Clinical Assessment of Prefrontal Lobe Functions (Behavioral Neurology and Psychiatry 2018)

Educational Objectives

The goal of this program is to improve diagnosis and treatment of behavioral and psychiatric disorders in patients presenting for neurologic evaluation. After hearing and assimilating this program, the clinician will be better able to:

1. Define prefrontal functions.
2. Use clinical history to determine the anatomic location of disorders of the prefrontal cortex.

Summary

Prefrontal functions: Refers to higher-order cognitive, social, and emotional functions typically associated with frontal lobes; term does not include other functions of frontal lobes such as motor cortices, frontal eye fields, and areas concerned with language.

Executive function: Term sometimes used erroneously; prefrontal and executive functions overlap but differ; executive function refers to set of interrelated cognitive processes required for complex, goal-directed activity; disruption of executive function may be associated with damage to lateral parts of prefrontal cortices; however, other prefrontal functions not considered executive functions; damage in areas outside prefrontal lobes may impair executive function.

Structure of frontal lobes: Discussion focuses on four important areas (superior medial prefrontal cortex [includes anterior cingulate cortex], lateral prefrontal cortex, ­orbitofrontal cortex above orbital plate, and frontal poles in most anterior part of prefrontal lobes); studies show that distinct syndromes arise from damage to different areas; prefrontal cortices do not function as single unit; networks that connect prefrontal cortices include loops from cortex to limbic, cerebellar, and subcortical areas; best known loop consists of frontal-subcortical circuits from cortex to striatum, pallidum, thalamus, and back to cortex; five to six loops can be traced, some of which control primary motor functions; other loops originate from anatomic areas of prefrontal cortex that serve cognitive and social-emotional functions (ie, dorsolateral prefrontal cortex, orbitofrontal cortex, and superior medial cortex); no loops associated with frontal pole (hypothesized to integrate information from other prefrontal regions).

Energization: Refers to capacity to initiate or sustain nonreflexive (internally directed) response; occurs when patient begins task; patients with bilateral damage to superior medial prefrontal cortex (including anterior cingulate cortex) have most dramatic deficits in energization.

Task setting and monitoring: Considered executive functions; task setting — cognitive capacity to develop and implement plan for carrying out activity; includes complex activities such as paying bills as well as simpler activities; monitoring — process of checking that one is remaining on task and adjusting behavior as needed to successfully complete task; damage to lateral prefrontal cortex — results in deficits in task setting and monitoring; left lateral prefrontal lesions more likely to cause difficulties with task setting, while right lateral prefrontal lesions more likely to cause problems with monitoring.

Behavioral and emotional regulation: Affected by lesions in orbitofrontal cortex; patients with such lesions may have normal findings on standard neuropsychological tests that measure task setting and monitoring but exhibit significant behavioral and emotional derangements.

Metacognitive processes: Affected by damage to frontal poles; metacognitive processes include awareness of self, effects of own actions and thoughts, and ability to impute mental states of others (theory of mind).

Approach to patient: When prefrontal dysfunction suspected, clinical history often more important than examination; collateral informant who knows patient well can describe behaviors, emotions, and social actions of patient who has little insight; before assessing complex functions, clinician should ascertain whether more basic functions intact; cognitive tests that require verbal, motor, or sensory output not appropriate in patient with aphasia or impaired motor and sensory functions; before performing cognitive assessment, clinician should ensure that patient alert and not in confusional or delirious state.

Superior medial prefrontal cortex: Involved in energization; abulia — decrease in initiation of cognitive responses; term not precisely defined in literature; apathy — differs from depression; refers to less severe expression of lack of initiation; history may reveal lack of motivation; apathy can exist with or without associated depression; depression — clinician should speak with patient to assess whether depression present; disturbances of gait — often associated with lesions of superior medial prefrontal cortex; may appear parkinsonian; difficulty with initiation of gait may reflect deficit in energization; in such patients, all movement (including gait) may be slow; frontal subcortical circuits directly influence gait; once gait initiated, patients may take small and slow steps (ie, marche à petit pas).

Lateral prefrontal cortex: Dysfunction in this area associated with typical deficits in executive function; patient may have problems with task setting and monitoring; prefrontal lobes important for working memory; experts debate whether working memory distinct construct versus component of executive function; patient may be unable to, eg, follow recipe, plan trip, project, or activity; to assess task monitoring, determine type of difficulty patient experiences with activities previously within his or her capabilities (eg, becoming distracted and engaging in other activities, making errors, becoming unable to focus on task).

