Chapter 38: Assessment of the Nervous System

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Welcome to the Deep Dive.

Today we're tackling one of the most foundational,

really critical subjects in nursing,

assessing the nervous system.

Absolutely fundamental.

This isn't just about hitting the books on anatomy.

It's really about seeing those structures in action and, well, spotting life -threatening changes fast.

It's the blueprint.

It really is.

And our goal here is efficiency for you.

We're pulling out the absolute essentials from the sources, the structure, the risks, the safety points.

We'll be zeroing in on four core concepts that honestly guide everything cognition, mobility, sensory perception,

and yeah, perfusion, crucial stuff.

Exactly.

We'll hit the key anatomy quickly, define those terms you absolutely have to know, like Bovinsky sign, decerebrate posturing, and then really dig into those rapid checks and the safety priorities for diagnostics.

So let's dive right in, maybe starting at the very beginning.

The neuron.

Okay, so the neuron, we all get the basics.

Cell body, dendrites, axon.

But clinically speaking, what's the big deal about the white matter?

Ah, the white matter.

It's critical.

Basically, that's your axon wrapped in myelin.

The myelin sheath.

Right, the sheath.

And myelin is all about speed.

It lets those nerve impulses literally jump along the axon.

Super fast transmission.

So if that myelin gets damaged, like you see in MS, multiple sclerosis, well, that impulse slows way down or stops.

And that directly explains the fatigue,

the loss of function.

Precisely.

It links right back to that anatomy.

Okay, so if we think of the nervous system like the complex highway system, we need to know which way the traffic flows.

We do.

You've got the CNS brain and spinal cord and the PNS, the peripheral nerves.

And information travels two main ways.

Afferent is sensory input signals going towards the brain and spinal cord.

Like touching something hot.

Exactly.

And then afferent is motor output signals going away from the CNS, telling muscles to move for mobility.

Got it.

And then there's the ANS, the autonomic nervous system, the stuff we don't consciously control.

This is where assessment gets really interesting, I think.

Oh, definitely.

It runs all the involuntary things, heart rate, breathing, digestion.

You've got the sympathetic side.

Fight or flight.

Right.

Fight or flight.

Think stress, shock, fast heart rate, maybe sweating.

Then there's the parasympathetic.

Feed and breed, sometimes called.

Yeah, or rest and digest.

It slows things down.

Understanding which system is sort of in charge at any moment tells you a lot about the patient's overall state.

Okay, let's zoom into the brain itself.

The cerebral cortex, that's the wrinkly outer layer, right?

Seat of intelligence, memory.

But it's specialized.

If you had to pick, say, two lobes where damage causes really dramatic, obvious changes for a nurse to spot.

Good question.

I'd probably highlight the frontal and temporal lobes.

The frontal lobe.

That's your executive suite.

Judgment, reasoning, planning,

even personality.

Plus, it's got the motor strip and Broca's area for forming spooch.

So damage there could mean huge personality shifts or trouble speaking.

Absolutely.

They might not be able to plan simple tasks or they might say things completely out of character or they struggle to get words out even if they know what they want to say.

That's Broca's aphasia.

And the temporal lobe.

What's key there?

Hearing, primarily.

But critically, it holds Wernicke's area.

That's where you understand language.

Ah, so different from Broca's.

Very different.

With Wernicke's aphasia, they might speak fluently, but it's often nonsensical and they can't comprehend what you're telling them.

Big implications for communication and safety.

We can't forget the cerebellum tucked away at the back.

Seems small, but it's mighty.

Oh, it's the master coordinator.

It controls movement on the same side of the body, ipsilateral control.

Essential for balance, equilibrium.

It lets you do smooth coordinated movements, judge distances, you know, like reaching for a cup without knocking it over.

So if that's damaged,

we'd see.

Clumsiness, staggering gait, maybe tremors when they try to do something specific in tension tremors.

Problems with fine motor skills.

