The report states that "there has been slight interval increase in size of the enhancing mass in the right internal auditory canal, now with a small mushroom shaped component that extends into the the right cerbellopontine angle cistern at the level of the porus acusticus internus." "The maximum traverse dimension is 1.2-1.3 cm, is approx. 6 mm in AP diameter in the intracanalicular portion and 5 mm in superoinferior dimension. The CP angle component measures 7-8 mm AP diameter and approx. 3 mm in traverse diameter." Can anyone explain what this means in simple layman terms that I can understand?
Frank, I believe the "interval increase in size" merely refers to the fact that the tumor appears larger in the latest MRI compared to the immediately preceding one. MRIs are taken at intervals, typically six months. Hence, the jargon. The cerebellopontine angle (CPA) is a roughly triangular, empty space bordered on one side by the cerebellum, on the second side by the pons (part of the brainstem), and on the third side by the inside surface of the skull (on your right side). The word "cistern" in "cerebellopontine angle cistern" is somewhat redundant. Cistern simply refers to the space inside the angle (versus one of the outside surfaces of the angle). Since the internal auditory canal (IAC) in most people is between 0.7 and 1.2 cm long, and your tumor is 1.2 to 1.3 cm in (horizontal) length, it makes sense that it would now be protruding slightly into the CPA -- there's nowhere else for it to go as it grows larger, as the fundus (or lateral/towards-the-outside extent) of the IAC is basically a bony dead-end with only tiny holes in it for the cranial nerves to pass through (coming from the inner ear, or labyrinth). If I remember correctly (take this next part with a grain of salt), the porus acusticus internus is a small hole at the medial end (the end deeper inside your skull) of the IAC, out through which the facial, hearing and vestibular cranial nerves traverse into the CPA and on their way to the brainstem. Your tumor is 6 mm across in the AP (antero-posterior, or front-to-back) plane in the intracanicular portion (that which is inside your IAC). [Note: more exactly, this measurement -- like the other two tumor measurements -- is taken
obliquely , or at an angle, and not necessarily exactly along a horizontal plane from front-to-back, in order to measure the greatest diameter in that approximate plane.] Outside your IAC, the tumor balloons slightly to 7-8 mm, only because it's now outside the restrictive bony canal that is the IAC and is free to expand in the empty space that is the CPA. Inside your CPA, the tumor measures 5 mm across from top to bottom -- this is the superoinferior dimension noted in the report; it is more commonly referred to as the (oblique) craniocaudal measurement in MRI reports. I'm not exactly sure what the "3 mm in traverse diameter" comment refers to. It most likely means the extracanicular (CPA cisternal) component of the tumor -- as measured along the oblique transvere plane (i.e., from medial extracanicular extent to lateral extracanicular extent) -- is 3 mm long; in plain English: the portion of the tumor that is outside your internal auditory canal and in the CPA angle is 3 mm as measured from the point it exits your IAC to the point where it presently terminates at the other end (at the deepest point inside your skull, closest to the brainstem).
I have seen such hazy jargon in my own MRI reports (not the ones originating from Stanford, which are very rigorous). Sometimes, the MRI report may even include erroneous language. For example, my first MRI report stated that the medial extent of my tumor was 1 to 2 mm away from the fundus of my IAC, which is impossible (that would've placed the tumor completely inside my labyrinth and not in the IAC). I pointed out to the medical staff that someone had apparently written "medial" instead of "lateral" (the correct word), and they agreed it was a mistake. Similarly, I have seen different radiologists refer to that part of the tumor that was inside the IAC (instead of that which was inside the CPA) as the "cisternal" portion of the tumor. Who is correct? A cistern is basically an enclosed area; both the IAC and the CPA are enclosed. You need to read the MRI report and grok what the radiologist is trying to say, because he might use his own language that differs from how another radiologist might describe the tumor.
Anyway, I hope this clarified for you what all the jargon in your MRI report means. Rest assured, there is nothing to be alarmed about in your report. Given that you have an AN, this is all pretty typical of how an AN progresses, and yours is progressing very, very slowly and is still pretty far away from your brainstem.
As a personal aside, I think you are on the right track in considering CK for treatment, if and when you deem it is necessary. I had CK and am very happy in my decision.
Best wishes,
TW
