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Craniovertebral Junction Instability: A Review of Facts about Facets.

Goel A - Asian Spine J (2015)

Bottom Line: The facets of atlas and axis form the primary site of movements at the craniovertebral junction.All craniovertebral junction instability is essentially localized to the atlantoaxial facet joint.Direct manipulation and fixation of the facets forms the basis of treatment for instability.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurosurgery, King Edward Memorial Hospital and Seth Gordhandas Sunderdas Medical College, Mumbai, India.

ABSTRACT
Craniovertebral junction surgery involves an appropriate philosophical, biomechanical and anatomical understanding apart from high degree of technical skill and ability of controlling venous and arterial bleeding. The author presents his 30-year experience with treating complex craniovertebral junction instability related surgical issues. The facets of atlas and axis form the primary site of movements at the craniovertebral junction. All craniovertebral junction instability is essentially localized to the atlantoaxial facet joint. Direct manipulation and fixation of the facets forms the basis of treatment for instability.

No MeSH data available.


Related in: MedlinePlus

Images of a 22-year-old female. (A) Computed tomography (CT) scan shows the craniovertebral junction. (B) Section through the facets shows type 2 atlantoaxial facetal instability. (C) T1-weighted magnetic resonance imaging (MRI) shows Chiari malformation and syringomyelia. (D) T2-weighted MRI showing the Chiari malformation and syringomyelia. (E) Postoperative CT scan following atlantoaxial fixation. (F) Atlantoaxial lateral mass plate and screw fixation. (G) Postoperative MRI showing reverse migration of the tonsils and reduction of syringomyelia.
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Figure 4: Images of a 22-year-old female. (A) Computed tomography (CT) scan shows the craniovertebral junction. (B) Section through the facets shows type 2 atlantoaxial facetal instability. (C) T1-weighted magnetic resonance imaging (MRI) shows Chiari malformation and syringomyelia. (D) T2-weighted MRI showing the Chiari malformation and syringomyelia. (E) Postoperative CT scan following atlantoaxial fixation. (F) Atlantoaxial lateral mass plate and screw fixation. (G) Postoperative MRI showing reverse migration of the tonsils and reduction of syringomyelia.

Mentions: Musculoskeletal changes associated with basilar invagination like short neck, torticollis, platybasia, Klippel-Feil abnormalities, and spondylotic spinal changes are manifestations of chronic and subtle atlantoaxial instability [1920]. The instability is more often of types 2 and 3 facetal dislocation. Following atlantoaxial fixation, all these secondary musculoskeletal alterations have a potential for reversal in the immediate postoperative phase [1920]. This fact suggests that the musculoskeletal alterations are not congenital defects or a result of embryonic dysgenesis, but are a manifestation of chronic instability, and essentially have a protective function. These musculoskeletal abnormalities are not primary in nature or the cause of the problem, but are a secondary effect or result of the problem. On similar lines, we have recently identified that Chiari malformation and syringomyelia are also secondary or protective formations and are a result of long-standing atlantoaxial instability [2122]. Chiari malformation can be simulated as nature's air bag that places it in position in the event of manifest or unidentified atlantoaxial instability. Like the air bag, the herniated tonsils act as a cushion that provides a protection to the neural structures and prevents pinching between bones. In the similar light, it appears that syringomyelia is also a protective self-neural destruction that works in the larger interest of the patient. It appears that the nature identifies the presence of instability and initiates a protective response much earlier than it is possible to recognize by alterations in the radiological parameters. The protective measures delay the onset of symptoms. The symptoms in such cases are subtle, long-standing and relentlessly progressive in nature. Presence of Chiari malformation and/or syringomyelia are indicators of atlantoaxial instability. This is similar to the fact that short neck, torticollis and bone fusions are manifestation of atlantoaxial instability. The treatment in cases having basilar invagination (groups A and B) with/without Chiari malformation and with/without syringomyelia should be directed towards atlantoaxial stabilization and aimed at segmental arthrodesis (Fig. 4). Inclusion of the occipital bone in the fusion construct provides a suboptimal form of stabilization and can be counter-productive. Foramen magnum bone or dural decompression is not necessary. Although the patient might improve following foramen magnum decompression, the results are frequently only temporary. The improvement simulates relief to the affected car driver following deflating a full air bag. Essentially, foramen magnum decompression may temporarily assist in amelioration of symptoms, but in the long run is counterproductive.


