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Do you know how to score a stroke?

鈥淎 stroke is an interruption of the flow of blood to the cells in the brain. And when that happens, those cells do die.鈥�

That was the basic definition of stroke presented by Leigh Poland, RHIA, CCS, CDIP, CIC, AHIMA Approved ICD-10-CM/PCS Trainer, during her presentation 鈥淯nlocking the Full Potential of Stroke Coding and Documentation鈥� at HEALTHCON 2025 in Orlando. Not only was the definition accurate, but it pointed to the role of coders in helping stroke patients recover with accurate ICD-10 coding.

鈥淚t鈥檚 important to be familiar with the anatomy of the stroke so we鈥檙e coding to the highest degree of specificity,鈥� explained Poland. It also helps if coders can quickly identify symptoms associated with stroke when choosing a stroke diagnosis code.

Check out this primer on how different parts of the brain are affected by stroke, and the symptoms that can indicate a patient is suffering from one.

Know Hemispheres First

The first step of many for coders is to 鈥渓earn about anatomical structures involved in cerebrovascular disease, because these are vital for accurate [diagnosis] code assignment,鈥� explained Poland, who is also a vice president at AGS Health.

Coders should start by familiarizing themselves with brain hemispheres. The brain is divided into right and left hemispheres.

鈥淎 stroke on the left hemisphere creates deficits on right side and vice versa. That means you should make sure your documentation is lining up,鈥� explained Poland. 鈥淚f your physician is treating a right-sided stroke, your diagnosis coding should be left-sided.鈥�

Within each hemisphere, there are four lobes. You should know this anatomy because each area controls a function; therefore, stroke symptoms can vary depending on where the stroke occurs:

• Frontal: This is the front of the brain, and it controls functions such as decision-making, problem-solving, and planning. 鈥淭hus, damage to this area may result in disinhibition and deficits in concentration, orientation, and judgment,鈥� according to the . 
• Parietal: This is the top midsection of the brain, and it controls sensory processing and coordination, as well as spatial awareness and navigation. 鈥淲hen a stroke affects the parietal lobe, it can cause sensory loss and vision problems,鈥� said Poland.
• Temporal: This is the side of the brain, close to the temples. 鈥淭emporal lobe strokes can cause aphasia or memory loss,鈥� explained Poland.
• Occipital: This is the back of the brain, which controls vision/visual processing. 鈥淒amage to a single occipital lobe can result in homonymous hemianopsia as well as visual hallucinations. Bilateral damage to the primary visual cortex can cause blindness (cortical blindness),鈥� according to the NIH. Visual illusions could also occur, in which 鈥渙bjects would appear larger/smaller than they actually are, or objects appear with abnormal coloration,鈥� per the NIH.

Best bet: Know all these areas 鈥� and the functions they control 鈥� to make ICD-10-CM coding easier when the claim comes around. For example, Poland says expressive aphasia (difficulty speaking, writing, or gesturing) 鈥渃an occur when a stroke affects the frontal lobe in the dominant hemisphere.鈥�

Know Common Stroke Symptoms

There is no set list of symptoms that automatically indicate a patient is suffering from a stroke. However, providers should 鈥渃onsider stroke in any patient presenting with acute neurologic deficit or any alteration in level of consciousness,鈥� urged Poland.

Common stroke signs and symptoms include the following:

• Abrupt onset of hemiparesis, monoparesis, or (rarely) quadriparesis
• Hemisensory deficits
• Monocular or binocular visual loss
• Visual field deficits
• Diplopia
• Dysarthria
• Facial droop
• Ataxia
• Vertigo (typically accompanied by other symptoms)
• Nystagmus
• Aphasia
• Sudden decrease in level of consciousness

鈥淎lthough such symptoms can occur alone, they are more likely to occur in combination鈥� when a patient suffers a stroke, said Poland.

Once the provider determines the patient suffered a stroke, you鈥檒l choose a code from the 鈥淐erebrovascular diseases (I60-I69)鈥� code set as a primary diagnosis. Look to future issues of RCI for more information on choosing ICD-10-CM codes for stroke patients.

Use NIHSS to Score Stroke

While the ICD-10-CM code for stroke is clearly the most important one, you should also use a code to represent the National Institutes of Health Stroke Scale (NIHSS) score (if known and applicable). This will help make the stroke diagnosis coding even more specific, ensuring the record reflects as much about the patient鈥檚 condition as possible.

The NIHSS is a neurologic examination that consists of 15 stroke symptoms. Each symptom is assigned a score range based on the severity of the symptom. For example, level of consciousness has a range of 0-3. Once you score all 15 stroke symptoms, you鈥檒l add up the totals for all 15 symptoms and choose an ICD-10-CM code based on the score.

The scores can be evaluated using this chart:

鈥淚t鈥檚 used to evaluate the effect of acute cerebral infarction on the levels of consciousness, language, neglect, visual-field loss, extraocular movement, motor strength, ataxia, dysarthria, and sensory loss,鈥� said Poland.  

There are five NIHSS categories, each of which requires a 6^th character to complete the diagnosis. These categories are:

• R29.70- (NIHSS score 0-9)
• R29.71- (NIHSS score 10-19)
• R29.72- (NIHSS score 20-29)
• R29.73- (NIHSS score 30-39)
• R29.74- (NIHSS score 40-42)

Best bet: Use these secondary diagnoses whenever possible to paint the most complete picture of the condition of your stroke patient.

Chris Boucher, MS, CPC, Senior Development Editor, AAPC