Notes on Imaging in Neurology Lecture by Dr. Rybinnik

Introduction

• Imaging is essential in neurology.
• The lecture aims to:
  • Introduce a case study.
  • Discuss an approach to reading imaging.
  • Review anatomical landmarks.
  • Assess symmetry/asymmetry in scans.
  • Explain hyperdensity and hypodensity on CT.
  • Discuss cytotoxic and vasogenic edema.
  • Review MRI sequences and enhancement patterns.

Case Study

• Patient: 73-year-old woman with:
  • Memory difficulties for weeks.
  • Increasing lethargy (10 days).
  • Urinary incontinence (3 days).
  • Mild left-sided weakness and rigidity.
• Imaging done: Head CT.

Approach to Reading Imaging

1. Identify the scan and slice.
2. Assess symmetry or asymmetry.
3. Identify the lesion causing asymmetry and its density/intensity.
4. Consider contrast enhancement patterns.
5. Locate the lesion in extra-axial or intra-axial compartments.

Anatomical Landmarks

• Non-Contrast Head CT: Most common imaging modality.
• Key Locations Identified:
  • Central sulcus ("omega" shape separates frontal and parietal lobes).
  • Head of caudate, thalamus, internal capsule, insula, anterior temporal lobe.
  • Sylvian fissure (location of middle cerebral artery).

Symmetry and Asymmetry

• Asymmetry indicates potential abnormalities.
• Lesion examples:
  • Subacute subdural hematoma.
  • Acute right middle cerebral artery stroke.

Hyperdensity on CT

• Bright signals from:
  • Mineralized structures (e.g., bone, calcium).
  • Acute blood (high sensitivity).
• Normal hyperdensities include calcified pineal, calcified choroid plexus, and bone.
• Abnormal hyperdensities indicate conditions such as neurocysticercosis and hemorrhage types.

Hypodensity on CT

• Dark signals indicating:
  • Chronic lesions, cysts, or cerebral edema.
• Example: Encephalomalacia due to chronic stroke.

Edema

• Cytotoxic Edema: Due to ischemia, characterized by loss of grey-white junction.
• Vasogenic Edema: Caused by breakdown of blood-brain barrier.
• MRI sequences: T1, T2, and FLAIR to identify edema types.

MRI Sequences

• T1: Anatomical sequence (grey/white matter).
• T2: Fluid is bright; used for identifying edema.
• FLAIR: Subtracts CSF signal, enhances visibility of abnormalities.
• DWI/ADC: Early detection of ischemia.

Bright and Dark Signals

• T2 Brightness: Cytotoxic edema, vasogenic edema, hydrocephalus, and inflammatory lesions.
• T1 Brightness: Paramagnetic substances, protein-rich lesions, fat, and subacute bleeding.
• Hypointensities on T2 correspond to similar conditions visible on T1.

Enhancements on MRI

• Common patterns when blood-brain barrier is compromised:
  • Dural tail (meningiomas).
  • Leptomeningeal (meningitis).
  • Subcortical nodular (metastasis).
  • Ring enhancement (abscess, glioblastoma).
  • Periventricular (lymphoma).

Conclusion

• Understanding imaging is key to diagnosing various neurological conditions.
• Practice reading imaging studies alongside radiologist reports.
• Emphasized importance of systematic approaches for accurate interpretation.