Colloid cyst of third ventricle - missed on MRI

17 year old male with headache  shows   tiny(3mm) almost iso intense, subtly enhancing (possibly septal veins) with relative T2 low signal contents  at anterior end 3rd ventricle  with no proximal hydrocephalus  with hyper dense  on NCCT  suggests colloid cyst (The lesion has been missed on Plain MRI in chronology of events ) 

Teaching points by Dr MGK Murthy

• NCCT is sometimes easier to pick the colloid cyst rather than plain MRI (when the size is small and contents are isointense as in this case ). Apparent subtle enhancement is possibly septal veins aetiology
• Commonest  3rd ventricular benign neoplasm (1%of all primary brain neoplasms) suspended to anterior Tela choroidea with viscous contents near the foramen of Monroe
•  Asymptomatic, Positional headaches,  Drop attacks,  Increased ICP ,  Seizures, aseptic meningitis, memory disturbance (due to forniceal compression) etc  are possible 
• CT hyperdensity is due to high cholesterol and not calciumor any metal. MRI can miss if isointense on T1 , however shows usually T1 high(cholesterol )  and T2 variable signal. Low T2 signal due to high viscous contents (suggesting difficult to  aspirate )and not due to paramagnetic/blood products 
• Xanthogranulomatous variety is rare (shown as solid-cystic on MRI) and can look mimic craniopharyngioma
• Treatment modalities include  percutaneous or stereotactic or endoscopic aspiration or open removal with shunt placement