Neurological radiologic landmarks

Neurological radiologic landmarks

Neurological radiologic landmarks

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Ventricular System - Fluid Freeway

  • Function: CSF production (choroid plexus), circulation, and brain protection.
  • Components: Four interconnected, CSF-filled cavities.
    • Lateral Ventricles (2): Largest, C-shaped; in cerebral hemispheres.
    • Third Ventricle: Slit-like; between the thalami.
    • Fourth Ventricle: Diamond-shaped; posterior to pons/medulla.
  • CSF Flow Path:

Sagittal view of CSF flow in brain and spinal cord

⭐ The cerebral aqueduct is the narrowest part, making it a common site for obstructive hydrocephalus (aqueductal stenosis), causing upstream ventricular enlargement.

📌 Mnemonic: "Love My 3 Silly 4 Lorn Magpies" (Lateral → Monro → 3rd → Sylvius → 4th → Luschka → Magendie).

Basal Ganglia & Thalamus - The Core Nuclei

Axial T2 MRI brain: basal ganglia and thalamus

  • Lentiform Nucleus: Comprises the putamen (lateral) and globus pallidus (medial).
  • Striatum: A functional unit combining the putamen and the head of the caudate nucleus.
  • Key Anatomical Borders:
    • Internal Capsule: A critical white matter tract separating the thalamus (medially) from the lentiform nucleus (laterally).
    • Caudate Head: Found anterolateral to the thalamus, characteristically bulging into the frontal horn of the lateral ventricle.

⭐ In Wilson's disease, copper deposition causes T2 hyperintensity in the basal ganglia, particularly the putamen, and may create the "face of the giant panda" sign in the midbrain.

Key White Matter Tracts - Cerebral Superhighways

Coronal brain view: white matter tracts & DTI

  • Association Fibers: Connect gyri in the same hemisphere.
    • Superior Longitudinal Fasciculus (SLF): Major fronto-parietal-temporal connector. The arcuate fasciculus (language function) is a key component.
  • Commissural Fibers: Connect homologous areas in opposite hemispheres.
    • Corpus Callosum: Largest commissure; connects the cerebral hemispheres.
    • Anterior Commissure: Connects temporal lobes & olfactory structures.
  • Projection Fibers: Connect cortex with subcortical structures (e.g., thalamus, brainstem, spinal cord).
    • Internal Capsule: Contains most ascending/descending projection fibers. Highly vulnerable to lacunar infarcts.

⭐ A lesion in the dominant inferior parietal lobule, involving the SLF, can cause Gerstmann Syndrome: agraphia, acalculia, finger agnosia, and left-right disorientation.

Vascular & Cisternal Landmarks - Vessels and Voids

Circle of Willis and major cerebral arteries

  • Arterial Landmarks (Hyperdense on non-con CT):

    • ICA (Internal Carotid Artery): Cavernous sinus & supraclinoid portions.
    • MCA (Middle Cerebral Artery): Horizontal (M1) segment in Sylvian fissure ("dot sign").
    • ACA (Anterior Cerebral Artery): Interhemispheric fissure.
    • Vertebrobasilar System:
      • Basilar Artery: Anterior to the pons.
      • PCAs (Posterior Cerebral Arteries): Course around the midbrain.
  • Cisternal Landmarks (CSF Spaces):

    • Suprasellar Cistern: Star-shaped; contains Circle of Willis.
    • Quadrigeminal Cistern: Posterior to colliculi; "smiley face" on axial.
    • Ambient Cistern: Lateral to the midbrain.

⭐ Effacement or asymmetry of the suprasellar cistern is an early and critical sign of impending transtentorial herniation.

High-Yield Points - ⚡ Biggest Takeaways

  • Internal capsule posterior limb lacunar infarcts cause contralateral pure motor stroke.
  • Caudate atrophy in Huntington's disease enlarges lateral ventricles (hydrocephalus ex vacuo).
  • The "Mickey Mouse sign" on axial imaging identifies the midbrain and cerebral peduncles.
  • Lenticulostriate artery rupture in the basal ganglia is a common cause of hypertensive hemorrhage.
  • Loss of the gray-white junction at the insular ribbon is an early sign of MCA stroke.
  • Agenesis of the corpus callosum is a key congenital midline brain defect.

Practice Questions: Neurological radiologic landmarks

Test your understanding with these related questions

A 67-year-old female patient is brought to the emergency department after her daughter noticed she has been having meaningless speech. When assessing the patient, she calls the chair a table, and at times would make up new words. She does not appear to be aware of her deficit, and is carrying on an empty conversation. Her speech is fluent, but with paraphasic errors. Her repetition is impaired. On physical examination, a right upper quadrant field-cut is appreciated, with impairment in comprehension and repetition. Which of the following structures is most likely involved in this patient’s presentation?

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Flashcards: Neurological radiologic landmarks

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The normal neonatal thymus appears "_____-shaped" on a Chest X-Ray

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The normal neonatal thymus appears "_____-shaped" on a Chest X-Ray

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