NLE Neurosensory Nursing — Neurologic Assessment and DiagnosticsCheat Sheet

Formulas

Common values

Important facts

• The skull is a rigid compartment — any increase in one component (brain, blood, CSF) must be offset by a decrease in another.
• Normal ICP is 5–15 mmHg; values above 20 mmHg begin to impair cerebral perfusion.
• Normal CPP is 60–100 mmHg; below 50 mmHg causes ischemia; below 30 mmHg is incompatible with viable brain tissue.
• The brain comprises ~80% of intracranial volume, blood ~10%, and CSF ~10%.
• Three major brain regions: cerebrum (higher functions), cerebellum (coordination), brainstem (vital functions via reticular activating system).
• Cushing's triad (rising SBP with widening pulse pressure + bradycardia + irregular respirations) is a LATE sign of dangerously elevated ICP.

Key definitions

Diagrams to know

• Monro-Kellie Doctrine: The three components in fixed skull volume and how compensatory mechanisms fail.
• Brainstem anatomy: midbrain, pons, medulla with associated vital functions.
• Cerebral perfusion cascade: MAP → ICP → CPP relationship and ischemia thresholds.

Formulas

Common values

Important facts

• GCS 4 for eye opening = spontaneous opening; 3 = opens to verbal command; 2 = opens to pain only; 1 = does not open.
• GCS 5 for verbal = oriented to person, place, time; 4 = confused conversation; 3 = inappropriate words; 2 = incomprehensible sounds; 1 = none.
• GCS 6 for motor = obeys commands (full strength); 5 = localizes to pain (reaches toward pain); 4 = withdraws from pain; 3 = abnormal flexion (decorticate); 2 = abnormal extension (decerebrate); 1 = no response.
• A fully normal person = E4 V5 M6 = GCS 15.
• A drop of 2 or more GCS points is CLINICALLY SIGNIFICANT and must be reported immediately.
• GCS ≤ 8 = coma = intubation threshold. Patient cannot protect airway.
• GCS is reassessed frequently (q1h, q15min if unstable) in acute settings — serial scores matter more than a single score.
• When documenting, DESCRIBE THE STIMULUS AND ACTUAL RESPONSE, not just the score. Example: 'Responds with confusion to voice; localizes left hand to pain over right shoulder' is better than 'GCS 11.'

Key definitions

Diagrams to know

• GCS scoring table with all components and ranges.
• Normal person breakdown: E4, V5, M6 = 15.
• Coma threshold and intubation decision tree.

Common values

Important facts

• A UNILATERAL fixed, dilated ('blown') pupil is a NEUROLOGIC EMERGENCY — indicates uncal herniation compressing CN III on that side.
• Pupils are assessed for SIZE (mm), SHAPE, EQUALITY, and REACTION to light — document all four.
• The light reflex should be BRISK (normally occurs within 20 milliseconds).
• CN III (oculomotor) controls pupil constriction (parasympathetic) and is compressed in uncal herniation, causing ipsilateral dilation.
• Bilateral fixed and dilated pupils carry a grave prognosis — indicate severe midbrain necrosis or irreversible brain damage.
• Pinpoint pupils suggest pontine hemorrhage, brainstem stroke, or opioid effect (use naloxone if opioid suspected).
• Anisocoria (unequal pupils) of ≤ 1 mm is sometimes benign; ≥ 2 mm is abnormal and needs investigation.
• Horner's syndrome (ptosis, miosis, anhidrosis) indicates sympathetic pathway damage (not CN III).
• Always note if pupils are reactive or fixed BEFORE performing neuro checks with pain stimuli, as pain can cause pupil dilation.

Key definitions

Diagrams to know

• CN III pathway and how uncal herniation compresses it laterally.
• Miosis/mydriasis causes and associated clinical syndromes.
• Brainstem anatomy with levels of pupillary control (midbrain vs pons).

