NLE Neurosensory Nursing — Neurologic Assessment and DiagnosticsRevision Notes

Formulas

Exam Tips

• Memorize the CPP formula: CPP = MAP − ICP. NLE questions may give you two values and ask you to calculate or interpret the third.
• Remember the three components of the skull (Monro-Kellie): brain (80%), blood (10%), CSF (10%) — the numbers add up to 100%.
• The brainstem houses vital centers (respiration, heart rate, consciousness). Brainstem damage = life-threatening. This is why decerebrate posturing is more ominous than decorticate.

Key Points

• The nervous system is divided into the Central Nervous System (CNS — brain and spinal cord) and the Peripheral Nervous System (PNS — cranial nerves, spinal nerves, and autonomic nervous system).
• The brain has three major regions: CEREBRUM (higher functions, movement, sensation, speech), CEREBELLUM (coordination and balance), and BRAINSTEM (midbrain, pons, medulla — controls vital functions and consciousness via the reticular activating system).
• MONRO-KELLIE DOCTRINE: The skull is a rigid, fixed-volume box containing three components — brain tissue (~80%), blood (~10%), and cerebrospinal fluid/CSF (~10%). If one component increases, another must decrease to maintain normal ICP; once compensation is exhausted, ICP rises sharply.
• Normal ICP is 5–15 mmHg in adults.
• CEREBRAL PERFUSION PRESSURE (CPP) = MAP − ICP. Normal CPP is 60–100 mmHg. CPP below 50 mmHg causes ischemia; below 30 mmHg is usually incompatible with viable brain tissue.
• CSF is produced by the choroid plexus, circulates in the subarachnoid space, and is reabsorbed by the arachnoid villi. Normal CSF is clear and colorless.
• The blood-brain barrier (BBB) protects the brain from toxins but also limits drug delivery — relevant when choosing antibiotics for meningitis (e.g., must cross the BBB).

Definitions

Section Title

Neurophysiology Review: CNS, PNS, and the Monro-Kellie Doctrine

Common Mistakes

• Confusing CPP and MAP — remember CPP = MAP MINUS ICP, not MAP alone.
• Forgetting that Monro-Kellie applies only inside the rigid skull; infants with open fontanelles have some ability to compensate by allowing the skull to expand.
• Assuming normal ICP is zero — normal is 5–15 mmHg.

Exam Tips

• NLE priority questions: if a neurologic patient shows a CHANGE IN LOC (even slight), this is the PRIORITY finding — report it immediately.
• Maslow prioritization: physiologic safety (airway, breathing, circulation, neurologic status) comes first. A declining LOC threatens all of these.
• The order of orientation loss: TIME is lost first, then PLACE, then PERSON. Orientation to person is the last to go.

Key Points

• LOC is the SINGLE MOST SENSITIVE indicator of neurologic change — a declining LOC is an early warning that precedes changes in vital signs and pupils.
• LOC continuum (least to most impaired): ALERT → LETHARGIC (drowsy but rousable) → OBTUNDED (difficult to arouse) → STUPOROUS (responds only to vigorous or painful stimuli) → COMATOSE (no purposeful response).
• Always document orientation: PERSON (knows own name) → PLACE (knows where they are) → TIME (knows date/day) → SITUATION/EVENT. Orientation to person is the last to be lost and first to recover.
• Describe the SPECIFIC STIMULUS used and the patient's ACTUAL RESPONSE rather than vague labels. Example: 'Patient opened eyes and moaned when sternal rub applied' is better than 'patient is stuporous.'
• Any DECREASE in LOC must be reported immediately — it is a priority nursing assessment finding under the nursing process (assessment → diagnosis → planning → implementation → evaluation).
• NANDA Nursing Diagnosis: Decreased Intracranial Adaptive Capacity related to increased ICP; Acute Confusion related to altered neurologic function; Risk for Ineffective Cerebral Tissue Perfusion.

Definitions

Section Title

Level of Consciousness (LOC) – The Most Sensitive Neurologic Indicator

Common Mistakes

• Using only the label (e.g., 'stuporous') without describing the stimulus and response — this is not objective documentation.
• Forgetting that LOC changes precede pupil changes and vital sign changes (Cushing's triad is a LATE sign).
• Confusing 'unresponsive' with 'comatose' — a patient may be unresponsive due to sleep, drugs, or metabolic causes, not necessarily structural brain damage.

