This article includes discussion of pathologic laughter: neurologic aspects, involuntary emotional expression disorder, pseudobulbar affect, pseudobulbar laughter, pathological laughter and crying, pseudobulbar palsy, and sleep-laughing (hypnogely). The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.
Pathologic laughter and crying occur in several neurologic disorders. This article describes the anatomical location of various brain centers for laughter and crying as well as the pathophysiology. Differential diagnosis, diagnostic workup, and management are described. In patients with cerebrovascular disease, pathologic laughter and crying may be warning signals that require prompt investigation and treatment of the underlying pathology. Antidepressants have been found to be useful in the management of these disorders.
• Pathologic laughter and crying are manifestations of neurologic disorders.
• Disturbances at various levels of the central nervous system are involved, although lesions of the brainstem are associated with pathologic laughter and crying.
• Neurologic investigations for these symptoms are aimed at detection of treatable lesions, eg, benign intracranial neoplasms.
• Antidepressants, particularly serotonin reuptake inhibitors, are usually effective for the symptomatic management of pathologic crying and laughter.
Historical note and terminology
Laughter has occupied philosophers from antiquity to modern times. It is generally associated with joy and humor. Laughter is elicited by a variety of stimuli and may be a reflex or a voluntary reaction to a certain situation or an expression of psychopathology. Pathologic laughter is defined as laughter that is inappropriate, uncontrolled, or dissociated from any stimulus. Pathologic laughter, often associated with crying, is also referred to as pseudobulbar affect and can occur as a part of emotional incontinence in neuropsychiatric disorders. Inappropriate laughter can occur in Witzelsucht and manifest as a tendency to tell inappropriate jokes or euphoric behavior due to focal right-orbitofrontal parenchymal lesions (Vardi et al 1994).
Less severe forms of the disorder following brain injury are often referred to as "emotionalism"; they are further specified as emotionalism-laughter or emotionalism-crying. Pathologic laughter or crying are included in the category of “involuntary emotional expression disorders” because they are disorders of emotional expression rather than affective mood disorders in which laughter and crying are associated with feelings of happiness or sadness. Episodes have been reported of spontaneous, uncontrollable laughter erupting from the congregations, even during times of solemn ceremony or messages from the pulpit. These episodes of "holy laughter" in charismatic Christian sects are not pathologic.
One of the oldest documented cases of pathologic laughter and crying is that by Ambroise Pare, the 16th-century French surgeon. He described women who wept and laughed without reason and did not respond to any treatment (Hamby 1960). A French physician, Trousseau, described pathologic laughter accompanying epileptic seizures (Trousseau 1877). Several isolated case reports in the literature over the past 20 years have described the association of pathologic laughter with a wide variety of neurologic disorders. The French refer to pathologic laughter preceding cerebrovascular ischemia as fou rire prodromique, which is translated as "prodrome of crazy laughter," and was first described by Charles Fere in 1903 (Fere 1903). Although laughing and crying are lumped together, either of these may be the only manifestation. Fere reported pathologic laughter heralding an apoplectic event and was also among the first to describe gelastic epilepsy (Gondim et al 2004). Seizures accompanied by crying are referred to the rare condition “dacrystic seizures” first described by Zilgien in 1904 (Zilgien 1906).
There has been considerable speculation in the past about the neural mechanisms of laughter. Wilson considered the mechanism to be in the region of the mesial thalamus, hypothalamus, and subthalamus (Wilson 1924). Papez hypothesized that supranuclear pathways, including those from the limbic system, mediate emotional expressions such as laughter and synapse in the reticular core of the brainstem (Papez 1937). This fits in with a later postulate that the tegmentum near the periaqueductal gray matter contains the integrative mechanism for emotional expression (Kelly et al 1946).
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