Neuroimaging in Psychiatry: Potentials and Pitfalls

Neuroimaging in psychiatry: Potentials and pitfalls

Robyn Thom, MD, and Helen M. Farrell, MD

dvances in neuroimaging over the neuroimaging biomarkers that can reliably past 25 years have allowed for an distinguish patients from controls, and no Aincreasingly sophisticated under- empirical evidence supports the use of standing of the structural and functional neuroimaging in diagnosing psychiatric brain abnormalities associated with psy- conditions.10 The current standard of clini- chiatric disease.1 It has been postulated cal care is to use neuroimaging to diagnose that a better understanding of aberrant neurologic diseases that are masquerad- brain circuitry in psychiatric illness will be ing as psychiatric disorders. However, Helen M. Farrell, MD critical for transforming the diagnosis and given the rapid advances and availabil- Department Editor treatment of these illnesses.2 In fact, in 2008, ity of this technology, determining if and the National Institute of Mental Health when neuroimaging is clinically indicated launched the Research Domain Criteria will likely soon become increasingly com- project to reformulate psychiatric diagnosis plex. Prior to the widespread availability based on biologic underpinnings.3 of this technology, it is worth considering In the midst of these scientific advances the potential advantages and pitfalls to the and the increased availability of neuroimag- adoption of neuroimaging in psychiatry. In ing, some private clinics have begun to offer this article, we: routine brain scans as part of a comprehen- • outline arguments that support the use sive psychiatric evaluation.4-7 These clinics of neuroimaging in psychiatry, and some of suggest that single-photon emission com- the limitations puted tomography (SPECT) of the brain • discuss special considerations for can provide objective, reliable psychiatric patients with first-episode psychosis (FEP) diagnoses. Unfortunately, using SPECT for and forensic psychiatry psychiatric diagnosis lacks empirical sup- • suggest guidelines for best-practice port and carries risks, including exposing models based on the current evidence. patients to radioisotopes and detracting from empirically validated treatments.8 Nonetheless, given the current diagnostic Advantages of widespread use DO YOU HAVE challenges in psychiatry, it is understand- of neuroimaging in psychiatry A QUESTION OR able that patients, parents, and clinicians Currently, neuroimaging is used in psychia- CONCERN ABOUT THE FUTURE OF alike have reported high receptivity to the try to rule out neurologic disorders such as PSYCHIATRY? use of neuroimaging for psychiatric diagno- ? ▶ Contact Dr. Farrell at sis and treatment planning.9 Dr. Thom is a Child and Adolescent Psychiatry Fellow, Massachusetts [email protected] While neuroimaging is central to the General Hospital/McLean Hospital, Boston, Massachusetts. Dr. Farrell is Lecturer, Harvard Medical School, and Psychiatrist, Beth Israel ▶ Include your name, address, search for improved understanding of Deaconess Medical Center, Boston, Massachusetts. and practice location the biologic foundations of mental illness, Disclosures progress in identifying biomarkers has The authors report no financial relationships with any companies whose products are mentioned in this article, or with manufacturers Current Psychiatry been disappointing. There are currently no of competing products. Vol. 18, No. 12 27 Psychiatry 2.0

seizures, tumors, or infectious illness that clinical acumen, the power of the therapeu- might be causing psychiatric symptoms. tic relationship, and the value of getting to If neuroimaging were routinely used for know patients over time.11 Overreliance this purpose, one theoretical advantage on neuroimaging for psychiatric diagno- would be increased neurologic diagnostic sis also carries the risk of becoming overly accuracy. Furthermore, increased adop- reductionistic. This approach may over- tion of neuroimaging may eventually help emphasize the biologic aspects of mental broaden the phenotype of neurologic dis- illness, while excluding social and psy- orders. In other words, psychiatric symp- chological factors that may be responsive toms may be more common in neurologic to treatment. disorders than we currently recognize. A Second, the widespread use of neuro- second advantage might be that early and imaging is likely to result in many inci- Clinical Point definitive exclusion of a structural neu- dental findings. This is especially relevant rologic disorder may help patients and because abnormality does not establish Using neuroimaging families more readily accept a psychiatric causality. Incidental findings may cause for diagnosis, diagnosis and appropriate treatment. unnecessary anxiety for patients and fami- assessment, and In the future, if biomarkers of psychi- lies, particularly if there are minimal treat- treatment planning atric illness are discerned, using neuro- ment options. may help increase imaging for diagnosis, assessment, and Third, it remains unclear whether wide- treatment planning may help increase spread neuroimaging in psychiatry will objectivity and objectivity and reduce the stigma associ- be cost-effective. Unless imaging results reduce stigma ated with mental illness. Currently, psy- are tied to effective treatments, neuro- chiatric diagnoses are based on emotional imaging is unlikely to result in cost sav- and behavioral self-report and clinical ings. Presently, patients who can afford observations. It is not uncommon for out-of-pocket care might be able to access patients to receive different diagnoses neuroimaging. If neuroimaging were and even conflicting recommendations shown to improve clinical outcomes but from different clinicians. Tools that aid remains costly, this unequal distribu- objective diagnosis will likely improve tion of resources would create an ethical the reliability of the diagnosis and help quandary. in assessing treatment response. Also, Finally, neuroimaging is complex and concrete biomarkers that respond to treat- almost certainly not as objective as one ment may help align psychiatric disor- might hope. Interpreting images will ders with other medical illnesses, thereby require specialized knowledge and skills decreasing stigma. that are beyond those of currently certified general psychiatrists.12 Because there is a great deal of overlap in brain anomalies Cautions against routine across psychiatric illnesses, it is unclear neuroimaging whether using neuroimaging for diagnos- There are several potential pitfalls to the tic purposes will eclipse a thorough clini- Discuss this article at routine use of neuroimaging in psychia- cal assessment. For example, the amygdala www.facebook.com/ try. First, clinical psychiatry is centered and insula show activation across a range MDedgePsychiatry on clinical acumen and the doctor–patient of anxiety disorders. Abnormal amyg- relationship. Many psychiatric clinicians dala activation has also been reported in are not accustomed to using lab measures depression, bipolar disorder, schizophre- or tests to support the diagnostic process nia, and psychopathy.13 or treatment planning. Psychiatrists may In addition, psychiatric comorbidity Current Psychiatry 28 December 2019 be resistant to technologies that threaten is common. It is unclear how much continued on page 33 Psychiatry 2.0