Important facts

• CN I (Olfactory) — Smell; test with coffee, orange, or vanilla; commonly lost in head trauma and anosmia.
• CN II (Optic) — Vision; test visual acuity and visual fields by confrontation.
• CN III (Oculomotor) — Eye movement, pupil constriction, eyelid elevation; unilateral dilation is herniation sign.
• CN IV (Trochlear) — Downward gaze, tested by 'down and in' eye movement; smallest nerve, easily missed.
• CN V (Trigeminal) — Facial sensation (3 divisions: ophthalmic, maxillary, mandibular) and chewing; test with cotton swab and ask to clench teeth.
• CN VI (Abducens) — Lateral gaze; easily affected by increased ICP (false localizing sign).
• CN VII (Facial) — Facial expression and taste (anterior 2/3 tongue); test smile, eye closure, raise eyebrows; weakness may be central (forehead spared) or peripheral (forehead affected).
• CN VIII (Vestibulocochlear) — Hearing and balance; test with whisper test or Weber/Rinne tuning fork tests.
• CN IX (Glossopharyngeal) and CN X (Vagus) — Swallowing, gag reflex, phonation, and soft palate elevation; test gag with tongue depressor, phonation ('ah' sound).
• CN XI (Spinal Accessory) — Shoulder shrug and head turning; test by resistance to shoulder shrug and head turn.
• CN XII (Hypoglossal) — Tongue movement; test by sticking tongue out (deviation toward lesion side indicates weakness).
• A brief 'cranial nerve screen' often tests only CN II (vision), CN III/IV/VI (eye movements), CN V (sensation), CN VII (face), and CN XII (tongue) when time is limited.
• Always test both eyes for CN II, III, IV, VI; test both sides of face for CN V and VII; test both shoulders for CN XI.

Key definitions

Diagrams to know

• All 12 cranial nerves with names, numbers, and basic functions.
• Extraocular muscles and which CN controls each (III, IV, VI).
• Six cardinal fields of gaze test for CN III, IV, VI.
• CN VII central vs peripheral facial palsy (forehead involvement).

Formulas

Common values

Important facts

• Test motor strength in major muscle groups: shoulders, elbows, wrists, fingers, hips, knees, ankles (bilateral).
• Grade 4 strength is broken into 4−, 4, 4+ to allow finer discrimination; most commonly used in practice.
• A drop in strength grade (e.g., from 5 to 4) on one side is significant and must be reported.
• Test pronator drift (arms extended, eyes closed, palms up for 20–30 seconds) to detect subtle weakness.
• Sensory testing includes light touch, pain, temperature, vibration, and proprioception; map the distribution (dermatomal, peripheral nerve, or 'stocking-glove').
• Deep tendon reflexes: normal is 2+; 0 = absent (LMN or neuropathy); 3–4+ = hyperactive (UMN or hyperreflexia).
• The Babinski reflex is ABNORMAL in adults; a positive Babinski = dorsiflexion of great toe + fanning of others = UMN lesion.
• Coordination testing: finger-to-nose (point to examiner's finger, then your own nose) and heel-to-shin (run heel down the opposite shin) — dysmetria suggests cerebellar lesion.
• Heel-to-toe walking tests gait and balance; inability to walk on heels or toes suggests weakness or cerebellar involvement.
• Document findings as 'R' (right) and 'L' (left) and compare; any asymmetry is ABNORMAL.

Key definitions

Diagrams to know

• Motor strength grading scale (0–5) with subcategories of 4.
• Dermatome map for sensory testing.
• Distribution patterns: dermatomal, peripheral nerve, glove-and-stocking.
• DTR grading scale and significance of clonus.

Important facts

• Cushing's triad is a LATE sign of increased ICP — neurologic impairment (declining LOC) precedes it.
• The triad reflects brainstem ischemia from compression: rising BP is a reflex attempt to maintain CPP, bradycardia indicates brainstem pressure, irregular respirations show medullary dysfunction.
• DO NOT wait for Cushing's triad to intervene — by the time it appears, herniation may already be occurring.
• Earlier signs of increased ICP: headache (often worsening), changes in LOC (lethargic → obtunded), projectile vomiting, pupil changes, motor changes.
• Headache from increased ICP is often WORSE in the morning (when intracranial compliance is reduced after sleep) and with Valsalva maneuvers.
• Temperature may rise if the hypothalamus is affected by swelling.
• Monitor serial neuro checks closely; a DECLINING LOC is the most sensitive early indicator of increased ICP.
• Interventions to lower ICP: elevate head 30°, maintain normothermia, maintain CO₂ at 35–40 mmHg (hyperventilation is a TEMPORARY emergency measure), avoid hypoxia, manage pain, avoid Valsalva, sedation if on ventilator.

