Cognitive Dysfunction and Its Relationship with Pseudobulbar Affect in MS Patients

Background: Pseudobulbar affect (PBA) is a neuropsychiatric syndrome in which an individual’s affect does not reflect their mood, and is characterized by periods of involuntary laughing or crying that may occur without any particular stimulus.  PBA has been reported in approximately 10% of Multiple Sclerosis (MS) individuals. Cognitive dysfunction (CD) has been estimated to affect about 60% of MS patients and may occur at early or late stages of the disease. Impairments in cognitive function have been postulated to be more common in MS patients with PBA than those without PBA. 

Objectives: To examine the frequency at which MS individuals with clinically proven CD have PBA. Secondary objectives include: assess the relationship of specific cognitive components such as memory, executive function, attention, information processing speed and motor skills with PBA. 

Methods: MS subjects with self-reported CD underwent computerized cognitive testing (NeuroTrax Mindstreams (NTM)) and completed questionnaires regarding PBA (Center for Neurologic Study-Lability Scale).

Results: Of a total of 32 participants, 24 (75%) had CD as measured by NTM of which 11 (46%) had PBA. Of those with self-reported CD that did not have demonstrable deficits by NTM, only 1 (12.5%) had PBA. Although of no statistical significance, patients with PBA scored lower than average on memory and motor skills. Scores on executive function, attention and information speed were better than on memory and motor skills.

Conclusions: We documented a high incidence of PBA in MS individuals with demonstrable CD, at a rate that far exceeds the reports of PBA in the overall MS population.  CD in PBA individuals was not driven by any specific domain and followed a similar pattern of those without PBA. Studies to evaluate these relationships at a greater scale are warranted and might reveal common pathophysiologic mechanisms.