These FTD patients illustrated the problem of sociopathic behavior from frontal brain disorders. They developed pedophilia and committed theft, sexual harassment, and automobile violations. All four had an awareness of their behavior at the time of the acts and understood that it was wrong. They had preserved knowledge of moral behavior and of potential consequences, but they went ahead anyway, in an unempathic, impulsive, and often compulsive, manner. In addition to manifesting the behavioral features of FTD, these patients had the spectrum of FTD-related conditions, including semantic deficits (Patient 2), an autosomal dominant inheritance (Patient 2), PSP (Patient 3), and MND (Patient 4).
The early diagnosis of FTD can be difficult, particularly in court. The clinical diagnosis of this disorder is based on the core behavioral criteria of an insidious and progressive personality change with impairments in social interpersonal conduct, impairments in regulation of personal conduct, early emotional blunting, and early loss of insight.8
There is no definitive test for FTD, and neuroimaging, which may show abnormalities in frontotemporal regions, is only supportive and not diagnostic. Hence, it is absolutely essential to document clinical changes in individuals by obtaining similar confirmatory information from third parties in the individual’s environment. Ultimately, only long-term clinical follow-up and documentation of clinical progression to cognitive impairments and dementia can establish the diagnosis of FTD.
Patients with usual behavioral variant FTD manifest inappropriate social behavior early in the disease, when the neurodegeneration is still localized or asymmetrical, and their general cognitive function is relatively intact. 8
Most commonly, there is a loss of social tact and propriety, improper verbal or non-verbal communication, and unacceptable physical contact.7
Socially inappropriate behavior expands to encompass a failure to conform to lawful behavior in greater than one-half of patients with FTD.3,15
Among these patients, investigators have reported stealing (shoplifting, stealing food), unethical job conduct, indecent exposure, inappropriate sexual comments or behavior, illegal driving acts, and physical assau1ts or violence. 12,15–17
In one study, 16 (57%) of the FTD patients had had sociopathic behavior compared with only 2 (27%) of the AD patients.3
The FTD patients with sociopathic acts were aware of their behavior and knew that it was wrong but did not prevent themselves from acting.3
They lacked premeditation and claimed subsequent remorse, but did not act on it or express concern for the consequences.
The behavior of FTD patients is reminiscent of the famous case of Phineas Gage who sustained bilateral vmPFC injury from an explosion that propelled an iron rod through his brain, except that, in FTD, the behavioral changes are gradual and insidious in onset.17,18
Acquired sociopathy occurs from focal vmPFC lesions,4,19,20
and, although poorly visualized on neuroimaging, the neuropathology of early FTD includes the vmPFc.9,21
Patients with vmPFC lesions have diminished emotional experience with reduced sociomoral emotions, such as compassion, shame, guilt, and regret.4,5,22–25
The vmPFC, with its rich interconnections with limbic structures, mediates these strong, automatic, negative “gut reactions” to moral violations that prevent individuals from implementing morally impermissible actions. 26-30
In a unique study, FTD patients were more impaired in their ability to respond immediately to emotionally based moral (personal) vignettes than were AD patients and normal control subjects,26,27,31
Yet, those with vmPFC lesions are aware of their actions, have preserved logical reasoning and knowledge of social and moral norms, and can anticipate outcomes. 6,10,32
In addition to vmPFC involvement, early FTD involves other brain areas that affect the occurrence of sociopathic behavior. In FTD, there is decreased emotional empathy, particularly associated with right anterior temporal disease, as in at least three of our patients.33,34
This variant of FTD is particularly prone to interpersonal coldness and a lack of responsiveness to other’s distress.34,35
In other studies of FTD patients, decreased emotional empathy and reduced responsiveness to victims correlates with damage to the right ventromedial-anterior temporal network.35–38
Finally, the lack of strong moral emotions in FTD and the loss of empathy cannot override drives, possibly released by orbitofrontal dysfunction, for disinhibition, compulsions, or behavioral tendencies, such as pedophilia. 7,39,40
In sum, the unique neuropathological involvement in FTD, particularly with right anterior involvement, makes these patients susceptible to committing sociopathic acts.
Do FTD patients have culpable mental states (mens rea
) at the time of their acts? Are they responsible agents? FTD patients with sociopathy would not pass most legal criteria for judgments of not guilty by reason of insanity. On the basis of a restrictive M’Naughten rule, the U.S. Congress passed the Comprehensive Crime Control Act in 1984, which requires an insanity defense to establish, by “clear and convincing evidence,” that “at the time of the commission of the acts constituting the offense, the defendant, as a result of a severe mental disease or defect, was unable to appreciate the nature and quality Of the wrongfulness of his acts” (18 U.S.C. § 17).41
Under these guidelines, FTD patients would not qualify for not guilty by reason of insanity, because their disease did not cause a “defect of reason,” They did not have a general decreased capacity for rationality nor would they be exonerated because of an internal coercion or irresistible impulse, Nevertheless, they have a specific, brain-based impairment in moral reasoning. Anglo-American jurisprudence distinguishes between reason-based law and a natural law based on what a reasonable person would do in a like circumstance. 11
Arguably, under the law, a reasonable person is someone whose impulses are restrained by intact moral cognition (i.e., moral rationality).42
Without the normal internal restraint of intuitive moral emotions and empathy, FTD patients may not possess the faculties of a reasonable person sufficient to bring reason to bear on their drives and to abstain from criminal violations. These considerations deserve a reappraisal of how we view criminal violations among brain-injured patients and how we can incorporate neurological factors involved in moral capacity or moral cognition.42
In conclusion, in FTD, sociopathic behavior is consistent with decreased emotional moral judgments plus a lack of empathy and disinhibited, compulsive drives consequent to the unique neuropathology of this disorder. FTD patients have impaired moral rationality from impaired moral cognition. These findings have implications for understanding brain-damaged patients and the law.