Neuromuscular N3 Lecture ORIGINAL

Brain

Spinal cord

the brain acts as the interpretation center

the spinal cord functions as the transmission pathway

Cranial nerves

Spinal (peripheral) nerves

Cranial nerves emerge directly from the brain

outside the brain and spinal cord

Relay information between the brain and the rest of the body

Sensory impulses to the brain

Motor responses from the brain to the body

Both

Transmission of impulses to or from the brain can be affected, leading to sensory or motor dysfunction

Disrupt pathways for nerve impulses --> impairs both sensory and motor functions

Brain may lose ability to properly interpret sensory information or send motor commands to the body

responsible for the sensory and motor functions of the head and neck

Vagus nerve

slows the formation of impulses in the sinus node

Can terminate SVT

Cerebral blood volume will INCREASE, outflow will DECREASE --> increased intracranial pressure

increased intracranial pressure stimulates the vagal nerve --> slows down formation of impulses in the SA node

Bearing down as with a bowel movement or even bending over --> increases thoracic pressure to slow the heart rate

Optic (CN II) --> visual acuity

Oculomotor (CN III) --> pupil constriction, eye movement

Trochler (CN IV) --> able to look down, towards, and away from the nose

Abducens (CN VI) --> able to look left and right

Olfactory (CN I)

Acoustic (CN VIII)

Trigeminal (CN V) --> clench teeth, close eyes, light touch to face

Facial (CN VII) --> facial movement, close eyes, smile

Spinal accessory (CN XI) --> turn head, lift shoulders

Glossopharyngeal (CN IX)

Vagus (CN X) --> uvular and palate movement

Hypoglossal (CN XII)

On --> Olfactory (CN 1)

Occasion --> Optic (CN 2)

Our --> Ocular (CN 3)

Trusty --> Trochlear (CN 4)

Truck --> Trigeminal (CN 5)

Acts --> Abducens (CN 6)

Funny --> Facial (CN 7)

Very --> Vestibulocochlear (CN 8)

Good --> Glossopharyngeal (CN 9)

Vehicle --> Vagus (CN 10)

Any --> Accessory (CN 11)

How --> Hypoglossal (CN 12)

Some Say Marry Money But My Brother Says Bad Business Marry Money

Begins at the bottom of the brainstem (medulla oblongata)

Ends in the lower back

The spinal cord runs from the C1 vertebra to approximately the L1 vertebra

about 18 inches

CSF (cerebrospinal fluid)

The meninges, which consist of the dura mater, arachnoid mater, and pia mater

Inside the spinal column, which is made up of 33 vertebrae

Five vertebrae are fused to form the sacrum (part of the pelvis)

Four small vertebrae are fused to form the coccyx (tailbone)

There are 31 pairs of spinal nerves and roots

Eight pairs of cervical nerves (C1-C8) pass through the cervical (neck) region.

Twelve pairs of thoracic nerves (T1-T12) pass through the thoracic region.

Five pairs of lumbar nerves (L1-L5) pass through the lumbar region.

Five pairs of sacral nerves (S1-S5) are located in the sacral (buttock) region.

One pair of coccygeal nerves (C0) passes through the coccyx.

A dermatome is an area on the body that relies on a specific spinal nerve.

The spinal nerve is critical because it carries all the nerve signals traveling between the dermatome and the brain.

in the epidural space

The cerebral cortex is the outermost layer of the brain that gives it a characteristic wrinkly appearance.

Divided lengthways into two cerebral hemispheres: the right and left

Each hemisphere is divided into four lobes: frontal, parietal, temporal, and occipital, connected by the corpus callosum.

Most brain functions rely on different regions working together, yet each lobe carries out the bulk of certain specific functions.

Touch perception

Movement control

Manipulation of objects

Visual reception

Local orientation

Shape perception

Coordination and balance

Relex motor acts

Voluntary movement

Planning

Intellect

Problem solving, abstract reasoning

Hearing and speech

Long term memory

Face recognition

Object perception

conduction tract for pain, temperature, and pressure sensation

Temperature is regulated by the hypothalamus

Midbrain

Pons

Medulla Oblongata

The midbrain is crucial for eye movement

The pons coordinates facial movements, hearing, and balance

The medulla oblongata regulates breathing, heart rhythm, blood pressure, and swallowing.

