What are the surgical steps for removing a third ventricle tumor?

Surgical Steps for Third Ventricle Tumor Removal

Primary Approach Selection

The interhemispheric transcallosal approach is the gold standard for most third ventricle tumors, particularly those extending anteriorly or located high along the splenial axis, providing bilateral visualization and adequate access to upper and posterior compartments. 1

Approach Decision Algorithm

• For anterior third ventricle tumors: Use interhemispheric transcallosal approach as the preferred corridor 1
• For large tumors invading the dorsal anterior third ventricle: Combine anterior callosal section with anterior interhemispheric (AIH) translamina terminalis approach 2
• For tumors with both supra- and infratentorial extension: Consider occipital transtentorial approach 1
• For low-lying pineal region lesions: Use midline or lateral supracerebellar approaches when straight sinus angle is favorable 1

Preoperative Management

Hydrocephalus Control

• Perform endoscopic third ventriculostomy (ETV) first, followed by tumor biopsy during the same surgery in centers with neuro-endoscopic expertise, as this allows simultaneous tissue sampling with lower complication rates than CSF shunting 1
• For acute intracranial hypertension, place external ventricular drain via frontal trajectory into the lateral ventricle for immediate ICP stabilization 1
• CSF shunting remains appropriate in limited-resource settings without endoscopic expertise 1

Imaging and Navigation

• Obtain image-guided neuronavigation planning to determine optimal entry point and minimize venous injury risk 1
• Fuse CT angiography with volumetric MRI for precise anatomical localization 3

Surgical Steps: Transcallosal Approach

Step 1: Positioning and Exposure

• Position patient supine with head elevated 15-30 degrees 4
• Perform bifrontal or parasagittal craniotomy centered over the coronal suture 4, 5
• Use straight incision for optimal cosmetic outcome 6

Step 2: Interhemispheric Dissection

• Dissect the interhemispheric fissure between frontal lobes, preserving all bridging veins as their cauterization significantly increases postoperative complications (p=0.04) 7
• Preservation of venous structures is paramount—cauterization of bridging veins correlates with major neurological complications 7
• Identify and protect the pericallosal arteries 4

Step 3: Callosal Opening

• Make a 2-3 cm longitudinal incision in the corpus callosum, staying in the midline to avoid injury to the cingulate gyri 4
• For large tumors invading the dorsal anterior third ventricle, perform anterior callosal section to access the caudal tumor portions while sparing the foramen of Monro and fornix 2
• Avoid self-retaining retractors—use retractorless technique with gentle manual retraction to prevent deep brain tissue injury 6

Step 4: Accessing the Third Ventricle

• Open the roof of the third ventricle between the fornices (interforniceal approach) 6
• Alternatively, for anterior tumors, incise the lamina terminalis after exposing it through the interhemispheric space 5
• The lamina terminalis is usually thin and expanded from hydrocephalus, allowing wide exposure without cortical incision 5

Step 5: Tumor Resection

• Pursue gross total resection as the primary goal, as GTR achieves significantly lower recurrence rates (3.8%) compared to near-total (9.4%) or subtotal resection (27.6%) 1
• Disconnect feeding arteries in circumferential fashion, preserving draining veins until final stages 3
• Use multiple corridors through the transcallosal approach for complete tumor visualization 4
• For giant tumors threatening life from blood loss, staged procedures with partial resection are appropriate, particularly in pediatric patients 1

Step 6: Closure

• Seal the corpus callosum opening with fibrin glue to prevent subdural hygroma and subcutaneous fluid accumulation 6
• Meticulous hemostasis to avoid postoperative hematoma 7
• Standard layered closure 4

Intraoperative Monitoring

• Somatosensory evoked potentials for brainstem monitoring 1
• Consider functional mapping if tumor approaches eloquent cortex 3

Expected Outcomes and Complications

Morbidity Profile

• Overall complication rate: 50% with major complications in 37% of patients 7
• Neurological complications occur in 34% (16% major) 7
• Postoperative neurological deficits: 12.9% with retractorless technique 6
• Mutism may occur but typically resolves within 3 weeks 6
• Surgical mortality: 8% 7

Risk Factors for Complications

• Increased age at surgery (p=0.04) 7
• Recurrent tumor status versus new tumor (p=0.01-0.03) 7
• Lower preoperative Karnofsky Performance Scale score (p=0.02-0.04) 7
• Tumor hemorrhage (p=0.04) 7
• Extent of resection (p=0.05) 7

Adjuvant Therapy Considerations

• For WHO grade II/III tumors, multiple relapses, or subtotal resection with residual disease, plan radiotherapy after recovery from primary surgery 1

Critical Pitfalls to Avoid

• Never cauterize bridging veins unnecessarily—this is the single most important factor in preventing major neurological complications 7
• Avoid constant retraction with self-retaining retractors, as retraction injury causes deep brain edema and neurological deficits 6
• Do not sacrifice venous drainage prematurely during tumor dissection 3
• Ensure adequate exposure before attempting resection—inadequate visualization leads to incomplete resection and increased complications 2