Validation of the CNS emotional lability scale for pseudobulbar affect (pathological laughing and crying) in multiple sclerosis patients

Abstract

Pseudobulbar affect (PBA) or pathological laughing and crying (PLC) is a disorder of affect that occurs in about 10% of multiple sclerosis (MS) patients. The objective of this study was to validate the CNS Emotional Lability Scale (CNS-LS) in MS patients and to correlate the results with the frequency and intensity of episodes of PLC. Physicians at seven private practice referral centers in the United States made a diagnosis concerning PLC based on patient interviews. Clinical coordinators separately administered the CNS-LS, a self-report measure of PLC with seven questions, to MS patients, including patients known to exhibit PLC, patients thought to be free of PLC, and newly diagnosed patients where PLC status was unknown, and the physician was blinded as to the results. A receiver operating characteristic (ROC) curve analysis was performed to define a cut-off best correlating with the physician's diagnosis. Of 90 MS patients selected to complete the survey, 50 were physician diagnosed with PLC; 40 were without PLC, and 15 of these 90 patients were newly diagnosed with MS (<6 months). Scores of 17 or higher corresponded to a sensitivity of 0.94 and a specificity of 0.83 (LR+ = 5.5, LR- = 0.07); 89% of patients were correctly diagnosed. The area under the ROC curve was 0.95. Symptoms were greater in patients diagnosed as PLC than in non-PLC patients as evidenced by mean number of episodes/week, number of days/week with episodes, duration of an episode and total time in an episode. Similar results were observed if patients were classified as PLC or non-PLC according to CNS-LS score > or = 17, suggesting that the CNS-LS is a valid measure for the assessment of PLC in MS patients and could be a useful instrument for clinical and research purposes.