Several bifurcations (where a bunch of blood vessels intersect), which make it more vulnerable to aneurysm formation

a filtering mechanism of the capillaries that carry blood to the brain and spinal cord tissue, blocking the passage of certain substances.

The BBB keeps substances in the bloodstream out of the cerebrospinal circulation and brain tissue.

Oxygen and CO2 (no shit sherlock)

Alcohol

Anesthetics

Water

Large molecules such as albumin, anything attached to albumin, and many antibiotics are prevented from passing.

Fentanyl rapidly crosses the blood-brain barrier

Fentanyl is rapidly transferred by the human early placenta

CSF reduces the brain's net weight from 1400g to just 50g by creating a fluid bath

CSF acts as a shock absorber, preventing damage from the brain hitting the cranium

CSF regulates the distribution of metabolites, keeping the brain's external environment stable

Waste products produced by brain cells are excreted into the CSF, which then drains into the bloodstream

CSF is produced by specialized cells in the ventricles of the brain

Approximately 500 ml of CSF is produced daily, ensuring continuous circulation around the CNS

The brain can only contain 120-150 ml of CSF

Excess CSF is drained into the bloodstream through the arachnoid villi

CSF is recycled about 3 times a day

CSF moves from the lateral ventricle --> third ventricle --> fourth ventricle

It moves into the subarachnoid space and/or the central canal of the spinal cord

the normal specific gravity is 1.007

the protein count is 14-45 mg/100 ml

0.5 - 5 cells/mm³

50-75 mg/100 ml

Immunoglobulins and electrolyte levels

Hyperglycemia

Infection --> bacteria or fungi

Inflammation of the CNS

Tumor

Lumbar puncture

Damage to small vessels during a lumbar puncture can cause increased glucose levels in CSF

Brain (80%)

Blood (10%)

CSF (10%)

They work together to maintain a stable intracranial pressure (ICP)

Increase in intracranial pressure --> reduced cerebral blood flow, nerve compression

It disrupts hemodynamic balance, impairing critical functions like heart rate and respiration.

Brain swelling from infection, stroke, or injury

Bleeding from stroke or trauma

Increased CSF production

An increase in CSF caused impaired absorption --> reduced absorption into the blood stream = increase in ICP

Normal ICP is 10-15 mmHg.

IICP can impair oxygen delivery and perfusion to the brain, leading to severe damage.

It can decrease blood flow to the brain or cause the brain to herniate through the opening at the back of the skull.

Rise in systolic blood pressure --> compensatory mechaism to maintain cerebral blood flow

Slow, bounding pulse

Respiratory irregularities

Concentration of PaCO2 in the blood and brain tissue

Increased PaCO2 = vasodilation --> increased cerebral blood flow and higher ICP

Decreased PaCO2 = vasoconstriction --> limits blood flow to the brain, decreased venous outflow

Decreased venous outflow --> increased cerebral blood volume, raising ICP

Ex: Valsalva maneuver

Ventilation helps regulate PaCO2 levels to maintain cerebral blood flow

CPP is the net pressure gradient that drives oxygen delivery to cerebral tissue

Like blood pressure, but for the brain --> maintains perfusion to the brain

Greater pressure = vasoconstriction

Less pressure = vasodilation to maintain blood flow

Decompensation --> hypoxia and cell death

Normal CPP is 70 - 100 mmHg

CPP = MAP (Mean Arterial Pressure) - ICP

(Systolic + 2*Diastolic)/3

above 70 mmHg

if CPP is between 50 - 70 mmHg

if CPP is below 50 mmHg

IICP compresses the brain stem, which contains the medulla, the respiratory center

