A generation ago stereotactic neurosurgery was indeed a niche subspecialty. The introduction of levodopa in the late 1960s drastically reduced the number of patients in whom surgical alleviation of Parkinson’s disease, or PD, was warranted. More generally, this welcome advance took the wind out of the sails of functional surgery, which now is practiced by only a handful of neurosurgeons dedicated to caring for the most disabled patients and to studying the human nervous system.
How times have changed. The last 25 years have seen the introduction of CT- and later MRI-guided biopsy (viewed for some time as a specialized “stereotactic” procedure); the widespread acceptance of stereotactic radiosurgery; functional neuroimaging; “frameless stereotaxy” (or surgical navigation); intraoperative MRI; increased interest in surgery for intractable epilepsy; and deep brain stimulation for a variety of functional disorders.
The latter field, that of DBS, deserves further elaboration. The revival of surgery for PD was fueled in the late 1980s by the realization that treatment with levodopa worked well only for a while, and that disease progression often required intolerable medication doses. The “rediscovery” of lesioning diencephalic targets (especially in the globus pallidus) showed that, done correctly, these procedures could alleviate symptoms and decrease medication requirements. DBS arose out of the search for a nonablative and adjustable method for PD. Better imaging, new physiological understanding, and modern electronics made this a practical reality. Now DBS is an accepted treatment for drug-resistant PD and for severe essential tremor. For patients with primary familial dystonia it is the treatment of choice.
As a result of the efficacy and very low morbidity of DBS for movement disorders, neurosurgeons and others are actively looking at other disorders that can be treated by modulating the brain. A great deal of activity is being directed toward patients with intractable psychiatric disorders, especially obsessive-compulsive disorder and depression. This work is not to be confused with the “psychosurgery” of the past. Today’s surgery for psychiatric disorders is being done with the utmost care and caution by multidisciplinary teams using strict selection criteria and advanced neuroimaging, and conducting the most scientific evaluation of results possible. Randomized clinical trials are in progress to evaluate the use of DBS of different targets in these patients. Results to date suggest that surgery will have an important role to play for patients in whom medical and other treatments (including electroconvulsive therapy) for depression and for obsessive-compulsive disorder have failed.
Functional neurosurgery is not limited to DBS, of course. Surgery for intractable epilepsy has moved beyond resection alone, although that method remains the best option for many patients. Neurosurgeons are evaluating various targets for DBS; implanted feedback systems that can electrically sense an aura and forestall an actual seizure by stimulation; and stereotactic radiosurgery as a minimally invasive means of ablating the epileptogenic cortex.
For patients with pain or spasticity, the implantation of intrathecal pumps may be offered. The development of new agents may revive the use of intraventricular pumps as the ideal means of drug delivery for these conditions as well as for other ailments that previously have had no surgical options. A dramatic example is the potential treatment of Alzheimer’s disease. Possible therapies being explored for this progressive condition include drug infusion, gene therapy, and DBS.
Of course, as Yogi Berra said, “it’s hard to make predictions, especially about the future.” Looking ahead some 40 years, it is certain that more advances await. Intraoperative imaging will become routine, further eliminating the guesswork involved in stereotactic biopsy and catheter or electrode placement. Targeting will be based on techniques not yet available, including MRI of 9T or higher, with imaging increasingly based on function and not just structure. Today’s implanted devices will appear quaintly cumbersome as a result of progress in electronics, computer processing speed and power, and materials engineering. Much of DBS as currently practiced may indeed be replaced by various biological modifiers. Improved understanding of neurophysiology and new treatments that arise will greatly increase the possibilities for neurosurgical interventions for patients with functional disorders.
At the same time, the levodopa experience of 40 years ago may be repeated. New medical advances may render some of today’s surgery extinct. Neurosurgeons should welcome any such knowledge that improves our patients’ lives, knowing that we can and will find new problems and techniques toward which we can apply our expertise. In this new era of scientific rationale and rigorous analysis of results, stereotactic and functional neurosurgery may be the most dynamic field of the 21st century.
Michael Schulder, MD, is a member of the AANS Neurosurgeon Editorial Board. He is the past president of the American Society for Stereotactic and Functional Neurosurgery, and vice chair of the Department of Neurosurgery at the North Shore Long Island Jewish Health System, Manhassett, N.Y. The author reported no conflicts for disclosure.