MRI of brain and cervical spine with T1 weighted echo train spin
 echo, T2 weighted echo train spin echo, fluid-attenuated
 inversion recovery echo train spin echo, MR diffusion imaging,
 time-of-flight MR angiogarphy with 3D maximum-intensity
 projection reconstruction, and with intravenous gadolinium-
 enhancement:

1. A long T1 and T2 lesion, about 6.1cm in greatest dimension,
   with heterogeneous ring-like contrast enhancement within
   marked expanded cervical spinal cord (red arrows in figures),
   at the level from foramen magnum to C2/3 junction, possibly
   due to intramedullary spinal cord tumor such as astrocytoma.
2. Presence of long T1 and T2 cystic lesions without contrast
   enhancement in medulla oblongata (yellow arrows in figures),
   just above the tumor, and in C3 spinal cord (green arrows),
   just  below the tumor, in favor of polar cysts.
3. Suspicious obstruction of foramen of Magendie from external
   compression by the polar cyst in medulla oblongata.
   Patency of bilateral foramen of Luschka.

Impression:
1. Intramedullary spinal cord tumor, C1-C2, nature to be determined.
   Polar cysts in medulla oblongata and C3.