Neuro

Nervous System Overview

• Two major components:
  • Peripheral nervous system (PNS): Includes sympathetic and parasympathetic nervous systems.
  • Central nervous system (CNS): Includes major parts of the brain.

Central Nervous System Components

• It's important to understand functions of each part of the brain to anticipate effects of damage to specific areas.

Cerebral Cortex

• Outermost layer of the brain; contains gray matter.
• Divided into two hemispheres.
• Contains lobes of the brain (e.g., frontal, parietal).

Corpus Callosum

• Connects the cerebral hemispheres via a large group of nerve fibers.

Basal Ganglia

• Located deep within the gray matter of the cerebral hemispheres.
• Controls motor function.

Thalamus

• Borders and surrounds the third ventricle.
• Comprised of tracts of gray matter.
• Center for pain, temperature, and tactile sensations.

Hypothalamus

• Lies beneath the thalamus.
• Responsible for secreting hormones (e.g., antidiuretic hormone, oxytocin).
• Regulates body temperature and secretion from exocrine glands (e.g., sweat, salivary glands).

Cerebellum

• Located in the posterior fossa.
• Controls coordination and balance.

Brain Stem

• Major nerve pathway between the cerebral cortex and the spinal cord.
• Contains the midbrain, pons, and medulla oblongata.
• Controls the respiratory center and involuntary functions of the body.

Meninges

• Layers over the brain: pia mater, arachnoid, and dura mater.
• Acronym PAD helps remember the order.

Pia Mater

• Innermost vascular meningi, laying directly on the brain’s surface.

Arachnoid

• Feathery middle layer.

Dura Mater

• Tough outer layer that is just below the cranium bones.

Subarachnoid Space

• Between the arachnoid and the pia mater.
• Contains the cerebrospinal fluid (CSF).

Cerebrospinal Fluid (CSF)

• Produced in the choroid plexus of the lateral third and fourth ventricles.
• Produced at a rate of about 500 milliliters per day.
• Flows through the ventricular system and enters the subarachnoid space via the fourth ventricle.
• Under normal conditions, CSF flows freely through the subarachnoid space and is reabsorbed through the arachnoid villi.

Ventricles

• Cavities containing CSF; four interconnecting chambers.
• Two lateral ventricles are located in the cerebral hemispheres.
• Lateral ventricles communicate with the third ventricle through the foramen of Monro at the level of the thalamus.
• The third ventricle then joins with the fourth ventricle through the aqueduct of Sylvius.
• Fourth ventricle is located at the level of the pons and medulla.
• CSF then flows into the subarachnoid space, allowing for distribution around the brain and spinal cord.
• Blockage of CSF flow can lead to hydrocephalus.

Peripheral Nervous System

• 12 pairs of cranial nerves arising from the brain.
• Some nerves have motor tracts, some have sensory tracts, and some have both.
• Mnemonic for remembering names and order: "On Old Olympus Towering Top, A Famous Vocal German Viewed Some Hops"
  • Olfactory
  • Optic
  • Oculomotor
  • Trochlear
  • Trigeminal
  • Abducens
  • Facial
  • Vestibulocochlear
  • Glossopharyngeal
  • Vagus
  • Spinal Accessory
  • Hypoglossal.
• Self-reviewing cranial nerves is important to understand their functions and expected findings with nerve damage.

Cranial Sutures and Fontanels

• Understanding when fontanels close is important to recognize abnormalities.
• Anterior fontanel closes around 16-18 months.
• Posterior fontanelle usually closes by two months.
• Premature fusion of sutures can result in craniosynostosis, which may require surgery.
• Assessing the fontanels is part of the physical exam of infants and toddlers.

Autonomic Nervous System

• Contains the parasympathetic and the sympathetic systems.
• Sympathetic nervous system prepares the body for intense muscular activity (fight or flight).
  • Effects include dilated pupils, inhibition of saliva flow, accelerated heartbeat, dilated bronchi, inhibition of peristalsis and gastric secretion, conversion of glycogen into glucose, and secretion of adrenaline and noradrenaline.
• Parasympathetic system balances the sympathetic and prepares the body for resting bodily functions.
  • Effects include pupil constriction, stimulation of saliva, slowed heartbeat, constricted bronchi, stimulation of peristalsis and secretion, and contraction of the bladder.

Brain Metabolism and Blood Flow

• The brain is a very metabolically active organ, receiving 20% of cardiac output.
• Requires constant oxygen delivery and does not tolerate hypoxia well.
• Dependent on aerobic metabolism and cannot function in anaerobic metabolism.
• Requires a constant and consistent delivery of glucose because it has minimal stores itself.
• Hypo- and hyperglycemia are detrimental to brain functioning.
• Monitor blood glucose levels closely in critically ill patients.

