Depression is a prevalent and often debilitating psychiatric disorder with a 6-month prevalence of approximately 5%. In the United States alone, approximately 20 million people have been diagnosed with depression at some point in their lives. Depression accounts for the greatest number of missed work days due to illness, with an estimated economic burden of approximately $40 billion per year.
When diagnosing depression, a distinction must be made between major depressive disorder (MDD) and major depressive episode (MDE). For the diagnosis of MDE, patients must present at least five of the following symptoms for a minimum of 2 weeks: depressed mood; markedly diminished interest or pleasure or significant apathy; significant change in appetite or weight; insomnia or hypersomnia; psychomotor agitation or retardation; fatigue or loss of energy; feelings of worthlessness, excessive or inappropriate guilt, or loss of self-esteem; indecisiveness or diminished ability to think or concentrate; and recurrent thoughts of death or suicidal ideas without a specific plan, a specific plan for suicide, or an actual attempt.
Diagnostic criteria for MDD include the occurrence of one or more MDEs with an absence of any history of manic, mixed (combined depressive and manic), or hypomanic episodes. MDEs may also occur in bipolar disorder, an illness characterized by a history of MDEs in addition to hypomanic, mixed, and manic episodes. The currently accepted diagnostic criteria for these and other psychiatric disorders are codified in the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) published by the American Psychiatric Association. It is worth noting that these criteria were not firmly established in their current form until 1980.
PSYCHOSURGERY - The history of neurosurgical intervention for psychiatric illness may be as old as the history of neurosurgery itself. The record of trephination to remove parts of the skull dates from as early as 10,000 BC. Although the exact purposes of such trephinations are disputed, some were clearly motivated by magicotherapeutic goals, with psychiatric illnesses mistakenly thought to arise from demonic possession. Written records of trephining for the “relief of unexplained and unbearable pain … melancholia … or to release demons” have been dated as early as 1500 BC.
In 1910, Ludwig Puusepp reported on the severing of fibers running from the frontal to the parietal lobes in three “bipolar” patients, but he ultimately considered these to be surgical failures. Fourteen other patients who underwent frontal leucotomy were relieved of their aggressive symptoms.
But later on, due to more surgical complications that started occurring, the process shifted from Lobectomy/Leucotomy to specific cortex based approach.
These so called limited lesions and selective undercutting procedures were conducted primarily at three targets: the orbitofrontal cortex, the superior convexity of the frontal cortex, and the medial prefrontal
cortex.
Orbitofrontal cortex - As early as the 1930s, it was realized that lesions closer to the orbital and inferior aspects of the frontal lobes produced changes in emotional tone, whereas lesions involving the superolateral aspects of the frontal lobe were associated with intellectual disturbance. In addition, stimulation of the orbitofrontal and medial prefrontal cortices was soon recognized to produce autonomic responses.
The procedure involved sectioning the brain parenchyma in a plane parallel to and approximately 1 cm dorsal to the orbital surface. The anteroposterior extent of the undercutting was dictated by the distance between the rostral portion of the frontal lobe and the point of emergence of the optic nerve from the optic foramen.
Superior convexity of frontal cortex - In contrast to orbitofrontal undercutting, selective lesions of the
superior convexity of the frontal cortex were performed mainly in patients with paraphrenia and severe psychotic disorders, including schizophrenia. This technique was eventually abandoned owing to poor clinical results.
Medial Prefrontal cortex - Lesions of medial prefrontal cortical structures were also attempted for the treatment of psychiatric disorders. These focused mainly on the cingulate gyrus, with the goal of disconnecting the frontal lobes from the limbic system.
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Spiegel and colleagues were the first to apply stereotactic techniques and reported promising results when lesions of the medial thalamic region were carried out to reduce emotional reactivity in psychiatric patients. Since then a variety of deep brain structures have been targeted to treat psychiatric illness.
(Complications of subcaudate tractotomy include confusion in the early postoperative period (usually the first day after surgery), with disorientation seen in 10% of the patients.)
Capsulotomy - The goal of capsulotomy is to disrupt the frontothalamic fiber systems running in the anterior limb of the internal capsule.
Deep Brain Stimulation (DBS) - Deep brain stimulation (DBS) involves the delivery of electrical
current to the brain parenchyma through implanted electrodes. One of the main advantages of DBS is that most of its side effects are reversible and can be managed by adjusting stimulation parameters. This enables the modulation of disease states without irreversibly destroying neural tissue, as occurs with ablative procedures. At present, the most commonly used DBS hardware has four main components: a quadripolar electrode that is implanted into the brain parenchyma at a specified target, a plastic ring or
adapter that is fixed to the cranium and holds the electrode in place, an implantable pulse generator (IPG), and extension cables that are tunneled subcutaneously from the cranial region to the chest or abdomen, connecting the DBS electrode to the IPG.
The above figure shows the placement of DBS electrode in Subgenual Cortical matter of brain.
The above image shows placement of DBS electrode in Thalamic and subthalamic cortical tissue
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Author - Dr. Yogiraj Karambelkar
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