Introduction

The collection of topics in this volume gives evidence that neuromodulation has transcended the treatment of pain. Activity of visceral structures, psychiatric disorders, and movement disorders have emerged as viable therapeutic targets. Advances in technology have led to the questioning of long-held notions such as the importance of patient-perceived concordant paresthesia and the necessity of an implanted power supply. Stimulator leads are being placed in or around the gut, periphery, nerve structures outside the spinal cord, and the brain. Patient selection, however, remains critical.

Unfortunately, the psychology involved in neuromodulation has not kept pace with other aspects of the therapy. Little more is actually known now than some 20 years ago. For example, one of the present authors (Doleys) reviewed 33 intrathecal therapy (IT) studies involving chronic-pain patients published from 1998 to 2010. Only 12 of the 33 referenced a preimplant psychological screening. Neither the testing results nor the criteria for considering the patient acceptable were outlined. Furthermore, no attempt was made to correlate the psychological data with treatment outcomes. There appear to be few, if any, systematic studies with sufficient follow-up to determine a positive or negative contribution of the psychological evaluation to outcomes.

As regards spinal cord stimulation (SCS), a Canadian study stated that only 25% of 13 centers reported performing a routine psychological screening ( ). Screening was carried out in 61% of surveyed centers in the UK ( ). Although in the United States Medicare (CMS) mandates a preimplantation psychological screening, such screening was only conducted on 25% of non-Medicare patients ( ). Possible reasons for the discrepancy between the support for psychological screening and its actual utilization include lack of, or inadequate, insurance coverage, lack of physician insistence, patient refusal, and lack of an appropriate evaluator.

The relative ease with which IT and SCS therapy could be reversed (hardware removed) has been considered one of the attractive features of the therapies. However, the “experience” of the therapy cannot be reversed. Furthermore, many of the therapies reviewed here, e.g., optogenetics and gene-based therapies, appear to be irreversible. This adds a new dimension to the psychology of the therapy.

Selective Literature Review

This section reviews some of the studies involving different disorders wherein psychological factors and assessment are noted. Psychological factors relating to the use of neuromodulation for chronic pain have received some attention. Chronic pain is known to be associated with depression, anxiety, posttraumatic stress disorder, and a history of physical/sexual abuse. Some 50%–80% of patients with chronic pain demonstrate signs of psychopathology ( ). This data was derived from reviews of the literature relating to the epidemiology of chronic pain and patient characteristics in studies exploring the use of opioids. The fact that any of these factors can influence the treatment outcome underscores the importance of psychological evaluation for those under consideration for SCS therapy.

A review by identified risk factors generally associated with unsuccessful SCS outcomes, including pain chronicity and duration, psychological distress, pain-related catastrophizing, a history of abuse or trauma, nicotine use and substance abuse history, poor social support, and significant cognitive deficits. reported depression, anxiety, somatization, poor coping, and hypochondriasis to be associated with poorer outcomes, including measures of pain, mood, and function. Furthermore, the levels of pain and functional limitations showed little association. concluded that depression and hysteria appeared to correlate negatively and mania possibly positively, while hypochondriasis was mixed. In Daniel et al. identified five “red flags”: personality disorders (Axis II diagnosis; Diagnostic and Statistical Manual of Mental Disorders, IV), drug dependence, unstable family and personal relationships, poor vocational adjustment, and involvement in litigation/compensation. These “red flags” appear have stood the test of time.

A 2013 review (Wolter et al.) concluded that preimplantation depression, anxiety, and perceived disability did not predict success during the trial or the long-term outcome. There was a strong inverse correlation between perceived self-efficacy and anxiety/depression scores as well as pain-related disability scores. Self-efficacy measured after implantation showed a tendency to correlate with pain reduction following SCS. Pain scores, depression scores, and pain-related disability, but not anxiety scores, were significantly reduced following SCS therapy.

The characteristics of the patient evaluated before a trial are likely to change after the trial and subsequent implant. This may account for the fact that as many as 50% of patients completing a trial and proceeding to SCS implant report loss of pain relief 12–24 months after implantation ( ). found that, of patients reporting success at 16 months post implantation, only 59% did so at 58 months.

The emergence of pathological states such as conversion disorder has been reported after SCS implant ( ). Without a thorough psychological evaluation, it is difficult to determine whether such psychological conditions somehow arose as a result of neuromodulation or preexisted in some form and manifested themselves in response to SCS or in association with changes in the targeted symptom.