Factors Determining Cerebral Blood Flow

• Arteriolar radius.
• Mean arterial pressure (MAP).
• Blood viscosity.

Cerebral Perfusion Pressure

• The difference between the pressure pushing up from the heart and the pressure pushing down from the brain and the cranium.
• Calculated as: $CPP = MAP - ICP$ where ICP is the intracranial pressure.
• Normal CPP:
  • $> 50$ mm Hg in children.
  • $> 60$ mm Hg in adolescents.
• CPP is important in managing traumatic brain injury and increased intracranial pressure.

Intracranial Dynamics

• The skull is a rigid structure that forms a protective vault around the brain.
• Intracranial components:
  • Brain (80%).
  • Cerebrospinal fluid (10%).
  • Blood (10%).
• The sum of the intracranial volume is constant; when one component increases, others must decrease to maintain equilibrium.
• The brain cannot decrease in volume, but CSF and blood compartments can compensate to a point.
• Compensation occurs by displacing CSF from the ventricles and subarachnoid space and moving venous blood out of the cranial vault.
• Increased pressure causes arterial blood displacement.
• This concept is known as the Monroe-Kelly doctrine.
• Important in conditions like expanding brain tumors or cerebral edema.

Hydrocephalus

• Increased amount of CSF.
• Unless the volume is relieved, the patient will experience increased intracranial pressure.

Hydrocephalus

• Results from an imbalance between the production and the absorption of cerebrospinal fluid.
• CSF is produced in the choroid plexus and then reabsorbed in the arachnoid villi.

Types of Hydrocephalus

• Communicating: No problem with CSF flow through the ventricular system, but the arachnoid villi are unable to reabsorb the CSF; Can occur as a consequence of meningitis.
• Non-communicating: Obstruction in the normal pathway of CSF flow; CSF is produced normally but cannot flow to the arachnoid villi to be reabsorbed; Obstruction can be from a tumor, cyst, or inflammation.
• Congenital: Associated with myelomeningocele, Chiari malformation, etc.
• Acquired: Caused by tumors that obstruct CSF flow, intraventricular hemorrhage, infection, or overproduction of CSF by a choroid plexus tumor.

Clinical Manifestations

• Vary depending on how rapidly the condition develops and how quickly the intracranial pressure increases.
• Increased head circumference (monitored in children under two).
• Non-specific symptoms like poor feeding, nausea, and vomiting.
• Headache (in older children).
• Sunsetting sign (eyes appear to be driven downward).
• Unsteady gait (in ambulatory children).
• Behavioral changes or changes in school performance.

Management

• Identify and correct any causes, if possible.
• Surgical placement of a shunt to drain the cerebrospinal fluid (e.g., ventriculoperitoneal shunt or VP shunt).
• Shunt malfunctions or blockages can demonstrate symptoms of hydrocephalus.

Strokes

• A neurologic injury that results from an interruption of cerebral blood flow to part of the brain because of either an occlusion or because of the rupture of a blood vessel.
• Rare in children; usually due to obstruction (embolus or thrombus).
• Extent of neurologic damage depends on location, size, and duration of vascular occlusion.

Risk Factors

• Cardiac disease (congenital heart defects, arrhythmias, artificial valves, endocarditis).
• Hematologic disorders, especially sickle cell disease.
• Central nervous system infections (meningitis, encephalitis).
• Trauma to the head and neck.
• Vasculopathies (e.g., Moyamoya syndrome).
• Certain medications (e.g., oral contraceptive pill).

Clinical Manifestations

• Focal neurologic deficits and seizures.
• Newborns and infants: Lethargy, apnea, hypotonia.
• Toddlers: Irritability, vomiting, and feeding issues.
• Older children: Hemiparesis, speech difficulties, facial droop, headache.

Diagnostic Studies

• Laboratory studies: Electrolytes, CBC, coagulation studies.
• Radiologic studies: Non-contrast CT (ischemic vs. hemorrhagic), CT angiography (intra- and extracranial circulation), MRI (ischemic and hemorrhagic strokes).
• Echocardiogram (to rule out cardiac embolism).

Management

• Supportive and based on the patient’s symptoms.
• Assess the patient's airway.
• Help them maintain oxygenation and ventilation.
• Perform ongoing neurologic exams.
• Control systemic hypertension and fever.
• Normalize glucose levels.
• Heparin for anticoagulation or tPA may be considered.
• Aspirin to help prevent future strokes.

Arterial Venous Malformations (AVMs)

• Direct connections between arteries and veins in the brain without capillaries.
• Malformation results in increased pressure and increased flow through the veins, and that causes them to become sclerotic, and then they become weak and distended.
• Can rupture, causing significant intracranial hemorrhage.
• Treatment varies based on size, location, and patient's condition (surgery, embolization, stereotactic radiosurgery).

