Brain Implants a Gentler Form of Electroshock

Results of a recent Harvard study using brain implants to treat medication resistant depression were reported to a conference of American neurosurgeons in San Diego yesterday.

"Imaging and transcranial magnetic stimulation studies have demonstrated that the left dorsolateral prefrontal cortex (DLPFC) area of the brain plays a critical role in patients with major depressive disorder (MDD). These findings prompted research in which we used an investigational epidural cortical stimulation system to deliver targeted stimulation to the left DLPFC in 12 patients with MDD," stated Dr. Eskandar.

The 12 patients were randomized to single blind active or sham stimulation for 8 weeks, and then all subjects received active stimulation. One patient was excluded from analysis due to a protocol deviation. During the procedure, the electrodes were placed epidurally, outside the dura, through a small craniotomy. Outcome assessments included the Montgomery-Asberg Depression Rating Scale (MADRS), the Hamilton Depression Rating Scale (HDRS), and the Global Assessment of Functioning (GAF). _MNT

This form of brain stimulation is more invasive than strong external electroshock (electroconvulsive ECT), but involves a much gentler electrical stimulation. Results from the study are encouraging:

-- In all patients, continued improvement was seen at 6 months (average HDRS: 20 percent) and 12 months (average HDRS: 33 percent).

-- At 12 months, patients whose electrodes were implanted >20 mm from the precentral sulcus averaged a 59 percent improvement in HDRS compared to a 12 percent improvement in patients (n=6) with electrodes <20mm _MNT

This study involves fairly timid electrode placement -- outside the dura, over the left dorsolateral prefrontal cortex. Such locations are quite safe, since by avoiding direct brain contact, neural scarring should be completely avoidable. In other words, the procedure should indeed be completely reversible -- unlike ECT and unlike many types of deep brain electrode placement.

An extension of this technique to allow simultaneous stimulation and inhibition of multiple areas of cortex should be the next step -- after confirming the result with larger numbers of medication-resistant depressed patients.

The extradural placement of the electrodes should also allow for creative "sheet-electrode" designs. This is where biocompatible materials and conductive polymers will earn their salt.