Formulas

Exam Tips

• MEMORIZE the GCS structure: Eye (1–4), Verbal (1–5), Motor (1–6). A normal person = E4 V5 M6 = 15. A totally unresponsive patient = E1 V1 M1 = 3.
• NLE frequently tests: 'What GCS score requires intubation?' Answer: 8 or below.
• Mnemonic for decorticate vs. decerebrate: 'Decorticate = Curl toward core (flexion); Decerebrate = Dead straight/extended (brainstem = worse).'
• Motor response carries the MOST prognostic weight in the GCS — pay close attention to changes in the motor score.
• NLE scenario tip: If a patient progresses from decorticate to decerebrate posturing, the PRIORITY action is to notify the physician/resident immediately and prepare for emergency interventions.

Key Points

• The GCS is the gold-standard, objective tool for grading consciousness. It tests THREE responses: Eye opening (E), Verbal response (V), and Best motor response (M).
• SCORING RANGE: Minimum = 3 (E1+V1+M1, deepest coma, no response); Maximum = 15 (E4+V5+M6, fully alert and normal).
• ALWAYS record individual scores (e.g., E3 V4 M5 = 12) — not just the total — for accurate serial comparison.
• EYE OPENING (E, scored 1–4): 4=Spontaneous, 3=To voice/verbal command, 2=To pain, 1=None.
• VERBAL RESPONSE (V, scored 1–5): 5=Oriented (knows name, place, date), 4=Confused (sentences but disoriented), 3=Inappropriate words (random words, no conversation), 2=Incomprehensible sounds (moans, groans), 1=None.
• BEST MOTOR RESPONSE (M, scored 1–6): 6=Obeys commands, 5=Localizes pain (purposeful movement toward stimulus), 4=Withdraws from pain, 3=Abnormal flexion/Decorticate, 2=Abnormal extension/Decerebrate, 1=None.
• INTERPRETATION: GCS 13–15 = Mild impairment; GCS 9–12 = Moderate impairment; GCS ≤8 = Severe/Coma.
• CRITICAL THRESHOLD: GCS of 8 or below is the classic threshold for intubation to protect the airway.
• A DROP OF 2 OR MORE POINTS in total GCS is clinically significant and requires immediate physician notification.
• DECORTICATE posturing (M3): Arms flexed and drawn toward the core (chest), wrists flexed, legs extended. Indicates damage to the CEREBRAL HEMISPHERES (above the brainstem). Less severe than decerebrate.
• DECEREBRATE posturing (M2): Arms extended, rigidly pronated (palms down), wrists flexed, legs extended and internally rotated. Indicates BRAINSTEM damage. More severe and ominous.
• Progression from DECORTICATE to DECEREBRATE signals neurologic DETERIORATION — an emergency.

Definitions

Section Title

Glasgow Coma Scale (GCS) – Standardized Consciousness Grading

Common Mistakes

• Recording only the total GCS score (e.g., 'GCS 10') without the individual component scores (e.g., E3 V3 M4) — components are needed for accurate trending.
• Confusing decorticate and decerebrate: Mnemonic — deCORticate = arms toward the CORE (flexed); deCEREbrate = arms EXTENDED like a 'straight' line (brainstem).
• Forgetting that the MINIMUM GCS is 3 (not zero) — a completely unresponsive patient scores 1+1+1=3.
• Applying the GCS to patients who are intubated or aphasic without noting that Verbal response cannot be accurately scored (record as 'V=T' for intubated/tracheostomy).
• Missing the significance of a 2-point drop — students sometimes only report a change when the total drops to ≤8, but ANY drop of ≥2 is reportable.

Exam Tips

• Mnemonic for CN types (sensory, motor, or both): 'Some Say Marry Money But My Brother Says Big Brains Matter More' — S=Sensory, M=Motor, B=Both (CN I-XII in order).
• BLOWN PUPIL = CN III compression = herniation = EMERGENCY. This is one of the most tested NLE scenarios in neurosensory nursing.
• For CN testing, remember the CORNEAL REFLEX tests both CN V (sensory) AND CN VII (motor/blink) — absence has implications for eye care (corneal lubricants, eye patching).
• If a patient has absent gag reflex (CN IX/X), your priority nursing diagnosis is Risk for Aspiration — position patient appropriately (HOB elevated, lateral if unconscious, NPO).