Traumatic Brain Injury (TBI)

• An insult to the brain caused by an external force, producing a diminished or altered state of consciousness resulting in an impairment of cognitive abilities or impairment of physical functioning.
• Can range from mild to severe.
• Goals for management are to maintain cerebral perfusion pressure and prevent secondary injury.

Clinical Manifestations

• Change in level of consciousness (irritability, lethargy).
• Change in response to painful stimuli.
• Tense, bulging fontanelle and increased head circumference (in infants).
• High-pitched cry (in infants).
• Nausea, vomiting, and poor feeding.
• Changes in pupillary response.
• Cushing’s triad (late sign): Bradycardia, hypertension with a widening pulse pressure, and irregular respirations that progress to apnea.

Measurement of Intracranial Pressure

• Types of catheters or bolts:
  • Intraventricular.
  • Intraparenchymal.
  • Subarachnoid.
• Intraventricular pressure monitor is the gold standard for ICP monitoring and allows for CSF drainage.

Management of Increased Intracranial Pressure

• Maintain effective cerebral perfusion pressure.
• Preserve cerebral function.
• Prevent secondary injury.

Interventions

• Support: Patient's oxygenation and ventilation.
• Provide: Relief from pain, relief from anxiety and agitation
• Allow: CSF to drain for a certain amount of time if the ICP is elevated
• Administer: Hypertonic saline, mild hyperventilation that can be used when the other therapies that I've mentioned so far have not been effective in correcting intracranial hypertension.
• Avoid: hypocarbia, hyperthermia
• Monitor: EEG continuously and seizures.
• Use: Barbiturates those will depress cerebral metabolism and reduce cerebral blood flow with a decrease in cerebral blood volume and a decreased ICP.
• Elevate: patient's head of bed should be elevated that promotes cerebral venous drainage.
• Cluster: Care for the Family and provide support

Types of Injuries

• Concussion: Blow to the head without radiographic findings; brief retrograde amnesia may be the only sign; long-term recovery can take months.
• Contusion: Bruise to the brain, causing edema; change in level of consciousness, signs of increased ICP, seizures; less common in young children.
• Coup and contrecoup: Sudden deceleration causes the brain to collide with the bony prominences of the inner skull; the point of the initial impact of the brain on the internal skull, this is referred to as the coup injury and the brain strikes the opposite side of the skull, which causes a contrecoup injury.

Skull Fractures

• Linear: Bones remain in alignment, and the underlying meninges are not torn.
• Depressed: One or more skull pieces are indented, with damage to underlying brain tissue.
• Compound: Open and depressed; scalp laceration and depressed skull fracture, allowing foreign bodies to pass into the skull cavity.
• Basilar: Fracture of the base of the skull; associated with specific manifestations:
  a. Battle sign: Bruising over the mastoid area.
  b. Raccoon sign: Black and blue bruising or periorbital edema around the eyes.

Important: Do not place a nasogastric tube in patients with suspected basilar fractures; use an orogastric tube instead. Monitor for CSF rhinorrhea or otorrhea.

• Diffuse Axonal Injury: Rotational forces cause tearing of the axons of the brain cells.

Hematomas

• Epidural: Tear of the middle meningeal artery, bleeding between the dura mater and the skull; lucid interval may be followed by a change in level of consciousness as pressure increases; may require emergency surgery.
• Subdural: Stretching and tearing of bridging veins in the subdural space, involving venous bleeding; more common in infants; common causes include birth trauma, accidental falls, and intentional injury; infants may have nonspecific symptoms.

Brain Death

• Clinical diagnosis based on absence of neurologic function in a patient with a clear history that has resulted in irreversible coma.
• Assessment should not begin until 24 hours after the acute brain injury or cardiopulmonary resuscitation event.
• Reversible conditions (hypothermia, metabolic/toxic disorders, drug intoxication) must be excluded.
• Two clinical exams separated by an observation period are required.

Clinical Exam:

• Absence of awareness and complete loss of consciousness.
• Flaccid tone and absence of spontaneous or induced movements to external painful stimuli (excluding spinal cord events).
• Complete loss of all brainstem reflexes:
  Pupils: Mid position, fully dilated, and nonreactive to light.
  Facial/Oropharyngeal Muscles: No movement in response to deep pressure.
  Absent: Gag, cough, sucking, and rooting reflexes.
  Absent: Corneal reflex

Reflex Testing

• Absent oculocephalic reflexes (doll’s eyes):

Test: Hold the patient’s eyelids open and move the head rapidly side to side. In an exam consistent with brain death, the eyes will always point in the direction of the nose, that lag behind, and do not move. This test is contraindicated in patients with cervical spinal injury.