Testing function of lateral prefrontal cortex: At bedside, patient who cannot copy alternating pattern may have dysfunction in monitoring; Luria hand sequence — ­repeated palm-fist-edge sequence often used to evaluate prefrontal cortex; go/no-go task — patient asked to tap once when examiner does and not to tap at all when examiner taps twice; conflicting instructions task — ­patient asked to tap twice when examiner taps once, and once when examiner taps twice.

Case: 72-year-old man with history of mild hypertension and dyslipidemia referred by family; he lost large sum of money in email scams; when son and patient’s wife confronted him about problem, patient could not understand reason for their concern; patient became cold and distant, with little response to his wife’s emotions, but became emotional about football scores; he lost interest in his usual hobbies and friends; patient became passive, viewed pornography on Internet, and developed binge eating; he made confabulatory and contradictory responses when asked about these behaviors; patient could answer direct questions but wandered from topic to topic; however, he performed within normal limits on Montreal Cognitive Assessment (MoCA); physical and neurologic examinations unremarkable.

Assessment of case: Behavioral and emotional dysregulation and difficulty with metacognitive processes suggest dysfunction of prefrontal lobes, including frontal pole; changes in behavior imply involvement of orbitofrontal cortex; passivity consistent with superior ­medial ­syndrome; basic executive functions preserved, illustrating that executive function not synonymous with prefrontal function; patient may have behavioral variant of frontotemporal dementia (imaging needed to corroborate diagnosis); although same pattern may be seen after trauma to frontal lobe, traumatic etiology not expected to cause progressive disease.

Behavioral variant frontotemporal dementia: Typically associated with early atrophy and damage in orbitofrontal cortex, anterior cingulate cortex, and frontal insula; dorsolateral prefrontal cortex usually spared until later in course of disorder.

Orbitofrontal dysfunction: Characterized by dysregulation in social and interpersonal conduct; patient behaves inappropriately despite retention of logical understanding of proper behavior; loss of social decorum may be striking and often brings patient to clinical attention.

Metacognitive function: Altered in injuries of frontal pole; refers to ability to understand and adopt perspective of others and to understand thoughts, actions, and emotions of self and others; theory of mind refers to ability to understand another person’s state of mind; psychological tests that test metacognitive function exist but not routinely used in clinic; false belief task involves asking patient to interpret story from perspective of one character in story; other options include asking patient to assess state of mind of character in cartoon or explain why cartoon humorous.

Readings

Henri-Bhargava A, Stuss DT, Freedman M. Clinical assessment of prefrontal lobe functions. Continuum (Minneap Minn) 2018;24(3 Behavioral Neurology and Psychiatry).

Stuss DT, Shallice T, Alexander MP, Picton TW. A multidisciplinary approach to anterior attentional functions. Ann N Y Acad Sci 1995 Dec 15;769:191-211.

Disclosures

For this program, the following was disclosed: Dr Henri-Bhargava has received funding for clinical trials from AstraZeneca, Boehringer Ingelheim Ltd, Eli Lilly and Company, F. Hoffman-La Roche Ltd, and TauRx, and has provided expert legal testimony in personal injury litigation for the law courts of British Columbia. Unlabeled Use of Products/Investigational Use Disclosure: Dr Henri-Bhargava reports no disclosures. To view disclosures of planning committee members with relevant financial relationships, visit: audiodigest.org/continuumaudio/committee. All other members of the planning committee report nothing to disclose.

Acknowledgements

CME/CE INFO

Accreditation:

The Audio- Digest Foundation is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.

The Audio- Digest Foundation designates this enduring material for a maximum of 0 AMA PRA Category 1 Credits™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

Audio Digest Foundation is accredited as a provider of continuing nursing education by the American Nurses Credentialing Center's (ANCC's) Commission on Accreditation. Audio Digest Foundation designates this activity for 0 CE contact hours.

Lecture ID:

CA070302

Expiration:

This CME course qualifies for AMA PRA Category 1 Credits™ for 3 years from the date of publication.

Instructions:

To earn CME/CE credit for this course, you must complete all the following components in the order recommended: (1) Review introductory course content, including Educational Objectives and Faculty/Planner Disclosures; (2) Listen to the audio program and review accompanying learning materials; (3) Complete posttest (only after completing Step 2) and earn a passing score of at least 80%. Taking the course Pretest and completing the Evaluation Survey are strongly recommended (but not mandatory) components of completing this CME/CE course.

Estimated time to complete this CME/CE course:

Approximately 2x the length of the recorded lecture to account for time spent studying accompanying learning materials and completing tests.