Chiari 1 - pre and post decompression surgery

Case contributed by Dr Bruno Di Muzio



Patient Data

Age: 24-year-old
Gender: Female

MRI Cervical and Thoracic spine

Technique: Multiplanar, multisequence imaging has been obtained through the cervical and thoracic spine.

Findings: Cerebellar tonsillar ectopia of 20 mm with marked crowding of structures at the foramen Magnum. There is also ligamentous hypertrophy around the dens.

Small disc bulges are seen at C4/5 and C6/7 indenting the ventral CSF space. There is a localized syrinx at the C7 level, measuring 8 mm in length and 2 mm in AP dimension. There is a mild prominence of the central canal above this.

Left paracentral disc protrusion at T11/12 which mildly displaces the cord, without cord abnormality. There is also mild left foraminal stenosis at this level.

Conclusion: Chiari malformation with localized syrinx at C7.​


CT Brain and upper cervical Spine

Cerebellar tonsillar ectopia with crowding at the foramen Magnum and effacement of CSF at the level of C1 again demonstrated. No acute hemorrhage or infarct. No hydrocephalus. The sulci appear slightly effaced, however the basal cisterns are patent and appearance is similar to the previous CT.​

Interval decompressive occipital craniectomy noted with dural thickening deep to the operative site. No intracranial hemorrhage or collection seen on the available images. No mass, midline shift or edema. No area of abnormal contrast enhancement. Size of ventricles and sulci is normal for the patient's age and there is normal grey-white differentiation with no CT evidence of focal or diffuse white matter change at this stage. Low position of cerebellar tonsils noted.

Bones, air sinuses and orbits appear normal. No fracture of cranial base or vault. No scalp hematoma.

CONCLUSION: Post-operative occipital change with decompressive occipital bone resection. There is some dural thickening. No surgically drainable component identified. Remainder of the brain appears normal.


In the position of imaging, the cervical lordosis is reversed. The neck is held flexed slightly, convex rightward.

No loss of vertebral body height or intervertebral disc height. Posterior elements of C1 incomplete, ? resected or absent. There is some minor osteophytosis around the anterior arch of C1.

No cervical fracture or dislocation. Subtle bony lucency through right side of T1 transverse process suggests a small undisplaced fracture here.

No evidence of a traumatic disc prolapse.

No prevertebral soft tissue swelling.

Visible paraspinal soft tissues appear normal.

CONCLUSION: Postsurgical changes. No acute injury is seen.


MRI Brain and Cervical Spine

Technique: Multiplanar, multisequence imaging has been obtained through the cervical spine without contrast.

Findings: Comparison is made to the previous imaging. Since then a posterior fossa decompression has been performed, with excellent decompression of the craniospinal junction. The cerebellar tonsil has elevated, there is copious CSF both posterior and anterior to the spinal medullary junction, and the areas of pre-syrinx formation at C6/7 has significantly decreased in signal intensity and geographic extent. There remains a mild reversal of the normal cervical lordosis and some degenerative changes with disc bulging at C6/7, C5/6, and C4/5.

Cerebral parenchymal signal intensity and architecture are normal.

Conclusion: Successful decompression of the posterior fossa, and marked improvement in the "pre-syrinx" appearance in the cervical cord.​

Case Discussion

Typical imaging features of a Chiari 1 malformationcerebellar tonsils extending below foramen magnum into the cervical spinal canal and a small syrinx. The posterior fossa decompression, as performed in this case, is the standard treatment for symptomatic patients. 

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Case information

rID: 42945
Published: 27th Feb 2016
Last edited: 14th Aug 2019
Tag: rmh
Inclusion in quiz mode: Included

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