Brain Hemispheres, Lobe Functions, and Structures

Brain Hemispheres

• The cerebrum is the largest part of the brain, split into left and right hemispheres
• The left hemisphere is responsible for logical functions, language, math, aphasias, and cautious awareness of deficits
• The right hemisphere is linked to creativity, impacts attention span, rapid performance, impulsivity, and spatial-perceptual awareness

Brain Lobe Functions

• Frontal lobe functions include decision-making, reasoning, problem-solving, personality, motor function, and expressive language
• Parietal lobe processes sensory data like touch, temperature, pressure, and aids in spatial perception
• The temporal lobe is involved in auditory processing, memory, and language comprehension
• Occipital lobe serves as the main center for visual processing and interpretation

Diencephalon Structures

• The diencephalon composes the Thalamus and the Hypothalamus
• Thalamus relays sensory data to the cerebral cortex and regulates sleep and alertness
• Hypothalamus regulates bodily functions like temperature, hunger, thirst, sleep, and pituitary hormone secretion

Other Brain Structures

• The limbic system, including the amygdala and hippocampus, contributes to emotions, memory, and motivation
• Basal ganglia are located deep within cerebral hemispheres and is vital for motor control, coordination, and movement
• The reticular activating system (RAS) spans the brainstem and is critical for consciousness, alertness, and sleep-wake cycles

Brainstem Overview

• The brainstem connects the brain to the spinal cord and is divided into three main parts: Medulla Oblongata, Pons and Midbrain
• The medulla oblongata regulates breathing, heart rate, and blood pressure
• The pons coordinates autonomic functions and relays signals between the cerebrum and cerebellum
• The midbrain plays a role in visual and auditory reflexes and impacts motor control
• Cranial nerves originate in the brain stem
  • The midbrain influences auditory and visual responses, motor movement
  • The pons impacts arousal and sleep
  • The medulla oblongata impacts heart rate and respiratory function

Cerebellum

• The cerebellum is at the base of the brain
• Coordination, balance, fine motor skills, and muscle tone are cerebellum functions
• Ataxic gait describes uncoordinated walking
• Proper posture and equilibrium depends on the cerebellum

Conditions Affecting Cerebellum Blood Flow

• Atherosclerosis
• Vertebral-basilar insufficiency (VBI) Both conditions are linked to affecting blood flood to the cerebellum

Nervous System Tracts

• Upper motor neurons that descend into the spinal cord make up the Corticospinal tract
  • 80% of upper motor neurons cross to contralateral side
  • 20% of those upper motor neurons remain on the ipsilateral side
  • The brain stem area of crossover is called the decussation
• The corticobulbar tract runs parallel to corticospinal tract
• Sensory neurons from periphery to brain are in the Spinothalamic tract which crosses over at some spinal cord level

Cranial Nerve Functions

• The 12 cranial nerves affect function of sensory and motor function in the head and neck region
• The Olfactory Nerve (CN I) is responsible for the sense of smell and transmits sensory information from nasal receptors to brain
• Optic Nerve (CN II) is responsible for vision and carries sensory information from the retina for visual perception
• Oculomotor Nerve (CN III) controls eye movements, including pupil constriction, lens shape, and upper eyelid elevation
• Trochlear Nerve (CN IV) primarily controls superior oblique muscle movement to allow downward and inward eye movement
• Trigeminal Nerve (CN V) is the largest cranial nerve, performs sensory and motor functions like facial sensation and chewing
• Abducens Nerve (CN VI) Primarily controls the lateral rectus muscle for outward eye movement
• Facial Nerve (CN VII) controls facial expressions, taste in the anterior two-thirds of the tongue, and regulates tear/saliva production
• The Vestibulocochlear Nerve (CN VIII) features two parts to control balance and hearing
• Glossopharyngeal Nerve (CN IX) controls taste in the posterior one-third of tongue, swallowing, blood pressure, and blood gas levels
• Vagus Nerve (CN X) controls parasympathetic innervation to organs, digestive function, speech and swallowing
• Accessory Nerve (CN XI) Primarily controls muscles related to head and shoulder movements with role in swallowing
• Hypoglossal Nerve (CN XII) controls the muscles of the tongue to enable speech and swallowing

