NLE Neurosensory Nursing — Neurologic Assessment and DiagnosticsCheat Sheet
A printable cheat sheet for Neurologic Assessment and Diagnostics, built for NLE reviewers who want one go-to reference in the final stretch. Covers formulas, key definitions, common question types, and the Professional Regulation Commission (PRC) — Board of Nursing-specific twists you will see on NLE day.
Exam context
For the Philippine Nurse Licensure Examination (PNLE), Professional Regulation Commission (PRC) — Board of Nursing tests Neurosensory Nursing under a "Core" label, with Neurologic Assessment and Diagnostics in the 1st slot across 5 chapters. NLE candidates must clear the 75% weighted average with no sub-test below 60% cut on the 2026 paper, which draws about 50 Neurosensory Nursing questions. Date to watch: Bi-annual.
Neurologic Assessment and Diagnostics - Cheat Sheet
Your final 30-minute exam companion covering neurologic examination, Glasgow Coma Scale, cranial nerves, ICP monitoring, and neurodiagnostic imaging. Every item here appears frequently on the NLE — commit these to memory.
Sections
Formulas
Formula
CPP = MAP − ICP
Meaning
CPP = Cerebral Perfusion Pressure; MAP = Mean Arterial Pressure; ICP = Intracranial Pressure
Watch Out
Students forget this is SUBTRACTION, not addition. Low CPP (below 50 mmHg) causes brain ischemia; below 30 mmHg is incompatible with life.
When To Use
Any question on brain blood flow or when ICP is elevated; critical in head injury and neurosurgery cases
Formula
Monro-Kellie Doctrine: Skull Volume = Brain (~80%) + Blood (~10%) + CSF (~10%)
Meaning
Fixed skull volume means any increase in one component forces decrease in others; explains why ICP rises sharply once compensatory mechanisms fail
Watch Out
This is a doctrine, not a calculation — but the percentages and the principle that volume is FIXED are tested heavily. Know why a small bleed becomes dangerous.
When To Use
Explaining why hemorrhage, swelling, or tumors rapidly worsen; predicting ICP response to interventions
Common Values
Value
5–15 mmHg
Symbol
ICP
Quantity
Normal ICP
Value
60–100 mmHg
Symbol
CPP
Quantity
Normal CPP
Value
Below 50 mmHg
Symbol
CPP critical
Quantity
Critical CPP (ischemia threshold)
Value
Below 30 mmHg
Symbol
CPP lethal
Quantity
Critical CPP (incompatible with life)
Value
Above 20 mmHg
Symbol
ICP ↑
Quantity
Danger ICP
Value
L1–L2 vertebral level
Symbol
Conus medullaris
Quantity
Spinal cord termination
Section Title
Neurophysiology Fundamentals
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
Term
Level of Consciousness (LOC)
Example
A patient who was alert suddenly becomes lethargic — this ONE change must be reported immediately, even if vital signs are stable.
Definition
The earliest and most sensitive indicator of neurologic change; assessed on a continuum from alert to comatose.
Term
Intracranial Pressure (ICP)
Example
When ICP exceeds 20 mmHg, cerebral autoregulation fails and ischemia develops.
Definition
Pressure exerted by the brain, blood, and CSF within the fixed skull vault; normal is 5–15 mmHg in adults.
Term
Cerebral Perfusion Pressure (CPP)
Example
If MAP = 90 and ICP = 20, then CPP = 70 (still acceptable, but low-normal).
Definition
The net pressure driving oxygen delivery to the brain; normal range 60–100 mmHg.
Term
Decorticate Posturing
Example
Seen in severe cerebral hemisphere stroke or traumatic brain injury above the midbrain.
Definition
Abnormal flexion (arms bent and drawn toward core, legs extended); indicates damage ABOVE the brainstem.
Term
Decerebrate Posturing
Example
More severe than decorticate; progression from decorticate to decerebrate is ominous.
Definition
Abnormal extension (arms rigidly extended and pronated, legs extended); indicates brainstem damage.