Key definitions

Diagrams to know

• Timeline of increased ICP symptoms: early (headache, LOC decline) → late (Cushing's triad, herniation).
• Mechanism: Why Cushing's triad develops (brainstem compression and ischemia).

Common values

Important facts

• CT is FASTER than MRI (minutes vs 30–60 minutes) — use CT in acute/emergency settings.
• CT is FIRST-LINE for acute stroke to distinguish bleeding (appears white/bright) from ischemia (appears dark initially).
• CT excels at detecting acute hemorrhage, skull fractures, and mass effect (midline shift, herniation signs).
• MRI gives SUPERIOR soft-tissue detail and is best for detecting early ischemia (within hours), tumors, demyelination (MS plaques), and chronic lesions.
• Before MRI, screen for metal: pacemakers, implanted defibrillators (ICDs), ferromagnetic aneurysm clips, cochlear implants, metallic fragments in eyes.
• Remove ALL metal objects before MRI: watch, jewelry, glasses, hearing aids, dentures (if metal), hairpins.
• MRI is LOUD and ENCLOSED — assess for claustrophobia; patient may need sedation.
• If contrast is used with CT: assess for iodine allergy (shellfish/iodine cross-reactivity) and renal function (risk of contrast-induced nephropathy).
• If gadolinium contrast used for MRI: assess renal function (risk in GFR <30); gadolinium contraindicated in severe renal disease due to nephrogenic systemic fibrosis (NSF) risk.
• Acute hemorrhage on CT appears as WHITE/BRIGHT (hyperdense); acute ischemia appears DARK (hypodense) but may not be visible for hours.
• In acute stroke, non-contrast CT is done first to rule out hemorrhage; if negative, CT angiography or perfusion CT may follow to assess vessel and tissue.

Key definitions

Diagrams to know

• CT vs MRI decision tree (when to use which, based on clinical scenario).
• What different findings look like on CT: hemorrhage (bright), ischemia (dark), mass effect.
• Metal screening checklist for MRI safety.

Common values

Important facts

• LP is performed between L3–L4 or L4–L5 (BELOW the spinal cord terminus at ~L1–L2) to avoid cord injury.
• Spinal cord ends at ~L1–L2 (conus medullaris), so LP at L3–L4 or below is safe.
• Position patient LATERAL RECUMBENT with knees drawn to chest (fetal position) to widen intervertebral spaces.
• Maintain STRICT STERILE TECHNIQUE — this is a direct CNS entry procedure.
• Normal CSF is CLEAR and COLORLESS; cloudy CSF suggests infection (bacteria, fungi, or high WBC); bloody or XANTHOCHROMIC (yellow/pink/orange) CSF indicates hemorrhage.
• LP IS CONTRAINDICATED if ICP is elevated — sudden CSF removal causes pressure differential that can precipitate FATAL BRAINSTEM HERNIATION.
• Check for papilledema (sign of raised ICP) on fundoscopy BEFORE LP; if present, do imaging (CT) first to rule out mass before considering LP.
• Complications: post-LP headache (from CSF leakage), infection (meningitis), hemorrhage, nerve root irritation.
• Post-LP care: keep patient LYING FLAT for several hours (to reduce CSF leak and headache risk); ENCOURAGE ORAL FLUIDS (to replenish CSF and prevent headache).
• Post-LP headache typically develops within 24–48 hours, is positional (worse when upright, better when lying down), and is caused by CSF leakage through the dura.
• CSF findings in bacterial meningitis: CLOUDY, HIGH WBC (often >1000, predominantly neutrophils), HIGH protein (>100 mg/dL), LOW glucose (<40 mg/dL or CSF:serum ratio <0.4).
• CSF findings in viral meningitis: CLEAR/SLIGHTLY TURBID, moderate WBC (100–500, lymphocytes predominate initially), normal/slightly elevated protein, NORMAL glucose.

