Introduction. Cranio-vertebral decompression remains the common denominator for the treatment of syringomyelia associated with Chiari I. On the other hand, the details of the procedure, remains controversial. The success of the surgery is to restore the circulation of cerebro-spinal fluid at the level of the foramen magnum. How is this circulation restored to the level of foramen is the question? We offer our attitude towards the treatment of syringomyelia with Chiari I.
 Material and method. Consecutive series of 32/121 patients benefiting from cranio-vertebral decompression associated with intrapial aspiration of cerebellar tonsils treated for syringomyelia with a Chiari I malformation in adults.
 Result. Motor deficits were present in 20 / 22 patients, representing 90% of the entire patient group. these motor deficits are improved in 16 out of 22 cases, and remained unchanged in 06cas. no motor aggravation occurred. in our study, bone decompression and intra pial aspiration of cerebellar tonsils (sub arachnoids manipulation) were found to be associated with favourable results on clinical signs and symptoms. However, sub arachnoids manipulation and intra pial aspiration of cerebellar tonsils showed a little more complication compared with bone decompression with dural plasty.
 Conclusion. The bone decompression with dural graft and intradural dissection of adhesions and reduction by intra pial aspiration or resection of the tonsils is indicated on the MRI aspect of cerebellar tonsils of considerable size totally obstructing the foramen Magnum, the intraoperative finding, through the arachnoid, of the absence of passage of the cerebro-spinal fluid because of the bulging of the cerebellar tonsils.