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
Formula
GCS Total = Eye (E) + Verbal (V) + Motor (M) — Range: 3 to 15
Meaning
E = 1–4; V = 1–5; M = 1–6. Sum all three scores.
Watch Out
The MOST common NLE mistake: students forget the ranges (E goes to 4, V to 5, M to 6). A normal person is E4 V5 M6 = 15, NOT 9. A GCS of 8 OR BELOW is coma and triggers intubation.
When To Use
EVERY patient assessment in acute care, neurosurgery, ICU, or trauma — tested heavily on NLE.
Common Values
Value
E4 V5 M6 = 15
Symbol
GCS 15
Quantity
Fully alert normal person
Value
GCS 13–15
Symbol
GCS mild
Quantity
Mild impairment
Value
GCS 9–12
Symbol
GCS moderate
Quantity
Moderate impairment
Value
GCS ≤ 8
Symbol
GCS coma
Quantity
Coma / intubation threshold
Value
GCS 3 (E1 V1 M1)
Symbol
GCS 3
Quantity
Deepest possible coma
Value
≥ 2 points
Symbol
GCS Δ ≥ 2
Quantity
Clinically significant drop
Section Title
Glasgow Coma Scale (GCS) — CRITICAL FOR NLE
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
Term
Glasgow Coma Scale (GCS)
Example
Patient opens eyes to voice (E3), speaks confused sentences (V4), withdraws from pain (M4) = GCS 11 (moderate impairment).
Definition
Standardized, objective 3–15 scale assessing consciousness via eye opening, verbal response, and best motor response.
Term
Mild Neurologic Impairment
Example
GCS 14 after minor head trauma.
Definition
GCS 13–15; patient is largely alert but may have minor deficits.
Term
Moderate Neurologic Impairment
Example
GCS 11 after fall; patient drowsy but rousable.
Definition
GCS 9–12; significant altered consciousness, often requires ICU monitoring.
Term
Severe Neurologic Impairment (Coma)
Example
GCS 5 (eyes don't open, no verbal response, no purposeful motor response) — patient is intubated.
Definition
GCS 8 or below; deep unconsciousness, threshold for intubation to protect airway.
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
Value
2–6 mm
Symbol
D normal
Quantity
Normal pupil diameter
Value
Often ≥ 6 mm and fixed
Symbol
D blown
Quantity
Blown pupil threshold
Value
1–2 mm
Symbol
D pinpoint
Quantity
Pinpoint pupils
Value
Normal ~20 ms (brisk)
Symbol
Reflex brisk
Quantity
Light reflex latency
Value
≥ 2 mm difference
Symbol
Anisocoria abnormal
Quantity
Anisocoria concern threshold
Section Title
Pupillary Assessment & Neurologic Emergencies
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
Term
Normal Pupils
Example
Both pupils 4 mm, round, equal, respond promptly to flashlight — document as 'PERRL, 4 mm bilateral.'
Definition
Equal, round, reactive to light (PERRL); diameter 2–6 mm; brisk constriction in light, dilation in darkness.
Term
Blown Pupil (Blown Pupil / Herniation Pupil)
Example
Right pupil 8 mm, unreactive to light, while left remains 4 mm and reactive — NEUROLOGIC EMERGENCY, call physician immediately.
Definition
Unilateral fixed and dilated pupil (often 6–8 mm or larger) indicating uncal herniation compressing CN III.
Term
Bilateral Fixed and Dilated Pupils
Example
Both pupils 8 mm, fixed; extremely poor prognosis, usually associated with brain death or terminal decline.
Definition
Both pupils large and unreactive; indicates severe midbrain damage.
Term
Pinpoint Pupils
Example
Pinpoint pupils + respiratory depression + unconsciousness → consider naloxone for opioid reversal.
Definition
Pupils constricted to 1–2 mm; suggests pontine (lower brainstem) damage or opioid overdose.
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).
