The patient came to the clinic 10-March-2014 complaining of LBP for 18 months with right sciatica for 4 months down to all toes right foot. She has occipital headache for 1 month. MRI cervical spine done 04-March-2014 showing an osseous bony tumor originating from the left side of the C1 lamina with severe compression of the spinal cord. MRI lumbar spine showed bulge L5-S1 disc.

On examination; the patient is not limping. SLRS was 60 degrees both sides without pain. Romberg stable with no cerebellar signs. There is weak left upper limb and both feet and the proximal muscles of the left lower limb 4/5. Babinski was positive both sides. MRI of the brain with MRA ruled out presence of any connection with the vascular structures.

Setting position. Skeletonization of the foramen magnum, C1 and C2 laminae. Drilling around the lesion, which was involving the left half of C1 and C2 laminae and forming a joint between the C1 and the foramen magnum. There was a joint between the pathologically changed C1 and C2 laminae in the medial and left parts of the laminae. The drilling was continued until the dura was seen all around. Elevation of the compressing bony mass, which was adherent to the dura. Sharp dissection was done to avoid traction tear of the dura. The dura of the spinal cord after completion of the elevation of the bony mass became lax and hanging free. There was a joint between the left half of C1 and C2 laminae and between the lamina of C1 and left side of the foramen magnum. The mass was sent for histologic studies. The left C1 root was seen. The left vertebral artery was seen within its canal at the C2 level. The left C2 root was seen in the lower left corner of the created bony defect. Checking for instability with the setting position with DORO fixed clamps is impossible. Using the C-am in the lateral position with 25 degrees rotation to both sides also gave insufficient data to rule out instability. Using the C-arm in AP in the setting position also was impossible.  Further dissection of the left lateral bony parts with manual inspection gave bony continuity of C1-2 for more than 20 mm, confirming the presence of sufficient stability. Routine closure of the wound.

Smooth postoperative recovery. The power of four limbs became normal. It was decided to perform CT-scan of the area to have more confirmation about the stability of the bony structures.

The patient has a bony mass of unusual morphology. The mass in consistency is bony hard but is different from healthy bone. It is more vascularized and having abnormal joints between the C1 and C2 laminae and the C1 and foramen magnum.

 The lesion is causing clinical deterioration. May be the deformity is congenital and with age start to manifest itself. The histologic result will clear the situation.

The final histologic result confirm the presence of normal bone and bone marrow. This means, that the patient has this rare congenital anomaly.