Key Points

• Pupils are assessed for SIZE (normal 2–6 mm), EQUALITY (both same size), SHAPE (round), and REACTION TO LIGHT (brisk constriction = PERRLA: Pupils Equal, Round, Reactive to Light and Accommodation).
• UNILATERAL FIXED, DILATED ('BLOWN') PUPIL = NEUROLOGIC EMERGENCY. Indicates uncal (tentorial) herniation compressing CN III (oculomotor nerve) on that side. Requires immediate intervention.
• BILATERAL FIXED AND DILATED pupils indicate severe midbrain damage; grave prognosis.
• PINPOINT PUPILS (miosis, <2 mm) suggest: PONTINE hemorrhage/damage OR opioid/narcotic toxicity (e.g., morphine overdose — common clinical scenario in Philippine hospitals).
• The 12 Cranial Nerves must be tested in a full neurologic exam. Mnemonic for names: 'On Old Olympus Towering Tops, A Finn And German Viewed Some Hops' (CN I through XII).
• CN I (Olfactory) — smell; CN II (Optic) — vision; CN III (Oculomotor), IV (Trochlear), VI (Abducens) — eye movements, pupil constriction, eyelid.
• CN V (Trigeminal) — facial sensation, mastication, corneal reflex (sensory limb); CN VII (Facial) — facial expression, taste anterior 2/3 tongue, corneal reflex (motor/blink limb).
• CN VIII (Vestibulocochlear/Acoustic) — hearing and balance; CN IX (Glossopharyngeal) and CN X (Vagus) — swallowing, gag reflex, phonation.
• CN XI (Spinal Accessory) — shoulder shrug (trapezius) and head turning (sternocleidomastoid); CN XII (Hypoglossal) — tongue movement.
• CORNEAL REFLEX: Tests CN V (sensory) and CN VII (motor/blink). Absent corneal reflex indicates CN V or VII dysfunction — important in comatose patients to assess risk of corneal injury.
• GAG REFLEX: Tests CN IX and X. Absent gag reflex in a patient with decreased LOC = HIGH RISK for aspiration — priority nursing diagnosis: Risk for Aspiration.

Definitions

Section Title

Pupillary Assessment and Cranial Nerve Testing

Common Mistakes

• Checking only one eye for light reaction — ALWAYS check direct AND consensual response in BOTH eyes.
• Forgetting that a unilateral blown pupil is IPSILATERAL (same side) to the herniation — the blown pupil indicates which side is herniating.
• Confusing pinpoint pupils: Both pontine hemorrhage AND opioid toxicity cause miosis — differentiate by context (trauma vs. medications, plus other clinical signs).
• Not knowing which cranial nerve controls what — NLE commonly tests CN-specific functions. Focus on CN II, III, V, VII, IX, X, XII as most commonly tested.

Exam Tips

• NLE tip: 'Positive Babinski in an adult' = always a wrong/abnormal finding = UMN lesion. Do NOT confuse with infants.
• Motor grading mnemonic: 0=Nothing, 1=Flicker, 2=Gravity gone, 3=Gravity only, 4=Some resistance, 5=Strong/normal.
• Cerebellar lesions produce IPSILATERAL signs (same side as lesion) — different from cortical/UMN lesions which produce CONTRALATERAL deficits.
• DTR of 2+ is NORMAL. Anything 0, 1+, 3+, or 4+ should be noted as abnormal and trended.

