Is this state, whether one of involuntary laughing or of crying, activated by an appropriate stimulus? In other words, does the emotional response accurately reflect the patient’s affect or feeling? There are no simple answers to these questions. One problem is to determine what constitutes an appropriate stimulus for the patient in question. Oppenheim and others stated that these patients need not feel sad when crying or mirthful when laughing, and at least in some cases, this is in agreement with our experience. Other patients, however, do report a general congruence of affect and emotional experience (mood), but the amplitude of the response is utterly excessive.
Noteworthy are the stereotyped nature of the initial motor facial response, and the relatively undifferentiated nature of the emotional reaction. As Poeck emphasized, laughter or crying may merge—reflective of the closeness of these two forms of emotional expression, a phenomenon that is particularly evident in young children. More impressive to us is the fact that in some patients with pseudobulbar palsy, laughing and crying are the only available forms of emotional expression; intermediate phenomena, such as smiling and frowning, are lost. In other patients with pseudobulbar palsy, there are lesser degrees of forced laughing and crying, perhaps bridging the gap between this phenomenon, and the type of emotional lability discussed earlier.
Two major supranuclear pathways control the ponto-medullary mechanisms of the movements required in laughing and crying. One is the familiar corticobulbar pathway that runs from the motor cortex through the posterior limb of the internal capsule and controls volitional movements; the other is a more anterior pathway that descends just rostral to the genu of the internal capsule, and contains facilitatory and inhibitory fibers. Unilateral involvement of the anterior pathway leaves the opposite side of the face under volitional control but paretic during laughing, smiling, and crying (emotional facial paralysis); the opposite is observed with a unilateral lesion of the posterior pathway. Wilson pointed out that both forced laughing and crying involve the same facial, vocal, and respiratory musculature and have similar visceral accompaniments (dilatation of facial vessels, secretion of tears, etc.). Wilson’s argument, based to some extent on clinicopathologic evidence, was that in pseudobulbar palsy resulted from interruption of the descending motor pathways that naturally inhibit the expression of the emotions. Of interest is the beneficial effect on distressing pseudobulbar displays of drugs such as imipramine and fluoxetine (Schiffer et al). Dextromethorphan combined with quinidine in the pseudobulbar state, as shown in a study of patients with amyotrophic lateral sclerosis (Brooks et al). In a few personally observed cases, both the emotional lability and pathologic laughter and crying were partially suppressed by these drugs; but in most others, however, there was no effect.
A rare but probably related syndrome is le fou rire prodromique (prodromal laughing madness) of Féré, in which uncontrollable laughter begins abruptly and is followed after several hours by hemiplegia. We have seen two such cases in which basilar artery occlusion evolved after a brief bout of such forced laughter. There are dramatic examples, cited by Martin, where patients laughed themselves to death. Again, the pathologic anatomy is unsettled. Protracted laughing and (less often) crying may occur rarely as a manifestation of epileptic seizures, usually originating in the temporal lobe. Ictal laughter is usually without affect (mirthless laughter); Daly and Mulder referred to these as “gelastic” seizures. The concurrence of gelastic seizures and precocious puberty is characteristic of an underlying hamartoma (or other lesion) of the hypothalamus (see Chaps. 26 and 27).
Aggressiveness, Anger, Rage, and Violence