Fluid restriction

Hypertonic solution --> brings fluids back to the vascular space

Administer diuretics --> Mannitol

Drain excess CSF

Decompressive hemicraniectomy --> literally remove a part of the skull to allow the brain to swell

Risk for infection, damage to exposed brain

Avoiding any vagal stimulation as it can result in increased ICP

Reduces cerebral edema by affecing osmotic gradient between plasma and brain cells

To summarize: moves fluids from brain --> vascular space

removes excess fluid in the vascular space (remember that mannitol and 3% saline moves fluids from brain to vascular)

reduces inflammation and swelling

Increased ICP has serious consequences, including seizures

Reduce fever --> Fever can increase cerebral metabolic demand, increasing ICP and the risk of worsening neurological injury

Decrease headache

Change in LOC (level of consciousness) --> decreased LOC (lethargy to coma, behavioral and speech changes)

presure on the vomiting center located in the medulla oblongata

Cushing's_Triad
- Bradycardia
- Increased systolic blood pressure and widening pulse pressure (difference between systolic and diastolic)
- Slowed, irregular respirations

does not appear until ICP is increased for some time

Indicates brain stem compression

Decreased LOC

Decreased motor response to commands

Decreased sensory response to painful stimuli

Alterations in pupil size and reactivity

Cheyne-Stokes_Respirations
a type of abnormal breathing characterized by a pattern of alternating periods of shallow and deep breathing, followed by pauses (apneas)

Bulging fontanels

Macewen sign --> tapping on skull to hear fluid

Irritability --> poor feeding, high-pitched cry

Setting-sun sign (eyes) --> see picture

Projectile vomiting unrelated to feeding

Early signs are subtle

As pressure increases, the manifestation of symptoms also increases

Irritability, restlessness --> increased restlessness indicates lack of oxygen to brainstem

Behavioral and personality changes

Motor weakness, discoordination

Seizures

Vomiting occurs with or without nausea

Diplopia --> double vision

somnolence

Environmental noise should be eliminated or minimized to reduce stress and prevent increases in ICP.

Suctioning should be questioned and used with caution, as it can increase ICP.

IV fluids and parenteral nutrition should be used initially --> caution to avoid overhydration

Later, gastric feeding via NG or G-tube can be introduced

Risk of aspiration increased due to impaired swallowing or neurological changes

Lumbar puncture can cause a rapid shift in pressure, potentially leading to brain herniation.

CT (Computed Tomography)

MRI (Magnetic Resonance Imaging)

It provides detailed images of blood vessels in the brain to identify blockages or abnormalities affecting ICP.

They evaluate cerebral metabolism and blood flow

It measures cerebral blood flow velocity to detect changes related to ICP.

It directly observes cerebral blood flow using sensors to detect alterations in perfusion.

It measures the brain’s electrical response to external stimuli, assessing neural function and integrity

GCS (Glasgow Coma Scale) score of 8 or less

A GCS score of <8 with respiratory assistance

Deteriorating neurologic condition

Clinicians may use their discretion based on patient status, even without meeting strict criteria.

Widening pulse pressure

Subarachnoid bolt or screw

Subdural/epidural catheter censor

Fiber-optic Transducer-tipped catheter

Ongoing pupil checks

Select cranial nerve assessment

Frequent vitals and ICP

GCS (Glasgow Coma Scale) evaluations

It helps identify any injury or infection that could have caused IICP.

It can reveal conditions or risks that may predispose the patient to increased ICP.

Complete neurological exams, including:
- mental status
- level of consciousness (LOC)
- cranial nerve function.

Cerebellar function

Assess the integrity of the nervous system

Detect neurological changes

To identify any deficits that might indicate worsening neurological status or localized damage.

Score of 15 = unaltered LOC

Score of 3 = extremely decreased LOC --> worst possible score

2.0 - 5.0 mm

oculomotor nerve (CN III)

It may indicate neurological compromise, such as increased ICP or brain herniation, and should be reported immediately.

It lies at the junction of the midbrain and tentorial notch, making it vulnerable to compression from brain herniation or changes in ICP.

