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Brain herniation imaging

CT and MR findings in brain herniation with reasoning

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Brain herniation imaging

  1. 1. BRAIN HERNIATION SYNDROME A Pictorial Review Thorsang Chayovan R1/Aj.Nuttha 22.11.2014
  2. 2. BRAIN HERNIATION • most common types –Subfalcine herniation –descending transtentorial herniation •Others –Posterior fossa herniations •ascending transtentorial herniation •tonsillar herniation –Transalar herniation •Rare but important types –transdural/transcranial herniations –brain displacements across the sphenoid wing
  3. 3. SUBFALCINE HERNIATION
  4. 4. Subfalcine herniation •most common •supratentorial mass in one hemicranium •affected hemisphere pushes across the midline under the inferior "free" margin of the falx, extending into the contralateral hemicranium
  5. 5. Subfalcine herniation: imaging Axial and coronal images show that •cingulate gyrus •anterior cerebral artery (ACA) •internal cerebral vein (ICV) are pushed from one side to the other under the falx cerebri. The ipsilateral ventricle appears compressed and displaced across the midline
  6. 6. Complications •unilateral obstructive hydrocephalus –foramen of Monro occlusion •Periventricular hypodensity with "blurred" margins of the lateral ventricle –Fluid accumulates in the periventricular white matter
  7. 7. Complications •When severe, the herniating ACA can be pinned against the inferior "free" margin of the falx cerebri  secondary infarction of the cingulate gyrus
  8. 8. TRANSTENTORIAL HERNIATION
  9. 9. Transtentorial herniations descending herniations ascending herniations
  10. 10. Descending transtentorial herniations •the second most common •a hemispheric mass •initially produces subfalcine herniation •As the mass effect increases, the uncus of the temporal lobe is pushed medially begins to encroach on the suprasellar cistern hippocampus follows hippocampus effaces the ipsilateral quadrigeminal cistern both the uncus and hippocampus herniate inferiorly through the tentorial incisura
  11. 11. "Dysautonomia, Multisystem Atrophy and Parkinson's." Dysautonomia, Multisystem Atrophy and Parkinson's. N.p., n.d. Web. 18 Nov. 2014
  12. 12. Descending transtentorial herniation •Unilateral •Bilateral ("central“) –Severe
  13. 13. unilateral DTH: imaging early uncus is displaced medially Ipsilateral aspect of the suprasellar cistern effaced Ipsilateral prepontine + cerebellopontine angle cistern enlarged
  14. 14. Descending transtentorial herniation As DTH increases hippocampus also herniates medially quadrigeminal cistern compression midbrain pushed toward the opposite side of the incisura
  15. 15. Descending transtentorial herniation severe cases entire suprasellar and quadrigeminal cisterns are effaced. The temporal horn can even be displaced almost into the midline
  16. 16. bilateral DTH both hemispheres become swollen the whole central brain is flattened against the skull base All the basal cisterns are obliterated hypothalamus and optic chiasm are crushed against the sella turcica
  17. 17. Complete bilateral DTH both temporal lobes herniate medially into the tentorial hiatus midbrain and pons displaced inferiorly through the tentorial incisura The angle between the midbrain and pons is progressively reduced from 90° to almost 0°
  18. 18. Complications •CN III (oculomotor) nerve compression –CN III palsy •PCA occlusion as it passes back up over the medial edge of the tentorium –secondary PCA (occipital) infarct
  19. 19. Kernohan notch •As the herniating temporal lobe pushes the midbrain toward the opposite side of the incisura –contralateral cerebral peduncle is forced against the hard edge of the tentorium •Pressure ischemia  ipsilateral hemiplegia –the "false localizing" sign
