Traumatic Prefrontal Encephalopathy and Amotivational Apathetic Syndrome: Revisiting the Historical Limitations of Standardized Neuropsychological Assessments

Abstract

The field of neuropsychology has made significant gains regarding the development and implementation of diagnostic measures and assessment techniques for frontal lobe pathology. Nevertheless, it is becoming increasingly evident that the existing battery of tests remains relatively insensitive to the ever-growing range of functions known to be mediated by the prefrontal regions. In the present study, a 62 year-old gentleman was involved in a pedestrian motor vehicle accident and suffered bilateral prefrontal, left parietal, and left occipital trauma (as evidenced by magnetic resonance imaging (MRI) scans). Secondary to this accident, he complained of significant depression, thought disturbances, and paranoia, while family members reported additional personality changes. A consistent diagnosis of frontal lobe syndrome was established across three independent neuropsychological evaluations, in which his postrehabilitative scores on a range of standardized assessments were consistently above average, regardless of his significant social, affective, and motivational changes following the accident. This case demonstrates the limitations and insensitivity that current standardized measures still obtain for assessing prefrontal lobe injury. The results are interpreted within the context of test development relevant to neuroscience rather than strictly psychometric concerns. The importance of these constraints on the evaluation of frontal lobe syndrome is discussed within the context of traumatic brain injury from contact sports and military combat. For the healthy left frontal lobe, intentional acts involve substantial energy, the desire or intent to engage socially, and the intent to engage in positive affective and verbally interactive activities. These appear to be diminished with the amotivational syndrome arising from dysfunctional left frontal lobe origin and medial frontal pathology with reduced activation of social reward systems and dopaminergic pathways (25, 24). While the patient with left frontal pathology may present with diminished energy and behavioral slowing or inertia, heightened energy or impulsivity may result from right frontal pathology and, by inference, the release of left frontal systems (e.g., decreased caution). Both are described in the scientific literatures as delayed response deficits. However, with left frontal pathology the patient may initiate only following inordinate delays with behavioral slowing or bradykinesia, whereas the patient with right frontal pathology may initiate substantially prior to implementing the organizational planning or caution for successful task completion. Hypoactivity bradykinesia may derive from medial frontal lobe or left frontal lobe pathology and hyperactive or impulsive features with pathology within the homologous regions of the right frontal lobe supplementary motor or orbitofrontal cortex (24, 29). Neuropsychological comprehension of frontal lobe functioning has grown exponentially in scope and research specificity. In the early to mid 1900's, diagnoses of mental illness and abnormal emotionality began to shift towards the implication of dysfunction in specific brain regions. Potential solutions included surgical resection of the brain via frontal lobotomy or lobectomy, which rapidly grew in popularity. German physiologist Friedrich Goltz, in the late 1800's, ablated canine neocortex. Goltz's (23) reporting of character changes in his subjects influenced Swiss physician Gottlieb Burkhardt to translate this early medical intervention to human patients. Portuguese neurologist Egas Moniz (41) was