Regarding IT, cautioned against patients who claimed they could not live without the pump, overused healthcare resources, declared they were misunderstood and asserted that “only you can help me doctor,” revealed major psychopathology, insisted their pain was their only problem, or demonstrated symptoms inconsistent with physical findings. examined preimplantation personality profiles and found that the patients reporting a greater reduction in pain showed a slightly more elevated profile. They reasoned this may have reflected a “normal” degree of distress while the other group may have adapted to their situation and were motivated by other considerations.

To date, most of the studies examining psychological factors as predictors of outcome in the treatment of chronic pain have not been well controlled and are usually observational or quasiexperimental in nature. Recommendations, opinions, and consensus are driven largely by clinical experience, systematic observation, and generalization of findings from other pain-related therapies ( ). No single psychological factor or set of factors has proven via replication to be superior; yet their importance appears incontrovertible, especially when the pain is more generalized and correlates poorly with known pathophysiology.

Tourette’s syndrome is a childhood-onset disorder with complex clinical features, including a waxing and waning course and frequent neuropsychiatric comorbidities. noted that most patients are likely to have comorbid attention deficit disorder, obsessive/compulsive disorder, depression, anxiety, or other nonmotor symptoms. They recommended that potential candidates be independently evaluated by each member of a multidisciplinary team; risks, benefits, the operative approach, and postoperative care should be discussed before a decision to act is made; regular postoperative evaluations be carried out, including tests of tic severity, attention, and suicidal tendencies; and (4) preexisting symptoms should be adequately treated and stable for a minimum of 6 months and should not be the major source of functional impairment. Special precaution was noted when evidence of self-injurious behaviors was present.

used vagal nerve stimulation (VNS) for the treatment of refractory depression. They reported robust recall of negative material viewed during “off cycles” of stimulation, at which time the patient viewed randomly presented positive, negative, or neutral words. Subsequent memory of negative words was attenuated during active VNS (“on” cycles). These effects were not apparent for neutral and positive words. also reported enhanced memory formation following VNS. However, these studies gave no indication that the type and kind of memories recalled or formed could be controlled. Therefore, one must assume that the potential for reducing the threshold for “flashbacks” or nightmares and for activating suppressed memories exists.

examined a group of patients treated with sacral stimulation for overactive bladder syndrome secondary to nonobstructive urinary retention. Patients completed a psychiatric history and tests of personality traits. Although the psychological screening data was not predictive of treatment outcome, the presence of a history of psychiatric disease was associated with a higher incidence of adverse events.

studied 397 females undergoing treatment for functional bowel disorders. Treatment responders and those expressing satisfaction with treatment reported confidence in the treatment, perceived control over illness and symptoms, and reduction in negative cognitions related to their symptom experience, regardless of which of the four treatments tested they were exposed to.

There is a fairly substantial literature relating to deep brain stimulation (DBS; subthalamic nuclei stimulation (STN)) for Parkinson’s disease (PD) and psychologic issues. recommended a psychological evaluation to rule out dementia and major psychiatric problems, including apathy, impulse control issues, and suicidality; determine if the patient is suitable from a neurocognitive, mood, behavior, and quality of life (QoL) perspective; assess expectations; and educate and prepare patients and family. Furthermore, the psychologist should participate in monitoring the impact of surgery, and provide counseling to improve postsurgical psychosocial adjustment. A number of postoperative psychological changes have been observed following STN DBS. Some may be related to the fact that the STN has subdivisions associated with emotions and cognitive functioning as well as movement. Declines in cognitive functioning including overall mental status scores, memory, and verbal fluency have been reported ( ). Increased apathy is not uncommon ( ). Mood elevation (e.g., euphoria and hypomania) has been described in up to 15% of patients, mania in less than 2% of cases, and up to 25% of patients had increased depression or the onset of depression, usually in the first few months after implant ( ).

reported worsening of depression after STN stimulation but improvement after pallidal stimulation, despite both groups showing improvement in motor symptoms and self-reported function ( ). Postoperative depression following STN DBS appeared to have a greater impact on QoL than motor outcomes ( ). Increased impulsivity scores have been reported ( ), but the findings are inconsistent ( ). Postoperative anxiety levels are usually less but there was a relatively high incidence of marital difficulties ( ). Finally, the onset of pathological gambling has also been noted ( ). The mechanism(s) responsible to these changes is unclear and may include position of the electrode, stimulation parameters, neurochemical changes, preimplant psychiatric disorders, personality traits, and psychosocial factors.

