🧲 Classic MRI Signs in Central Pontine Myelinolysis
Trident Sign
T2/FLAIR hyperintensity in central pons with a trident or "bat-wing" configuration — sparing the periphery and corticospinal tracts
Sequence of Choice
MRI T2 & FLAIR most sensitive. DWI (diffusion-weighted imaging) may show early restricted diffusion before T2 changes appear
Timing of MRI Changes
MRI may be normal in the first 2 weeks; repeat imaging at 2–4 weeks for definitive findings if clinical suspicion is high
Extrapontine Lesions
Seen in ~10% of cases — basal ganglia, thalamus, cerebellum, subcortical white matter (Extrapontine Myelinolysis — EPM)
⚗️ Golden Rules for Sodium Correction
Safe Correction Rate
Maximum 8–10 mEq/L per 24 hours; never exceed 18 mEq/L per 48 hours
Overcorrection Rescue
If Na rises >10 mEq/L/day, administer Desmopressin (DDAVP) 2 mcg IV + 5% Dextrose to re-lower sodium within 24 hours
Symptomatic Hyponatraemia
Raise Na by 1–2 mEq/L/hour for first 2–3 hours using 3% hypertonic saline to control seizures/herniation — then resume slow correction
Fluid of Choice
3% NaCl for severe/symptomatic; Normal saline for mild cases with volume depletion; restrict free water in SIADH
📚 Historical Note & Eponym: Central Pontine Myelinolysis was first described in 1959 by Adams, Victor, and Mancall in alcoholic and malnourished patients. The term "Osmotic Demyelination Syndrome (ODS)" is now preferred as it encompasses both pontine and extrapontine variants. The condition is pathologically characterised by demyelination without inflammation — distinguishing it from inflammatory demyelinating conditions.