Stereotactic surgery is a surgical technique that uses three-dimensional coordinates to pinpoint anatomical structures inside the body, usually the brain. Stereotactic surgery allows for the minimally invasive application of energy fields to the brain and other structures inside the skull. This ability to precisely target one specific part of the brain minimizes the surgeon’s chances of inadvertently damaging nearby parts of the brain. The stereotactic technique is used to insert electrodes, to remove tissue samples for examination, and to destroy small amounts of abnormal tissue.
Two British neurosurgeons performed the first stereotactic brain surgery on a monkey in 1906. Steady technical advances have improved the technique ever since. The widespread availability of computed tomography (CT) has driven the growth of stereotactic surgery. The clear images of CT scans allow a surgeon to develop the precise mapping coordinates needed for successful stereotactic surgeries.
Stereotactic surgical techniques are used to treat Parkinson’s disease, some cancers, chronic pain syndromes such as trigeminal neuralgia, and movement disorders such as spasmodic torticollis. Doctors are also investigating whether application of these techniques can help better target areas of the brain associated with severe depression.
How Stereotactic Neurosurgery Works
Today’s stereotactic systems are computer-based. They commonly consist of a calibrated frame to hold the patient’s head securely and a planning system that includes a stereotactic “atlas” that shows all the major structures of the brain. The atlas allows the neurosurgeon to assign three coordinates along the x, y, and z axes to each “landmark” inside the skull. Once the patient’s head is secured into the frame, the surgeon uses the frame’s guide bars in the x, y, and z directions to precisely locate the structure they will target. The surgeon then accesses the brain with a small incision and hole instead of the large incision needed for open-field surgeries.
Treatments Using Stereotactic Surgery
DBS for Depression
Deep brain stimulation (DBS), which is well established for treating Parkinson’s disease, is now being tested to target severe depression. Patients should be aware, however, that the U.S. Food and Drug Administration has not yet approved it for this use. In DBS, the surgeon uses the stereotactic technique to implant tiny electrodes into the part of the brain that regulates mood. The electrodes are then connected to a battery-powered electrical stimulator that the surgeon implants under the collarbone. The stimulator’s pulses appear to change the brain’s “metabolism” back to a state of equilibrium. DBS seems to improve the patient’s mood while creating a sense of calm, though it is unclear how the electrical pulses achieve this effect.
Parkinson’s Disease Treatments
Treatments for Parkinson’s disease include several different stereotactic neurosurgeries. A progressive neurological disorder, Parkinson’s disease is believed to be caused by loss of nerve cells in various parts of the brain. The type of surgery depends on the patient’s specific symptoms, which might include tremors, rigidity, and involuntary or slow movements. For example, patients with tremors might benefit from a thalamotomy, in which a needle electrode placed into the thalamus destroys a small portion of it thus bringing relief from tremors. Another common procedure is pallidotomy, in which the surgeon uses the electrode to destroy a small part of the palladium with the hope of improving a patient’s rigidity, abnormally slow movements, or tremors. A third stereotactic surgical option is implantation of brain electrodes for deep brain stimulation.