Key Points

• MOTOR STRENGTH GRADING (0–5 scale): 0=No contraction, 1=Flicker/trace contraction (no movement), 2=Full ROM with gravity eliminated, 3=Full ROM against gravity (no additional resistance), 4=Movement against some resistance (less than normal), 5=Normal full strength against full resistance.
• Compare bilateral muscle strength — asymmetry (one side weaker) suggests a unilateral lesion (e.g., stroke affecting one hemisphere).
• PRONATOR DRIFT TEST: A subtle test for upper extremity weakness. Ask the patient to extend both arms with palms up and eyes closed for 20–30 seconds. Downward drift and pronation of one arm indicates contralateral hemisphere weakness.
• CEREBELLAR FUNCTION tests: Finger-to-nose (dysmetria = past-pointing indicates cerebellar lesion), heel-to-shin, rapid alternating movements (dysdiadochokinesia), and gait assessment (ataxia = broad-based, unsteady gait).
• SENSORY TESTING evaluates: Light touch (cotton wisp), pain (pin-prick), temperature, vibration (tuning fork on bony prominences), and proprioception (position sense). Compare bilateral responses.
• DEEP TENDON REFLEXES (DTR) graded 0–4+: 0=Absent, 1+=Diminished, 2+=Normal, 3+=Increased/brisk, 4+=Hyperreflexic (clonus may be present). Graded 0 or 4+ are abnormal.
• BABINSKI REFLEX (plantar reflex): Stroke the outer sole of the foot from heel to toe with a blunt instrument. NORMAL in adults = toes CURL DOWN (flexor plantar response). ABNORMAL (POSITIVE BABINSKI) in adults = GREAT TOE DORSIFLEXES (extends upward) with FANNING of other toes. A positive Babinski in adults indicates an UPPER MOTOR NEURON (UMN) LESION (brain or spinal cord).
• Upper Motor Neuron (UMN) lesion signs: spasticity, hyperreflexia, positive Babinski, minimal muscle atrophy. Lower Motor Neuron (LMN) lesion signs: flaccidity, hyporeflexia/areflexia, significant muscle atrophy, fasciculations.

Definitions

Section Title

Motor, Sensory, and Reflex Testing

Common Mistakes

• Confusing the Babinski reflex in adults vs. infants — POSITIVE Babinski is NORMAL in infants (incomplete myelination) but ABNORMAL in adults (UMN lesion).
• Forgetting to compare bilateral strength and reflexes — laterality is key to localizing lesions.
• Confusing UMN and LMN signs: UMN = SPASTIC and HYPERREFLEXIC; LMN = FLACCID and HYPOREFLEXIC.
• Using a motor grade of 0–5 incorrectly: Grade 3 means movement against GRAVITY ONLY (not against resistance).

Exam Tips

• Cushing's triad mnemonic: 'BBC' — Blood pressure up (BP↑ with wide pulse pressure), Bradycardia (B), Crazy/irregular breathing (C). This is a LATE and LIFE-THREATENING sign.
• EARLY signs of increased ICP: declining LOC, headache (worse in the morning or with Valsalva), nausea/vomiting (often projectile), papilledema.
• NLE priority: If a patient develops Cushing's triad, the PRIORITY is to notify the physician IMMEDIATELY and implement ICP-reducing measures (elevate HOB 30°, hyperventilate if ordered, prepare for osmotic diuresis/mannitol).
• Know the respiratory patterns and their associated lesion levels: Cheyne-Stokes = hemispheres/diencephalon; Central neurogenic hyperventilation = midbrain; Ataxic = medulla (worst).

Key Points

• SERIAL NEURO CHECKS ('neuro vitals') combine: LOC/GCS, pupil assessment (PERRLA), motor and sensory function, and vital signs at regular intervals. Frequency increases when the patient is unstable (e.g., every 15–30 minutes in acute settings).
• CUSHING'S TRIAD is a LATE and OMINOUS sign of severely increased ICP and impending brainstem herniation. It consists of THREE components: (1) RISING SYSTOLIC BLOOD PRESSURE with a WIDENING PULSE PRESSURE, (2) BRADYCARDIA (slow heart rate), and (3) IRREGULAR/SLOW RESPIRATIONS.
• Think of Cushing's triad as the body's last-ditch attempt to maintain cerebral perfusion when ICP is dangerously high — the brainstem triggers a massive sympathetic surge to raise BP, with reflex bradycardia via the vagus nerve.
• RISING TEMPERATURE may reflect hypothalamic involvement (the hypothalamus regulates temperature — damage = neurogenic fever) or infection (meningitis, abscess).
• BLOOD PRESSURE: Hypertension in a neurologic patient often represents Cushing's response — do NOT treat BP without considering ICP context (lowering BP may further reduce CPP).
• RESPIRATORY PATTERNS in neurologic patients: Cheyne-Stokes (bilateral hemispheric damage — crescendo-decrescendo with apnea), Central neurogenic hyperventilation (midbrain damage — deep, rapid breathing), Ataxic/Biot's (medullary damage — completely irregular = MOST OMINOUS, impending respiratory arrest).
• POSITIONING: Keep head of bed (HOB) at 30–45 degrees unless contraindicated to promote venous drainage and reduce ICP. Avoid extreme flexion/extension of the neck and hip flexion >90°.
• Priority NANDA Diagnoses for Increased ICP: Decreased Intracranial Adaptive Capacity; Ineffective Cerebral Tissue Perfusion; Risk for Aspiration; Impaired Gas Exchange.