Oculomotor nerve compression

Sympathetic pathway disruption from brainstem involvement or certain drugs like morphine.

atropine

extreme stress

Pupils are normally round

Oval pupil may indicate elevated ICP

In millimeters, often using a pupil gauge available on flowsheets.

Indicates deterioration of the upper brainstem (particularly the midbrain and upper pons)

It is an abnormal posturing with rigidity, flexed arms, clenched fists, extended legs, and the arms bent inward toward the body with wrists and fingers held on the chest.

It suggests severe damage to the brain, specifically to the corticospinal tract, and requires immediate medical attention.

Decorticate posture is usually more favorable than decerebrate posture, although both are serious signs.

Yes, decorticate posture may progress to decerebrate posture, or the two may alternate.

It can occur on one or both sides of the body, or only in the arms, and may alternate with decorticate posture.

Yes, a person can display decorticate posture on one side and decerebrate posture on the other.

Pathological sign of neurological injury

Medical emergency

Only 37% of patients with decorticate posturing survive after head injury

Only 10% of patients with decerebrate posturing survive after head injury

LOC --> Glasgow coma scale

Pupillary reaction

Motor and sensory function --> ROM, push/pull against pressure

Vital signs

Reflexes

Open = injury broke skin over the fracture

Closed = injury didn't break skin over the fracture --> Most common

A break in the bone that does not cause movement of the bone

Simplest type of fracture

It involves the bone being pressed inward

May occur with or without a scalp laceration

Involves a fracture at the base of the skull

Often accompanied by bruises around the eyes ("raccoon eyes") and behind the ear ("Battle's sign")

the bone is shattered into multiple pieces

Involves a skull fracture or penetration by an object that violates the integrity of the brain and dura, exposing them to environmental contaminants

Infection (either from the penetrating object or from the environment)

Damage may occur to:
- underlying vessels
- dural sinuses
- brain tissue
- cranial nerves.

Gunshot wounds (GSWs)

Knife injuries

Presence of:
- Battle's sign (bruise behind the ears)
- Raccoon eyes (periorbital ecchymosis)

CSF draining from the nose (rhinorrhea) or ears (otorrhea)

A type of traumatic brain injury caused by a bump, blow, or jolt to the head, or by a hit to the body that causes rapid movement of the head and brain.

Bruising of the brain tissue

Scattered areas of bleeding on the surface of the brain

Most common closed head injury

loss of consciousness

retrograde amnesia (loss of memory for events before injury)

anterograde amnesia (inability to form new memories after the injury)

Headache , vomiting

Psychomotor impairment

Tinnitus

Sensitivity to light and sound

Cervical spine immobilization until spinal injury ruled out --> use log roll to move patient

Nonopioid analgesics --> acetaminophen, ketorolac

CSF leakage --> more serious injury (like a skull fracture or brain injury)

Neuro and mental status assessments should be performed --> monitor cognitive function and any changes in condition

Seizure precautions --> due to risk of seizures following a traumatic brain injury

Damage to brain tissue directly beneath point of impact

Occurs when a force strikes one side of the head hard enough to cause the brain to shift in the opposite direction, leading to injury on the opposite side of the impact

Tears in brain tissue caused by a foreign object or pushed-in bone fragments from a skull fracture --> can lead to secondary hemorrhage and cerebral edema

AKA brain shearing

Occurs when brain is subjected to rapid acceleration and deceleration forces, causing widespread damage to the axons

Acceleration/deceleration forces can lead to the brain rebounding or rotating on the brain stem, resulting in diffuse axonal injury and functional impairment.

An acceleration injury occurs when an external force, such as a vehicle colliding with another, suddenly places the head in motion, such as being rear-ended in a motor vehicle accident (MVA).

Occurs when a moving head is suddenly stopped or strikes a stationary object, leading to potential injury from the sudden halt

These forces can cause the cerebrum to rotate about the brainstem, resulting in shearing, straining, and distortion of brain tissue, particularly affecting the axons in the brainstem and cerebellum.

