Gray Matters: Bringing Polemic Issues with Inchoate Guidelines into Sharper Focus
Case: Colloid Cyst

Douglas Anderson, MD, FAANS; Maywood, Ill.
The expert says:
The decision to continue conservative follow-up or pursue surgical therapy is complicated in the case described by Vikram Prabhu, MD, MS, FAANS, by elements in the patient’s history, including her anxiety. It should be discussed with the patient that the symptoms she is experiencing may not be related to the presence of the colloid cyst. But, complaints of twice weekly moderate headaches (with or without positional incitement), intermittent dizziness and episodic lower extremity weakness and fatigue, should not be ignored in the decision-making process, despite her normal examination. The size of the colloid cyst, any increase in size, and its relation to the foramina of Monro also suggests that surgery is a rational option. In my experience, the use of the operative microscope and an inter-hemispheric transcallosal approach to these tumors provides excellent visualization of the cyst, and allows for complete removal.

In the systematic review of 1,278 patients who underwent colloid cyst resection, the completeness of removal was statistically superior in the microsurgical approaches. While this is likely reflective of a learning curve, the variety of surgeons, and several other variables, for me, the use of microsurgical instruments with the capability of “bimanual” functionality is helpful in separating the adherent portions of the cyst from the fragile third ventricular structures. That being said, the rate of complications seems lower in the endoscopic group, including fewer episodes of post-operative seizure and venous infarction. Post-operative hematomas, although rare, were more common with endoscopic technique. It is important to distinguish between the trans-cortical and inter-hemispheric microsurgical approaches and their different risks as enumerated in the study above.

My own experience with inter-hemispheric transcallosal approach for colloid cyst resection has left me with these impressions.

1. Position can vary, but we use three-pin head fixation and slight head elevation, with the head straight up.

2. The incision, which can be crescentic or other, is necessarily larger than that for endoscopic approach and while persistent incisional pain in rare, it is not unheard of. We instill long-acting local anesthetic prior to incision.

3. The craniotomy should be inclusive of and primarily slightly anterior to the coronal suture, and should allow for midline retraction of the dural flap.

4. It is essential to evaluate the venous anatomy pre-operatively with MRI, to select an appropriate pathway, ensuring that no veins are transgressed during the inter-hemispheric dissection even if it alters the dural opening and corridor.

5. The identification and protection of the pericallosal arteries is critical and obvious.

6. A corpus callosotomy of 1-1.5 cm in length, neuro-navigationally directed toward the right anterior horn is our usual approach in these midline lesions.

7. Routine micro-instrumentation with 2mm malleable suction tube and a second instrument as needed are used to separate the capsule from the neuropil. Extreme care is taken to avoid harm to the forniceal pathways. Veins are identified and protected. Choroid plexus if adherent can be bipolarized at low power. If the capsule is extremely adherent, the lesion can be entered and decompressed with suction. Micro-cottonoids are used to prevent migration or spill of the albumin material within the cyst. Once decompressed, dissectors can be used to separate the slack capsule from the ventricular wall.

8. The ability to achieve complete resection with preservation of memory and avoidance of post-operative complications is the goal.

While the preservation of memory is complex and demanding to test with metrics, short-term memory formation is a very noticeable; it can be observed by other family members, and it has not been an issue in the many colloid cysts I have resected unless memory was an issue pre-operatively. Post-operative seizures with the transcallosal approach are very uncommon, and we do not use prophylactic AEDs. We do not continue to drain the ventricle with EVD. We obtain surveillance images at three-to-six weeks post-operatively and at one year to document complete resection.