AANS Neurosurgeon : Features

The Experts Weigh In: Mark Souweidane, MD, FAANS

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

Mark Souweidane, MD, FAANS; New York
The expert says:
Decision-making in this situation is far from straightforward. First, it is not clear that colloid cyst treatment in an asymptomatic patient is beneficial. Avoidance of acute deterioration and sudden death are the obvious advantage of removal in the absence of symptoms. Additionally, the patient also is afforded the ability to be involved in selecting a treating surgeon and treatment options when the decision can be performed in a non-emergent situation. In my mind, factors that should influence decision-making include the patient’s age, the size of the cyst, and the risk profile of surgery. A younger age implies a greater life-long potential of sudden deterioration, even though the annual rate of such is negligible. There is some evidence that indicates that a maximal cyst diameter exceeding 10 mm is associated with greater risk of sudden death. The published risk profile for endoscopic and microsurgical removal is acceptable in justifying removal in this setting, and I would recommend such.

With the advent of endoscopic removal and personal experience, my threshold to treat has been lowered during the span of my career. In fact, next to endoscopic third ventriculostomy for non-communicating hydrocephalus, endoscopic techniques have had the greatest positive impact in neurosurgery when implemented for colloid cyst removal. The clinical outcome following endoscopic removal is well described and is favorable relative to microsurgical removal. Surgeon experience is crucial to an honest assessment of outcome. The newness of the technique and the rarity of this tumor currently limit a wide-ranging talent pool. Admittedly, a realistic appraisal of postoperative cognitive performance has not been done or reported, and this factor remains the only uncertainty in my mind in universally adopting prophylactic removal in the asymptomatic patient. With that being said, the patient’s involvement in this decision is critical, and all options need to be presented in a comprehensive and thorough manner.

Preferred Approach
With regard to the approach, I would favor an endoscopic transventricular route. I would reserve selecting laterality pending a more detailed evaluation (high resolution T2 and post-gadolinium T1 MR imaging) of the venous anatomy surrounding the foramina of Monro. Anticonvulsants are not used since I have not seen a postoperative seizure in my own series of more than 100 endoscopic removals. I do use perioperative corticosteroids with the intent to reduce intraventricular inflammation stemming from spillage of cyst contents. I use a precoronal and parasagittal entry that is defined by navigational guidance. A trajectory that most closely approximates a tangent that parallels the roof of the third ventricle is best.

The Surgical Plan
This surgical plan with a 30-degree-angled solid lens affords a very good view of the cyst interface at the tela choroidea of the third ventricle. Prior to endoscopic cannulation, steretotactic placement of a ventricular catheter is recommended, the path of which is used to guide the endoscopic approach. Once cannulated constant ventricular insufflation with isotonic warm irrigation is performed using a gravity-dependent (20cm) method with a constant egress port. The removal of the cyst is then performed by a technique that employs sequential cyst aspiration and rotational blunt dissection. Coaxial instruments are valuable in performing this maneuver. A tissue-shaving device is sometimes helpful when the cyst contains a more solid matrix, usually predicted based by a dropout of signal on T2 MR imaging. I do not adhere to the principle of cyst evacuation and coagulation of the cyst wall as sufficient since recurrence rates have been shown to be dependent upon complete capsular removal.

After the cyst and cyst membrane is completely removed, a thorough inspection of the third ventricle is performed and any blood present within the inferior third ventricle is removed. Externalized ventricular drainage is seldom used when the third ventricle is void of clot. Postoperative imaging should be performed to confirm patency of the third ventricular outflow into the aqueduct, but is not relevant to predicting residual capsule. Surveillance MR imaging is performed first at three months, then annually.

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