Meningitis Overview

• Meningitis is a viral or bacterial cause of inflammation of the meninges
• Symptoms for meningitis include:
  • Headache
  • Nuchal Rigidity
  • Photophobia
  • Fever/chills
  • Nausea/vomiting
  • Altered LOC
  • Kernig's/Brudzinski’s Signs
  • Hyperreactive DTRs
  • Tachycardia
  • Seizure
  • Red Macular rash
  • Restlessness/irritability
• Bacterial Meningitis is identifiable using a spinal sample of cerebrospinal fluid (CSF) which finds cloudy, decreased glucose
• Meningitis complications include increased intracranial pressure (ICP), SIADH, Septic emboli
• Risk of increased intracranial pressure (ICP) can lead to herniation of the brain and death requiring neurological evaluation every 4 hrs
• Early indications include a decreased level of consciousness, Cushing's triad, and and changes in pupillary reaction

Traumatic Brain Injury (TBI)

• Usually caused by falls, TBI are characterized as a sudden, physical damage to brain
• TBIs may be closed or penetrating, generally affect males more
• Simple TBIs resolve without complication within 10 days, also called concussions, have mild/transient symptoms and appear normal in imaging
• Complex TBIs may have symptoms that for longer, a longer loss of consciousness, or be moderate/severe

Symptoms and Recovery of TBIs

• Characteristics of TBIs are severe, have prolonged loss of consciousness, memory deficits, and neurological impairments with abnormal images
• TBI recovery can be lengthy and require intensive medical/ rehabilitative care

Concussions

• Falls or blows to the head, car accident, and recreational activities are leading causes
• A concussion is a mild traumatic brain injury due to a blow or jolt to head or body leading to confusion, memory problems, dizziness, and a range of physical, cognitive, and emotional issues

TBI Risk Factors

• Sports
• Falls
• Motor Vehicle Accidents
• Military Service
• Recreational Activities
• Physical Assault
• Concussion History
• Gender/age
• Occupational hazards
• Medical Conditions

Coup and Contrecoup Injuries

• Sudden brain tissue injuries from a blow or falls can cause coup and contrecoup injuries to brain colliding with skull
• A coup inury occurs at the trauma site where the brain can move inside the skull, and that trauma damage is found at impact point
• Contrecoup injury results from the impact on the opposite side of the brain from the trauma site inside the skull
• Symptoms may lead to a variety of neurological conditions based on the extent of the injury

Diffuse Axonal Injury (DAI)

• Severe traumatic brain injury (TBI) can cause widespread damage to brain's axons from acceleration or deceleration
• Rotational or shearing trauma can cause axons to stretch and tear the axons disrupts
• Brain signals are disrupted due to functional impairments ranging from mild to severe with possible persistent vegetative state
• These are challenging injuries are difficult to detect on standard imaging studies like CT scans which can affect diagnosis and delay treatment

Penetrating Brain Injuries

• They are unique from skull fracture blast injury
• Penetrating brain injury happens when that object enters the brain tissue such as a bullet, knife, or shrapnel object through a wound
• Surgical interventions are usually performed but have varying success rate

Skull Fractures

• Damage to the skull are classified as fractures, depressed fractures, or basilar fractures
• They are directly related to a trauma and can cause neurological symptoms or bleeding
• Racoon Eyes (Periorbital Ecchymosis) includes bruising or discoloration and is associated with skull fractures that may be the result of a blood build up due to tissue damage around the eyes
• Battle's Sign includes bruising or discoloration behind the ear over the mastoid process and is associated with skull fractures where blood may track behind the ear/mastoid
• Halo Sign for CSF Leak involves drops of fluid on sterile surface (e.g. gauze), which forms a halo effect
  • Observation or surgery may be required.

