Head Trauma Imaging

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Indications & Modalities - First Look, Right Scan

  • Glasgow Coma Scale (GCS): Severity & Action
    • Mild: 13-15
    • Moderate: 9-12
    • Severe: ≤8 (📌 Consider intubation)
  • CT Head - Key Indications (Canadian CT Head Rule for GCS 13-15):
    • GCS < 15 at 2h post-injury
    • Suspected open/depressed skull fracture
    • Signs of basal skull fracture (e.g., Battle's sign, raccoon eyes)
    • Vomiting ≥2 episodes
    • Age ≥65 years
    • Amnesia before impact >30 min
    • Dangerous mechanism (e.g., fall >3ft/5 stairs, MVA)
  • Imaging Choice:
    • CT (NCCT): Primary scan in acute trauma. Fast; detects bleeds, fractures.
    • MRI: Subacute/chronic phase, suspected Diffuse Axonal Injury (DAI), if CT inconclusive.

Canadian CT Head Rule Criteria

⭐ In minor head trauma (GCS 13-15), CT is indicated if high/medium risk factors as per the Canadian CT Head Rule are present to rule out clinically important brain injury.

Skull Fractures & Extracranial - Bone Deep & Beyond

  • Linear Fracture: Most common, simple break.
  • Depressed Fracture: Fragment displaced in; >1 cm depression may need surgery.
  • Basilar Fracture: Skull base. Signs: 📌 Battle's sign, Raccoon eyes, CSF leaks (otorrhea/rhinorrhea), hemotympanum.
  • Diastatic Fracture: Widens sutures (infants).
  • Associated Complications: Vascular injury (MMA tear → EDH), Cranial Nerve (CN) palsy (CN VII/VIII).
  • Scalp Hematomas:
    • Caput Succedaneum: Edema, crosses sutures, at birth.
    • Cephalohematoma: Subperiosteal, respects sutures, hours post-birth.
    • Subgaleal: Crosses sutures, large blood loss risk. CT: Depressed skull fracture & subdural hematoma

⭐ Linear fractures are the most common type of skull fracture.

Intracranial Hemorrhages - The Bleeding Brain

CT scans comparing EDH, SDH, SAH, ICH

FeatureEpidural Hematoma (EDH)Subdural Hematoma (SDH)Traumatic Subarachnoid Hemorrhage (tSAH)Intracerebral Hemorrhage (ICH) / Contusion
LocationSkull-Dura (potential space)Dura-Arachnoid (potential space)Subarachnoid space (sulci, cisterns)Brain parenchyma
CT AppearanceBiconvex (lentiform) 📌 Lemon; hyperdense. Does NOT cross sutures.Crescentic 📌 Banana; hyperdense (acute), isodense (subacute), hypodense (chronic). CAN cross sutures.Hyperdense in sulci, cisterns, fissures.Hyperdense areas; coup/contrecoup injuries.
SourceMiddle meningeal artery (arterial)Bridging veins (venous)Ruptured pial/cortical vesselsSmall penetrating arteries/capillaries
Key AssociationYoung, skull fracture, lucid intervalElderly, alcoholics, anticoagulation, brain atrophyMost common traumatic bleedDirect impact, acceleration-deceleration
  • General CT Signs: Assess for mass effect (sulcal/ventricular effacement) and midline shift (significant if >5mm).
  • Intraventricular Hemorrhage (IVH): Blood within ventricles. Often indicates severe injury and poorer prognosis. Can be an extension from tSAH or ICH.
  • CT Density: Acute blood is hyperdense (~60-80 HU).

Parenchymal Injury & Herniation - Brain Bruises & Squeezes

  • Diffuse Axonal Injury (DAI):
    • Mechanism: Shearing (acceleration-deceleration).
    • Locations: Grey-white matter junction, corpus callosum, brainstem.
    • CT: Often normal or tiny petechiae. MRI (T2/FLAIR, SWI) best for lesions.

    ⭐ MRI, especially SWI/GRE sequences, is far more sensitive than CT for detecting DAI.

  • Cerebral Edema: CT shows loss of grey-white differentiation, sulcal effacement.
  • Raised ICP Signs (CT): Effaced sulci/cisterns, compressed ventricles (slit-like), midline shift.
  • Herniation Syndromes:
    • Subfalcine: Cingulate gyrus under falx → midline shift; ACA compression risk.
    • Uncal (Transtentorial): Medial temporal lobe (uncus) through tentorial incisura → ipsilateral CN III palsy (dilated pupil), contralateral hemiparesis (Kernohan's notch).
    • Tonsillar: Cerebellar tonsils >5 mm below foramen magnum → brainstem compression, cardiorespiratory compromise (Cushing's triad). Brain herniation types diagrams and MRI of Diffuse Axonal Injury (DAI))

High‑Yield Points - ⚡ Biggest Takeaways

  • NCCT Head is initial choice for acute head trauma.
  • EDH: Lentiform, arterial, not crossing sutures. Lucid interval is key.
  • SDH: Crescentic, venous, crosses sutures, respects dural folds.
  • Traumatic SAH: Blood in sulci/cisterns. Consider CTA for vascular injury.
  • DAI: Shearing injury; CT often normal, MRI superior. Look for punctate lesions.
  • Signs of ↑ICP: Effaced sulci, compressed ventricles, midline shift >5mm.
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Head Trauma Imaging - Free Indian Medical PG Review