Improvement in the primary symptom, motor disability, was not necessarily accompanied by improvement in psychological function and QoL. found increased abnormalities in five main areas: social maladjustment, decompensation of psychiatric disorders, anxiety, emotional hyper-reactivity, and severe behavioral disorders. This lack of generalized improvement may be related to the presence of preoperative personality disorders and decompensation associated with previous psychiatric disorders in PD patients who were otherwise thought to be suitable candidates for STN DBS, or chemically induced by the electrical field.

A multicenter study ( ) examined the incidence of suicide following STN in PD. Approximately 0.90% (48 of 5311) of patients attempted suicide. The rate of suicide completion was 50% (24 of 48). Suicide rates were higher in the first postoperative year and remained high in the fourth year when compared to the expected rate in the general population. Postoperative depression, being single, a previous history of impulse-control disorders, and compulsive medication use accounted for 51% of the variance for risk of attempted suicide. Completed suicides were associated with postoperative depression. There was no association with gender or preoperative depression, but 80% had postoperative psychiatric diagnoses and 47% had a major relationship or residential change or were socially isolated. The increase in impulsivity seen in some cases ( ) may be a contributing factor.

In summary, psychological symptoms warrant assessment and management before and after DBS for PD. The nature and severity of these symptoms may represent a contraindication ( ). In addition, adequate education and informed consent should be a priority. This may require cognitive testing to ensure the patients are capable of evaluating the consequences and making appropriate decisions. This brief literature review reinforces the notion that regardless of the technology and the targeted symptom (disorder), neuromodulation is conducted within the psychosocial context of the patient. Both preimplant psychological predispositions and postimplant psychological consequences require investigation and intervention. To be effective, psychologists (mental health clinicians) will have to become acquainted with therapies and technology that may be foreign to their usual practice. The use of specialized tests (see below) tailored to a given disorder may be required.

Historical and Recommended Approach to the Psychological Evaluation

Historically, the psychological evaluation has occurred prior to internalization of the neuromodulation technology. A variety of psychological tests/questionnaires commonly used in the setting of chronic pain have been employed. Assessments of personality, coping patterns, and mood are the most common, and are customarily done in the context of a clinical interview. Some have relied upon computer-based interpretations. Rarely have “cut-off” scores been given. The interaction, if any, among treatment team members has not been outlined. Expectations are reviewed, but little is reported as to what these were. No reports could be found wherein family/support persons were involved. The modal approach was to “accept or reject.” The percentage of patients rejected and reasons for rejection are rarely given. In cases where testing was done and follow-up information obtained, the approach was linear, i.e., to determine any statistically significant correlation between preimplant data and outcome measures. Unfortunately, the absence of any standardized protocol has resulted in a diverse array of outcomes, leaving the field without any validated and reliable guidelines.

The implicit assumptions underlying this approach appear to echo the (paraphrased) assertion of Sir William Osler that “it is equally important to know the patient as it is to know the disease that the patient has.” The recognition that chronic pain has an emotional/affective (i.e., psychological) component and Daniel et al.’s comment that “electrode implantation can serve as the initial step in a treatment plan followed by psychotherapy (to address psychological factors influencing pain)” (p. 776; ) seem to recognize the value of postimplant psychological therapy. The literature appears void of any efforts to study this. The current approach suggests a static view of the patient: psychological factors present preimplantation will remain stable and their effect constant over time. Therefore, an “acute” (one-time) evaluation is used to predict a “long-term” outcome. This, of course, is inherently and intuitively unsettling, but descriptive of the present philosophy, intended or not.

More in keeping with the true narrative of human behavior is the recognition of the ever-changing impact of neurochemical/neurophysiological, personality/behavioral, social/environment, and political/economic factors. The patient and clinician function within a dynamic and complex set of circumstances. This would suggest the benefit of considering an alternative philosophy to guide the evaluation and treatment process involving neuromodulation.

General systems theory (GST) ( ) has a history in psychology ( ) and medicine ( ). It views phenomena in terms of relationships and integration. Systems (individuals) are considered to be integrated wholes. The property of the whole is “more than” the sum of its component parts and cannot be comprehended merely by the study of its parts (reductionism). By way of an illustration, chloride (chlorine) is a deadly poison, and when tossed into water sodium causes an explosion. Yet together sodium chloride (common table salt) serves a vital function in the human body, and we could not live without it.

