Pseudobulbar Palsy

Pseudobulbar Palsy

Definition

When fully developed, this syndrome is characterized by emo-tional incontinence (also known as “pathological laughing and crying”), dysarthria, dysphagia, a brisk jaw-jerk and gag reflex, and difficulty in protruding the tongue.

The most remarkable aspect of the syndrome is the emotional incontinence. Here, patients experience uncontrol-lable paroxysms of laughter or crying, often in response to minor stimuli, such as the approach of the physician to the bedside (Lieberman and Benson, 1977). Importantly, despite the strength of these outbursts, patients do not experience any corresponding sense of mirth or sadness; some may attempt to stop the emotional display, only to become acutely distressed at their inability to do so: one patient, who experienced “gales of laughter” whenever he attempted to speak, “felt foolish and ashamed, and had tears in his eyes because he could not ‘con-trol the laughter’ ” (Davison and Kelman, 1939). Some may go out of their way to avoid having these paroxysms. In one case, described by Wilson (1924), the patient “used to walk about the hospital with his eyes glued to the ground (because) if he so much as raised them to meet anyone else’s gaze he was im-mediately overcome by compulsory laughter, which sometimes lasted for 4 or 5 minutes”.

Etiology and Pathophysiology

Pseudobulbar palsy results from bilateral interruption of corti-cobulbar fibers, with this interruption occurring anywhere from the cortex through the centrum semiovale to the internal capsule and down to the midbrain and pons. Thus “released” from upper motor neuron control, the bulbar nuclei act reflexively, creating, in a sense, a kind of “spasticity” of emotional display. The vari-ous disorders capable of causing such a bilateral interruption are listed in Table 33.10.

Vascular disorders are by far the most common cause of bilateral interruption of the corticobulbar tracts, as may be seen with infarctions of the cortex or with lacunar infarctions in the corona radiata or internal capsule. Although in some cases it appears that the syndrome occurs after only one stroke, further investigation typically reveals evidence of a preexisting lesion on the contralateral side, a lesion which had been clinically “si-lent” (Besson et al., 1991). Other vascular causes include Bin-swanger’s disease, characterized by diffuse white matter damage in the centrum semiovale, and CADASIL (Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoen-cephalopathy), characterized by both subcortical infarctions and a widespread leukoencephalopathy.

Of the neurodegenerative disorders associated with pseudobulbar palsy, the most prominent is amyotrophic lateral sclerosis, wherein approximately one-half of patients are eventu-ally so affected (Gallagher, 1989).

Of the miscellaneous causes, cerebral tumors which bilaterally compress or invade the brainstem are particularly important

Assessment and Differential Diagnosis

The diagnosis should be suspected whenever patients present with exaggerated and uncontrollable emotional displays. Labil-ity of affect, as may be seen in mania, is ruled out by the fact that the labile patient, while displaying the affect, also experiences a congruent emotional feeling: by contrast, in emotional incon-tinence the patient often feels nothing, except perhaps conster-nation at the unmotivated and uncontrollable emotional display. Inappropriate affect, as may be seen in schizophrenia, is similar to emotional incontinence in that patients with schizophrenia may not experience any corresponding feeling: in schizophre-nia, however, one sees other accompanying symptoms, such as mannerisms, hallucinations and delusions, symptoms which are absent in pseudobulbar palsy. “Emotionalism”, as may be seen after strokes, may suggest the diagnosis, especially given the clinical setting, however here, as with lability, patients also experience a concurrent feeling that is congruent with the emo-tional display.

Findings on the neurologic examination are also helpful. Bilateral interruption of corticobulbar tracts, as noted above, typically leads to cranial nerve dysfunction with dysarthria, dys-phagia and brisk jaw-jerk and gag reflexes. Given the proximity of the corticospinal tracts, one often also finds evidence of long-tract damage, such as hemiplegia or Babinski signs.

MRI scanning is generally diagnostic in cases secondary to vascular lesions, tumors and multiple sclerosis. Amyotrophic lateral sclerosis is suggested by the gradual progression of upper and lower motor neuron signs and symptoms; progressive supra-nuclear palsy by the presence of parkinsonism and supranuclear gaze palsy, and Alzheimer’s disease by the long history of a grad-ually progressive dementia.

Epidemiology and Comorbidity

Pseudobulbar palsy is not uncommon: as noted above, it is found in almost half of patients with amyotrophic lateral sclerosis. It may also be seen in a much smaller, but still clinically significant, proportion of patients with vascular lesions, Alzheimer’s disease and multiple sclerosis.

Course

The overall course of the syndrome reflects the course of the etio-logic disorder. The appearance of dysphagia, however, is an omi-nous sign, carrying, as it does, the risk of aspiration.

Treatment

In addition to treating, if possible, the underlying cause, various medications may be used to reduce the severity of the emotional incontinence, including tricyclics and SSRIs. Among the tricy-clics, both amitriptyline (in doses of 50–75 mg) and nortriptyline (in doses up to 100 mg) are effective, with nortriptyline generally better tolerated. Of the SSRIs, citalopram, in a dose of 20 mg, was effective, and there are also case reports of the effectiveness of paroxetine, sertraline and fluoxetine (Seliger and Hornstein, 1989). Overall, it is probably best to begin with an SSRI, and to hold nortriptyline in reserve.