Definitions

Section Title

Neuro Checks, Vital Signs, and Cushing's Triad

Common Mistakes

• Thinking Cushing's triad is an EARLY sign — it is LATE (LOC changes and headache are EARLY signs of increased ICP).
• Treating the hypertension of Cushing's triad aggressively without considering ICP — lowering MAP can reduce CPP and worsen ischemia.
• Forgetting the three components of Cushing's triad: many students remember the BP change but forget bradycardia or irregular respirations.
• Not increasing neuro check frequency when a patient's condition is deteriorating — assessment intervals should be based on acuity.

Exam Tips

• NLE high-yield: The correct LP level is L3–L4 or L4–L5 (BELOW L1–L2 where the cord ends). The reason: avoid spinal cord injury.
• Priority nursing action BEFORE LP: Assess for signs of increased ICP (papilledema, CT mass effect) — if present, LP is CONTRAINDICATED.
• Priority nursing action AFTER LP: Keep patient FLAT for ordered time AND encourage increased fluid intake.
• Post-LP headache: position-dependent (worse sitting/standing, better lying flat) = CSF leak. Treatment = flat, fluids, analgesia; if refractory = blood patch.
• Remember CSF color significance: Clear = normal; Cloudy = infection; Bloody or Xanthochromic = hemorrhage.

Key Points

• LUMBAR PUNCTURE (LP) / Spinal Tap: Samples CSF from the subarachnoid space, usually between L3–L4 or L4–L5 (below the spinal cord terminus at approximately L1–L2 to avoid cord injury).
• INDICATIONS: Diagnosis of meningitis, subarachnoid hemorrhage (SAH), multiple sclerosis, Guillain-Barré syndrome; measurement of opening CSF pressure; administration of intrathecal medications.
• ABSOLUTE CONTRAINDICATION: Suspected or confirmed INCREASED ICP (papilledema, CT evidence of mass effect). Sudden pressure release at the lumbar level with high cranial ICP can precipitate fatal downward brainstem (tonsillar) herniation.
• NORMAL CSF CHARACTERISTICS: Clear and colorless ('like water'), opening pressure 6–20 cmH2O (or 5–15 mmHg), protein 15–45 mg/dL, glucose 50–80 mg/dL (approximately 60–70% of serum glucose), 0–5 WBC (lymphocytes), no RBCs.
• ABNORMAL CSF: CLOUDY = infection (meningitis — increased WBCs, protein↑, glucose↓); BLOODY or XANTHOCHROMIC (yellow-tinged) = subarachnoid hemorrhage (xanthochromia from RBC breakdown products — differentiates true SAH from traumatic tap).
• PRE-PROCEDURE NURSING CARE: Verify informed consent (in line with RA 9173 and patient rights), obtain baseline vital signs and neuro assessment, verify no contraindications (assess for papilledema, review CT results), ensure bladder is empty, explain procedure and positioning.
• PATIENT POSITIONING: LATERAL RECUMBENT (fetal position) — knees drawn to chest, chin to chest, back arched outward — to maximize separation of vertebral spaces. Alternative: sitting position leaning forward over a table.
• INTRA-PROCEDURE: Maintain strict STERILE TECHNIQUE. Assist with positioning and help patient remain still. Monitor for pain, paresthesia, or sudden headache.
• POST-PROCEDURE NURSING CARE: Keep patient FLAT (supine) for 4–8 hours (physician-ordered) to equalize pressure and prevent CSF leakage through the puncture site. ENCOURAGE INCREASED ORAL FLUIDS (increase CSF production to replace what was removed). Monitor for complications: post-LP headache, bleeding, infection, neurologic changes.
• POST-LP HEADACHE (positional/spinal headache): Caused by CSF leakage through the puncture site, lowering CSF pressure. WORSENS when upright, RELIEVES when lying flat. Treatment: flat positioning, increased fluids, analgesics, caffeine; refractory cases may need a BLOOD PATCH (injection of autologous blood into the epidural space to seal the leak).

