MR flair reveals one or more focal or regional supratentorial, intraaxial or extraaxial lesions (tumor, bleed, abscess, asymmetric vent size, etc.) providing enough mass effect to produce subfalcine shift, and/or downward lateralized uncal or parahippocampal transtentorial herniation.

MR flair reveals one or more focal or regional infratentorial intraaxial, or extraaxial, lesions (dural-based tumor, bleed, empyema, etc.) providing enough mass effect to produce downward tonsillar herniation, and/or upward incisural herniation.

There is evidence of obstructive lateral ventriculomegaly (hydrocephalus) or bilateral intra or extraaxial lesions or global brain swelling providing enough mass effect to cause downward central transtentorial herniation.

There is evidence of sequestered 4th ventriculomegaly or bilateral intra or extraaxial posterior fossa lesions providing enough mass effect to cause upward, central, transtentorial herniation.

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

Downward uncal or parahippocampal herniation has compressed the ipsilateral cerebral peduncle producing motor paresis and 3rd CN dysfunction.

Downward uncal or parahippocampal herniation has compressed the ipsilateral PCA causing an ischemic event producing visual cortex injury.

Downward central transtentorial herniation has interrupted perforator blood supply to the tuber cinereum, mammillary bodies and hypothalamus producing hypothalamic dysfunction and Parkinson-like movement disorders.

Trans-sphenoidal herniation has obstructed the superior sylvian vein causing frontotemporal edema or venous ischemic event.

Trans-sphenoidal herniation has damaged the uncinate fasciculus (can produce personality changes).

Subfalcine herniation has buckled the ipsilateral ICA over the interclinoid ligament causing an ICA ischemic event.

Subfalcine herniation has buckled the ipsilateral ACA over the free margin of the falx causing an ACA ischemic event.

Subfalcine herniation has displaced the mesencephalon enough to cause compression of the opposite side mesencephalon against the opposite side free tentorial dural margin producing motor paresis and 3rd CN dysfunction.

Subfalcine herniation is enough to obstruct CSF flow at either the foramen of Monroe or at the 3rd ventricular level.

Upward herniation is sufficient to obstruct CSF flow by compressing the cerebral aqueduct.

Downward tonsillar herniation causes compression of the cervicomedullary cord potentially causing apnea or hydromyelia.

Concurrent downward incisural and tonsillar herniation in intracranial hypotension causes severe unrelenting headaches.

There is evidence of focal arterial compression (ACA beneath falx, PCA over tent, ICA for interclinoid ligament, PICA over foramen magnum.

There is a post compressive reperfusion hemorrhage in the mesencephalon (i.e." Duret hemorrhage"); this can occur after transtentorial herniation.

There is subfrontal contusion related midline shift over the crista galli.

No other concurrent significant abnormality is present.