs (CT, etc) obtained at different times?
it is important to remember that MRI findings often don't correlate well with symptoms. This holds true of all MRI appearances, not just for arachnoiditis. Also remember, MRIs are a static picture that doesn't show what happens when the patient sits/stands/walks
Hope that helps!
regards
DocSarah