Definitions

Section Title

Lumbar Puncture (LP) – Procedure, Nursing Care, and Contraindications

Common Mistakes

• Forgetting that INCREASED ICP is an ABSOLUTE contraindication to LP — a common NLE scenario asks what to do before LP (ensure no signs of ICP elevation; review CT scan).
• Positioning the patient SITTING for an LP and forgetting the lateral fetal position is standard for most cases.
• Not instructing the patient to remain FLAT after LP — this is a critical post-procedure instruction.
• Confusing 'xanthochromia' with a 'traumatic tap' — xanthochromia indicates blood was in the CSF BEFORE the tap; a traumatic tap produces bloody CSF that clears in subsequent collection tubes.
• Forgetting to encourage FLUIDS after LP — students often think rest alone is sufficient.

Exam Tips

• NLE gold standard = EVD/Ventriculostomy: most accurate + can drain CSF. Highest infection risk.
• Transducer leveling point: TRAGUS OF THE EAR or OUTER CANTHUS OF THE EYE = Foramen of Monro. This is the most commonly tested nursing action for ICP monitoring.
• Plateau/A waves = EMERGENCY. B waves = concerning but less critical. C waves = least significant.
• For ICP reduction: position (HOB 30°), avoid hypercapnia (hyperventilate if ordered), avoid Valsalva, administer mannitol as ordered, drain CSF via EVD.
• Remember: Normal ICP = 5–15 mmHg; treatment threshold = >20 mmHg sustained; CPP goal = 60–100 mmHg.

Key Points

• ICP MONITORING is indicated for patients at high risk of intracranial hypertension: severe TBI (GCS ≤8), post-neurosurgery, massive stroke, or any condition with suspected ICP elevation.
• Normal ICP: 5–15 mmHg in adults. Sustained ICP >20 mmHg requires treatment.
• TYPES OF ICP MONITORS: (1) INTRAVENTRICULAR CATHETER / VENTRICULOSTOMY / EXTERNAL VENTRICULAR DRAIN (EVD) — GOLD STANDARD; inserted into the lateral ventricle; most accurate; allows therapeutic CSF drainage to reduce ICP; highest infection risk. (2) Subarachnoid bolt (screw) — placed in the subarachnoid space; less accurate, no drainage capability. (3) Epidural sensor — between skull and dura; lowest infection risk; least accurate. (4) Intraparenchymal (fiberoptic) sensor — placed in brain tissue; accurate; no drainage.
• LEVELING THE TRANSDUCER: The transducer must be zeroed and leveled at the FORAMEN OF MONRO, which corresponds to the TRAGUS OF THE EAR or the OUTER CANTHUS OF THE EYE at the bedside. Incorrect leveling gives false readings.
• MAINTAIN CLOSED STERILE SYSTEM to prevent ventriculitis/meningitis — the most serious complication of EVD.
• ICP WAVEFORMS: A (Plateau) waves = sustained ICP >50 mmHg for 5–20 minutes = MOST DANGEROUS, indicates severely impaired compliance; B waves = rhythmic oscillations 20–50 mmHg, related to respirations; C waves = small oscillations related to arterial pulsations, less significant.
• NURSING CARE FOR EVD: Level transducer correctly; maintain closed sterile system; monitor waveforms; clamp the drain per protocol when repositioning the patient; document ICP, CPP, and CSF drainage output (color, clarity, amount); assess insertion site for CSF leak or infection signs.
• INTERVENTIONS TO REDUCE ELEVATED ICP: HOB 30–45°, avoid neck flexion/compression of jugular veins, avoid Valsalva maneuvers (straining, coughing), prevent hypercapnia (CO2 causes cerebral vasodilation → ↑ICP), controlled hyperventilation (brief, to reduce CO2), osmotic therapy (Mannitol 20% IV, Hypertonic saline), sedation/analgesia, CSF drainage via EVD, decompressive craniectomy (surgical).

Definitions

Section Title

Intracranial Pressure (ICP) Monitoring

Common Mistakes

• Forgetting to level the transducer at the foramen of Monro (tragus of ear or outer canthus of eye) — this is a critical and commonly tested nursing action.
• Not clamping the EVD when repositioning the patient — failing to do so can cause uncontrolled CSF drainage and a sudden change in ICP.
• Confusing the types of ICP monitors — EVD is the GOLD STANDARD and the ONLY ONE that can drain CSF; all others only measure.
• Not recognizing plateau (A) waves as an emergency — these indicate impending herniation.

