Head Trauma Imaging

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.

⭐ 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.

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

Intracranial Hemorrhages - The Bleeding Brain

• 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). 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.