Neurological radiologic landmarks

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:

⭐ 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

• 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

• 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

• 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.