Trauma to the Central Nervous System

Trauma to the Central Nervous System

Trauma to the Central Nervous System

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CNS Trauma Overview - Impact Insights

  • Primary Injury: Immediate mechanical damage from impact (e.g., Diffuse Axonal Injury, contusion).
  • Secondary Injury: Delayed cascade; key mediators: hypoxia, hypotension, excitotoxicity (glutamate), inflammation, edema.
  • Monro-Kellie Doctrine: $V_{intracranial} = V_{brain} + V_{blood} + V_{CSF} + V_{lesion}$ = constant. Explains ↑ICP.
  • GCS (Eye, Verbal, Motor): Assesses severity. Mild: 13-15; Moderate: 9-12; Severe: ≤8.

⭐ Secondary brain injury, driven by factors like hypoxia, hypotension, and excitotoxicity, is a major determinant of outcome post-TBI and a key target for neuroprotective strategies.

Brain herniation types in traumatic subdural hematoma

Skull & Scalp Trauma - Cranial Crack Chronicles

  • Scalp Layers 📌 SCALP:
    • Skin
    • Connective tissue (dense)
    • Aponeurosis (galea)
    • Loose areolar tissue (danger area due to spread of infection)
    • Pericranium Layers of the Scalp Diagram
  • Skull Fractures:
    • Linear: Most common; simple break.
    • Depressed: Bone fragment pushed inwards. Significant if depression >1 bone thickness.
    • Comminuted: Multiple bone fragments.
    • Basilar: Fracture at skull base. Key signs:
      • Battle's sign (mastoid ecchymosis)
      • Raccoon eyes (periorbital ecchymosis)
      • CSF rhinorrhea/otorrhea
      • Hemotympanum

⭐ Basilar skull fractures often present with 'Raccoon eyes' (periorbital ecchymosis) and 'Battle's sign' (mastoid ecchymosis), indicating fracture of the anterior or middle cranial fossa respectively.

Intracranial Hemorrhages - Hemorrhage Hotspots

  • Key types of traumatic intracranial bleeds:
FeatureEpidural Hematoma (EDH)Subdural Hematoma (SDH)Traumatic Subarachnoid Hemorrhage (tSAH)Intracerebral Hemorrhage (ICH)
SourceSkull fractureHead movement (acceleration/deceleration)Direct trauma, vessel ruptureDirect trauma, contusion
VesselMiddle Meningeal Artery (MMA)Bridging VeinsCortical arteries/veins, aneurysmsSmall intraparenchymal vessels
CT ShapeBiconvex / Lentiform (Lens-shaped)Crescent-shaped (Concavo-convex)Blood in sulci, cisterns, fissuresHyperdense lesion within parenchyma
ClinicalLucid interval, rapid deteriorationAcute: ↓LOC; Chronic: gradual, elderly/infantSevere headache, meningismus, ↓LOCFocal deficits, ↓LOC, ↑ICP

Types of Intracranial Hemorrhage

⭐ An epidural hematoma (EDH) classically presents with a 'lucid interval' after initial loss of consciousness, followed by rapid neurological decline, and appears as a biconvex (lentiform) hyperdensity on CT scan.

  • Intracerebral/Intraparenchymal Hemorrhage: Often associated with coup (at site of impact) and contrecoup (opposite site of impact) injuries. Can be single or multiple. Location varies (frontal/temporal lobes common).

Parenchymal Injury & Sequelae - Core Carnage Consequences

  • Concussion: Transient LOC; reversible functional disturbance.
  • Contusion: Brain bruise (hemorrhage, necrosis).
    • Coup (impact site) & Contrecoup (opposite site). Coup-contrecoup injury mechanism diagram
  • Laceration: Tissue tearing; often with penetrating trauma/depressed skull fractures.
  • Diffuse Axonal Injury (DAI):
    • Shearing forces → widespread axonal damage.
    • Punctate hemorrhages (corpus callosum, brainstem).
    • $\beta$-APP stain highlights axonal swellings.

⭐ Diffuse Axonal Injury (DAI) is characterized by widespread damage to axons in the white matter, often not visible on initial CT but a major cause of coma and poor outcome; $\beta$-amyloid precursor protein ($\beta$-APP) immunohistochemistry highlights axonal swellings (retraction balls) within hours to days.

  • Herniation Syndromes (↑ICP):
    • Subfalcine: Cingulate gyrus under falx → ACA compression.
    • Transtentorial (Uncal): Uncus through tentorial notch → CN III palsy, PCA compression, Duret hemorrhages.
    • Tonsillar: Cerebellar tonsils through foramen magnum → Brainstem compression (cardiorespiratory arrest). 📌 "CUT the CONE" (Cingulate, Uncal, Tonsillar).

High‑Yield Points - ⚡ Biggest Takeaways

  • Epidural Hematoma (EDH): Middle meningeal artery rupture, lucid interval, lentiform (biconvex) CT.
  • Subdural Hematoma (SDH): Bridging veins tear, crescentic CT, common in elderly/alcoholics.
  • Subarachnoid Hemorrhage (SAH): Ruptured berry aneurysm, "worst headache of life", bloody CSF.
  • Diffuse Axonal Injury (DAI): Shearing forces (acceleration-deceleration), widespread axonal damage, often normal CT.
  • Brain Herniation: Critical complication of ↑ICP; e.g., uncal, subfalcine, tonsillar.
  • Coup-Contrecoup Injury: Brain contusions at impact site and directly opposite_site_

Practice Questions: Trauma to the Central Nervous System

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Which of the following represents a secondary brain injury mechanism?

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Flashcards: Trauma to the Central Nervous System

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Loss of _____ matter of the brain on post-mortem is seen in cyanide poisoning

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Loss of _____ matter of the brain on post-mortem is seen in cyanide poisoning

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