New ways of imaging the brain show provocative findings.
Better Diagnostic Tools
Currently mood disorders are diagnosed based upon a patient’s symptoms and history, but what if we could perform a lab test that would detect depression? This very thing may be available in the future.
Magnetic resonance imaging (MRI) and other imaging tools have produced several provocative findings. Views of the subcortical white matter in bipolar patients, especially elderly ones, reveal an unexpectedly high number of bright spots in certain brain regions known to be involved in mood. Also, the volume of various brain structures is reduced in long-term sufferers of depression. Among these is the hippocampus, a part of the limbic system (involved in emotion and memory). This finding is consistent with animal data suggesting that chronic oversecretion of cortisol, as occurs in many depressed individuals, can destroy hippocampal cells.1
Positron emission tomography (PET) has shown that patients with major depression compared with normal persons show different patterns of activity in several limbic and cortical brain areas. In addition, one PET analysis revealed that increased activity in a region of the limbic system–the amygdala of the left hemisphere–might be an indicator of heightened vulnerability to future depression.2
Functional imaging technology can also be used to examine the concentrations of neurotransmitters, so that densities of those molecules can be compared. Traceable substances that bind to the serotonin reuptake transporter and to one type of serotonin receptor have been developed and should provide information about which brain areas show depleted serotonin activity in depressed patients.3
Although scientists do not fully understand the implications of these findings and how they might be used to develop a definitive test for mood disorders, it may be only a matter of time before diagnosis goes high tech.
A Pacemaker for the Brain
Research is increasingly showing a compelling link between depression and epilepsy. A recent study found that older adults who are clinically depressed are six times as likely to have a seizure as their peers, suggesting that a common factor may be the cause of both depression and seizures.4
Not surprisingly, some individuals who have not responded to antidepressants do respond to anticonvulsants such as Lamotrigine (Lamictal)5, Gabapentin (Neurontin)6, and Topiramate (Topamax)7. These medications are currently only approved for people who have seizures, but there are many case reports supporting their use for treatment resistant mood disorders.
Following this link to it’s logical next step, researchers have begun to investigate the use of an epilepsy treatment called Vagus Nerve Stimulation (VNS) as a treatment for depression. Results of the VNS pilot study showed that 40% of the treated patients displayed at least a 50 percent or greater improvement in their condition, according to the Hamilton Rating Scale for Depression. Half the patients also had at least a 50% improvement on the Montgomery Asberg Depression Rating Scale. The condition of several patients improved so substantially that they were able to return to work or other normal activities.8
The device used for this therapy (currently only approved for epilepsy treatment), the NeuroCybernetic Prosthesis System (NCP), is often referred to as a “pacemaker for the brain”. The system consists of a pulse generator and a nerve stimulator electrode that is usually programmed to send 30-second electrical impulses every 5 minutes to the left vagus nerve, via connecting leads. The generator is surgically placed in a pocket formed under the skin, below the left collarbone. It’s disc shaped and about the size of an baby’s palm. It is similar in appearance and size to a cardiac pacemaker. The surgery takes about forty-five minutes, and is considered a safe procedure with very little risk. The generator’s “dosage of stimulation” is adjusted non-invasively through the skin using a computerized programmer.9
A new therapy showing great promise for replacing Electroconvulsive Therapy (ECT) is Transcranial Magnetic Stimulation. (TMS). It appears to affect the brain in a similar way to ECT, but without the need for anesthesia or side-effects such as memory loss and any risks associated with seizure and general anesthesia.. In the pilot rTMS (repetitive Transcranial Magnetic Stimulation) study, the only reported side effects were that two patients developed mild headaches, treatable with aspirin.10
TMS involves passing current through an electromagnetic coil to generate a magnetic field. The magnetic field acts as the medium between electricity in the coil and induced electrical currents in the brain. The current depolarizes neurons in the brain up to a depth of about two centimeters below the brain’s surface. It does not requires any sort of anesthesia or analgesics.11 This treatment is under investigation in several locations all over the world.12