Exam Tips

• NLE standard: CT scan FIRST in acute stroke — to RULE OUT HEMORRHAGE before giving thrombolytics (tPA). If it's hemorrhagic, NO tPA.
• MRI safety mantra: No metal near the magnet. SCREEN for pacemakers, aneurysm clips, cochlear implants, orthopedic hardware.
• EEG prep: CLEAN HAIR (no oils/gels), hold caffeine and stimulants (not usually anti-seizure meds unless specifically ordered).
• Post-angiography (femoral approach): monitor puncture site, distal pulses (pedal pulse), keep leg straight, push fluids.
• Brain death EEG finding: FLAT LINE = electrocerebral silence = no brain activity.

Key Points

• CT SCAN (Computed Tomography): FAST, widely available (standard in most Philippine DOH hospitals), FIRST-LINE in ACUTE settings. Best for detecting ACUTE HEMORRHAGE (blood appears BRIGHT/WHITE/hyperdense on CT), skull fractures, midline shift, and mass effect. USED IMMEDIATELY in suspected stroke to differentiate hemorrhagic from ischemic stroke (treatment differs — thrombolytics for ischemic are CONTRAINDICATED in hemorrhagic stroke).
• CT WITH CONTRAST: Enhances tumors, abscesses, AVM, active inflammation. Assess for IODINE or SHELLFISH ALLERGY (iodinated contrast agent) and check RENAL FUNCTION (creatinine/BUN — contrast nephropathy risk) before administration.
• MRI (Magnetic Resonance Imaging): Superior SOFT-TISSUE DETAIL; detects early ischemia (especially within first hours — diffusion-weighted MRI/DWI), demyelination (multiple sclerosis plaques — periventricular white matter lesions), posterior fossa lesions, spinal cord pathology, and tumors. TAKES LONGER than CT — not ideal for unstable or uncooperative patients.
• MRI SAFETY SCREENING (CRITICAL): MRI uses a powerful magnetic field — screen ALL patients for METAL IMPLANTS (pacemakers, cochlear implants, metallic aneurysm clips, orthopedic hardware, shrapnel/bullet fragments). Remove ALL metal objects (jewelry, hairpins, O2 tanks — must use MRI-compatible equipment). Assess for CLAUSTROPHOBIA — patient may need sedation or an open MRI.
• EEG (Electroencephalography): Records brain's ELECTRICAL ACTIVITY via scalp electrodes. Used to diagnose seizure disorders (identifies epileptiform activity), classify seizure type, monitor seizure activity in status epilepticus, and confirm BRAIN DEATH (electrocerebral silence = flat line). PRE-EEG CARE: Wash hair thoroughly (no oils, sprays, gels); withhold stimulants (caffeine, ephedrine) and sedatives only as specifically ordered; some anti-seizure medications may or may not be held per physician order.
• CEREBRAL ANGIOGRAPHY: Invasive procedure using catheter and contrast to visualize cerebral blood vessels. GOLD STANDARD for diagnosing cerebral aneurysms, arteriovenous malformations (AVM), and vasospasm. PRE-PROCEDURE: Allergy and renal function assessment (contrast), NPO, consent, baseline neuro and VS. POST-PROCEDURE: Monitor PUNCTURE SITE for hematoma/bleeding; assess DISTAL PULSES (femoral approach — check pedal pulses bilaterally); keep extremity straight/immobile; push fluids for contrast excretion; monitor for delayed allergic reaction.
• TRANSCRANIAL DOPPLER (TCD): Non-invasive ultrasound that measures blood flow velocity in cerebral arteries. Used to detect vasospasm after subarachnoid hemorrhage, monitor for emboli, and assess cerebrovascular autoregulation.
• SKULL X-RAY: Rarely used now (largely replaced by CT) but may still appear in NLE. Detects skull fractures, calcifications, and foreign bodies.

Definitions

Section Title

Neurodiagnostic Imaging: CT Scan, MRI, EEG, and Cerebral Angiography

Common Mistakes

• Thinking CT is better than MRI for all conditions — CT is better for ACUTE hemorrhage and is faster; MRI is better for early ischemia, demyelination, and posterior fossa/spinal cord lesions.
• Forgetting to screen for metal implants and pacemakers BEFORE MRI — this is a critical safety step; a pacemaker in an MRI machine is a life-threatening emergency.
• Not checking for iodine/shellfish allergy and renal function before CT with contrast or cerebral angiography.
• Forgetting post-angiography care — monitoring the femoral puncture site and distal pulses is essential to prevent limb-threatening arterial occlusion.