Craniovertebral Junction Instability: A Review of Facts about Facets.

Goel A - Asian Spine J (2015)

Images of a 22-year-old female. (A) Computed tomography (CT) scan shows the craniovertebral junction. (B) Section through the facets shows type 2 atlantoaxial facetal instability. (C) T1-weighted magnetic resonance imaging (MRI) shows Chiari malformation and syringomyelia. (D) T2-weighted MRI showing the Chiari malformation and syringomyelia. (E) Postoperative CT scan following atlantoaxial fixation. (F) Atlantoaxial lateral mass plate and screw fixation. (G) Postoperative MRI showing reverse migration of the tonsils and reduction of syringomyelia.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4522459&req=5

Figure 4: Images of a 22-year-old female. (A) Computed tomography (CT) scan shows the craniovertebral junction. (B) Section through the facets shows type 2 atlantoaxial facetal instability. (C) T1-weighted magnetic resonance imaging (MRI) shows Chiari malformation and syringomyelia. (D) T2-weighted MRI showing the Chiari malformation and syringomyelia. (E) Postoperative CT scan following atlantoaxial fixation. (F) Atlantoaxial lateral mass plate and screw fixation. (G) Postoperative MRI showing reverse migration of the tonsils and reduction of syringomyelia.
Mentions: Musculoskeletal changes associated with basilar invagination like short neck, torticollis, platybasia, Klippel-Feil abnormalities, and spondylotic spinal changes are manifestations of chronic and subtle atlantoaxial instability [1920]. The instability is more often of types 2 and 3 facetal dislocation. Following atlantoaxial fixation, all these secondary musculoskeletal alterations have a potential for reversal in the immediate postoperative phase [1920]. This fact suggests that the musculoskeletal alterations are not congenital defects or a result of embryonic dysgenesis, but are a manifestation of chronic instability, and essentially have a protective function. These musculoskeletal abnormalities are not primary in nature or the cause of the problem, but are a secondary effect or result of the problem. On similar lines, we have recently identified that Chiari malformation and syringomyelia are also secondary or protective formations and are a result of long-standing atlantoaxial instability [2122]. Chiari malformation can be simulated as nature's air bag that places it in position in the event of manifest or unidentified atlantoaxial instability. Like the air bag, the herniated tonsils act as a cushion that provides a protection to the neural structures and prevents pinching between bones. In the similar light, it appears that syringomyelia is also a protective self-neural destruction that works in the larger interest of the patient. It appears that the nature identifies the presence of instability and initiates a protective response much earlier than it is possible to recognize by alterations in the radiological parameters. The protective measures delay the onset of symptoms. The symptoms in such cases are subtle, long-standing and relentlessly progressive in nature. Presence of Chiari malformation and/or syringomyelia are indicators of atlantoaxial instability. This is similar to the fact that short neck, torticollis and bone fusions are manifestation of atlantoaxial instability. The treatment in cases having basilar invagination (groups A and B) with/without Chiari malformation and with/without syringomyelia should be directed towards atlantoaxial stabilization and aimed at segmental arthrodesis (Fig. 4). Inclusion of the occipital bone in the fusion construct provides a suboptimal form of stabilization and can be counter-productive. Foramen magnum bone or dural decompression is not necessary. Although the patient might improve following foramen magnum decompression, the results are frequently only temporary. The improvement simulates relief to the affected car driver following deflating a full air bag. Essentially, foramen magnum decompression may temporarily assist in amelioration of symptoms, but in the long run is counterproductive.

Bottom Line: The facets of atlas and axis form the primary site of movements at the craniovertebral junction.All craniovertebral junction instability is essentially localized to the atlantoaxial facet joint.Direct manipulation and fixation of the facets forms the basis of treatment for instability.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurosurgery, King Edward Memorial Hospital and Seth Gordhandas Sunderdas Medical College, Mumbai, India.

ABSTRACT
Craniovertebral junction surgery involves an appropriate philosophical, biomechanical and anatomical understanding apart from high degree of technical skill and ability of controlling venous and arterial bleeding. The author presents his 30-year experience with treating complex craniovertebral junction instability related surgical issues. The facets of atlas and axis form the primary site of movements at the craniovertebral junction. All craniovertebral junction instability is essentially localized to the atlantoaxial facet joint. Direct manipulation and fixation of the facets forms the basis of treatment for instability.

No MeSH data available.


Related in: MedlinePlus