Blast-Induced Neurotrauma Injuries

• Blast injuries result from explosions generated shockwaves which cause rapid overpressure in the brain
• Blast-induced neurotrauma may yield brain injuries, such as primary (direct impact shockwave), secondary (flying debris), or tertiary (being thrown)

Brain and Neurological Assessment

Mental status examination including patient awareness of surroundings, time, and personal identity Coordination of motor function through finger to nose tests Reflex function evaluation of reflexes of knees and ankles Observing gait or walking pattern

Brain Injury Diagnostics and Assessment

• Initial evaluation of vital signs, respiratory rate, and evaluation trauma to determine Glasgow Coma Scale
• CT scans to determine bleeding and fractures and MRI to provide detail of the brain structure
• A comprehensive neurological examination is essential. Includes cranial nerves, motor/sensory function, reflexes, coordination, and gait
• In cases of moderate/severe brain injury, Intracranial pressure (ICP) monitoring to prevent secondary brain damage
• Cerebral Angiography is also done to identify vascular abnormalities and malformations through assessing blood vessels in the brain
• Psychological evaluation through Neuropsychological testing that can identify cognitive impairment and performance

Managing Elevated ICP

• Control airway obstructions or respiratory failure to maintain ICP with medication to ensure oxygenation and surgical intervention for injuries
• Meds to control ICP, reduce pain, and administer antibiotics for open head injuries while being monitored
• Rehabilitation is needed depending on the severity to regain functions with physical occupational and speech therapy
• There are psychological factors that impact recovery requiring counseling, social support, and emotional therapy
• Preventative measures require lifestyle changes and education
• Frequent monitoring is essential

Glasgow Coma Scale (GCS)

• The scale is a way to assess severity of brain injury by rating eye, verbal, and motor activity
• It has a Lower score of 3 and a highest score of 15: "Less than 8 = intubate" There are three measured responses:

1. Eye Response (E):
   • 4 points (E4): Patient opens their eyes spontaneously
   • 3 points (E3): Patient opens their eyes in response to verbal stimuli, such as their name being called
   • 2 points (E2): Patient opens their eyes in response to pain or physical stimuli, like gentle pressure on the nail bed
   • 1 point (E1): The patient's eyes do not open, regardless of the stimulus
   • 1 point (E0): The patient's eyes remain closed due to physical injury or other factors
2. Verbal Response (V):
   • 5 points (V5): The patient is oriented and can converse coherently.
   • 4 points (V4): The patient is confused but can provide some meaningful responses
   • 3 points (V3): The patient speaks inappropriately and exhibits disoriented or non-specific responses
   • 2 points (V2): The patient only emits incomprehensible sounds
   • 1 point (V1): The patient does not make any verbal response -1 point (V0): The patient is unable to produce sounds due to injury or other factors
3. Motor Response (M):
   • 6 points (M6): The patient obeys commands by performing specific motor actions
   • 5 points (M5): The patient localizes painful stimuli by moving towards the source of the pain
   • 4 points (M4): The patient withdraws from painful stimuli but does not localize it
   • 3 points (M3): The patient exhibits abnormal flexion (decorticate posturing) in response to pain
   • 2 points (M2): The patient displays abnormal extension (decerebrate posturing) in response to pain
   • 1 point (M1): The patient does not exhibit any motor response to pain
   • 1 point (M0): The patient is unable to move due to injury or other factors

• The GCS score is calculated by summing the points from each of the measured responses (E + V + M), with scores ranging from 3 (deep coma) to 15 (fully alert/oriented). A reduced GCS score signals lowered consciousness, and possible impairment

Epidural Hematoma

• Epidural hematomas have the potential for life-threatening consequences and are a result of head trauma
• Rapid arterial bleeding can lead to pressure on the brain causing possible neurological symptoms, increased ICP, and Edema and Ischemia
• Patients with Epidural hematomas may present alternating periods of alertness and unconsciousness (Lucid Interval)
• Burr hole is performed to help reduce the pressure one the brain

Subdural Hematoma

• Usually caused by tearing blood vessels in the subdural space (space below the dura mater)
• Common trauma events can rupture blood vessels that results in venous bleeding and a mass effect to raise intracranial pressure (ICP) and trigger inflammation
• Accumulation of blood may cause altered mental status, headache, and or confusion
• Chronic types may result in milder symptoms over week or months

Intercranial Pressure

• Elevated intercranial pressure is dangerous and can lead to permanent damage such as brain swelling or obstruction of CSF flow
• Cushing triad is a key identification of elevate ICP resulting in hypertension, widening pulse pressure and/or Bradycardia
• Mannitol will be administered to help prevent cerebral edema

Cerebral Perfusion

• It's dependent on mean arterial pressure (MAP) and ICP where decreasing CPP can lead to vasodilation
• Cytotoxic cerebral edema and compression affects the increase ICP which then reduces oxygen
• External drainage for the CSF, lowering carbon dioxide pressure, or removing brain tissue, could help treat ICP