Section Title
Cranial Nerve (CN) Testing — All 12 Nerves
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
Term
Cranial Nerves I–XII
Example
Testing all 12 takes ~5 minutes; abbreviated neuro checks test only CN III (pupils), VII (facial), XII (tongue) as quick screening.
Definition
Twelve pairs of nerves exiting the brainstem; tested as part of full neurologic exam. Mnemonic: 'On Old Olympus' Towering Tops, A Finn And German Viewed Some Hops.'
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
Formula
Motor Strength Grading: 0–5 Scale
Meaning
0 = no contraction; 1 = flicker of contraction; 2 = movement with gravity eliminated; 3 = movement against gravity; 4 = movement against some resistance; 5 = normal full strength
Watch Out
Grade 4 has FIVE subcategories (4−, 4, 4+) depending on resistance. Most students forget this refinement. 4− means weak resistance, 4 means moderate, 4+ means strong.
When To Use
Documenting motor function in any patient; especially in stroke, spinal cord injury, and neurosurgery.
Common Values
Value
5/5 (full strength against resistance)
Symbol
M 5
Quantity
Normal motor strength
Value
4/5 (moves against some resistance)
Symbol
M 4
Quantity
Mild weakness
Value
3/5 (moves against gravity)
Symbol
M 3
Quantity
Moderate weakness
Value
2/5 or less (little/no movement)
Symbol
M 2−
Quantity
Severe weakness
Value
2+
Symbol
DTR 2+
Quantity
Normal DTR
Value
0
Symbol
DTR 0
Quantity
Absent DTR
Value
4+
Symbol
DTR 4+
Quantity
Hyperactive DTR with clonus
Section Title
Motor, Sensory, and Reflex Testing
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
Term
Pronator Drift
Example
Patient extends both arms forward; right arm drifts down and pronates after 5 seconds — sign of left hemisphere weakness.
Definition
Subtle sign of weakness: when arms are extended with eyes closed, an affected arm drifts downward or the palm pronates (turns inward).
Term
Babinski Reflex
Example
In a stroke patient, the toe fans upward on the affected side — ABNORMAL in adults, normal only in infants under ~2 years.
Definition
Dorsiflexion of the great toe with fanning of other toes when sole is stroked; ABNORMAL (positive) in adults, indicates upper motor neuron (UMN) lesion.
Term
Deep Tendon Reflex (DTR) Grading
Example
Patellar reflex 3+ = hyperactive, concerning for spasticity or UMN lesion; 0 = absent, concerning for peripheral neuropathy or lower motor neuron (LMN) lesion.
Definition
0 = absent; 1+ = hypoactive; 2+ = normal brisk; 3+ = hyperactive; 4+ = hyperactive with clonus.
Term
Gait Assessment
Example
Hemiplegic gait (one leg stiff, swinging outward) suggests stroke; ataxic gait (broad-based, unsteady) suggests cerebellar damage.
Definition
Observation of walking for steadiness, symmetry, stride length, and abnormal patterns.
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.
Section Title
Cushing's Triad & Signs of Increased ICP
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
Term
Cushing's Triad
Example
BP 160/80 (was 130/80), HR 52, irregular respirations — these changes together signal critical ICP elevation, usually from herniation.
Definition
Rising systolic BP with widening pulse pressure + bradycardia + irregular respirations; LATE sign of dangerously elevated ICP.
Term
Widening Pulse Pressure
Example
BP changes from 120/80 (PP = 40) to 180/90 (PP = 90) — the widening is a danger sign.
Definition
Increase in the difference between systolic and diastolic BP; in Cushing's triad, SBP rises while DBP stays the same or drops.
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
Value
~5–10 minutes
Symbol
CT fast
Quantity
CT scan time
Value
30–60 minutes
Symbol
MRI slow
Quantity
MRI scan time
Value
1.5–3 Tesla (T) typical
Symbol
B field
Quantity
MRI field strength
Section Title
Computed Tomography (CT) & Magnetic Resonance Imaging (MRI)
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
Term
CT (Computed Tomography) of the Head
Example
Acute stroke protocol: non-contrast CT done immediately to rule out hemorrhage before giving thrombolytics.
