Many of the foregoing ideas about the role of the limbic system have come from experimentation in laboratory animals. Only in relatively recent years have neurologists, primed with the knowledge of these studies, begun to relate emotional disturbances in patients with disease of limbic structures. These clinical observations, summarized in the following pages, form an interesting chapter in neurology. Table 24-1 lists the most readily recognized disturbances of emotion. The list is tentative, as our understanding of many of these states, particularly their pathologic basis, is incomplete. Only a small number of these derangements can be used as indicators of lesions and diseases in particular parts of the human brain. Taken in context, however, these disturbances are useful diagnostically. As knowledge of emotional disorders increases, an understanding of the functioning of limbic structures will continue to bring together large segments of psychiatry and neurology.
Threatened by imaginary figures and voices that seem real and inescapable, the hallucinating, delirious patient trembles, struggles to escape, and displays the full picture of terror. The patient’s affect, emotional reaction, and visceral and somatic motor responses are altogether appropriate to the content of hallucinations. We have seen a patient slash his wrists and another try to drown himself in response to hallucinatory voices that admonished them for their worthlessness and the shame they had brought on their families. Beyond a derangement solely of emotional expression, the abnormality in these circumstances is one of disordered perception and thinking.
There also occurs a state, difficult to classify, of overwhelming emotionality in patients who are in severe, acute pain. The patient’s attention can be captured only briefly, and within moments, there is a return to an extreme state of angst, groaning, and anger. We have encountered this with spinal subdural hemorrhage, subarachnoid hemorrhage, explosive migraine, trauma with multiple fractures, and intense pelvic, renal, or abdominal pain.
Disinhibition of Emotional Expression
It is a commonplace clinical experience that cerebral diseases of many types, seemingly without respect to location, weaken the mechanism of control of emotional expression. A patient whose cerebrum has been damaged, for example, by a series of vascular lesions, may involuntarily cry in public upon meeting an old friend or hearing the national anthem, or display uncontrollable laughter in response to a mildly amusing remark. There may also be easy vacillation from one state to another, an emotional lability. In this type of emotional disturbance, the response, while excessive, does not quite reach the degree of forced emotionality described as pseudobulbar (see below); furthermore, it is appropriate to the stimulus and the affect is congruent with the visceral and motor components of the expression. Lesions of the frontal lobes are the most common identifiable cause of this state. However, emotional lability is also a frequent accompaniment of diffuse cerebral conditions, such as Alzheimer disease. Also under this heading might be included the shallow facetiousness (witzelsucht), tearfulness and facile mood, and behavioral disinhibition of the patient with frontal lobe disease.