Small areas of hemorrhage may develop near impact site

Adjacent brain tissue can be destroyed, leading to significant neurological impairment

A mild brain injury (such as a concussion), has no evidence of significant brain injury

May present with headaches and dizziness

Management may include administering acetaminophen q.4h for headaches

A moderate brain injury involves a loss of consciousness lasting from 30 minutes to 6 hours, with a Glasgow Coma Scale score of 9-12.

Patients typically require a short ICU stay to prevent complications such as brain edema, intracranial bleeding, and inadequate tissue perfusion

A severe brain injury is characterized by a loss of consciousness for more than 6 hours and a Glasgow Coma Scale score of 3 to 8.

Patients with a severe brain injury require intensive management in the ICU

Amnesia

Headaches

Dizziness

Seizures --> MOST SERIOUS

Loss of consciousness

Sleepiness/drowsiness

Restlessness or irritability

Disorientation or confusion

Fluids are often restricted in the first 24 hours following a head injury to manage and reduce the risk of cerebral swelling.

Pupil changes

Papilledema (eyeball swelling)

Cushing's triad --> HTN, widened pulse pressure, bradycardia

Hypovolemic shock --> hypotension, tachycardia

Nuchal rigidity --> neck stiffness

Nuchal rigidity can indicate a CSF leak, which may be associated with a severe brain injury

Drainage that is positive for glucose indicates leakage of CSF

Provider should be notified STAT if drainage tests positive for glucose

Hypotension and hypoxia

Increased intracranial pressure

Cerebral edema

Hydrocephalus

Hemorrhage leading to hematomas

Brain herniation

ALL hematomas are potentially life-threatening because they act as space-occupying lesions and are surrounded by edema

a collection of blood located between the dura and arachnoid layer

A subarachnoid hematoma refers to blood located in the subarachnoid space (below the arachnoid layer)

Blood accumulation between the dura mater and the skull

Blood that accumulates within the brain tissue itself

Too much CSF in the brain (specifically the ventricles)

Decreased reabsorption of CSF at the arachnoid villi

Interference or blockage with CSF outflow from the ventricular system

If not treated --> further ICP elevations

Excess fluid puts harmful pressure on the brain

Imaging --> CT, MRI, ultrasound

Lumbar puncture

ICP monitoring

The main treatment involves inserting a shunt into the brain, which is connected to a flexible tube that drains excess CSF into the chest cavity or abdomen

a procedure where a hole is made in the third ventricle in order to divert CSF and alleviate hydrocephalus

Headache

Double vision

Nausea and vomiting

Low grade fever

Seizures

Tenderness along shunt track

Increased sleepiness or exhaustion

Literally just s/s of increased ICP --> may be due to shunt blockage or ineffective CSF drainage

increased ICP --> decreased cerebral perfusion --> brain ischemia and edema

If left untreated --> brain herniates downward towards brainstem OR laterally from a unilateral lesion to cerebral hemisphere

Can lead to irreversible brain damage and possibly death

When, where, and how did the injury occur?

Was there a loss of consciousness involved? If yes, how long?

Has there been any change in the level of consciousness?

Hand dominance (left or right)

Any eye injuries

Allergies

Was the patient a victim of violence?

ABC's --> airway, breathing, circulation

A change in LOC is an early indicator of brain injury and helps detect neurological deterioration.

Headache

Vomiting

Altered mental status

Pupil changes

Cushing's triad --> bradycardia, widened pulse pressure, irregular respiration

Treat all traumatic brain injury patients as if they have a spinal cord injury unless ruled out by imaging

Greater risk for C1 and C2 spinal cord injuries, which can be life-threatening

CT scan --> quickly identifies fractures, bleeding, or swelling

MRI is used to detect soft tissue damage, small contusions, and diffuse axonal injuries (DAI) that may not appear on a CT scan.

non-invasive assessment of raised intracranial pressure, cerebral autoregulation and diagnosis of intracranial haematoma and other space-occupying lesions

Assess function of optic nerves and electrical response to external stimuli, revealing damage to sensory pathways

