The human brain contains several caverns (the ventricles) filled with cerebrospinal fluid (CSF), which is a clear liquid appearing as transparent as water. Each day 500ml of CSF is produced and it constantly flows through the ventricles towards the brain surface where it is re-absorbed.
Within this ventricular system, various tumor entities can arise (e.g. ependymomas, neurocytomas, astrocytomas, plexus tumors, meningeoms, pineal tumors, metastasis, cavernomas and colloid cysts). Although they differ regarding their microscopic origins, their symptoms are very similar:
Once a mass in the ventricles obstructs the CSF
flow, the intracranial pressure rises and a hydrocephalus occurs. This may lead
to a variety of symptoms, including headaches, nausea, vomiting, impaired vision
or even loss of consciousness. If the hydrocephalic pressure rises slowly over
weeks and months, these symptoms may initially be very subtle and may be
accompanied by urinary incontinence, gait instability and dementia.
The treatment of choice of symptomatic intraventricular masses is the neurosurgical resection. Since the ventricle are surrounded by important deep brain structures it is imperative to plan the surgical access towards the tumor carefully. Most tumors can be removed with microsurgical minimally invasive techniques combining microscopic and endoscopic visualization.
Since transparent CSF surrounds intraventricular lesions, endoscopes, which are inserted through small pathways, grant a panoramic “under water view” towards them. In selected cases it is even possible to remove the entire lesion purely endoscopically via a burr hole.
If the tumor size or position doesn’t allow excision, a surgical intervention can be performed to establish a collateral CSF circulation to drain the trapped CSF. Either this is accomplished by endoscopic fenestration of one of the ventricles establishing a connection to the subarachnoid space, or by implantation of a ventriculoperitoneal shunt (VP-shunt). In the latter method, the CSF is channelled via fine catheter, which is positioned under the skin, from the ventricles to the abdominal cavity where it is re-absorbed.
The ventricular system is coated by ependymal cells, which are part of the glial cells that form the supporting tissue of the brain. 3-9% of all tumors in the CNS are ependymomas, which are a type of glioma, and they can occur anywhere in the ventricular system or spinal cord. Often they appear in the forth ventricle, arising from its floor.
Symptoms are often caused by CSF flow obstruction or pressure on the brainstem and include headache, nausea, dizziness, vomiting, visual disturbances or problems with balance and movement.
Diagnosis on imaging is best achieved with Magnetic resonance imaging (MRI), where they appear as inhomogeneous contrast enhancing lesions.
The best treatment for empendymomas is complete surgical removal. The location and extend of ependymomas can vary considerably, and hence detailed 3D surgical planning along with the right choice of microinstruments, endoscopes and the use of electrophysiological monitoring greatly facilitates complete and safe tumor removal.
Central neurocytomas usually occur in the lateral ventricle where they are attached to the septum pellucidum, which is a fine cellular membrane that separates the two lateral ventricles. Sometimes they are found in the third ventricle. Central neurocytomas most frequently occur in young adults and they are considered a WHO grade II tumor.
Symptoms are usually related to increased intracranial pressure due to CSF flow obstruction and enlarged ventricles and include headache, dizziness, vomiting and urinary incontinence.
MRi is the preferred imaging technique for diagnosis and surgical planning, showing moderate to strong contrast enhancement and isointense T1 and hyperintense T2 signal. MR spectroscopy often shows a glycine peak.
The best treatment for central neurocytomas is complete surgical resection, which is often curative. The surgical access route needs to be carefully planned in order to be able to gain comprehensive access and overview, especially in large tumors adjacent to important structures like blood vessels or deep brain tissue.
If the tumor size, shape or location does not allow complete excision, radiation therapy, stereotactic radiosurgery and in rare cases chemotherapy can be considered.
Segregated cavities coated by a cell layer of epithelium are called cysts. Colloid cysts are slow growing, benign masses of the brain, that account for less than 1% of all intracranial tumors. They contain a mucoid or hyloid substance and usually they are located in the third ventricle. If large enough, a colloid cyst obstructs the flow of cerebrospinal fluid (CSF), resulting in enlargement of the ventricles and elevated brain pressure.
Like with other ventricular lesions, the symptoms are usually related to elevated intracranial pressure. Many patients initially present with headaches, which may be followed by dizziness, urinary incontinence or drowsiness. Once symptomatic, a colloid cysts need to me removed quickly in order to prevent sudden neurological deterioration or even death.
Most colloid cysts can be removed
with minimally invasive techniques by using an endoscope. In case of total or
near-total cyst removal the rate of recurrence is very low.