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Pseudobulbar affect in primary lateral sclerosis and amyotrophic lateral sclerosis


Meredith Pasmantier Photo

The George Washington University School of Medicine and Health Sciences (District of Columbia)

Background

Pseudobulbar affect (PBA) is a disorder of emotional expression consisting of uncontrollable outbursts of laughter or crying that are often exaggerated compared to the patient’s true emotional state. Episodes may be unprovoked or incongruent to mood and circumstances. Although this study focused on PBA in motor neuron disease, it is seen in a number of other neurological conditions, including multiple sclerosis and stroke.PBA in amyotrophic lateral sclerosis (ALS) has been described in the literature in some detail. PBA has also been noted in primary lateral sclerosis (PLS) but it has not been specifically evaluated up to this point. While ALS is characterized by death of corticospinal neurons (upper motor neurons) and motor neurons (lower motor neurons), PLS affects corticospinal neurons with relative sparing of motor neurons. PBA is classically associated with spastic bulbar (pseudobulbar) palsy. “Bulbar” refers to lower motor dysfunction of the corticobulbar tract, whereas “pseudobulbar refers to upper motor neuron dysfunction. Although several theories have been proposed, the pathway of PBA remains unclear.

Objective

To determine whether there is a constellation of clinical signs associated with PBA that may give clues to pathways beyond the motor cortex that may be disrupted.

Methods

The medical records of 87 PLS and ALS patients seen between August 2000 and July 2013 were retrospectively reviewed. All patients were examined by a neurologist and the following clinical signs were noted: facial weakness, dysarthria, frontal release signs, cranial reflexes, bladder urgency, startle response.Logistic regression adjusted for diagnosis was used to determine the association of clinical signs with PBA (p-value ≤ 0.01 was used to determine significance). Age and gender were not significant covariates. In the analysis, ALS and PLS were evaluated together.

Results

Among the 87 cases, 43 had PBA and 44 did not. PBA was more common in PLS than ALS, however this difference is likely due to chance given our sample. Previous studies have reported a prevalence of 50% for PBA in ALS, which is roughly the prevalence determined for PBA in PLS in this study. Finger tapping was the only variable significantly associated with PBA (p-value = .002), indicating that those patients were likely to have limb involvement as well. There were 5 clinical signs associated with PBA (p-value ≤ .01): dysarthria, myerson’s sign, facial weakness, startle responseand gag. All patients with PBA also had dysarthria, but it is not specific because approximately half of the patients without PBA also had dysarthria. All brainstem signs were more prominent in PBA. The startle response, which has been associated with the reticulospinal tract, is exaggerated more frequently in PBA. Finally, the Myerson’s sign is associated with PBA and is also thought to occur with basal ganglia dysfunction.

Conclusions

Of the 5 clinical signs associated with PBA, only 3 are controlled solely by the corticospinal tract. Therefore, the full constellation of clinical signs cannot be explained by a disruption in the corticospinal tract alone. These results suggest that pathways outside the motor system are involved in the pathophysiology of PBA.

Last updated November 27, 2013