in this question all choices are some sort of neoplasms, but overall most common cause of conus medullaris is supposed to be
lumbar canal stenosis followed by spinal trauma followed by disc prolapse. and then comes neoplasias (metastasis, astrocytoma, meningioma, neurofibroma etc.)
Intradural extramedullary tumors account for approximately 20% of all spinal tumors, with intradural-intramedullary tumors accounting for less than 5% of all spinal tumors.
In the adult population, ependymomas (intradural intramedullary) are the most common intra-axial tumors of the conus medullaris and filum terminale.
UpToDate just says "Conus Medullaris Syndrome: Lesions at vertebral level L2 often affect the conus medullaris. There is early and prominent sphincter dysfunction with flaccid paralysis of the bladder and rectum, impotence, and saddle (S3-S5) anesthesia. Leg muscle weakness may be mild if the lesion is very restricted and spares both the lumbar cord and the adjacent spinal and lumbar nerve roots. Causes include disc herniation, spinal fracture, and tumors."
DynaMed does not seem to mention conus medullaris syndrome at all, and their info on cauda equina syndrome is uncharacteristically sparse
I couldn't find any review articles on PubMed.
So maybe there is no absolutely knowable right answer. I guess I'll stick with the Emedicine version, since it's what's already in my head and I'm not sure how much more room I've got up there...:indifferent:
So I think that in general the most common cause is MVA. So patients with CMS are not obligeted to have one of these ( i.e. dermoid tumor / LIPOMA /Ependymoma /nerve root tumor). So in this kind of question we have to choose the suitable answer and it is Ependymoma In my point of view of cousre
i seriously doubt ependymoma as an answer.
reason #1: since the main nerve area involved in conus medullaris is situated at a relatively peripheral area of the spinal cord, the tumour that presses from outside will have more early and severe impact on the S345. in contrast the tumours that press from inside the spinal cord cause anaesthetic features as pain and temperature fibres travel more centrally. and as we all know that ependymoma is a central tumour i.e. intradural and intramedullary.
reason #2: intradural and extramedullary tumours are more common than intradural intramedullary tumours (ependymoma > astrocytomas)
reason #3: main feature of conus medullaris is involvement of perneal region in the form of saddle anaesthesia. but intradural and intramedullary tumours have sacral sparing effect in the beginning, although they may involve S345 eventually.
so nerve root tumours seems to be the best answer...