continued from page 28 neuroimaging will add diagnostically when Forensic psychiatry. Two academic disci- a patient presents with multiple psychiat- plines—neuroethics and neurolaw—attempt ric disorders. Comorbidity of psychiatric to study how medications and neuroim- and neurologic disorders also is common. aging could impact forensic psychiatry.19 A neurologic illness that is detectable by And in this golden age of neuroscience, structural neuroimaging does not neces- psychiatrists specializing in forensics may sarily exclude the presence of a psychiatric be increasingly asked to opine on brain disorder. This poses yet another challenge scans. This requires specific thoughtful- to developing reliable, valid neuroimaging ness and attention because forensic psy- techniques for clinical use. chiatrists must “distinguish neuroscience from neuro-nonsense.”20 These specialists will need to consider the Daubert standard, Areas of controversy which resulted from the 1993 case Daubert Clinical Point First-episode psychosis. Current practice v Merrell Dow Pharmaceuticals, Inc.21 In this guidelines for neuroimaging in patients case, the US Supreme Court ruled that evi- Neuroimaging may with FEP are inconsistent. The Canadian dence must be “‘generally accepted’ as reli- overemphasize the Choosing Wisely Guidelines recom- able in the relevant scientific community” biologic aspects of mend against routinely ordering neuro- to be admissible. According to the Daubert mental illness and imaging in first-episode psychoses in the standard, “evidentiary reliability” is based exclude social and absence of signs or symptoms that sug- on scientific validity.21 psychological factors gest intracranial pathology.14 Similarly, the American Psychiatric Association’s Practice Guideline for the Treatment of How should we use neuroimaging? Patients with Schizophrenia recommends While neuroimaging is a quickly evolv- ordering neuroimaging in patients for ing research tool, empirical support for whom the clinical picture is unclear or its clinical use remains limited. The hope when examination reveals abnormal find- is that future neuroimaging research will ings.15 In contrast, the Australian Clinical yield biomarker profiles for mental ill- Guidelines for Early Psychosis recom- ness, identification of risk factors, and mend that all patients with FEP receive predictors of vulnerability and treatment brain MRI.16 Freudenreich et al17 describe 2 response, which will allow for more tar- philosophies regarding the initial medical geted treatments.1 workup of FEP: (1) a comprehensive medi- The current standard of clinical care for cal workup requires extensive testing, and using neuroimaging in psychiatry is to (2) in their natural histories, most illnesses diagnose neurologic diseases. Although eventually declare themselves. there are no consensus guidelines for when Despite this inconsistency, the overall to order imaging, it is reasonable to con- evidence does not seem to support routine sider imaging when a patient has22: brain imaging for patients with FEP in the • abrupt onset of symptoms absence of neurologic or cognitive impair- • change in level of consciousness ment. A systematic review of 16 studies • deficits in neurologic or cognitive assessing the clinical utility of structural examination neuroimaging in FEP found that there was • a history of head trauma (with loss “insufficient evidence to suggest that brain of consciousness), whole-brain radiation, imaging should be routinely ordered for neurologic comorbidities, or cancer patients presenting with first-episode psy- • late onset of symptoms (age >50) chosis without associated neurological or • atypical presentation of psychiatric Current Psychiatry cognitive impairment.”18 illness. Vol. 18, No. 12 33 continued Psychiatry 2.0

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