Question 25

Highest mark
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Pass rate
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Other SAQs in this topic:
Other SAQs in this paper:

a)    Describe the various types of brain herniation with clinical features and radiological features.
(70% marks)

b)    Describe the role of decompressive craniotomy in Traumatic Brain Injury.    (30% marks)
 

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College answer

Not available.

Discussion

a) Different types of brain herniation:

Herniation Radiological features Clinical features
Subfalcine, or "midline shift"
  • Displacement of the cingulate gyrus under the falx cerebri
  • Midline shift of the septum pellucidum
  • Leg weakness
  • A decreased level of consciousness, proportional to the degree of shift.
Uncal
  • Uncus and medial temporal lobe displaced medially
  • Effacement of the suprasellar cistern
  • The hippocampus obliterates the quadrigeminal cistern
  • midbrain effaced and displaced laterally
  • Ipsilateral fixed dilated pupil (3rd nerve palsy)
  • Decreased level of consciousness
  • Hemiparesis
  • Cortical blindness
Central (descending transtentorial)
  • Obliteration of basal subarachnoid cisterns
  • Increased brainstem sagittal diameter 
  • Inferior displacement of the basilar artery
  • Coma​
  • Parinaud's syndrome:
  • Diabetes insipidus
Tonsillar
  • Cerebellar tonsil below the foramen magnum
  • Coma
  • Apnea
  • Hypertension
Upward (ascending transtentorial)
  • Flattened quadrigeminal cistern
  • "Spinning top" midbrain
  • Hydrocephalus
  • Coma
  • Miosis (reactive)
  • Absent or assymmetric doll's eye
  • Decerebrate posuring
Transcalvarial
  • Depends where the defect is
  • Depends where the defect is

b) Note that the college asked to "discuss" the practice of decompressive craniectomy in TBI, not "critically evaluate" it.  Still:

Rationale for decompressive craniectomy:

  • Raised intracranial pressure contributes to secondary brain injury and morbidity/mortality from TBI
  • Intracranial pressure is governed by the Monro-Kellie Doctrine, where intracranial content is confined within a finite space and any expansion of one component produces increased pressure on other components
  • Decompressive craniectomy increases the volume available to the intracranial contents
  • The consequence should be decreased ICP and decreased secondary brain injury.

Advantages:

  • Maybe some sort of mortality benefit (cohort studies such as Sonuca et al, 2010; as well as RESCUIicp)
  • Shorter ICU stay
  • Less ICP-targeting interventions
  • Lower ICP

Complications of decompressive craniectomy:

  • Herniation though the defect
  • Delayed paradoxical herniation
  • Subdural hygroma
  • Infection
  • Bleeding
  • Post-traumatic hydrocephalus
  • "Sinking Flap Syndrome"
  • Bone resorption

Evidence for decompressive craniectomy in TBI:

  • DECRA: Unchanged mortality; worse disability outcome
  • RESCUEicp: Improved mortality; worse disability outcome

References

Hahn, F. J., and J. Gurney. "CT signs of central descending transtentorial herniation." American Journal of Neuroradiology 6.5 (1985): 844-845.

Brazis, P., J. Masdeu, and Jose Biller. "Localization in Clinical Neurology." 2007 Lippincott Williams & Wilkins

Cuneo, Richard A., et al. "Upward transtentorial herniation: seven cases and a literature review." Archives of neurology 36.10 (1979): 618-623.

Cooper, D. James, et al. "Decompressive craniectomy in diffuse traumatic brain injury." New England Journal of Medicine 364.16 (2011): 1493-1502.

Hutchinson, Peter J., et al. "Trial of decompressive craniectomy for traumatic intracranial hypertension." New England Journal of Medicine 375.12 (2016): 1119-1130.

Torres, Roland. "DECRA… Where do we go from here?." Surgical neurology international 3 (2012).

Muñoz, Javier, et al. "Primary decompressive craniectomy in neurocritical patients. a meta-analysis of randomized controlled trials, cohort and case-control studies." Journal of Emergency and Critical Care Medicine 2.9 (2018).

Riveros Gilardi, Berta, et al. "Types of cerebral herniation and their imaging features." Radiographics 39.6 (2019): 1598-1610.

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