The systems approach is nonlinear; that is, it underscores the principles of organization instead of concentrating on component parts. The emphasis is on the interaction among the parts of the system ( Fig. 2.1 ). The organism therefore is understood to be a dynamic and complex adaptive system ( ) that actively responds to, and in turn has an impact upon, other aspects of the system. Systems are intrinsically dynamic; the component parts manifest their “own” behavior and may or may not respond in accordance with a predetermined mathematical equation to any particular input. For example, a recent conceptualization of brain functioning features the existence of modules, hubs, and hierarchical networks ( ). Some aspect of brain function or connectivity is hypothesized to change with each exposure to an event or experience ( ).

Bronfebrenner’s ecological systems theory. Licensed under CC BY-SA 3.0 via: wikipedia.org/wiki/Ecological_systems_theory .

The application of GST transforms neuromodulation from a procedure into a process. The component parts (i.e., selection, trial, implant, management, etc.), though having their own idiosyncrasies, are viewed as interacting with one another. Rather than concerns over simply “clearing” the patient, emphasis is placed on obtaining a description of the patient and the system within which they function. This notion mimics Benedetti’s ( ) description of a placebo as a “contextually sensitive treatment.” The ultimate outcome becomes an emergent property of this interaction, and is itself subject to ongoing variation. Rather than merely entering the psychological testing scores into some multifactorial regression equation in an effort to determine a single matrix, such as the r ² value of a particular variable, the outcome of testing is used descriptively as a means of attempting to understand the complex interaction of the various psychological/social factors involved.

Assessment

Many of the psychological variables thought to be related to neuromodulation outcomes fluctuate significantly during the patient’s life. Affective states, particularly depression, vary greatly in terms of symptom severity, duration, and chronicity. There is a qualitative and quantitative difference between a patient with situational depression and one with a life-long history of mood instability, i.e., bipolar disorder. A differential diagnosis, including a detailed history and psychological testing, could be critical when treating mood disorders, e.g., VNS for depression. reported a higher incidence of major depression, anxiety, mood/anxiety disorders, and suicidal ideation in patients with epilepsy when compared to controls. Although depressive symptoms and pain have been shown to improve following neuromodulation, found that the presence of a recurrent depressive disorder would jeopardize long-term efficacy of the therapy. Furthermore, severity of depression, especially after implantation, has been strongly associated with suicide following STN DBS for PD. This data emphasizes the need for ongoing monitoring versus pretrial assessment only.

Patient expectations and beliefs may change with new information. For example, experiences during a trial may significantly alter patient beliefs and expectations and thus the acceptability of therapy. Physiological factors also change over time. The emergence of comorbid illnesses can affect overall functioning and QoL. In addition, many illnesses that neuromodulation is beginning to address are considered to be complex progressive disease processes, rather than a static disease. Furthermore, there are likely to be many changes in marriages, extended families, economic status, work status, living arrangements, treatment providers, treatment regimens, insurance coverage, etc., that can impact patients and their ability to cope with the demands of therapy and an ongoing chronic disease.

Assessment in the area of chronic pain has primarily focused on patient variables as they relate to subjective reports of pain levels. It assumes that changes in reported levels of pain will be associated with changes in functioning and patient satisfaction, and predictive of long-term outcomes. This somewhat linear and ideographic approach to the patient may inherently limit the usefulness of the psychological evaluation as currently conceptualized. When addressing a complex and potentially progressive disorder, a multifactorial and multisystems perspective seems more appropriate. The assessment should recognize that treatment is an ongoing process involving the patient and clinician as well as the various social, economic, environmental, and political systems within which they exist. The focus of assessment should encompass more than a one-time clearing of a patient based on a set of red-flag variables if the assessment is to provide optimal value.

From a GST perspective, many factors outside the traditional patient (ideographic) variables become important and also need to be considered. Therefore, the pretreatment assessment has two primary focuses: to determine the characteristics of the patient and the systems he/she functions within, which serve as barriers or facilitators to an adaptive adjustment across the natural history of the illness; and to determine what other possible interventions may be applied along with neuromodulation to enhance and/or maintain the long-term efficacy of treatment.

Assessment focuses on the dynamic interaction among various systems that collectively form the basis of the patient’s responses. One cannot separate individuals from the systems and contexts within which they live and function without compromising an accurate understanding of the patient and the disorder. The application of GST suggests the need to considered five systems: the individual patient (microsystem), ancillary relationships (mesosystems), contextual effects (exosystems), cultural effects (macrosystems), and life experiences (chronosystems) (see Fig. 2.1 ).