When a tumor occurs in one of the five regions of the lateral ventricle (cavity) of the brain, a transcortical surgery technique (an operation going through the cortex of the brain) makes it possible to resect (remove) these lesions (vascular malformations, foreign object, or a tumor). The key to a successful and effective transcortical approach is an understanding of the functional anatomy, the location of the lesion, and its blood supply. (Figure 1)

Tumors of the lateral ventricle are uncommon, but not rare. Because of the complex anatomy of the lateral ventricle, there are several possible approaches for removal of the lesion. While the complete resection (removal) of many ventricular lesions may be accomplished through either the transcortical or transcallosal route, the transcortical route is safe, often simpler and provides excellent working space and flexibility in removing the tumor.

Symptoms

Tumors of the lateral ventricle are generally slow growing and can become large before causing symptoms. Symptoms occur after the tumor begins to impair the normal structure and function of the brain, generally develop late in the growth of the lesion and are often very nonspecific in nature. They may include headache, imbalance, visual field deficits, memory difficulty, personality changes, cognitive impairment, weakness and seizures. Often, children with lateral ventricular tumors also have increased ICP (intracranial pressure), resulting in headache, vomiting and general malaise. Hemiparesis (weakness on one side of the body) as well as seizure are also possible symptoms.

Obstruction of normal cerebrospinal fluid (CSF) (watery, colorless fluid that bathes and protects the brain and spinal cord pathways), the compression of adjacent neural structures, or hydrocephalus (accumulation of excess cerebrospinal fluid in the brain) are all indications of the presence of a ventricular tumor.

Diagnosis

Diagnosis of tumors in the lateral ventricle depends on several factors: the age of the patient, the location of the tumor, and the specific radiological characteristics of the lesion. Radiological characteristics may be determined through CT scanning, MR imaging, MR angiography and angiography. MR imaging uses radio waves and a strong magnetic field rather than x-rays to provide clear and detailed pictures of internal organ tissues. Angiography is the radiographic (x-ray) study of blood vessels.

Case Reports

There are many distinct transcortical approaches for the removal of a ventricular tumor. The various routes are based on location and size of the tumor, absence/presence of hydrocephalus, and the vascularity of the lesion (extent of blood vessels supplying the tumor). Regardless of the unique characteristics of the tumor, there are several universal goals for the removal of any ventricular lesion.

Ultimately, the neurosurgeon must choose an approach that causes the fewest complications, offers the most working space, and allows removal of as much tumor as possible.

All patients who undergo removal of a ventricular tumor require close supervision and expert care with an experienced operative and post-operative team following surgery. A stay in the neurological Intensive Care Unit (ICU) is essential, since nurses and ICU intensivists (medical doctors specializing in hospital care) provide 95% of the post-operative care in the ICU and wards and are experienced taking care of patients with brain tumors. Patients who exhibit persistent ventriculomegaly (increased size of ventricles in the brain) or subdural hygroma (excessive collection of fluid in the area of the brain beneath the tough membrane [dura] covering the brain and spinal cord) may require the implantation of a drain, also known as a catheter or shunt. While this device is present, the patient receives antibiotic therapy. Post-operatively, patients also receive anticonvulsant medication, and are closely monitored and treated to maintain electrolyte balance.

The potential for complications in the operative treatment of lateral ventricular tumors exists regardless of surgical approach but can be kept to a minimum if the surgeon has the proper team and experience in performing these surgeries. While some ventricular lesions may be removed via callosal sectioning, other tumors targeted by this route cannot be accessed without some form of cortical incision.

Overall, the complication rate of transcortical resections of lateral ventricular tumors is better than before the advent of microsurgical techniques. Microsurgery generally refers to a surgical technique that uses a special binocular microscope to operate on tiny, delicate, or hard-to-reach tissues such as those found in the brain. Today at the University of Washington Medical Center, the morbidity (complication rate) of the transcortical approach is less than 10%.

There are some post-operative complications to lateral ventricular tumor resection that cannot be avoided. However, these risks can be anticipated and, thus, managed. In procedures where tumors are approached from purely the occipital approach, a temporary visual field loss occurs in 100% of patients treated. Visual field loss is less likely when undertaking a parietal or temporal approach.

Patients may also suffer from epilepsy (neurological disorder caused by abnormal, unpredictable electrical and chemical activity of neurons that is manifested as brief episodes of diminished consciousness) following the removal of a ventricular lesion. The true incidence of epilepsy is hard to monitor, however, because many factors contribute to a seizure disorder. These may include: tumor type, if seizures existed preoperatively, if any portion of the tumor remains after surgery, the presence of a subdural hygroma, and the presence of an electrolyte imbalance. Also, it is important to note that any patient who undergoes a craniotomy (procedure in which a piece of the skull is removed to gain access to the tumor) is at risk for postoperative seizure.

Hemiparesis (weakness on one side of the body) is also a potential complication of the transcortical approach. Most weakness is likely the result of retraction of the tumor during surgery and often resolves. However, permanent motor loss has been rare.

Language impairment may occur following surgery. This is possible if the tumor is based in the “dominant hemisphere.” The brain is physically divided into two halves or hemispheres, right and left, with one hemisphere usually dominant over the other. In all right-handed people and the majority of left handed people, the left hemisphere is dominant. Following the removal of a lateral ventricular tumor of the dominant hemisphere, about 10% of patients suffer new speech impairment or worsening of their preoperative deficit that may be temporary or permanent.

A subdural hygroma may form following surgery. As explained, this phenomenon is characterized by an excessive collection of fluid in the area of the brain beneath the dura and spinal cord. Patients with extraordinarily large tumors associated with ventriculomegaly are especially susceptible to developing a subdural hygroma. To alleviate the excess fluid, a shunt or temporary external drain is implanted.

Some patients who have undergone transcortical resection of a ventricular tumor may experience some form of meningeal irritation. Meningitis is generally defined as an inflammation of the brain (the meninges, specifically) and spinal cord, most often caused by a bacterial or viral infection and characterized by fever, vomiting, intense headache and stiff neck. This condition is caused by the presence of blood products in the cerebrospinal fluid following surgery to remove a ventricular tumor. This type of chemical meningitis can be treated by administering pain medication and a tapered course of steroid medication.

Despite the risks associated with the transcortical resection of a lateral ventricular tumor, morbidity rates in the microsurgical era are much less than 10%. Currently, with advanced technology and microsurgical techniques, this procedure is difficult but quite reasonable and safe in experienced hands.

Brain tumors grow. This growth can lead to worsened symptoms and can make an operable tumor unsafe for surgery.

As mentioned, brain tumors can grow to an inoperable size and symptoms may worsen and permanently damage crucial structures in the brain.