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Head injury

Head injury. FM Brett MD FRCPath. At the end of this lecture you should be able to: Know basic facts about the incidence of head injury Know the difference between focal and diffuse injury Know the difference between missile and non-missile head injury Be able to classify ICH

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Head injury

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  1. Head injury FM Brett MD FRCPath

  2. At the end of this lecture you should be able to: • Know basic facts about the incidence of head injury • Know the difference between focal and diffuse injury • Know the difference between missile and non-missile head injury • Be able to classify ICH • Know the difference between traumatic and spontaneous SAH • Be able to list the complications of Raised ICP

  3. Head Injury - Facts • Whether accidental, criminal or suicidal • leading cause of death < 45 • Accounts 1% of all deaths, 30% traumatic • deaths and 50% of RTA deaths • Severity assessed by GCS

  4. GCS 1. Best eye response - (max 4) 2. Best verbal response - (max 5) 3. Best motor response - (max 6) GCS- 13+ mild H I 9-12- moderate H I 8 or less – severe H I

  5. HI • May result in LOC • Longer unconscious and deeper coma > • likelihood that pt has suffered severe HI • 60% good recovery • Based on US, UK and Netherland figures • for every 100 HI, 5 VS, 15 severely disabled, 20 minor problems, 60 full recovery

  6. Nature of lesions in HI • Non - missile- RTA • Missile • Distribution of lesions • Focal • Diffuse

  7. Primary damage • scalp laceration • skull fracture • cerebral contusions • ICH • DAI TIME COURSE Immediate Delayed • Secondary damage • ischemia • hypoxia • cerebral oedema • infection

  8. Pattern of damage in non -missile HI Focal Scalp- contusion, laceration Skull - fracture Meninges - haemorrhage, infection Brain - contusions, laceration, infection Diffuse damage Brain, DAI, DVI, HIE, Cerebral oedema

  9. ICH is a complication of 66% of cases of non-missile head injury

  10. Haemorrhage May be EXTRADURALINTRADURAL - subdural, subarachnoid intracerebral

  11. EDH • Found in 2% HI • Usually associated • with skull fracture • Peak 10-30 yrs • Rare < 2 and >60 • Arterial bleed - • usually meningeal • vessels

  12. Subdural haemorrhage • Usually venous • Rupture of bridging • veins

  13. Subdural haematoma: classification 48-72 hours –acute composed of clotted blood 3-20 dys – subacute – mixture of clotted and fluid blood 3 weeks + - chronic encapsulated haematoma

  14. SAH • Berry aneurysm • Traumatic • Infectious • Fusiform aneurysm • AVM • CAA

  15. CIRCLE OF WILLIS

  16. Berry aneurysms • Congenital • Risk of bleeding inc; • Hypertension • AVM • systemic vascular • disease • defects collagen • polcystic renal disease

  17. Traumatic SAH • may result from severe contusions • Fracture of skull can rupture vessels • IVH may enter SAS • RULE OUT ANEURYSM

  18. Cerebral contusions • Superficial bruises of the brain • Frequent but not inevitable after • head injury

  19. Various types of surface contusions and lacerations ~ Coup – at point of impact ~ Contrecoup- diametrically opposite point of impact ~ Herniation – at point of impact between hernia ~ Fracture related to # of skull

  20. Sites of cerebral contusions • Frontal poles • Orbital surfaces of the frontal • poles • Temporal poles • lateral and inferior surfaces of • occipital poles • cortex adjacent to sylvian fissure

  21. Uncommon types of focal brain damage • Ischaemic brain damage due to traumatic • dissection and thrombosis of vertebral or carotid • arteries by hyperextension of the neck • Infarction of pituitary - due to transection • of pituitary stalk • pontomedullary rent

  22. Infection • complication of skull fracture • Open HI • Incidence is increased even after closed • HI as devitalised tissue prone to infection

  23. Diffuse brain injury – term coined by clinicans to describe head-injured patients who have global disruption of neurological function without a lesion on CT scan that would account for their clinical state Implies widespread structural damage which neuropathologically is likely to be traumatic or hypoxic/ischaemic in origin

  24. Diffuse damage • DAI - widespread damage to axons in the • CNS due to acceleration/deceleration of the • head • Pts usually unconscious from moment of • impact • Lesser degrees compatible with recovery of • consciousness

  25. Pathogenesis of DAI • Primary axotomy - almost immediate • Large axolemmal tears- influx of CA++ • - activation of calcium activated proteases • - severe cytoskeletal disruption- disconnection

  26. Secondary axotomy • Ca++ activated proteases focally damage the • the axonal BUT immediate disconnection does • not occur • Failure of cellular repair mechanisms or • secondary neuronal damage results in axonal • disconnection • Axoplasmic transport continues and results in • proximal axonal swelling

  27. Diffuse vascular injury Multiple petechial haemorrhages in the white matter of the frontal and temporal lobes Probably results from traction and shearing of parenchymal BV

  28. Brain swelling and raised ICP • Results from: • cerebral vasodilation - inc cerebral blood vol • damage to BV - escape of fluid through BBB • inc water content of neurones and glia- cytotoxic • cerebral oedema

  29. Three patterns of brain swelling in • HI • Swelling adjacent to contusions • Diffuse swelling of one cerebral hemisphere • e.g evacuation of ASDH • Diffuse swelling both hemispheres

  30. ICH Herniation Subfalcine herniation Tentorial herniation Tonsillar herniation

  31. End result of herniation is compression and Duret haemorrhages as seen in the pons

  32. Ischemic damage - likely if: • clinically evident hypoxia • hypotension with systolic < 80mmHg • for at least 15 mins • episodes of inc BP i.e > 30 mm Hg

  33. MISSILE HEAD INJURY • Caused by objects propelled through air • Injury may be: • Depressed • Penetrating • Perforating

  34. Traumatic spinal cord injury Nature of lesions - Indirect/direct Distribution - 60-70% cervical, 25% thoracic, 6-15% lumbar. Fractures C1/2, C4-7, T11-L2

  35. Principal causes of spinal cord compression ~ Lesions in vertebral column- prolapsed disc, kyphoscoliosis, #, Metastatic tumour ~ Spinal extradural lesions – metastatic carcinoma, lymphoma, myeloma, abscess ~ Intradural extramedullary lesions – Meningioma, Schwannoma ~ Intramedullary lesions - Astrocytoma, ependymoma, cyst formation

  36. CONCLUSIONS ~ HI – leading cause of death under age of 45 ~ Can be missile or non-missile. ~ Distribution of lesions – focal or diffuse. ~ ICH may be extradural or intradural ~ SAH may be traumatic or spontaneous ~ Main complication of HI is raised ICP.

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