CNRN cheat sheet

Monro-Kellie hypothesis: intracranial volume equals brain plus blood plus cerebrospinal fluid; in the closed skull, an increase in one component must be offset by a decrease in another or intracranial pressure rises.

Cerebral perfusion pressure (CPP) = mean arterial pressure (MAP) - intracranial pressure (ICP); normal adult ICP is about 5-15 mm Hg, and ICP >20 mm Hg is generally treated.

Cerebral autoregulation keeps cerebral blood flow stable across a MAP of about 50-150 mm Hg in healthy adults; autoregulation is impaired after traumatic brain injury and ischemia.

Total cerebrospinal fluid volume in adults is about 150 mL; the choroid plexus produces about 500 mL/day, so CSF turns over roughly 3-4 times daily.

The corticospinal tract carries voluntary motor commands; the dorsal columns carry vibration and proprioception; the spinothalamic tract carries pain and temperature.

The cerebellum coordinates movement, balance, and posture; the basal ganglia modulate movement; the brainstem contains respiratory, cardiac, and cranial nerve nuclei.

The blood-brain barrier uses tight junctions between capillary endothelial cells to restrict large and hydrophilic molecules; lipid-soluble drugs and gases cross more readily.

GABA is the main inhibitory neurotransmitter; glutamate is the main excitatory neurotransmitter; dopamine, acetylcholine, serotonin, and norepinephrine modulate specific pathways.

Cranial nerve III carries pupillary parasympathetic fibers; cranial nerve VII controls facial movement and tastes from the anterior tongue; cranial nerve X supports voice, swallow, and parasympathetic function.

Glasgow Coma Scale: eye opening 1-4, verbal response 1-5, motor response 1-6; total 3-15; intubated verbal response is recorded as 1T.

NIH Stroke Scale ranges from 0-42; higher scores indicate greater stroke deficit and the scale assesses consciousness, gaze, vision, motor function, sensation, language, and neglect.

Cushing triad is hypertension with widened pulse pressure, bradycardia, and irregular respirations; it is a late sign of increased intracranial pressure and herniation.

A fixed and dilated pupil suggests cranial nerve III compression or herniation; pinpoint pupils suggest pontine injury or opioid effect.

Decorticate posturing shows flexed arms and extended legs; decerebrate posturing shows extended arms and legs; both indicate severe brain dysfunction.

ICP waveform: P1 is percussion, P2 is tidal, and P3 is dicrotic; a P2 taller than P1 suggests poor intracranial compliance.

Brain death requires coma, absent brainstem reflexes, and an apnea test; confounders such as sedatives, hypothermia, and shock must be excluded.

A change in level of consciousness often precedes other signs of herniation; neuro checks trend consciousness, pupils, motor response, and vital signs.

Delirium is an acute fluctuating disturbance of attention and awareness; dementia is chronic and progressive, and depression can mimic cognitive impairment.

Eligible ischemic stroke: alteplase 0.9 mg/kg IV, maximum 90 mg; give 10% as a bolus and the remainder over 60 minutes, generally within 4.5 hours of onset.

Mechanical thrombectomy is used for selected large-vessel occlusion up to 24 hours after onset when imaging criteria are met.

Aneurysmal subarachnoid hemorrhage: nimodipine 60 mg PO or NG every 4 hours for 21 days; hypotension and vasospasm are monitored.

Aneurysm precautions include blood pressure control, avoiding Valsalva and strain, and a quiet environment; rebleeding risk is highest early after rupture.

ICP management includes head of bed 30 degrees, midline head, and avoidance of neck compression; short-term hyperventilation to PaCO2 30-35 mm Hg is used for herniation.

Osmotherapy with mannitol 0.25-1 g/kg bolus requires monitoring of osmolality, sodium, renal function, and fluid balance; hypertonic saline is an alternative.

TBI: avoid hypoxia and SBP <90 mm Hg; CPP target is 60-70 mm Hg; BTF age-based SBP thresholds are >=100 mm Hg for 50-69 years and >=110 mm Hg for 15-49 or >70 years.

Spinal shock is transient flaccid paralysis and areflexia after spinal cord injury; neurogenic shock is hypotension with bradycardia from loss of sympathetic tone.

Autonomic dysreflexia occurs with spinal cord injury at T6 or above; noxious stimuli such as bladder distention cause severe hypertension, bradycardia, headache, and sweating.

Multiple sclerosis is immune-mediated central nervous system demyelination; common deficits include fatigue, optic neuritis, sensory loss, weakness, and bladder dysfunction.

Uhthoff phenomenon is temporary worsening of multiple sclerosis symptoms with heat or exercise; core temperature elevation slows demyelinated nerve conduction.

