出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/03/15 15:10:05」(JST)
Pseudobulbar affect (PBA), emotional lability, labile affect or emotional incontinence refers to a neurologic disorder characterized by involuntary crying or uncontrollable episodes of crying and/or laughing, or other emotional displays.[1] PBA occurs secondary to neurologic disease or brain injury. Patients may find themselves crying uncontrollably at something that is only moderately sad, being unable to stop themselves for several minutes. Episodes may also be mood-incongruent: a patient might laugh uncontrollably when angry or frustrated, for example.
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Historically there have been a variety of terms used including pseudobulbar affect, pathological laughter and crying, emotional lability, emotionalism, emotional dysregulation, or, more recently, involuntary emotional expression disorder (IEED).[2]
Terms such as forced crying, involuntary crying, pathological emotionality, and emotional incontinence have also been used, although less frequently.[3] Following FDA approval of a treatment indicated for pseudobulbar affect or PBA, this term is likely to become the preferred name in clinical and research use.
The cardinal feature of the disorder is a pathologically lowered threshold for exhibiting the behavioral response of laughter, crying, or both. An affected individual exhibits episodes of laughter and/or crying without an apparent motivating stimulus or in response to stimuli that would not have elicited such an emotional response before the onset of their underlying neurologic disorder. In some patients, the emotional response is exaggerated in intensity but is provoked by a stimulus with an emotional valence congruent with the character of the emotional display. For example, a sad stimulus provokes a pathologically exaggerated weeping response instead of a sigh, which the patient normally would have exhibited in that particular situation. Patients with Lyme Disease can also present with anxiety and significant emotional disturbances. Misdiagnosis with multiple sclerosis is not uncommon and physicians must do a full panel including Lyme ELISA and Western Blot to determine the clinical diagnoses prior to treating a brain disorder.[citation needed]
However, in some other patients, the character of the emotional display can be incongruent with, and even contradictory to, the emotional valence of the provoking stimulus or may be incited by a stimulus with no clear valence. For example, a patient may laugh in response to sad news or cry in response to stimuli with no emotional undertone, or, once provoked, the episodes may switch from laughing to crying or vice versa.[4]
The symptoms of PBA can be severe, with persistent and unremitting episodes.[3] Characteristics include:
Many patients with neurologic disorders exhibit uncontrollable episodes of laughing, crying, or both that are either exaggerated or contradictory to the context in which they occur. Where patients have significant cognitive deficits (e.g., Alzheimer's) it can be unclear whether it is true PBA as opposed to a grosser form of emotional dysregulation, but patients with intact cognition often report the symptom as disturbing. Patients report that their episodes are at best only partially amenable to voluntary control, and unless they experience a severe change of mental status, they often have insight into their problem and judge their emotional display as inappropriate and out of character. The clinical impact of PBA can be severe, with unremitting and persistent symptoms that can be disabling to patients, and may significantly impact quality of life for caregivers.
PBA was first described in the medical literature more than 130 years ago. Charles Darwin described elements of the condition in his seminal text The Expression of the Emotions in Man and Animals.[5] Although the symptoms of PBA have been recognized for more than a century, the specific pathophysiology involved in this frequently debilitating condition is still under investigation, the primary pathogenic mechanisms of PBA remain controversial.[6] One hypothesis, established by early researchers such as Wilson and Oppenheim, placed emphasis on the role of the corticobulbar pathways in modulating emotional expression in a top-down model, and theorized that PBA occurs when bilateral lesions in the descending corticobulbar tract cause failure of voluntary control of emotion, which leads to the disinhibition, or release, of laughing/crying centers in the brainstem.[7] Other theories implicate the prefrontal cortex.[8]
Pseudobulbar affect is a condition that occurs secondary to neurological disease or brain injury, and is thought to result from disruptions of neural networks that control the generation and regulation of motor output of emotions. PBA is most commonly observed in people with neurologic injuries such as traumatic brain injury (TBI) and stroke,[9][10] and neurologic diseases such as dementias including Alzheimer's disease,[11] multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), Lyme Disease, PANDAS in children and adults, and Parkinson's disease (PD).
PBA has also been observed in association with a variety of other brain disorders, including brain tumors, Wilson’s disease, syphilitic pseudobulbar palsy, and various encephalitides. Rarer conditions associated with PBA include gelastic epilepsy, dacrystic epilepsy, central pontine myelinolysis, olivopontinocerebellar atrophy, lipid storage diseases, chemical exposure (e.g., nitrous oxide and insecticides), fou rire prodromique, and Angelman syndrome.