Surgical Interventions for Intercranial Pressure

• Craniectomy: Involves the temporary removal of part the skull to remove abnormalities, tumors, or blood accumulation under affected areas in the skull
• Cranioplasty: Surgery to repair or restore a defect or damage of the skull
• Burr Hole to reduce the pressure in affected a reas of the skull

Posturing of the Brain

• It involves unique body movements, including abnormal reactions to pain from brain injuries or neurological issues
• There are two main body positions that affect pressure including Decorticate and Decerebrate
• Decorticate posturing shows abnormal flexion of the body, affecting hemispheres that could lead to ICP pressure
• Decerebrate posturing shows the four limbs all extended outward in rigid form by damaging upper brainstem

Cerebrovascular Circulation & Metabolism

• Irreversible damage may occur if circulation of blood in the brain due to anaerobic metabolism
• Hypoglycemia affects brain functions and can mimic strokes. Always check blood glucose during stroke evaluation
• Internal Carotid arteries supply oxygen to the area by posterior circulation
• Circle of Willis is the common site for aneurysms

Stroke

• Ischemic means blood flow in the brain is restricted where as Hemorrhagic is blood that is leaking outside of brain causing damages
• The location where the stroke occurs affects physical attributes of which part of the body is affected
• Middle cerebral artery is the most common type of location for the stroke
  • With the result of Motor and or sensory deficits
• Subarachnoid hemorrhages SAH result in a thunderclap headache
• Vertebrobasilar VBI cause dizziness, vertigo, and headache
• 1 in 4 people are likely to have a stroke from a Transient Ischemic Attack stroke or TIA

FAST acronym

Balance- check for the person's balance with walking or coordination Eyes- Check the person's vision Face- Ask the person to smile checking for facial drooping Arms- Ask the person to raise both arms checking for any weakness Speech- Ask the person to repeat to check for slurred speech or difficulty talking Time- To call for medical help immediately

Two primary ischemic stroke subtypes.

• Thrombotic Stroke has a blood form within an artery by the brain
• Embolic Strokes has a blood form in a different part of the body causing it to travel to the brain

TPA

• Only effective if stroke symptoms persist no longer than 4.5 hours before administering
• Risk of using tPA increases risk of hemorrhage affecting the brain.
• Alerteplase helps dissolve the clot to allow blood to flow in affected parts of the brain within 6- 24 hours
• The monitoring and after care for the stroke should be monitored including any complication while providing any assistive devices or items.

Hemorrhagic Stroke Treatment

• Main aim is to control bleeding, reduce ICP, and provide supportive care
• Monitor airway and vital stabilization through blood pressure control
• Diagnostic image to identify areas of bleeding and hemorrhages through neurological imaging,
• Emergency neurosurgery will needed and if there is life affecting hemorrhages
  • With supportive care needed as monitoring, reducing infection to support stroke rehabilitation

High ICP

• Reduce stimuli and elevate head to maintain pressure.
• Seizure prophylaxis are given to prevent seizures that my hinder any rehab and affect the brain.

Transient Ischemic Attack ( TIA )

• Also known as a mini stroke with out acute infection which can be caused by a disruption of blood flow
• Emboli, atherosclerosis, and cardiac issues or the most known form of TIA
• There are temporary similar symptoms to the acronym FAST which can involve
• Sudden Weakness
• Speech Difficulty
• Vision and balance issues.
• Antiplatelet drugs will be given to help prevent clot formation.

Acute Brain Injury and Epilepsy

• Status epilepticus is long a series of seizures or long seizures that are in prolonged state without recovery which results in damage.
• Seizures stem from acute Brain injuries, Metabolic Disturbances or any Infections
• Benzodiazepines are the most common medication to end seizures
• Remove any hazardous objects within the surrounding area while maintaining space from head to avoid injury.

GUILLAIN-BARRÉ SYNDROME

• Serious auto immune that affect nervous and spinal areas which are characterized by a sudden loss of weakness or tingling.
• Individuals with a history with GBS often experience numberless or pain and have respiratory issues that can lead to ventilatory

Retinal Detachment

Pain associated with sudden vision loss can lead to retinal detachment which requires immediate medical attention