Okay, structure function,

but none of it works without good plumbing.

Perfusion, blood flow to the brain.

Talk about the circle of Willis.

Why is that structure so important, especially thinking about strokes?

It's this amazing arterial circle at the base of the brain fed by the carotids and vertebrals.

It's like a traffic roundabout, providing backup routes if one artery is blocked.

But the major arteries branch off that circle, like the middle cerebral artery, the MCA, which is notorious in stroke.

Exactly.

It supplies a huge territory of the cerebrum.

So an MCA stroke often causes massive deficits, face, arm, maybe speech problems, depending on the side.

It highlights how critical perfusion is.

And don't forget the blood brain barrier that specialized lining in the brain's capillaries.

Right, the gatekeeper.

Pretty much.

It keeps harmful substances out, which is great, but it also makes it tricky to get some medications into the brain.

Okay, so we have this incredibly complex high -speed system.

Now let's add layers.

How does normal aging change things and what risks should we be advising patients about?

Well, some advice is pretty straightforward, though maybe hard to follow.

Avoiding super risky stuff, diving in shallow water, extreme sports without helmets, definitely avoiding substance abuse.

But linking back to perfusion smoking is a huge one.

Because it constricts blood vessels.

Everywhere,

including the brain.

It directly reduces cerebral perfusion, jacks up stroke risk.

It's a major modifiable risk factor we have to counsel on.

Right.

Now, shifting gears to aging,

this is so key for assessment knowing what's a normal slowdown versus a red flag, what cognitive changes are expected.

Yeah, this trips people up.

It's completely normal for cognitive processing speed to slow down a bit, so you just need to give older adults a little more time to think and respond.

Don't rush them.

Okay, it will.

Recent memory might decline slightly.

Not profound dementia, but maybe forgetting where they put their keys more often.

Reinforcing teaching, using memory aids, that becomes important.

So slower processing,

maybe slightly fuzzier recent memory.

That's normal.

Severe confusion is not.

Absolutely not.

Significant cognitive decline isn't a normal part of aging.

It points towards pathology.

What about physical changes?

Things that directly impact safety.

Sensory perception changes are big, especially touch and vibration sense often decreased in the feet and legs.

Which affects their balance.

Directly.

It impairs proprioception, that sense of where your body parts are without looking.

Huge fall risk.

Also, sleep patterns often change.

They might go to bed earlier, wake up earlier, nap more during the day.

That's usually normal.

Okay, so if you know your patient has decreased touch sensation in their feet,

what's the critical nursing advice?

The safety check.

Two key things.

First,

constantly remind them to look down and see where they're placing their feet when they walk.

They can't rely on feel as much.

Second, water temperature.

Because they might not feel heat accurately, they are at high risk for burns.

They need to use a thermometer or have someone else check bath or shower water.

Crucial safety point.

And speaking of safety, what's the single most important uh -oh sign in an older adult's neuro status?

The one that screams investigate now.

An acute change in mental status.

Sudden confusion, delirium that is never just old age.

Never normal.

Never.

It's often the first sign, sometimes the only sign, of a serious underlying issue that might not even be in the brain.

Think UTI, pneumonia causing low oxygen, or even low blood sugar.

You have to look for those systemic causes immediately.

All right, let's get into the nuts and bolts of the focused assessment.

The checks you do at the bedside, sometimes minute to minute.

If you had to rank findings by importance, what's number one?

Easy.

Level of consciousness.

LOC.

Always LOC.

Always.

A change in LOC, or orientation, is the earliest, the most sensitive indicator that something is going wrong centrally.

Before anything else changes, usually, you need that scale down, Pat.

Alert, lethargic.

Drowsy, but wakes up easily.

Right.

Then stuporous, only wakes up with vigorous, shaking, or painful stimulus.

And finally, comatose unarousable.

And we try to standardize this with the GCS, the Glasgow Coma Scale.

Yeah.

Why is getting that baseline GCS score so critical?

