giant cisterna manga

I had an MRI done and was told it was normal.  In reading the reportI noted that it said I had a "giant cisterna manga which is probably congenital." What does this mean? Would it ever possibly be anything of concern?

[dr_simran]

Hello dear,
The cisterna magna is one of three principal openings in the subarachnoid space between the arachnoid and pia mater layers of the meninges surrounding the brain.. The cisterna magna is located is located between the cerebellum and the back of the medulla oblongata. Cerebrospinal fluid produced in the fourth ventricle drains into the cisterna magna via the lateral apertures and median aperture.
The term mega cisterna magna has been loosely applied to a large retrocerebellar cerebrospinal fluid (CSF)–appearing space with a normal vermis and normal cerebellar hemispheres.
Mega cisterna magna has been associated with infarction, inflammation, and infection, particularly cytomegalovirus, as well as with chromosomal abnormalities, especially trisomy 18.
In the absence of other findings to suggest a posterior fossa lesion, a mega cisterna magna is unlikely to be clinically significant.It is normal if there are no signs abd symptoms.
Best

[cvette]

I am a Nurse Anesthetist.  I have been having increased health problems, especially since Jan. 2008.  At that time I woke at 2 AM with severe involutary muscle jerking of my neck, head and jaw with lasted about 5.5 hrs.  I had weakness, dizziness, nausea, high blood pressure, palpatations and memory loss.  I went to the ER and an MRI showed a mega cisterna magna("normal variant").  There "is also a CSF signal intensity extra axial mass in the posterior fossa on the left, which causes some mass effect on the left cerebeller hemisphere.  The cyst measures5.7X1.9X7.5cm."

This was blown off, including by the Neurologist.  I have since had an episode about every month lasting several days with similar symptoms, but only some facial muscle twitching.  The big thing has been dizziness, fatique, hypertension, night sweats and chills, nausea a spacey brain.  

Having done a lot of anesthesia for a surgeon who is noted for being a pioneer in relieving pressure on the brain stem related to Chari Malformation and hypoplastic posterior fossa, I had asked my Doctors if there was a Chari because my symptoms were so like scores of patients I had cared for.  

I am collecting my medical records for yet another consult and I noted this on my MRI and decided to research it.  I have much more to do but it makes sense to me that pressure on my brainstem is no different, in effect, than the patients I have cared for.  Anybody else have any useful thoughts or suggestions?   Thanks