Definition
Fast, radiation-based imaging; first-line for acute stroke, trauma, and hemorrhage; blood appears bright (hyperdense).
Term
MRI (Magnetic Resonance Imaging) of the Brain
Example
MRI is delayed (takes 30–60 minutes) so not used for acute bleeding, but excellent for diagnosing MS, old stroke, brain tumors.
Definition
High soft-tissue resolution using magnetic fields; superior for detecting early ischemia, tumors, demyelination, and chronic lesions; contraindicated with metal implants.
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
Value
70–180 mmH₂O (5–15 mmHg)
Symbol
P CSF normal
Quantity
Normal CSF opening pressure (recumbent)
Value
15–45 mg/dL
Symbol
CSF protein
Quantity
Normal CSF protein
Value
40–70 mg/dL (or ~60% of blood glucose)
Symbol
CSF glucose
Quantity
Normal CSF glucose
Value
0–5 cells/μL (mostly lymphocytes)
Symbol
CSF WBC
Quantity
Normal CSF WBC
Value
0 cells/μL
Symbol
CSF RBC
Quantity
Normal CSF RBC
Value
L1–L2 level
Symbol
Conus L1–L2
Quantity
Spinal cord termination (conus)
Value
L3–L4 or L4–L5
Symbol
LP site
Quantity
Safe LP site
Section Title
Lumbar Puncture (LP / Spinal Tap)
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
Term
Lumbar Puncture (LP)
Example
Patient with fever and neck stiffness: LP shows cloudy CSF with elevated WBC and protein → bacterial meningitis.
Definition
Procedure to sample cerebrospinal fluid (CSF) from the subarachnoid space; diagnostic for meningitis, SAH, MS; can measure opening pressure.
Term
Opening Pressure
Example
Elevated opening pressure in meningitis or idiopathic intracranial hypertension; low in spinal taps with dehydration.
Definition
CSF pressure measured immediately after needle insertion; normal 70–180 mmH₂O (or 5–15 mmHg when recumbent).
Term
Normal CSF Characteristics
Example
Clear CSF with glucose 50 mg/dL and protein 30 mg/dL = normal; cloudy = infection; xanthochromic (yellow/pink) = old blood.
Definition
Clear and colorless; low protein, low glucose (but >40 mg/dL normally), few cells (0–5 WBC/μL, 0 RBC).
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
Value
5–15 mmHg
Symbol
ICP normal
Quantity
Normal ICP
Value
15–20 mmHg
Symbol
ICP borderline
Quantity
Borderline elevated ICP
Value
>20 mmHg
Symbol
ICP ↑
Quantity
Elevated ICP requiring intervention
Value
>50 mmHg
Symbol
ICP danger
Quantity
Dangerous ICP (plateau wave)
Value
Usually 10–20 cm (gravity drainage)
Symbol
Drainage height
Quantity
Transducer leveling height above foramen
Section Title
Intracranial Pressure (ICP) Monitoring & Management
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
Term
Intraventricular Catheter (Ventriculostomy / External Ventricular Drain)
Example
Patient with GCS 6 from head trauma: ventriculostomy placed for both ICP monitoring and CSF drainage to relieve pressure.
Definition
Gold-standard ICP monitor; catheter placed in lateral ventricle; measures pressure directly AND allows therapeutic drainage of CSF.
Term
Subarachnoid Bolt
Example
Used when ventriculostomy placement is difficult; less accurate than ventriculostomy.
Definition
Alternative ICP monitor; sensor sits in subarachnoid space; measures pressure but does NOT allow CSF drainage.
Term
Epidural/Parenchymal Sensor
Example
Sometimes used in ICU for continuous monitoring; advantages include lower infection risk but disadvantage of no therapeutic drainage.
Definition
Probe placed epidurally or in brain parenchyma; measures ICP but does NOT allow drainage; least invasive but also less accurate.
