Makindo Medical Notes

🧠 Colloid Cyst in the Third Ventricle: Rare, benign brain lesions that can have life-threatening consequences. Symptomatic cases require urgent neurological and neurosurgical assessment.

📌 About

• Developmental cystic abnormality, lined by a single layer of cuboidal/columnar epithelium.
• Contents: gelatinous, viscous, often PAS-positive material.
• Represents ~0.5–1% of primary brain tumours.
• Classically located in the anterior third ventricle, at the foramen of Monro.
• Typical age: 20–50 years; no gender bias.
• Though histologically benign, their location can cause CSF obstruction → acute hydrocephalus.

🧬 Aetiology & Pathophysiology

• Arise from embryonic endodermal remnants or abnormal neuroepithelial development.
• Symptoms due to:
  • Obstruction of CSF flow at the foramen of Monro → ventricular enlargement.
  • Acute ICP rise if blockage is sudden → collapse or coma.
  • Compression of nearby structures (e.g. fornix) → memory/cognitive deficits.
• Rare reports of sudden death from acute obstruction or brain herniation.

🩺 Clinical Features

• Asymptomatic: Incidental finding on neuroimaging.
• Intermittent Hydrocephalus:
  • Positional headaches (worse lying flat).
  • Nausea, vomiting, blurred vision.
• Raised ICP: Headache, vomiting, papilloedema, visual obscurations, collapse/coma.
• Neuropsychiatric: Memory loss, apathy, hypomania.
• Seizures: Rare, from raised ICP or secondary irritation.

🔬 Investigations

• Clinical: Episodic symptoms + neurological exam for ICP signs.
• CT: Hyperdense, spherical lesion in anterior 3rd ventricle; ventricular dilatation if obstructed.
• MRI:
  • T2 hyperintense, sometimes with central hypointensity (viscous content).
  • Non-enhancing; FLAIR hyperintense if proteinaceous.
• ❌ Lumbar puncture: Contraindicated if raised ICP (risk of herniation).

⚠️ Complications

• Acute obstructive hydrocephalus.
• Brain herniation → fatal if untreated.
• Permanent cognitive deficits from fornix compression.
• Rare cases of sudden death in young adults.

📊 Risk Stratification

• Mortality in symptomatic cases ~3%.
• Higher risk if:
  • Age <65 years.
  • Symptomatic with headaches/ICP features.
  • Cyst ≥7 mm diameter.
  • Hyperintense on FLAIR MRI.

💊 Management

• Observation:
  • Asymptomatic small lesions → serial MRI + clinic follow-up.
• Symptomatic Treatment: Analgesics for headache; ICP-lowering measures.
• Definitive Surgery:
  • Endoscopic resection – minimally invasive, first-line in many centres.
  • Craniotomy – reserved for complex or inaccessible lesions.
  • Ventriculoperitoneal shunt – for persistent/refractory hydrocephalus.
• Postoperative Care: Infection/bleeding monitoring; repeat imaging to check resection and CSF flow.

🌟 Prognosis

• Excellent if treated promptly.
• Symptomatic relief common after resection.
• Incomplete resections may require long-term monitoring.