Radiologic Evaluation of Basilar Invagination Without Obvious Atlantoaxial Instability (Group B Basilar Invagination): Analysis Based on a Study of 75 Patients

Beyond radiological imaging: Direct observation and manual physical evaluation of spinal instability

“…The treatment of Chiari malformation, syringomyelia, basilar invagination, cervical spondylosis, ossified posterior longitudinal ligament, and several such issues can be radically and rationally altered on the basis of evaluation of their relationship with instability of atlantoaxial joint. [1415161718192021] The fact that atlantoaxial dislocation can be diagnosed on the basis of clinical parameters and direct observations during manual manipulations of the bones of the atlantoaxial region has expanded the scope of treatment of craniovertebral junction instability.…”

Chiari Formation: Atlantoaxial Instability is the Cause

“…We identified that in cases with Chiari formation there is excessive cerebrospinal fluid (CSF) content within the spinal cord (syringomyelia) or outside the spinal cord (external syringomyelia) [13][14][15]. Similarly, there is excessive or more than normal amount of CSF within the brainstem (syringobulbia) or around the brainstem (external syringobulbia).…”

External syrinx introduction of a new term

“…In the spinal canal, the increased collection of CSF may be in the extramedullary space (external syrinx), inside the spinal cord (syringomyelia) or both inside and outside the spinal cord. [15] An excessive amount of CSF is also present in the posterior cranial fossa, inside the brainstem (syringobulbia), anterior and around the brainstem (external syringobulbia) and around the cerebellum. [15] The cerebellum, more in its superior vermis and superior cerebellum, becomes atrophic allowing an increased collection of CSF.…”

“…[15] An excessive amount of CSF is also present in the posterior cranial fossa, inside the brainstem (syringobulbia), anterior and around the brainstem (external syringobulbia) and around the cerebellum. [15] The cerebellum, more in its superior vermis and superior cerebellum, becomes atrophic allowing an increased collection of CSF. [16] Superior vermis is atrophied, but the herniated part of the tonsil is never atrophied, probably because a firm cerebellar tissue is necessary to provide a compact cushion.…”

“…In this respect, it seems that the pathogenesis and function of CSF, whether it is inside the cord in the form of syringomyelia (or syringobulbia) or whether it is outside the spinal cord in the form of the external syrinx (or external syringobulbia) is essentially the same. [15] Syringomyelia is more often seen when the odontoid process is either in its normal position or is vertically herniated into the posterior cranial fossa. External syringomyelia is more often when the odontoid process is posteriorly angulated or horizontal in its lay.…”