BRAIN HERNIATION Pathology classes q.pptx

Anatomy pathology

1. BRAIN HERNIATION EWURUM UCHECHI

2. OUTLINE Introduction Classification Aetiology Pathogenesis Clinical features Conclusion

3. Introduction Herniation can be defined as the protrusion of a part of the brain (brain parenchymal shift) following decompensated raised intracranial pressure(ICP). It is a neurosurgical emergency and may be fatal if appropriate and timely medical and/or surgical interventions are not instituted.

4. Classification Based on part of brain involved and its relationship to a specific structure Subfalcine ( Cingulate ) h erniation Transtentorial ( uncal , mesial temporal) herniation Cerebellar tonsillar herniation Others: Transalar ( transphenoidal ) herniation Transcalvarial herniation

5. Classification Based on receiving compartment Internal herniation ( intracranial or intraspinal ) Subfalcine ( cingulate ) Transtentorial ( uncal , mesial temporal) Cerebral tonsillar Transalar / Transphenoidal External herniation ( extracranial ) Transcalvarial

6. Aetiology Increased brain volume Intracranial mass lesion Extradural haematoma Subdural haematoma Brain tumours Cerebral abcesses Vascular malformations Brain oedema Head injury(concussion, contusion) Cerebral infarction Meningitis Eclampsia

7. Aetiology Hypertensive encephalopathy Acute hyponatremia Hepatic encephalopathy Reye’s syndrome Increased CSF volume Obstructive hydrocephalus Non-obstructive hydrocephalus Choroid plexus papilloma Increased blood volume Intracerebral haemorrhage Subarachnoid haemorrhage Cerebral venous thrombosis

8. Pathogenesis Raised ICP within rigid dural folds Failure in compensatory mechanisms (compression of veins, displacement of CSF) Herniation of part of brain parenchyma Pressure damage on brain tissue and neurovascular structures Specific signs and symptoms/ death

9. Subfalcine cingulate herniation Ipsilateral cingulate gyrus migrates beneath the falx cerebri due to unilateral or asymmetric expansion of cerebral hemisphere May result in infarction along the distal territory of the anterior cerebral artery

10. Transtentorial herniation In the lateral form, uncus of temporal lobe herniates downwards across tentorum cerebeli Oculomotor is compressed against tentorial edge Compression of the calcarine branch of posterior cerebral artery Compression of aqueduct of sylvius

11. Transtentorial herniation With further displacement of midbrain, contralateral peduncle may be forced against tentorial edge, creating Kernohan’s notch and damaging corticospinal tract. If central (ascending and descending central transtentorial herniation ), brainstem descends through incisura processes and ultimately through foramen magnum ( rubrospinal & vestibulospinal tracts and cardiorespiratory centres may be damaged) Duret haemorrhages result from venous congestion and stretching of small perforators

12. Cerebellar tonsillar herniation Increased pressure in posterior fossa forcing the cerebellar tonsils to herniate through the foramen magnum Lower part of brainstem and upper cervical cord compressed Usually occurs alongside ascending & descending central transtentorial herniation Post. Inferior cerebellar arteries, vertebral areteries and branches, and origins of ant. spinal artery involved

13. Other hernations Transalar / Transphenoidal : There may be infarction in middle cerebral artery territory due to its compression against sphenoid ridge(Post. Transalar ) In Ant. Transalar , compression of supra- clinoid segment of Internal carotid artery against anterior clinoid process results and cause infarction in ACA & MCA territories Transcalvarial : May result from decompressive hemicraniectomy There may be compression of corical vessels by bony margins leading to haemorrhagic infarction in areas of supply

14. Clinical features Subfalcine hernation : Lower limb weakness Transtentorial herniation : Uncal herniation is associated with ispilateral anisocoria with contralateral motor weakness In kernohan’s notch phenomenon, there would be ipsilateral weakness as well With further raised ICP, there would be lateral shift of the diencephalon leading to altered sensorium (RAS) and hydrocephalus

15. Clinical features Downward transtentorial herniation may be marked by presence of deocorticate and cerebrate posturing, alongside loss of brainstem reflexes There may be altered respiratory patterns, and ultimately respiratory arrest Cerebellar tonsillar herniation : Respiratory arrest

16. Conclusion Brain herniation is an important complication of raised ICP Timely diagnosis and intervention could be life-saving

17. PRACTICE QUESTIONS Write a short note on aetiology of cerebral herniation Write a short note on Tentorial hernation a. Classify cerebral herniation