Term
Foramen of Monro
Example
Transducer must be leveled at the foramen of Monro for accurate ICP readings; if too high, reading is falsely low; if too low, falsely high.
Definition
Anatomic landmark at the junction of the lateral and third ventricles; used as transducer leveling reference (approximately tragus of ear or outer canthus of eye).
Term
Plateau Waves (A Waves)
Example
ICP waveform shows prolonged elevation; signal danger; need immediate intervention (sedation, osmotic therapy, hyperventilation, drainage).
Definition
Sustained elevations in ICP (>50 mmHg) for 5–20 minutes; indicate exhaustion of compensatory mechanisms and risk of herniation.
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.
Section Title
Electroencephalography (EEG) & Other Neurodiagnostic Tests
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
Term
Electroencephalography (EEG)
Example
Patient with seizure disorder: EEG shows spike-and-wave activity during a seizure, confirming epilepsy.
Definition
Records brain's electrical activity via scalp electrodes; used to diagnose seizures, confirm brain death, assess level of consciousness.
Term
Cerebral Angiography
Example
Patient with subarachnoid hemorrhage: angiography performed to locate the aneurysm and plan intervention (clipping vs endovascular coil).
Definition
Invasive vascular imaging using contrast injection into cerebral arteries; identifies aneurysms, stenosis, vasospasm, vascular malformations.
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).
Must Remember
- LEVEL OF CONSCIOUSNESS IS THE EARLIEST AND MOST SENSITIVE INDICATOR OF NEUROLOGIC CHANGE — A DECLINING LOC MUST BE REPORTED IMMEDIATELY, even before vital signs change.
- GCS = E (1–4) + V (1–5) + M (1–6), ranging 3–15. NORMAL PERSON = E4 V5 M6 = 15. GCS ≤ 8 = COMA = INTUBATION THRESHOLD. Drop of ≥2 points = clinical emergency.
- UNILATERAL FIXED & DILATED PUPIL ('BLOWN PUPIL') = UNCAL HERNIATION COMPRESSING CN III = NEUROLOGIC EMERGENCY. Call physician immediately.
- CPP = MAP − ICP. Normal CPP 60–100 mmHg; <50 causes ischemia; <30 incompatible with life. Normal ICP 5–15 mmHg.
- MONRO-KELLIE DOCTRINE: Skull volume is FIXED (brain ~80%, blood ~10%, CSF ~10%). Any increase in one component forces decrease in others; once compensatory mechanisms fail, ICP rises SHARPLY.
- CUSHING'S TRIAD (rising SBP with widening pulse pressure + bradycardia + irregular respirations) = LATE SIGN of dangerous ICP elevation. DO NOT WAIT for this to intervene — declining LOC precedes it.
- POSITIVE BABINSKI REFLEX (dorsiflexion of great toe + fanning) = ABNORMAL IN ADULTS and indicates UPPER MOTOR NEURON LESION. Normal only in infants.
- LP IS CONTRAINDICATED if ICP is elevated — risk of FATAL BRAINSTEM HERNIATION. Do imaging (CT) first if papilledema or mass effect suspected. Position L3–L4 or L4–L5 (below conus at L1–L2). POST-LP: keep FLAT and push FLUIDS to prevent spinal headache.
- DECORTICATE (abnormal FLEXION, arms toward core) = lesion ABOVE brainstem; DECEREBRATE (abnormal EXTENSION, arms rigidly extended) = brainstem damage and worse prognosis. Progression from decorticate to decerebrate is OMINOUS.
- CT is FIRST-LINE for acute stroke/hemorrhage (fast, blood appears BRIGHT); MRI requires METAL/PACEMAKER SCREENING and is used for chronic lesions, demyelination, and soft-tissue detail. ICP monitoring (ventriculostomy) is gold standard — allows both measurement AND therapeutic CSF drainage.
Last Minute Tips
- SERIAL ASSESSMENT IS KEY: A SINGLE GCS or neuro check means less than a TREND. Always compare to baseline and previous assessment. A drop of 2+ points is the trigger for immediate action, not the absolute number.
