Makindo Medical Notes

Brain MRI Collection

Eye of the Tiger Sign

🐯🧠 What it means: Classic MRI pattern seen in PKAN (Pantothenate Kinase–Associated Neurodegeneration), part of the NBIA disorders.
🧲 Expected imaging findings:
• On T2-weighted MRI: central hyperintensity in the globus pallidus surrounded by hypointensity from iron deposition (“eye of the tiger”).
• The peripheral low signal reflects iron accumulation; the central bright area reflects gliosis/vacuolisation.
🩺 Clinical context: childhood/teen onset dystonia, parkinsonism, spasticity, dysarthria ± cognitive/psychiatric features.
⚠️ Pearl: Similar patterns can rarely be seen in other NBIA conditions, but this sign is strongly associated with PKAN.

Lacunar Stroke

🧠 Expected imaging findings:
• Small (<15 mm) deep infarcts due to small vessel lipohyalinosis.
• Common sites: internal capsule, basal ganglia, thalamus, pons.
• CT may be normal early; later shows small hypodense cavity (“lacune”).
• MRI DWI is most sensitive acutely (restricted diffusion).
🎯 Classic syndromes: pure motor, pure sensory, ataxic hemiparesis, dysarthria-clumsy hand.

PRES (Posterior Reversible Encephalopathy Syndrome)

⚡ Expected imaging findings:
• Symmetric vasogenic oedema in posterior regions (parieto-occipital lobes) on MRI FLAIR/T2.
• Often subcortical predominance; can involve frontal lobes, cerebellum, brainstem.
• Typically no restricted diffusion (helps distinguish from infarct), though severe cases may show mixed patterns.
• Causes: severe hypertension, eclampsia, renal failure, sepsis, cytotoxic/immunosuppressive drugs.
🚨 Presents with headache, seizures, visual disturbance, encephalopathy — treat trigger and BP.