The Canadian Neurological Scale (CNS) is a validated tool used to assess stroke severity. It's particularly useful for nurses as it provides a quick and reliable assessment of a patient's condition. The CNS evaluates several components, including comprehension, level of consciousness, speech, and motor function (specifically, face, arm, and leg movements).

Interpretation of Scores:

Lower Scores Indicate Greater Severity: The CNS is scored on a scale from 0 to 10, with lower scores indicating more severe strokes.

Stroke Severity Categories: Stroke severity is categorized as follows:

Mild Stroke: CNS score ≥ 8

Moderate Stroke: Score of 5-7

Severe Stroke: Score of 1-4

Comatose Patients: Comatose patients automatically receive a score of 0 on the CNS.

Components of the CNS:

Mentation: This section evaluates the patient's cognitive state, including level of consciousness, orientation, and speech. Patients are scored based on their responses to questions and commands. Comatose patients receive a score of 0 in this section.

Motor Function (Section A1 and A2): Motor function is assessed differently based on the patient's comprehension abilities.

Section A1: For patients without comprehension issues (normal speech or expressive deficit only).

Section A2: For patients with comprehension problems (e.g., receptive deficit in speech). Motor function can be evaluated using either fixed posture or response to noxious stimuli.

Assessment in Section A1:

Face: The observer assesses facial symmetry by asking the patient to show their teeth or gums. Symmetry is noted if there is no asymmetry in the smile.

Arm Proximal: The patient's upper limb strength is tested by asking them to raise their arms to a certain position. The observer applies resistance and notes any weakness.

Arm Distal: The patient's ability to make fists and extend wrists is evaluated, and strength is assessed by applying resistance.

Leg: The patient's hip flexion and dorsiflexion of the foot are tested. Strength is graded based on the patient's ability to overcome resistance.

Assessment in Section A2:

Face: Symmetry is assessed by having the patient mimic the observer's grin. Grimacing in response to a painful stimulus can also be tested.

Arms and Legs: The observer places the patient's limbs in fixed positions and assesses their ability to maintain the posture. Alternatively, the observer applies pressure to the patient's nailbeds or sternum to elicit a response.

Validity and Usefulness:

Inter-Rater Agreement: Previous studies have shown good to excellent inter-rater agreement for the CNS, indicating its reliability.

Comparison with NIHSS: The CNS is comparable to the National Institutes of Health Stroke Scale (NIHSS) but requires less extensive evaluation and is quicker to administer. A simple formula can convert CNS scores to NIHSS scores.

The formula to convert Canadian Neurological Scale (CNS) scores to National Institutes of Health Stroke Scale (NIHSS) scores is: NIHSS=23−(2×CNS).