What scale or questionnaire is used to assess pseudobulbar affect?

Pseudobulbar Affect Assessment Scales

The two validated scales for assessing pseudobulbar affect are the Center for Neurologic Study-Lability Scale (CNS-LS) and the Pathological Laughing and Crying Scale (PLACS). 1

Primary Assessment Tool: CNS-LS

The Center for Neurologic Study-Lability Scale (CNS-LS) is the most widely used and validated instrument for quantifying PBA symptoms and supporting diagnosis. 1, 2, 3

Key Features of CNS-LS:

• Seven-item self-report questionnaire that quantifies the frequency and severity of involuntary laughing and crying episodes 4
• Scoring threshold: CNS-LS ≥13 indicates clinically significant PBA 2, 5
• Validated across multiple neurological conditions including stroke, ALS, MS, and Parkinson's disease 2, 4, 5
• Contains separate subscales for crying and laughing symptoms 6
• Available in multiple languages including Danish translation 4

Clinical Application:

The CNS-LS demonstrates strong correlations with:

• Depression severity (Spearman correlation coefficient = 0.64) 5
• Mental health quality of life scores (negative correlation = -0.70) 5
• Social impact measures, particularly with crying subscores 6

Secondary Assessment Tool: PLACS

The Pathological Laughing and Crying Scale (PLACS) is an alternative validated instrument mentioned in stroke guidelines. 1, 7

Important Clinical Caveat:

Using a single scale alone may be insufficient for definitive diagnosis. 7 A study in Argentine stroke patients found that while 21-29% had positive PLACS scores and 26-58% had positive CNS-LS scores, only 16% had both scales positive, highlighting the importance of:

• Combining scale results with clinical diagnostic criteria
• Differentiating PBA from post-stroke depression, which frequently coexists 7
• Recognizing that emotional lability must be disproportionate to context and incongruent with underlying mood 3

Underrecognition Problem

PBA remains significantly underdiagnosed despite available screening tools. In a Danish ALS cohort, only 12.1% had diagnosed PBA, yet 30.6% scored ≥13 on CNS-LS, meaning 23.2% had symptomatic but undiagnosed PBA. 2 These undiagnosed patients were significantly less likely to receive appropriate treatment (12.5% vs 47.4%, p=0.009). 2

Clinical Implications:

• Systematic screening with CNS-LS should be routine in at-risk populations
• Most patients are unaware PBA is common in their neurological condition 6
• Early recognition enables timely pharmacological intervention with FDA-approved dextromethorphan/quinidine or SSRIs 1