Makindo Medical Notes

Colloid Cyst in the Third Ventricle: These are rare, benign brain masses that can have potentially life-threatening complications. Symptomatic cases require urgent neurological and neurosurgical assessment and management.

About

• A developmental cystic abnormality, typically lined by a single layer of columnar or cuboidal epithelial cells.
• Often contains gelatinous material, which may be viscous and is frequently PAS-positive (Periodic acid–Schiff).
• Represents approximately 0.5–1% of all primary brain tumors.
• Located in the anterior part of the third ventricle, near the foramen of Monro.
• More common in adults aged 20–50 years, with no significant gender predilection.
• Though benign, its location can cause critical complications due to obstruction of CSF flow.

Aetiology

• Thought to arise from embryonic endodermal remnants or developmental abnormalities in neuroepithelial cells.
• May present as an incidental finding or cause symptoms due to:
  • Obstruction of cerebrospinal fluid (CSF) flow, leading to hydrocephalus.
  • Increased intracranial pressure (ICP) due to acute CSF blockage.
  • Compression of nearby brain structures, including the fornix, which can affect memory and cognition.
• Rarely associated with sudden death, particularly in children or young adults, due to brain herniation or neurocardiac reflex effects.

Clinical Features

• Asymptomatic: Many cases are discovered incidentally during neuroimaging for unrelated conditions.
• Symptoms of Intermittent Hydrocephalus:
  • Positional headaches, often worse when lying flat or during certain head movements.
  • Episodes of nausea, vomiting, or blurred vision.
• Symptoms of Raised Intracranial Pressure:
  • Headache, vomiting, and papilloedema.
  • Visual disturbances, including transient visual obscurations.
  • Sudden collapse or coma in acute cases.
• Neuropsychiatric Symptoms:
  • Cognitive impairment, such as progressive memory loss or dementia.
  • Behavioral changes, including hypomania or apathy.
• Seizures: Rarely reported but can occur due to increased ICP or secondary brain irritation.

Investigations

• Clinical Assessment:
  • Detailed history, focusing on episodic or positional symptoms.
  • Neurological examination to identify signs of raised ICP or focal deficits.
• Imaging:
  • CT Scan:
    • Hyperdense, spherical lesion in the anterior third ventricle.
    • Evidence of hydrocephalus, including lateral ventricular enlargement.
    • Chronic cases may show cortical thinning or brain atrophy.
  • MRI:
    • T2 hyperintense with possible hypointense center due to viscous content.
    • Does not typically enhance with contrast.
    • FLAIR sequences may highlight high-intensity regions if the cyst content is proteinaceous.
• Avoid Lumbar Puncture: Contraindicated if there is any suspicion of raised ICP to prevent brain herniation.

Complications

• Acute Hydrocephalus: Sudden onset may lead to rapid neurological deterioration.
• Brain Herniation: Potentially fatal if not managed promptly.
• Permanent Neurological Deficits: Memory or cognitive impairment due to chronic compression of the fornix or ventricles.
• Sudden Death: Rare but reported, particularly in cases of acute obstruction and ICP elevation.

Risks

• Mortality risk in symptomatic cases is approximately 3.1%.
• Increased risk of symptomatic lesions in:
  • Patients younger than 65 years.
  • Those presenting with headache or other ICP-related symptoms.
  • Cysts ≥7 mm in diameter.
  • Cysts showing hyperintensity on FLAIR MRI.
  • Lesions located in high-risk zones of the third ventricle.

Management

• Observation:
  • Asymptomatic patients may be monitored with periodic neuroimaging.
  • Regular clinical evaluations to assess for new or worsening symptoms.
• Medical Management:
  • Symptomatic relief with analgesics for headaches.
  • Anti-edema measures, such as corticosteroids, may be used in select cases.
• Surgical Options:
  • Endoscopic Resection: Preferred for minimally invasive removal of the cyst and restoration of CSF flow.
  • Craniotomy: Used in cases where endoscopy is not feasible.
  • Ventriculoperitoneal Shunt: Indicated for persistent hydrocephalus not resolved by cyst removal.
• Postoperative Care:
  • Monitor for complications such as infection, bleeding, or residual hydrocephalus.
  • Repeat imaging to ensure complete resection and resolution of CSF flow obstruction.

Prognosis

• Generally excellent if treated promptly.
• Symptomatic improvement is common following surgical intervention.
• Long-term monitoring may be required in cases with incomplete resection or persistent hydrocephalus.