Because it gives us objective numbers.

Eye opening, motor response, verbal response.

It avoids vague descriptions.

It creates a baseline everyone can refer back to.

And here's the absolute must -know safety point.

A drop of two or more points in that GCS total score.

That's clinically significant, full stop.

Don't wait.

Do not wait.

You call the provider, you call the rapid response team immediately.

Waiting for pupils to blow or for posturing is waiting too long.

You've lost time, potentially brain function.

Okay.

Speaking of pupils, cranial nerve, the third check.

We all learn pure LA.

Pupils equal, round, reactive to light and accommodation.

Yes, fundamental check.

But, and this is important to understand the timing, major pupil changes, like fixed and dilated pupils or pinpoint pupils.

Those are actually late signs of serious trouble.

So the LOC and GCS change first.

Almost always rely on those as your earliest warnings.

Pupil changes confirm things are bad, but hopefully you've acted before then.

Moving to motor function.

Before someone becomes totally unresponsive, how can we pick up subtle weak?

The pronator drift test is excellent for this.

Simple, but very telling about cerebral or brain function.

Have the patient hold both arms straight out in front of them, palms facing up, eyes closed,

hold for about say 15, 30 seconds.

If one side is weak due to a central problem, that arm will start to drift downwards and crucially the palm will turn inward.

It pronates.

A subtle sign, but indicates a problem.

Exactly.

Catches weakness early.

And if things progress, if the damage is severe, we might see abnormal posturing.

These look scary.

Decorticate versus decerebrate.

What's the difference and what do they tell us?

They are very serious signs.

Decorticate posturing usually means damage is higher up in the corticospinal tracts.

The arms flex inward towards the core, fists clenched, legs extended and internally rotated.

Arms towards the core, decorticate.

Right.

Decerebrate posturing indicates deeper, more severe damage, usually involving the brain stem.

It's generally a worse sign.

Here, the arms and legs are rigidly extended.

Arms or pronated palms turned outwards backwards and the back might even be arched.

Opsotnos.

Extended pronated arms decerebrate.

Worse prognosis.

Generally, yes.

It signals significant brain stem dysfunction.

Okay, one more reflex before diagnostics.

The Babinski sign.

Ah, the plantar reflex.

Normally, if you stroke the sole of the foot in an adult or child over two, the toes curl downward flex.

The abnormal response, the Babinski sign, is when the big toe goes up, bursa flexes, and the other toes fan out.

And what does that mean if you see it?

It means there's disease or damage somewhere along the central nervous system's motor pathways.

It's a clear sign of an upper motor neuron lesion.

Got it.

And quickly, gait and balance the Romberg test.

This helps differentiate the type of balance problem.

Patient stands feet together, arms at first with eyes open, then closed.

If they sway significantly only when their eyes are closed, the problem is likely proprioception.

They've lost that sense of body position, which they can usually compensate for visually.

Makes sense.

But if they sway badly with eyes open and closed, that points more towards a cerebellar problem, an issue with the brain's coordination center itself.

Okay, we've done our bedside assessment.

We've spotted some worrying signs.

Now we move to diagnostics.

What's the initial prep, thinking labs, and basic imaging safety?

You'll definitely want baseline labs, a BMP, to check electrolytes, glucose is critical, maybe blood gases to rule out hypoxia or CO2 issues.

And before any MRI or CT, that safety screen is non -negotiable.

Any metal implants, pacemaker, old shrapnel, aneurysm clips, especially vital for MRI.

Right.

Now let's talk contrast dye, used in CT angiography, other vascular studies, kidney safety's paramount here.

Who is at high risk for contrast -induced kidney injury?

Okay, key risk factors.

Anyone with pre -existing kidney disease, usually defined as a creatinine around 1 .5 or higher, or a GFR below 60.

Also patients with diabetes, those with heart failure, and generally older adults are at increased risk.

So if you have a high -risk patient needing contrast, what are the absolute must -do nursing precautions?

