True os-odontoideum is rare. Ossiculum terminale is nonunion of the apex at the secondary ossification center is much more common. Two anatomic types are orthotopic: Ossicle moves with the anterior arch of C1 and dystopic: Ossicle is functionally fused to the basion, and may subluxate anterior to the C1 arch.
Presentation of os-odontoideum included occipitocervical/neck pain, myelopathy and intracranial signs and symptoms.[7
Most patients are neurologically intact and present with atlantoaxial instability which may be discovered incidentally. Many symptomatic and asymptomatic patients have been reported with no new problems over many years of follow-up.[8
] Conversely, cases of precipitous spinal cord injury after seemingly minor trauma have been reported.[9
Generally, patients with an occipital encephalocele are operated in the prone position with controlled ventilation and close temperature monitoring. Aspiration of the cerebrospinal fluid prior to incision in patients with large encephalocele helps in dissection of the sac. For a circular encephalocele with a small occipital bone defect, a transverse incision is ideal. The sac is separated from the flap. Patients in whom the encephalocele extends above and below the posterior fossa need a vertical incision. Sometimes, the brainstem and occipital lobe are present in the sac. Care must be taken to identify the contents of the sac. Rarely, the sagittal sinus torcular and the transverse sinus are in the vicinity of the sac. It is preferable to preserve the neural tissue. The dura is repaired meticulously to get a water tight closure. The dural defect can be repaired by using the pericranium as a graft. In neonates and infants, no attempt should be made to cover the bone defect by a bone graft.[10
A large number of factors influence the outcome in patients with occipital encephaloceles. These are the site, the size, the amount of brain herniated into the sac, the presence of brainstem or occipital lobe with or without the dural sinuses in the sac and the presence of hydrocephalus.[12
Previous authors described a 4-day-old boy was admitted with a large posterior fontanelle encephalocele. The baby had a small head with a circumference of 30 cm only and encephalocele with a circumference of 37 cm. Excision and repair of encephalocele was done without neurological postoperative complications or neurological deficit.[16
] In our case, simultaneously presented with torcular encephalocele with os-teminale and there was only neck pain and no neurological deficit.
There was no hydrocephalus. X-ray of the cervical region showed os-terminale , split atlas, both anterior and posterior arch defect [Figure and ].
Lateral X’Ray CVJ showing OS Terminale
(a) Sagittal and (b) axial view CT CV junction show OS terminale and encephalocele with bone defect
The patient was operated in a prone position, and immobilized neck by hard cervical collar during surgery. At operation, there was gliosed brain inside the sac, which was excised. Bone defect was 3 cm in diameter. Dura was closed using 5-0 vicryl and wound was closed in multiple layers. Patient had an uneventful recovery was discharged on 8th postoperative day. She was followed-up after 15 days, when she had no problem.
We advised use a cervical collar and regular monthly follow-up at neurosurgery outpatient department, for os-terminale, which may need a surgery, if required.