4.2 Acute Ischemic Stroke Assessment & NIHSS
Key Takeaways
- The phrase 'Time is Brain' emphasizes that roughly 1.9 million neurons are lost every minute during an untreated ischemic stroke, necessitating hyper-acute assessment.
- The NIHSS is a 15-item, 42-point neurological assessment tool that quantifies stroke severity, predicts patient outcomes, and guides thrombolytic decision-making.
- The NIHSS must be administered exactly as prescribed without coaching the patient; score what the patient actually does, not what the examiner thinks they can do.
- A baseline NIHSS score should be documented immediately upon arrival, prior to any intervention, and repeated consistently to detect neurological deterioration.
- NIHSS scores of 1-4 indicate minor stroke, 5-15 indicate moderate stroke, 16-20 indicate moderate to severe stroke, and 21-42 indicate severe stroke.
Acute Ischemic Stroke Assessment
The initial assessment of a patient presenting with an acute ischemic stroke is one of the most time-critical events in emergency neuroscience nursing. The core philosophy driving acute stroke care is encapsulated in the phrase "Time is Brain." Research estimates that approximately 1.9 million neurons, 14 billion synapses, and 7.5 miles of myelinated fibers are irrevocably lost for every single minute an acute stroke goes untreated. Therefore, rapid, standardized, and highly accurate neurological assessment is paramount to identifying candidates for time-sensitive reperfusion therapies.
Upon arrival, the primary survey focuses immediately on the ABCs (Airway, Breathing, Circulation). Concurrently, a focused neurological assessment is initiated, primarily utilizing the National Institutes of Health Stroke Scale (NIHSS). Vital signs are closely monitored, with a specific focus on blood pressure, as strict parameters dictate the eligibility for thrombolytic administration.
The NIHSS: Administration and Scoring
The NIHSS is a standardized, reliable, 15-item (grouped into 11 categories) ordinal scale utilized to precisely quantify the neurological impairment caused by a stroke. It provides a baseline, helps guide treatment decisions, facilitates standardized communication among the healthcare team, and accurately predicts patient outcomes. The total score ranges from 0 (normal) to 42 (severe impairment).
Golden Rules of NIHSS Administration
Before detailing the items, several critical rules must govern the administration of the NIHSS to ensure inter-rater reliability:
- Do not coach the patient. Do not provide verbal encouragement or physical cues.
- Score what the patient actually does, not what you think they can do. If a patient cannot perform a task, score the failure, regardless of the suspected underlying reason (e.g., scoring a failed motor command due to severe aphasia rather than true paresis).
- Perform the items in the exact order listed. Do not skip around.
- Administer all items. Only record "Untestable" (UN) in very specific, strictly defined circumstances (e.g., amputations, intubation).
The 11 Categories of the NIHSS
1a. Level of Consciousness (LOC):
- This assesses the patient's overall arousal.
- Score 0 (Alert) to 3 (Coma). The patient is evaluated based on their response to verbal or noxious stimuli.
1b. LOC Questions:
- Ask the patient the current month and their current age.
- Score 0 (Answers both correctly), 1 (Answers one correctly), or 2 (Answers neither correctly). Aphasic patients who cannot comprehend the question must score a 2. There is no partial credit for being "close."
1c. LOC Commands:
- Ask the patient to open and close their eyes, and then to grip and release their non-paretic hand.
- Score 0 (Performs both correctly), 1 (Performs one correctly), or 2 (Performs neither correctly). Pantomiming the command is explicitly allowed if the patient is profoundly deaf or aphasic.
2. Best Gaze:
- Assesses only horizontal eye movements. Establish eye contact and ask the patient to follow your finger side to side.
- Score 0 (Normal), 1 (Partial gaze palsy - gaze is abnormal in one or both eyes, but forced deviation is not present), or 2 (Forced deviation, or total gaze paresis not overcome by the oculocephalic maneuver).
3. Visual Fields:
- Test the upper and lower quadrants of vision in both eyes using confrontation.
- Score 0 (No visual loss), 1 (Partial hemianopia), 2 (Complete hemianopia), or 3 (Bilateral hemianopia or cortical blindness).
