Treatment
Medical Therapy
Medical treatment of these lesions is not appropriate nor indicated if the patient is symptomatic.
Surgical Therapy
Surgery is often indicated for these lesions and should be performed in a timely manner. The goals are to relieve hydrocephalus and to remove the risk of deterioration in clinical status.
Preoperative Details
If the patient appears obtunded, urgent ventricular drainage is usually indicated and bilateral ventricular drainage may be frequently required as well. If no neurological deterioration has occurred and the patient is stable, CSF diversion is not indicated because enlarged ventricles can facilitate the surgical approach.
Intraoperative Details
The 3 approaches most commonly used are the transcortical approach, the interhemispheric transcallosal approach, and the endoscopic approach. Stereotactic drainage/aspiration has been used, but it is a blind technique that may fail because the cyst contents may be too viscous to drain. Further, the recurrence rate is high because the cyst wall is usually retained.
Transcortical approach
The transcortical approach involves making a corticectomy over the middle frontal gyrus and proceeding to the frontal horn of the lateral ventricle. Intraoperative ultrasonography may aid in the approach to the ventricle. The foramen of Monro is visualized at the convergence of the septal veins, the thalamostriate vein, and the choroid plexus. The fornix arches over the superior and anterior margins of the foramen. Avoiding the fornix is important because unilateral fornix damage has been associated with amnesia (both anterograde and retrograde).
The cyst should be readily visualized through the foramen. The cyst is then punctured and the contents are aspirated, internally decompressing the walls of the cyst. Avoiding excessive retraction of the walls of the lateral ventricle is important because the genu of the internal capsule is in the subependyma. Other concerns include damaging the thalamostriate veins, which can result in basal ganglia damage. After the cyst has been decompressed, completely removing it to prevent recurrence is essential. Leaving a small portion of the cyst behind may occasionally be necessary if it is attached to either the thalamostriate or internal cerebral veins.
Interhemispheric transcallosal approach
The interhemispheric transcallosal approach avoids incising the cortex. A frontal (usually right) craniotomy is made from about two-thirds anterior to one-third posterior to the coronal suture, crossing the midline to expose the superior sagittal sinus. The right frontal lobe is then retracted laterally, and the corpus callosum is exposed. Draining cortical veins must be avoided if possible. The preoperative MRI can help identify potential veins. A 1-cm incision is made in the corpus callosum, allowing entry to the lateral ventricle. The foramen of Monro can then be visualized, and the septum pellucidum may be divided to see the contralateral foramen. Either ventricle may be entered through a standard right frontal transcallosal approach. Close inspection of the orientation of the choroid plexus, the caudate nucleus, and the foramen of Monro helps determine which of the ventricles has been entered.
Endoscopic approach
The endoscopic approach is the same as the transcortical approach, except that the former is accomplished through a burr hole. The cyst is punctured and aspirated through the working channels of the endoscope. Instrumentation is limited by the size of the working channels, as is the ability to perform bimanual tasks. Use of the endoscope also requires the presence of a fluid environment, which reduces visibility, clarity, and effectiveness of the cautery.
A combination of microsurgery and stereotactic guidance of a rigid endoscope overcomes many of the limitations of conventional open craniotomy and the pure endoscopic approach. The ventriculostomy is performed using stereotactic guidance, thus allowing the surgeon to approach the foramen of Monro with minimum trauma to the brain. A sheath can be placed, allowing sufficient room for placement of an endoscope. This also allows for specially designed instrumentation to be placed for dissection and electrocautery. Cerebrospinal fluid (CSF) can be removed, which improves visualization through the endoscope and also use of the instruments. Removal of the colloid cyst is the same as with conventional microinstruments. Depending on variations of anatomy, variations in technique have also been developed. In patients with a cavum septum pellucidum, the transcavum septum pellucidum interforniceal approach has been described, although higher risks are involved.4
Postoperative Details
Each approach has specific risks and complications. The transcortical approach carries an increased incidence of epilepsy. The transcallosal approach decreases the risk of postoperative epilepsy but risks venous infarction and contralateral leg weakness from prolonged retraction. An extensive callosal resection may also cause temporary mutism. Excessive manipulation of the fornix may affect memory. The endoscopic approach is the least invasive, but it can be used only on cysts that can be aspirated. Large cysts can not be removed with this technique. A steeper learning curve exists with the endoscopic technique.
Hydrocephalus can persist after surgery, even after resection of the cyst. This complication may be secondary to spillage of the cyst contents or to bleeding during surgery. A ventricular catheter may be placed intraoperatively to safeguard against ventricular dilatation.
Follow-up
Colloid cysts are usually cured after successful aspiration and complete resection. Hydrocephalus may develop despite removal of the cyst, and periodic CT scans should be performed.
Complications
Potential complications of surgery include seizures, postoperative hematoma, infection, venous infarct, memory deficit, mutism, and hemiplegia.
More on Colloid Cysts |
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| Workup: Colloid Cysts |
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References
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Further Reading
Keywords
colloid cysts, neuroepithelial cyst, paraphyseal cyst, obstructive hydrocephalus, primary brain tumors, intraventricular masses, increased intracranial pressure, hydrocephalus, anterior third ventricle, increased intracranial pressure