ABGs --> evaluate oxygenation

CBCs --> check for infection or bleeding

CMP --> electrolytes and organ function

ECG --> monitor cardiac functioning

Toxicology screen --> detect drug or ETOH involvement

Preventing increased ICP to avoid further brain injury and maintain cerebral perfusion

Careful monitoring of electrolytes (esp. sodium) and fluid intake to prevent dehydration or cerebral edema

Elevate HOB 30-45 degrees --> promote venous drainage

Avoid neck flexion or extreme hip flexion --> can increase ICP

used to reduce cerebral metabolism and ICP in severe brain injuries when other interventions fail

Maintain airway patency and oxygenation

Prevent aspiration pneumonia and monitor for respiratory distress

Reduce risk of DVT, pressure ulcers, and pneumonia

Decompressive craniectomy --> relieve ICP

Hematoma evacuation --> stop bleeding

Placement of ventricular drains --> remove excess CSF

To track ICP levels continuously, guiding treatment decisions to prevent brain herniation.

Isometric exercises --> can increase ICP by raising intrathoracic and venous pressure

Mannitol is an osmotic diuretic that reduces ICP by pulling fluid from brain tissues into the bloodstream.

As a loop diuretic, it supports Mannitol by removing excess fluid and reducing cerebral edema.

Reduce inflammation and cerebral edema

Use is controversial due to risk of infection and hyperglycemia

These sedative agents manage agitation, anxiety, and ventilator asynchrony to promote healing.

Can suppress respiration

Can obscure neurological assessments

antiepileptic used to prevent or control seizures following brain injury

Helps control fever and mild pain

not used for fevers caused by HYPOTHALAMIC INJURY due to risk of bleeding

Review interventions for IICP, such as positioning, diuretics, and ICP monitoring, to prevent further damage.

every 1-2 hours or as ordered by the provider

Cardiac and blood pressure changes can indicate autonomic dysfunction, cerebral perfusion issues, or a deteriorating neurological status.

Target ranges for blood pressure (to ensure cerebral perfusion) and heart rate are established and adhered to, adjusting interventions accordingly.

It is managed with cool-air hypothermia techniques, such as sponge baths, cooling blankets, or ice packs.

Reduces brain metabolism and prevents secondary brain injury by lowering the body's temperature

Monitor for shivering (can increase metabolism) and electrolyte imbalances that can occur during rewarming

Hyperventilation can lead to cerebral vasoconstriction, reducing cerebral perfusion and worsening brain injury during this critical period.

PaCO2 should be maintained between 35-38 mm Hg to avoid vasodilation or vasoconstriction that could affect ICP and cerebral blood flow.

PaO2 should remain between 80-100 mm Hg to ensure adequate oxygenation of the brain.

Avoid aggressive hyperventilation, which can lead to excessive reductions in PaCO2, impairing cerebral blood flow.

IV lidocaine suppresses the cough reflex and reduces cerebral metabolic demands by inhibiting sodium channels, potentially lowering ICP.

Collaborate with respiratory therapy to provide humidified air and chest physiotherapy to prevent complications like pneumonia.

Elevate the HOB to 30˚ to promote venous drainage and reduce ICP.

Ensure log rolling during repositioning to maintain spinal alignment.

Maintain CPP > 70 mm Hg to ensure adequate oxygen delivery and prevent secondary brain injury.

ICP waveform monitoring helps guide interventions and optimize CPP by tracking pressure changes in real-time.

Many patients with severe TBI do not survive due to the extensive brain damage

1. Persistent coma

2. Absence of brainstem reflexes

3. Inability to breathe independently

At least one neurologic examination is required, but protocols may vary based on institutional or national guidelines.

Reflexes such as pupillary, corneal, gag, and oculocephalic reflexes must be absent.

An apnea test evaluates the ability to breathe independently by monitoring CO₂ levels without ventilator support.

the C4 spinal nerve

High cervical injuries (C3-C5) can impair the ability to breath

remember C4 innervates the diaphragm