NIHSS score 21

This code indicates a National Institutes of Health Stroke Scale (NIHSS) score of 21, reflecting a severe neurological deficit following an acute stroke. The NIHSS is a standardized, systematic assessment tool used to quantify the severity of stroke-related neurological impairment. A score of 21 suggests significant functional impairment across multiple neurological domains.

This code is used when a patient has experienced an acute ischemic or hemorrhagic stroke and a clinician has formally assessed their neurological status using the NIHSS, resulting in a score of 21. Documentation must clearly state the NIHSS score and the date of assessment, typically performed in the acute phase of stroke management.

• Always ensure the medical record explicitly documents an NIHSS score of 21. Do not infer the score from narrative descriptions of symptoms.
• This code should be sequenced after the primary diagnosis code for the specific type of stroke (e.g., I63.x for ischemic stroke, I61.x for hemorrhagic stroke).
• Be aware that other codes exist for different NIHSS score ranges; verify the exact score before assigning.