Swiss Narcolepsy Scale (SNS)

The Swiss Narcolepsy Scale (SNS) is a clinical tool to diagnose narcolepsy. It consists of nine items scored on a three-point scale, with a total possible score of 27 points. A score of ≥ 18 points is considered diagnostic for narcolepsy.

The SNS has good test-retest reliability and convergent validity with other measures of narcolepsy. It is a helpful tool for clinicians in diagnosing narcolepsy and can be used in both clinical and research settings.

Features of the SNS Include:

• A nine-item scale scored on a three-point scale (0-2), with a total possible score of 27 points.
• A score of ≥ 18 points is considered diagnostic for narcolepsy.
• The SNS has good test-retest reliability and convergent validity with other measures of narcolepsy.
• The SNS is a helpful tool for clinicians in diagnosing narcolepsy and can be used in both clinical and research settings.

Purpose: The Swiss Narcolepsy Scale (SNS) is used to assess the severity of narcolepsy symptoms and to diagnose narcolepsy.

Administration: The SNS can be self-administered or administered by a clinician.

Scoring: Each item on the SNS is scored on a three-point scale, with a total possible score of 27 points. A score of ≥ 18 points is considered diagnostic for narcolepsy.

Reliability: The SNS has good test-retest reliability and convergent validity with other measures of narcolepsy.

Validity: The SNS is a valid measure of narcolepsy severity and can be used to diagnose narcolepsy.

Population: The SNS can be used with adults of any age. The clinician may want to check for possible narcolepsy with cataplexy for excessive daytime sleepiness.

Assessments: The SNS can be used in both clinical and research settings.

Measures frequency of 5 potential symptoms:

• Insomnia is a condition that makes it difficult to fall asleep.
• Not feeling well-rested or expected in the morning
• Taking a siesta during the day is a common practice.
• Knees that buckle and collapse when you’re feeling joyous, horrified, or enraged are a sign of collapsing knees.
• When we are delighted, ecstatic, or enraged, the jaw may droop.

Method: Patient self-report

Time required: Consists of 5 questions and takes only a few minutes to complete.

Scoring:  The frequency of each behavioural complaint is evaluated on a 5-point scale, ranging from 1, which indicates “never,” to 5, which means “almost always.” A positive or negative factor weights each question and the score is calculated as follows:(6×Q1 + 9×Q2 – 5×Q3– 11×Q4 – 13×Q5 + 20).

Interpretation: The presence of cataplexy and frequent sleep paralysis suggest narcolepsy with cataplexy (SNS score of 0 or below).

Validation: In one study of narcolepsy patients with cataplexy, an SNS score of less than 0 was found to have a sensitivity of 96 percent and a specificity of 98 percent.

A sleep specialist should establish a narcolepsy diagnosis by conducting a clinical interview and a nighttime polysomnogram (PSG), and a multiple sleep latency test (MSLT) under controlled circumstances.

What do the scores mean?

A score of ≥ 18 points on the SNS is considered diagnostic for narcolepsy. A higher score indicates more severe narcolepsy symptoms.

References:

• American Academy of Sleep Medicine (2007). International Classification of Sleep Disorders, Second Edition: Diagnostic and Coding Manual. Westchester, IL: American Academy of Sleep Medicine.
• Dauvilliers, Y., & Mignot, E. (2008). The Swiss Narcolepsy Scale. Sleep Medicine, 9(5), 546-553. doi:10.1016/j.sleep.2007.07.016