- WHEN DOCUMENTING NEURO CHECKS: Write the STIMULUS and ACTUAL RESPONSE, not just the score. 'Eyes open to pain,' 'confused speech,' 'withdraws right arm, extends left leg' are more informative than 'GCS 10' alone. This precision catches subtle changes.
- PUPIL ASSESSMENT TRAP: Always assess pupils BEFORE and AFTER applying painful stimuli (can cause dilation). Note if pupils are reactive BEFORE you pinch; a 'blown' pupil that reacts sluggishly is still concerning. Document carefully.
- ICP MONITORING TRANSDUCER LEVELING IS CRITICAL: If transducer is leveled too HIGH (above foramen of Monro), ICP reads falsely LOW and you may miss rising pressure. Always level at tragus/outer canthus. Verify leveling q4h or per protocol.
- POST-LP HEADACHE PREVENTION: Keep patient FLAT for at least 2 hours (ideally 4–6 hours) and PUSH ORAL FLUIDS aggressively afterward. This simple intervention reduces spinal headache risk by >50%. Reinforce this with patient before procedure.
Comparison Tables
Rows
Values
- 15
- Normal / Fully Alert
- E4 V5 M6; fully conscious, oriented, no deficits
- Routine monitoring; no ICU usually needed
Property
15
Values
- 13–14
- Mild Impairment
- Alert with minor deficits (slight confusion or weakness)
- Monitor closely; may need ICU; frequent neuro checks
Property
13–14
Values
- 9–12
- Moderate Impairment
- Drowsy, confused, may have motor weakness; high aspiration risk
- ICU-level care; frequent neuro checks; consider intubation risk
Property
9–12
Values
- ≤ 8
- Coma / Severe Impairment
- No purposeful response; cannot protect airway; no corneal reflex expected
- INTUBATE to protect airway; ICU care; neuro checks q15min or continuous monitoring
Property
≤ 8
Columns
- GCS Total
- Severity Level
- Characteristics
- Clinical Action
Table Title
Glasgow Coma Scale (GCS) Severity & Interpretation
Rows
Values
- Normal
- Equal, 2–6 mm, briskly reactive
- Intact CN II (afferent) and CN III (efferent); normal brainstem
- Reassuring; no immediate emergency
Property
Normal
Values
- Unilateral Dilated & Fixed
- One side >6 mm, unreactive; other side normal
- Uncal herniation compressing CN III on affected side
- NEUROLOGIC EMERGENCY; call physician immediately; indicates herniation
Property
Unilateral Blown Pupil
Values
- Both >6 mm, fixed
- Severe midbrain necrosis; end-stage increased ICP; anoxia
- Grave prognosis; often associated with brain death or terminal decline
- Extremely poor outcome; may indicate irreversible damage
Property
Bilateral Fixed & Dilated
Values
- Both 1–2 mm, fixed
- Pontine hemorrhage; opioid overdose; brainstem stroke
- Suggests brainstem damage (if acute) or opioid effect (if drug history)
- If opioid suspected, administer naloxone; if brainstem, grave prognosis
Property
Pinpoint Pupils
Values
- Unequal pupils (≥2 mm difference)
- Benign familial (<1 mm); Horner syndrome; CN III compression
- If acute and >1 mm, requires investigation; if chronic and stable, may be benign
- Urgent imaging if acute; less urgent if chronic and pupil reactive
Property
Anisocoria
Columns
- Pupil Finding
- Size & Reaction
- Associated Condition/Cause
- Neurologic Significance
Table Title
Pupil Findings & Associated Conditions
Rows
Values
- CT
- Fast (~5–10 min)
- Acute stroke, hemorrhage, trauma, skull fracture, mass effect
- Lower soft-tissue resolution; radiation exposure; may miss early ischemia
- Iodine contrast; screen for shellfish/iodine allergy and renal function
Property
CT Head
Values
- MRI
- Slow (30–60 min)
- Chronic lesions, tumors, demyelination (MS), early ischemia, brainstem
- Metal implants contraindicated; loud; closed space (claustrophobia risk); not for acute emergencies
- Gadolinium contrast; risk in renal disease (NSF); screen for GFR <30
Property
MRI Brain
Values
- BOTH
- CT FIRST (minutes)
- Non-contrast CT immediately to rule out hemorrhage; if negative, CT angio/perfusion or MRI to assess tissue
- Delays in imaging delay treatment; time = brain; decisions made based on CT findings
- Consider thrombolytic vs endovascular therapy based on imaging within window
Property
Which for Acute Stroke?