Parkinson disease results from loss of dopaminergic neurons in the substantia nigra; cardinal signs are resting tremor, rigidity, bradykinesia, and postural instability.

Levodopa/carbidopa: carbidopa blocks peripheral decarboxylation; long-term therapy can cause on-off fluctuations and dyskinesias.

Amyotrophic lateral sclerosis causes upper and lower motor neuron degeneration; sensory function is usually spared; riluzole may slow progression.

Myasthenia gravis causes fatigable ptosis, dysphagia, and weakness from neuromuscular junction antibodies; crisis causes respiratory failure.

Guillain-Barre syndrome causes ascending symmetric areflexic weakness; vital capacity is monitored, and IVIG or plasma exchange is used.

Alzheimer disease is progressive cognitive decline; cholinesterase inhibitors are used for mild-moderate disease, and memantine for moderate-severe disease.

After spinal cord injury, upper motor neuron bladder lesions cause spastic bladder and lower motor neuron lesions cause flaccid bladder; intermittent catheterization is common.

Noncontrast head CT is first-line for acute intracranial hemorrhage; MRI is more sensitive for ischemia, demyelination, and soft-tissue detail.

CTA and MRA identify large-vessel occlusion, aneurysm, and vascular malformation; contrast risk includes kidney injury and allergic reaction.

EEG detects seizure activity and status epilepticus; continuous EEG is used in unexplained coma or after cardiac arrest to detect nonconvulsive seizures.

EMG and nerve conduction studies distinguish axonal from demyelinating peripheral nerve disease and can assess neuromuscular junction disorders.

Lumbar puncture: normal adult opening pressure is about 10-20 cm H2O; CSF is sent for cell count, protein, glucose, Gram stain, culture, and targeted tests.

CSF glucose is normally about 60% of serum glucose; low CSF glucose suggests bacterial or fungal meningitis or carcinomatous meningitis.

Transcranial Doppler detects vasospasm after subarachnoid hemorrhage by increased cerebral artery flow velocities; it is also used for sickle cell stroke screening.

Evoked potentials assess visual, auditory, or somatosensory pathways and are useful when the neurological examination is limited.

PET and functional imaging show metabolic activity and are used in epilepsy and dementia evaluation.

Phenytoin and fosphenytoin require cardiac monitoring during loading; therapeutic total phenytoin is about 10-20 mcg/mL, and free phenytoin is measured in hypoalbuminemia.

Levetiracetam is renally cleared; dose adjustment is required in renal impairment, and adverse effects include somnolence, irritability, and behavioral change.

Valproate is broad-spectrum antiseizure medication; risks include hepatotoxicity, pancreatitis, thrombocytopenia, and teratogenicity.

Carbamazepine can cause hyponatremia from SIADH, agranulocytosis, and enzyme induction; sodium and complete blood count are monitored.

Nimodipine is a calcium channel blocker used after subarachnoid hemorrhage; it is not given IV, and hypotension is a major adverse effect.

Mannitol is an osmotic diuretic that pulls water from brain tissue; serum osmolality, sodium, renal function, and fluid balance are monitored because rebound edema can occur.

Hypertonic saline raises serum sodium and pulls water from brain tissue; sodium is monitored closely to avoid rapid correction.

Corticosteroids reduce vasogenic edema around brain tumors; steroids are not recommended for traumatic brain injury or acute ischemic stroke.

Dopamine antagonists can worsen Parkinsonism; metoclopramide and antipsychotics require caution in Parkinson disease.

Fall risk increases with gait and balance impairment, sedatives, orthostatic hypotension, and cognitive impairment; validated screening identifies high-risk patients.

After stroke, oral intake is withheld until a bedside swallow screen is passed; failed or unscreened patients remain NPO to prevent aspiration pneumonia.

Seizure precautions include padded rails, available suction and oxygen, and avoidance of restraints during seizure; seizure duration is timed and the airway protected.

External ventricular drain safety: the system is kept at the prescribed height, zeroed at the tragus, and protected from disconnection; sudden drainage changes are reported.

Restraint use requires a written order, time limits, and frequent monitoring of circulation, skin, and safety; restraints are never tied to side rails.

Structured handoff using SBAR or I-PASS reduces omissions; content includes neuro status, medications, pending tests, and code status.

Delirium risk is reduced by reorientation, sleep hygiene, early mobility, glasses and hearing aids, and avoiding deliriogenic drugs.

VTE prophylaxis after neurosurgery is risk-balanced; mechanical prophylaxis is often first, and anticoagulation timing depends on bleeding risk.

ALARA means keeping radiation exposure as low as reasonably achievable; time, distance, and shielding reduce dose to patients and staff.