Section 1

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CB1150

Findings

Axial head CT or MR

There is evidence of one or more focal or regional supratentorial, intraaxial, masses (tumor, bleed, abscess, asymmetric vent size, etc.) producing or contributing to subfalcine shift (crossing the plane of the falx cerebri), and/or lateralized downward uncal and/or parahippocampal brain herniation (crossing the plane of the incisura from above), and/or an ipsilateral trans-sphenoidal herniation.

There is evidence of one or more focal or regional supratentorial, extraaxial, masses (dural-based tumor, bleed, empyema, etc.) producing or contributing to a lateralized subfalcine shift (crossing the plane of the falx cerebri from one side to the other), and/or lateralized downward incisural herniation (crossing the plane of the incisura from one side), and/or an ipsilateral trans-sphenoidal herniation.

There is evidence of bilateral, symmetric, counter-balancing mass effects (intraaxial, ventricular, extraaxial or admixture) producing little or no midline shift but causing centralized, downward, incisural herniation. Common lesions include hydrocephalus (dilated bilateral lateral vent and/or 3rd ventricular enlargement), and/or bilateral intraaxial (usually global edema), or concurrent, extraaxial, similar-sized, lesions (usually bilateral subdurals), or enough subfalcine herniation from unilateral mass obstructing the contralateral foramen of Monroe causing contralateral (counter-balancing) hydrocephalus.

There is of transcranial brain herniation through diastatic fractures or craniotomy defects.

There is evidence of mesial and/or downward, transtentorial, uncal herniation related to mid temporal mass effect.

There is evidence of downward, transtentorial, posterior parahippocampal gyrus herniation related to posterior temporal mass effect.

There is evidence of focal anterior temporal fossa or latero-ventral frontal regional mass effect resulting in trans-sphenoidal herniation.

There is evidence of downward incisural displacement originating from mass effect in the caudal 3rd ventricle, or pineal gland or splenium (corpus callosum).

There is evidence of one or more focal or regional infratentorial, intraaxial, masses (tumor, bleed, abscess) producing enough mass effect to shift midline structures and to result in an asymmetric (lateralized) upward transtentorial herniation and/or unilateral cerebellar tonsillar herniation.

There is evidence of one or more focal or regional infratentorial, extraaxial, masses (tumor, bleed, abscess) producing enough mass effect to shift midline structures and to result in an asymmetric (lateralized) upward transtentorial herniation and/or unilateral cerebellar tonsillar herniation.

There is evidence of bilateral intra of extraaxial posterior fossa mass effect(s) to produce symmetric downward cerebellar tonsillar displacement approaching or crossing the plane of the foramen magnum, and/or central upward transtentorial herniation, and compressing but not shifting midline structures (i.e. the 4th ventricle and vallecula).

There is unexplained symmetric or lateralized cerebellar tonsillar ectopia into the cisterna magna, or less than 6mms below the plane of the foramen magnum without effacement of cisterns and without downward incisural herniation. This likely reflects developmental variation and not tonsillar herniation.

There is unexplained symmetric or lateralized cerebellar tonsillar downward displacement into the cisterna magna, greater than 6mms below the plane of the foramen magnum usually with effacement of cisterns and possible hydromyelia, but without any concurrent downward incisural herniation. This likely reflects developmental Chiari malformation.

There is evidence of concurrent downward central transtentorial and bilateral downward tonsillar herniation without evidence of any apparent cause other than intracranial hypotension with acquired Chiari-like tonsillar features.

Does the overall mass effect(s) match the degree and direction of the herniation or not?

No other concurrent significant abnormality is present.