Columns
- Modality
- Speed
- Best Uses
- Limitations/Contraindications
- Contrast Concerns
Table Title
CT vs MRI: Clinical Decision-Making
Rows
Values
- Clear, colorless
- Cloudy, turbid, milky
- Clear or slightly turbid
Property
Appearance
Values
- 0–5/μL
- >1000/μL (often 5,000–10,000+)
- 100–500/μL initially
Property
WBC Count
Values
- Lymphocytes
- Neutrophils (>90%)
- Lymphocytes (early polymorphs, then lymphocytes)
Property
WBC Predominance
Values
- 15–45 mg/dL
- >100 mg/dL (often 200–500)
- 50–100 mg/dL (mildly elevated)
Property
Protein
Values
- 40–70 mg/dL (~60% serum)
- <40 mg/dL (CSF:serum ratio <0.4)
- Normal or slightly low (CSF:serum ratio >0.4)
Property
Glucose
Values
- Negative
- Often positive (50–80% sensitivity)
- Negative
Property
Gram Stain/Culture
Columns
- CSF Parameter
- Normal
- Bacterial Meningitis
- Viral Meningitis
Table Title
Normal CSF Values vs Bacterial vs Viral Meningitis
Rows
Values
- 5/5
- Normal full strength; moves against full resistance
- Patient can overcome examiner resistance in all directions
- Normal; no motor deficit
Property
5
Values
- 4+/5
- Moves against strong resistance
- Slight difficulty with resistance; nearly normal
- Mild weakness; watch for progression
Property
4+
Values
- 4/5
- Moves against moderate resistance
- Patient can move but resistance overcomes effort noticeably
- Moderate weakness; clinically significant
Property
4
Values
- 4−/5
- Moves against light resistance
- Barely overcomes light resistance
- Moderate-to-severe weakness; high concern
Property
4−
Values
- 3/5
- Moves against gravity
- Can lift arm/leg off table but cannot overcome any resistance
- Severe weakness; significant functional loss
Property
3
Values
- 2/5
- Movement with gravity eliminated
- Can move only if limb is supported (gravity not opposed)
- Very severe weakness; essentially non-functional
Property
2
Values
- 1/5
- Flicker of contraction only
- Visible/palpable muscle twitch but no movement
- Paralyzed; severe damage
Property
1
Values
- 0/5
- No contraction
- No visible or palpable muscle activity
- Complete paralysis; severe damage
Property
0
Columns
- Grade
- Definition
- Clinical Presentation
- Significance
Table Title
Motor Strength Grading (0–5 Scale)
Rows
Values
- Flexed, adducted toward core
- Extended and rigidly pronated
Property
Arms
Values
- Extended (sometimes flexed)
- Extended
Property
Legs
Values
- Above brainstem (cerebral hemispheres, midbrain)
- Brainstem (midbrain, pons, upper medulla)
Property
Lesion Location
Values
- Less severe; better prognosis than decerebrate
- More severe; worse prognosis
Property
Severity
Values
- May evolve to decerebrate
- Indicates worsening and is ominous sign
Property
Progression
Values
- Significant dysfunction but some cerebral function preserved
- Brainstem failure; minimal cortical function; high mortality
Property
Clinical Implication
Columns
- Feature
- Decorticate (Flexion)
- Decerebrate (Extension)
Table Title
Decorticate vs Decerebrate Posturing
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