  20. 20. Duret hemorrhage "Top-down" mass effect displaces the midbrain inferiorly closes the midbrain-pontine angle Perforating arteries from basilar artery are compressed and buckled secondary hemorrhagic midbrain infarct
  21. 21. Brainstem hemorrhage Brainstem hemorrhage Dorsolateral Primary injury Severe DAI Ventral paramedian Duret
  22. 22. Hemorrhage in diffuse axonal injury •Gray-white junction •Corpus callosum •Brainstem
  23. 23. hypothalamic and basal ganglia infarcts complete bilateral DTH perforating arteries from the circle of Willis compression against the central skull base hypothalamic and basal ganglia infarcts
  24. 24. POSTERIOR FOSSA MASS: TONSILLAR HERNIATION ASCENDING TRANSTENTORIAL HERNIATION
  25. 25. Tonsillar herniation •The cerebellar tonsils are displaced inferiorly and become impacted into the foramen magnum. •congenital (e.g., Chiari 1 malformation) – mismatch between size and content of the posterior fossa •Acquired –an expanding posterior fossa mass pushing the tonsils downward—more common –intracranial hypotension: abnormally low intraspinal CSF pressure •tonsils are pulled downward
  26. 26. Tonsillar herniation: imaging •Diagnosing tonsillar herniation on NECT scans may be problematic. Cisterna magna obliteration
  27. 27. Tonsillar herniation: imaging •MR: much more easily diagnosed •In the sagittal plane –the tonsillar folia become vertically oriented –the inferior aspect of the tonsils becomes pointed –Tonsils > 5 mm (or 7 mm in children) below the foramen magnum are generally abnormal •especially if they are peg-like or pointed (rather than rounded)
  28. 28. Tonsillar herniation: imaging •In the axial plane, T2 scans show that the tonsils are impacted into the foramen magnum –obliterating CSF in the cisterna magna –displacing the medulla anteriorly
  29. 29. Complications •obstructive hydrocephalus •tonsillar necrosis
  30. 30. ASCENDING TRANSTENTORIAL HERNIATION
  31. 31. Ascending transtentorial herniation •caused by any expanding posterior fossa mass –Neoplasms > trauma
  32. 32. Complications •Acute intraventricular obstructive hydrocephalus –caused by compression of the cerebral aqueduct
  33. 33. OTHER LESS COMMON HERNIATION: TRANSALAR TRANSDURAL/TRANSCRANIAL HERNIATIONS
  34. 34. Transalar Herniation •brain herniates across the greater sphenoid wing (GSW) or "ala" •ascending > descending
  35. 35. Ascending transalar herniation •caused by a large middle cranial fossa mass •An intratemporal or large extraaxial mass Temporal lobe + sylvian fissure + MCA up and over the greater sphenoid wing
  36. 36. Descending transalar herniation •caused by a large anterior cranial fossa mass Gyrus rectus is forced posteroinferiorly over the GSW displacing the sylvian fissure and shifting the MCA backward
  37. 37. Transdural/Transcranial Herniation •Rare •Sometimes called a "brain fungus" •can be life-threatening Lacerated dura + a skull defect + increased ICP
  38. 38. Transdural/Transcranial Herniation •Traumatic –infants or young children with a comminuted inward skull fracture •Iatrogenic –a burr hole, craniotomy, or craniectomy
  39. 39. Transdural/Transcranial Herniation •MR best depicts these unusual herniations. •The disrupted dura –discontinuous black line on T2WI –Brain tissue, blood vessels, and CSF, are extruded through the defects into the subgaleal space
  40. 40. Kaewlai, R. Imaging of Traumatic Brain Injury. 2013.
  41. 41. Wikipedia
  42. 42. References •Osborn, Anne G. "Secondary Effects and Sequellae of CNS Trauma."Osborn's Brain: Imaging, Pathology, and Anatomy. Salt Lake City, UT: Amirsys Pub., 2013. N. pag. Print. •Osborn, Anne G. "Cerebral Vasculature: Normal Anatomy and Pathology."Diagnostic Neuroradiology. St. Louis: Mosby, 1994. N. pag. Print. •Kaewlai, R. Imaging of Traumatic Brain Injury. 2013. Web.

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CT and MR findings in brain herniation with reasoning

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