Chiari I malformation associated with ventral compression and instability: one-stage posterior decompression and fusion with a new instrumentation technique.
OBJECTIVE
We describe an alternative surgical technique for treatment of Chiari I malformation associated with ventral compression and instability of the region. An expansive suboccipital cranioplasty and a rigid occipitocervical fixation are performed in one stage.


METHODS
The occipitocervical fixation is performed by use of metal rods fixed on the cranial side by screws inserted into the diploic layer of occipital bone and on the caudal side by screws inserted into the pedicle of the axis or in a transarticular fashion into the lateral masses of axis and atlas vertebra. A large piece of autologous bone is placed in the region between the rostral edge of cranial decompression and the axis, with the aim of achieving both expansive suboccipital cranioplasty and occipitocervical fusion.


RESULTS
We performed this procedure in two patients with Chiari I malformation associated with basilar invagination and occipitalization of the atlas. Postoperatively, decompression of the brainstem and restoration of normal cerebrospinal fluid flow at the craniovertebral junction were confirmed radiologically, and the patients were relieved of their symptoms. At 1 and 3 years of follow-up, respectively, solid bone fusion was observed between the occipital bone and axis in both patients.


CONCLUSIONS
Simultaneous posterior decompression and occipitocervical fixation with an alternative instrumentation technique is discussed. The procedure can be performed regardless of the size of suboccipital craniectomy. Screw insertion into the diploic layer of the occipital bone has not been described previously.
Nishikawa
Misao
M
Department of Neurosurgery, Osaka City University Graduate School of Medicine, Osaka, Japan.
Ohata
Kenji
K
Baba
Motoki
M
Terakawa
Yuzou
Y
Hara
Mitsuhiro
M
D000328:Adult; D001139:Arnold-Chiari Malformation / Q000150:complications / Q000601:surgery*; D002574:Cervical Vertebrae / Q000601:surgery; D003388:Cranial Fossa, Posterior / Q000601:surgery*; D019299:Decompression, Surgical / Q000295:instrumentation / Q000379:methods*; D005260:Female; D006801:Humans; D016268:Internal Fixators; D007593:Joint Instability / Q000209:etiology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D009777:Occipital Bone / Q000601:surgery; D013117:Spinal Cord Compression / Q000209:etiology / Q000601:surgery*; D013123:Spinal Fusion / Q000295:instrumentation / Q000379:methods*