It is hypothesized that these primary neurologic injuries and diseases impact chemical signaling in the brain, which in turn disrupts the neurologic pathways that control emotional expression.[12][13][14]
While not as profoundly disabling as the physical symptoms of these diseases, PBA can have a significant impact on individuals' social functioning and their relationships with others. Such sudden, frequent, extreme, uncontrollable emotional outbursts may lead to social withdrawal and interfere with activities of daily living, social and professional pursuits, and have a negative impact on overall healthcare. For example, patients with ALS and MS are often cognitively normal; however, the appearance of uncontrollable emotions is commonly associated with learning disabilities; this may lead to severe embarrassment and avoidance of social interactions for the patient, which in turn has an impact on their coping mechanisms and their careers.[3][15][16][17][18]
PBA may often be misdiagnosed as depression; however, many clear distinctions exist.
In depression and grief syndromes, crying is typically a sign of sadness, whereas the pathological displays of crying which occur in PBA are often in contrast to the underlying mood, or greatly in excess of the mood or eliciting stimulus. In addition, a key to differentiating depression from PBA is duration: PBA episodes are sudden, occurring in a brief episodic manner, while crying in depression is a more sustained presentation and closely relates to the underlying mood state. The level of control that one has over the crying episodes in PBA is minimal or nonexistent, whereas for those suffering from depression, the emotional expression (typically crying) can be modulated by the situation. Similarly, the trigger for episodes of crying in patients with PBA may be nonspecific, minimal or inappropriate to the situation, but in depression the stimulus is specific to the mood-related condition. These differences are outlined in the adjacent Table.
In some cases, depression and PBA may co-exist. In fact, depression is one of the most common emotional changes in patients with neurodegenerative disease or post-stroke sequelae. As a result, it is often comorbid with PBA. Comorbidity implies that depression is distinct from PBA and is not necessary for, nor does it exclude, a diagnosis of PBA.[2]
PBA is surprisingly prevalent, affecting both patients and those that care for them.[15] Prevalence estimates place the number of people with PBA between 1.5 and 2 million in the United States alone. However, given the fact that PBA is a relatively common disorder among patients with various neurologic conditions, its actual prevalence may be higher. Furthermore, PBA is generally thought to be under-recognized and undertreated because clinicians are unfamiliar with the disorder.[19] [1]
PBA is one of the most frequently reported poststroke behavioral syndromes, with a range of reported prevalence rates from 28% to 52%.[20][21][22] The higher prevalence rates tend to be reported in stroke patients who are older and/or who have a history of prior stroke.[23][24] The relationship between poststroke depression and PBA is complicated, because the depressive syndrome also occurs with high frequency in stroke survivors. Poststroke patients with PBA are more depressed than poststroke patients without PBA, and the presence of a depressive syndrome may exacerbate the weeping side of PBA symptoms.[20][25]
Recent studies suggest a lifetime prevalence of PBA of approximately 10% in patients with MS.[26][27] PBA is generally associated with later stages of the disease (chronic progressive phase).[22] PBA in MS patients is associated with more severe intellectual deterioration, physical disability, and neurological disability.[28]
A study designed specifically to survey for prevalence found that 49% of patients with ALS also had PBA.[15] PBA does not appear to be associated with duration of amyotrophic lateral sclerosis.[29][30] It is a symptom of ALS that many patients are unaware of and do not get information about by their physician.[31]
One study of 301 consecutive cases in a clinic setting reported a 5% prevalence. PBA occurred in patients with more severe head injury and coincided with other neurological features suggestive of pseudobulbar palsy.[32]
Brain Injury Association of America (BIAA) indicates that approximately 80% of survey respondents experience symptoms of an additional neurologic condition called pseudobulbar affect (PBA). [33]
Results from a recent investigation estimates the prevelance of pseudobulbar affect associated with traumatic brain injury to exceed more than 55% of survivors.[34]
Recognition is crucial for the treatment of PBA. Education of patients, families, and caregivers is an important component of the appropriate treatment of PBA. Crying associated with PBA may be incorrectly interpreted as depression; laughter may be embarrassing. It is therefore critical for families and caregivers to recognize the pathological nature of PBA and the reassurance that this is an involuntary syndrome that is manageable. Traditionally, antidepressants such as fluoxetine, citalopram, or amitriptyline have been prescribed with moderate efficacy.[citation needed]
Dextromethorphan/quinidine (Nuedexta) is the first FDA-approved drug for the treatment of PBA. Treatment with dextromethorphan/quinidine significantly decreased laughing and crying episodes in patients with amyotrophic lateral sclerosis (ALS) or multiple sclerosis (MS) as compared with placebo in a 12-week, randomized, double-blind study (n=326).[35]
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| リンク元 | 「感情失禁」「情動障害」 |
| 関連記事 | 「emotional」「incontinence」「emotion」 |