4. Facial Palsy:
- Ask the patient to show their teeth, raise their eyebrows, and tightly close their eyes.
- Score 0 (Normal), 1 (Minor paralysis - e.g., flattened nasolabial fold), 2 (Partial paralysis - near or total lower face paralysis), or 3 (Complete paralysis of one or both sides, upper and lower face).
5. Motor Arm (Left and Right):
- The patient must extend their arms 90 degrees (if sitting) or 45 degrees (if supine) with palms down. The examiner counts out loud and on their fingers for 10 seconds. Score each arm separately.
- Score 0 (No drift for 10 full seconds), 1 (Drift - arm falls before 10 seconds but doesn't hit the bed), 2 (Some effort against gravity - arm falls to bed before 10 seconds), 3 (No effort against gravity - limb falls immediately, but some muscle flicker exists), or 4 (No movement whatsoever).
6. Motor Leg (Left and Right):
- The patient must elevate each leg 30 degrees while supine. The examiner counts for 5 seconds. Score each leg separately.
- Scoring follows the exact same 0-4 criteria as the motor arm section, but is timed for only 5 seconds.
7. Limb Ataxia:
- Tests for cerebellar lesions via the finger-to-nose and heel-to-shin tests. It is only scored if the ataxia is out of proportion to the identified muscular weakness.
- Score 0 (Absent), 1 (Present in one limb), or 2 (Present in two limbs). If the patient cannot understand or is paralyzed, the score is 0.
8. Sensory:
- Test response to a pinprick (noxious stimulus) on the face, arms, trunk, and legs to assess for hemisensory loss.
- Score 0 (Normal), 1 (Mild-to-moderate sensory loss - patient feels the pin but it feels less sharp/dull on one side), or 2 (Severe to total sensory loss - patient does not feel the pinprick at all on one side).
9. Best Language:
- Assesses for aphasia using a standardized picture, a naming sheet, and a list of sentences.
- Score 0 (Normal), 1 (Mild-to-moderate aphasia - communication is possible but difficult), 2 (Severe aphasia - all communication is through fragmentary expression), or 3 (Mute, global aphasia).
10. Dysarthria:
- Assesses the mechanical clarity of speech by having the patient read a standard list of words (e.g., "mama, tip-top, fifty-fifty").
- Score 0 (Normal), 1 (Mild-to-moderate dysarthria - slurs some words but is generally understandable), or 2 (Severe dysarthria - speech is entirely unintelligible, or patient is anarthric/mute). Intubated patients are scored as 'UN'.
11. Extinction and Inattention (Neglect):
- Synthesizes findings from earlier sections (visual, sensory) and specifically tests double simultaneous stimulation to see if the patient neglects one side of their body or space.
- Score 0 (No abnormality), 1 (Visual, tactile, auditory, spatial, or personal inattention to one side), or 2 (Profound hemi-inattention or extinction to more than one modality).
Interpretation and Clinical Utility
The total NIHSS score categorizes stroke severity:
- 1-4: Minor stroke
- 5-15: Moderate stroke
- 16-20: Moderate to severe stroke
- 21-42: Severe stroke
The NIHSS is performed at baseline to determine thrombolytic eligibility, frequently post-intervention (e.g., every 15 minutes during tPA administration) to monitor for acute deterioration, and daily to track functional recovery. A sudden increase in the NIHSS score by 4 or more points is a critical clinical warning sign strongly suggestive of a hemorrhagic conversion, cerebral edema, or stroke extension, warranting an immediate cessation of thrombolytics and an emergent non-contrast head CT.
During the administration of the NIHSS, the nurse asks the patient to state their age and the current month. The patient, who has severe expressive aphasia, cannot answer verbally but correctly holds up fingers to indicate their age. How should the nurse score item 1b (LOC Questions)?
A patient with an acute ischemic stroke is receiving intravenous tPA. During a routine neurological check, the nurse notes that the patient's NIHSS score has suddenly increased from a baseline of 6 to a 12. What is the most appropriate initial nursing action?
When assessing item 5 (Motor Arm) of the NIHSS on a supine patient, the patient's right arm drifts down and hits the bed after 6 seconds of being held at 45 degrees. Which score should be assigned to the right arm?