• Absent oculovestibular reflexes (cold caloric):

Test: We only perform this test if the tympanic membrane is intact. Elevate the patient’s head 30 degrees, and then ice water is injected by syringe deep into the ear canal. and we'll see slow horizontal nystagmus. If the brain stem is intact or If this reflex is absent, then the eyes will remain fixed in mid position. and it's indicative to Brain Death

• Apnea testing should be performed with each neurologic examination to determine brain death in all patients unless there's a medical contraindication.
  There are some very specific steps to performing the apnea test, and I would refer you to review the published guidelines for the determination of brain death in infants and children for more specific details.

Ancillary Studies:

Not required to establish brain death, and they should not be used as a substitute for the neurologic exam:

• Four vessel cerebral angiography
• Radionuclide cerebral blood flow
• EEG

Patient death is declared after completion of the second clinical exam in apnea test

Spinal Cord Injuries

• Complete: Complete loss of motor and sensory function; quadriplegia or paraplegia.
• Incomplete: Some loss of motor and sensory function with sparing of function.
  Spinal cord injury without radiographic abnormality is more common in pediatric patients than it is in adults.
• Etiology: Motor vehicle crashes, severe trauma to the vertebral column, particularly with acceleration deceleration injuries.

Management

• Initial: Stabilizing the spine Through traction or through surgical fixation.
• Remain: supportive much of it falls within the realm of excellent nursing care.
• Help: the patient maintain both oxygenation and ventilation.
• Prevent: pressure injuries to the skin and using measures to prevent deep vein thrombosis.

Neurogenic Shock

• Occurs when spinal trauma interrupts sympathetic nervous system signals.
• Causes uncontrolled vasodilation, decreasing preload and afterload.
• Results in hypotension and a wide pulse pressure; also, decreased heart rate.
• Treatment: Intravascular fluid volume, medications that increase vasomotor tone (e.g. norepinephrine).

Steroids are no longer recommended for the management of acute spinal cord injury.

Spinal Fusion

• Surgically fusing things like screws and plates, and then bone grafting to help the bones heal together, can either be Posterior,Anterior, VATS
  that's used for scoliosis or spinal fractures.
• Monitor: Frequent neurovascular assessments of the lower extremities Monitor for signs that a hematoma,oxygenation,airway clearanc, pain

Encephalopathy

• Any neurological condition that produces altered level of consciousness and a generalized disturbance in brain metabolism., or metabolic disorders
• Etiology: hypoxic ischemic encephalopathy, lead poisoning, other hypoxic events, hypertension
  Signs and symptoms vary from mild to severe, and
• The treatment is mainly to support the signs and symptoms like seizures., irritability,
• Symptoms can include, decreased level of consciousness, seizures, and motor and sensory deficits., and irritation

Neurologic Infections (Meningitis)

• Acute inflammation of the, Positive Gram stain and meninges with bacterial a bacterial pathogen is evident in the Cerebrospinal fluid or positive bacterial culture. We see
• Etiology: Most common in children less than 1 year old.

CSF Analysis

• Bacterial:Increased white blood cell count Increased protein, decreased to to the glucose,
• Viral: Only a slightly. Increased light a slightly elevated the protein and the a slightly protein normal normal increased white blood cell count
• Symptoms for :fevers, complain child is old enough, he might photophobia, the child, stiff neck
  Pain with extension of the legs , that stretches the lumbar root, hip and flexion of the knee for bending sign
  ecording broad and then the antibiotics will be changed to to isolate the child from policies,
• We'll isolate the child treatment that is controversial in and and for our doctor or you to the MRI to get a out or hydrocephalus or to rule out
  for alteration is that would make us concerned for that develop to treat these conditions if they develop that or the develop the

Seizures

• Abnormal electrical discharges that can arise from any part of the brain.
• Brief seizures (less than five minutes) are most common.
• Status epilepticus: A continuous seizure that lasts more than five minutes, or recurrent seizure activity where the patient doesn’t return to baseline between seizures.

ICU monitoring: And supportive care because Seizures are broadly classified as being either focal or generalized.:

• Focal: Start in one part of the brain, focal seizures.
• Generalized: Children a fever may occur in experiencing most common causes or and

Management

• We generally use anti convulsant is to
  In-depth an or make sure you's that the of this because of oxygenation,
  They may need is and And patients make is area in the brain that's
  child experience we're and then to

Delirium

• Experiences and and level child's behavior can and it can
  the child may have the or
• Prevent in that and the to We
  And include to be

Congenital Neurologic Abnormalities (Spinal Neural Tube Defects)

Myelomeningocele

• spinal cord and can in the So you
• that that are bony to that
  in through we want need CSF
• the in on an brain % of We location on.
• the of
• So it to personal
  to and
  .