Key definitions

Diagrams to know

• LP insertion site (L3–L4 or L4–L5) relative to spinal cord terminus.
• Fetal position (lateral recumbent with knees flexed) to widen intervertebral space.
• CSF sampling: appearance, cell types, and differentials (clear = viral/aseptic; cloudy = bacterial/fungal).

Common values

Important facts

• ICP monitoring indications: GCS ≤ 8, abnormal CT (hemorrhage, contusion, edema), severe head trauma requiring mechanical ventilation.
• The INTRAVENTRICULAR CATHETER (ventriculostomy) is the gold standard because it both MEASURES and DRAINS CSF, allowing therapeutic relief of pressure.
• Keep ICP catheter and tubing as a CLOSED STERILE SYSTEM — opening it increases infection risk; infection (ventriculitis) is a major complication.
• Level the transducer at the FORAMEN OF MONRO (approximately the tragus of the ear or outer canthus of the eye) for accurate readings.
• If transducer is positioned too HIGH, ICP reading is falsely LOW; if too LOW, falsely HIGH — leveling is critical.
• Normal ICP is 5–15 mmHg; values 15–20 are borderline; >20 require intervention.
• Cerebral autoregulation fails when ICP exceeds ~20 mmHg or CPP drops below 50 mmHg.
• Waveform changes: normal shows three components (P1, P2, P3); P2 elevation or 'plateau' (A waves) indicates poor compliance and risk of sudden ICP spikes.
• A waves (plateau waves) are dangerous — they represent episodes of sustained high ICP (>50 mmHg) and signal imminent herniation risk; require immediate intervention.
• CSF drainage: if ventriculostomy is used, CSF is drained into a collection bag at a level typically 10–20 cm above the foramen of Monro (allows passive drainage and limits siphoning).
• Maintain strict sterile dressing around the catheter entry site; change dressing per protocol; monitor for signs of infection (fever, purulent drainage, cloudy CSF).
• Common complications: infection/ventriculitis, hemorrhage at insertion, catheter migration, CSF leak.
• Sedation and analgesia are used to reduce ICP by decreasing cerebral metabolic demand; commonly used agents include propofol and opioids.
• Hyperthermia increases cerebral metabolic demand and ICP — maintain normothermia.

Key definitions

Diagrams to know

• Ventriculostomy placement anatomy: lateral ventricles and position relative to foramen of Monro.
• ICP waveform components and what abnormal (A wave/plateau) waveforms indicate.
• Closed sterile system maintenance: collection bag leveling, tube patency, sterile dressing.

Important facts

• EEG is valuable in seizure diagnosis, brain death confirmation, and assessing level of consciousness in ICU patients.
• Before EEG: verify orders for holding medications (stimulants and sedatives may be held per protocol); avoid caffeine; ensure hair is clean and free of products (oils interfere with electrode contact).
• EEG takes ~30–60 minutes; patient lies still while electrodes record activity; hyperventilation may be done to provoke seizure activity.
• Brain death confirmation: EEG shows COMPLETE ABSENCE of electrical activity (isoelectric line) for ≥30 minutes (confirmatory test).
• Cerebral angiography is invasive: femoral artery access, contrast injection, fluoroscopic imaging; similar risks and post-care to cardiac catheterization.
• Before angiography: assess for contrast allergy (iodine/shellfish), renal function (contrast-induced nephropathy risk), and anticoagulation status.
• After angiography: monitor access site (groin) for hematoma, bleeding, or thrombosis; assess distal pulses; maintain bed rest per protocol; monitor for contrast-related complications (renal injury, allergic reaction).
• Angiography risks: stroke (from plaque dislodgement), vasospasm, perforation, allergic reaction, renal injury.
• CT angiography (CTA) and MR angiography (MRA) are less invasive alternatives to cerebral angiography but may not allow therapeutic intervention.

Key definitions

Diagrams to know

• Normal EEG pattern vs abnormal (spike-and-wave, slowing).
• Cerebral angiography procedure and common findings (aneurysm, stenosis, vasospasm).
• Access site assessment post-angiography (pulse checks, hematoma monitoring).