Hydration, hydration, hydration.

Usually IV normal saline given for several hours before and continued after the scan.

Helps flush the kidneys.

Some protocols might include antecedal cysteine, though evidence varies.

But the critical thing is holding certain meds.

Which ones?

Anything that can stress the kidneys or reduce perfusion.

Metformin is the classic one, hold it usually 24 to 48 hours before and after.

Also, NSI's should typically be held.

Always check facility policy and provider orders, but be vigilant about those meds.

Okay, moving to more invasive tests.

Cerebral angiography, the gold standard for looking at brain blood vessels.

It is.

Great for finding aneurysms, blockages, malformations.

But it's invasive, a catheter goes up, usually via the femoral artery in the groin, right into the brain's arteries.

Which means significant post -procedure risks.

What's the nurse's immediate safety checklist after angiography?

Top priority,

the insertion site.

Check that dressing constantly for any sign of bleeding or swelling, a hematoma.

Keep that leg straight and immobilize as ordered usually for several hours to allow the artery to seal.

And circulation checks.

Absolutely critical.

Check pulses, color, temperature, capillary refill in the foot on that affected side, distal to the site.

Compare it to the other side.

If you see active bleeding,

apply firm manual pressure immediately right on the site and call for help urgently provider or rapid response.

That's a vascular emergency.

Got it.

Okay, another common invasive procedure, lumbar puncture, LP or spinal tap.

You get CSF fluid.

What's the biggest safety contra indication?

When should you not do an LP?

The absolute major contraindication is suspected severely high intracranial pressure, ICP.

Why is that?

Because if you suddenly release that pressure from below by removing CSF, you risk causing the brainstem to herniate downwards through the base of the skull.

It's potentially fatal.

So often a CT scan is done first if high ICP is suspected.

Makes sense.

And during the procedure itself?

Patient positioning is key, usually side lying, curl in a fetal position to open up the spaces between vertebrae.

And they absolutely must hold still.

Movement can cause injury.

Afterwards, monitor the site for CSF leakage and watch for complications like severe headache, nausea, or any change in LOC, which could signal problems like infection or changes in ICP.

Remember, normal CSF should be clear and colorless.

Okay, just to round out diagnoses, quick comparison, CT versus MRI.

When do you use which?

CT is fast, really good for bones and excellent for spotting acute bleeds quickly.

Uses x -rays, so there's radiation exposure.

MRI uses magnets, no ionizing radiation.

It's much better for looking at soft tissues, the brain substance itself, spinal cord, nerve roots.

Takes longer, noisy, and has those metal contraindications.

And briefly EEG and EMG.

EEG, electroencephalogram, records the brain's electrical activity, thinks seizure disorders, it helps pinpoint where they're starting.

Key prep, clean hair, no caffeine or sedatives beforehand,

usually.

EMG, electromyography, tests nerve and muscle function together, sticks small needles into muscles to record electrical activity, used for things like myasthenia gravis, neuropathies, hashtag, hashtag, outro.

So we've really walked through the whole framework, haven't we?

From the neuron and that speedy myelin sheath, through the normal changes of aging, those key assessment points, and the critical safety for diagnostics, it all comes back to those core concepts.

Cognition, mobility, sensory perception, and keeping that perfusion adequate.

Your skill in getting that baseline assessment and catching subtle changes like that LOC shift or GCS drop, well that's what protects neurologic function.

That really is the heart of it.

The nervous system operates at incredible speed, right?

Impulse transmission is almost instantaneous.

So here's the thought to leave you with.

If neurodeterioration, that GCS drop, the appearance of posturing can happen that fast, how do you ensure your assessment, your recognition, and crucially your communication to the team is just as rapid?

How do you match that speed to intervene effectively and preserve your patient's neurological future?

Thank you for joining us for this deep dive into assessing the nervous system.

We hope this really helps streamline things and makes you feel well informed.