Pathophysiology Exam 3 - Review
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Transcript of Pathophysiology Exam 3 - Review
Waqas A. Gill
Pathophysiology Exam 3 - Review
Ch. 13 – Brain & Cranial Nerves
Understand the function of brain structures
The brain is a part of CNS contained in the cranial cavity, whereas its associated Cranial Nerves are
a part of the PNS, even though they arise from the brain (2 from cerebrum & 10 from brainstem).
o Brainstem: Connects Spinal-cord Brain; Integration of
reflexes necessary for survival. Consists of the:
Medulla: Lower region that controls swallowing,
heart rate, breathing, vomiting, coughing, sneezing
Cranial nuclei: 5, 9-12
i. Pyramids: Control the Visual Reflex – When
seeing/hearing an intense light/sound, your
attention turns towards the stimulus.
ii. Olives: Responsible for modulating sound
Pons: Mid-region w/ fiber tracts (Sleep center)
Pontine: Relays information b/w the cerebrum
& cerebellum + has a respiratory center.
Midbrain: Upper region that contains the visual reflex
center and auditory pathways.
Cranial nuclei: 3-5
Tectum (Roof) & Tegmentum (Floor)
i. Red nuclei of Tegmentum: Aid in unconscious
regulation and coordination of motor
activities
ii. Substantia nigra: Melanin pigmentations that
interconnect w/ cerebrum basal nuclei
iii. 2 Superior Colliculi: Visual reflex
iv. 2 Inferior Colliculi: Sense auditory signals
Reticular formations: Diffused neurons that control
cycles (Sleep-wake cycle).
o Cerebellum: Involved in control of locomotion, balance, & posture.
Cerebellar peduncles: Fiber tracts that communicate with other parts of brain:
Superior (Midbrain), Middle (Pons), Inferior (Medulla)
Parts:
Folia: Folded ridges of the gray cortex.
Arbor Vitae: White-matter that resembles a tree-shape.
Purkinje Cells: The largest cell in the CNS (receive 200,000 synapses),
where the Inhibitory Cortex has 1012 more neurons that the Cerebral cortex.
Damage to these cells (alcohol) can lead to difficulty balancing.
Functions:
Flocculonodular Lobe: Balance and eye-movements
Nystamus: Horizontal eye-movement
Vermis & Medial hemispheres: Posture,
locomotion, & fine-motor coordination
Leading to smooth, flowing movements
(like dancing).
Lateral hemispheres: Major portion that works
w/ cerebrum to plan, practice, & learn complex
movements (like playing guitar).
o Diencephalon: Located b/w the brainstem & cerebrum.
Thalamus: Motor function, mood modification, emotion regulation, & sensory integration.
This is where sensory information synapses before projecting to the cerebrum.
Intermediate mass: Connects the 2 lateral portions, & surrounded by the 3rd ventricle
Subthalamus: Involved in controlling motor function.
Contains: Subthalamic nuclei, Red nuclei, & Substantia nigra.
Epithalamus: Helps regulate our biological clock, and may influence the onset of puberty.
Pineal Gland: May influence sleepiness
Habenular Nucleus: Emotional & visceral responses to odor (memories).
Hypothalamus: Most inferior portion that’s important for mood regulation, emotions,
sexual pleasure, satiation, rage, and fear. Also aids swallowing and shivering.
Receives input from viscera, taste receptors, limbic system, nipples, external
genitalia, & prefrontal cortex.
Mammillary bodies: Olfactory reflexes & emotional responses to odors.
Infundibulum: Stalk extending from the floor, which connects the hypothalamus to
the posterior pituitary gland (controls the endocrine system).
o Cerebrum: The largest portion of the brain responsible for conscious thought & control
Lobes
Frontal lobe: Voluntary motor function, motivation, aggression, sense of smell, mood
Parietal lobe: Reception & evaluation of sensory info., except smell, hearing, and vision
Occipital lobe: Reception and integration of visual input
Temporal lobe: Reception and evaluation for smell and hearing; memory, abstract thought,
judgment. Insula is within.
Fissures
Longitudinal fissure: Separates the two hemispheres
Lateral fissure: Separates temporal lobe from frontal and parietal lobes
Central sulcus: Separates frontal and parietal lobes, located between the precentral gyrus
(primary motor cortex) and postcentral gyrus (primary somatic sensory cortex)
Components
Gyri: are folds
Sulci: are depressions
Medulla: center
Nuclei: gray matter within the medulla
Corpus Striatum: Basal nuclei “Caudate & Lentiform” (also in diencephalon+ midbrain)
Fibers
Association fibers: Connections within the same hemisphere
Commissural fibers: Connect different hemispheres together
Projection fibers: Tracts b/w the cerebrum and other parts of
the brain and spinal cord
Important brain cell types and functions
o Basal cell Nuclei: Found in the Cerebrum, diencephalon, and midbrain.
Cerebrum: “Lentiform & Caudate” Motor function control
o Limbic System: Part of the cerebrum & diencephalon
Survival functions: memory, reproduction, nutrition & emotions
Membranes and fluid components of their brain and their functions
o Meninges: Connective brain-tissue membranes:
i. Dura mater: superficial layer, tightly bound to internal periosteum except:
Falx cerebri in longitudinal fissure between the two cerebral hemispheres
Tentorium cerebelli between cerebellum & cerebrum
Falx cerebelli between the two cerebellar hemispheres
Venous sinuses form at the bases of these three folds Accumulates blood in the
Dural Sinuses (middle gap) – Superior sinus (largest sinus in head)
ii. Arachnoid mater: Middle, thin, wispy layer that gives way to the:
Subdural space: Serous fluid contained b/w the Dura & Arachnoid mater.
iii. Pia mater: Inner, thin, delicate layer bound to brain that follows external contours.
Subarachnoid space: Web-like arachnoid strands, vessels, & CSF
o Ventricles: Lateral Interventricular 3rd Cerebral Aqueduct 4th Sub-arachnoid Spine
Lateral ventricles: Produce the most CSF (most ependymal cells) w/in cerebral hemispheres
Interventricular Foramina: Join lateral ventricles with third ventricle
Third ventricle: within diencephalon
Cerebral Aqueduct: Join 3rd ventricle with 4th ventricle
Fourth ventricle Associated with pons and medulla oblongata by the, continuous with spine
o CSF: Similar to serum, but with most proteins removed. It bathes/protects the CNS
Choroid Plexus: Ependymal cells, their support tissue, and associated vessels, which produce
the CSF to fill ventricles, and compose the:
Blood-Cerebrospinal fluid barrier: Very selective barrier of endothelial cells attached
to tight-junctions, where substances must pass through cells, not b/w them.
o Brain arteries:
Main arteries: Cerebral, Carotid, & Vertebral
Cerebral Angiography: Used to sketch out arterial network
Blood brain barrier
o Formed by endothelial cells (lining all capillaries) that have tight junctions b/w them.
o Capillary permeability is influenced by:
Astrocyte foot-processes
Lipid-soluble substances (nicotine, heroin, ethanol) passing through by diffusion, and
Water-soluble substances (AA’s, glucose) passing through by mediated transport.
Cranial nerves: types and function; lesions when damaged
o 12 nerves that have 1 or more of sensory, somatic (motor), & parasympathetic (autonomic) function
o Special senses: Hearing, taste, sight, smell, balance and _________
o General senses: Temperature, vibration, touch, pressure
I. Olfactory: Sensory nerve that detects the special sense of smell Temporal region of the Cerebellum.
Damage to this nerve can lead to the inability to smell/.
II. Optic: Sensory nerve that detects the special sense of vision Occipital region of the Cerebellum.
Optic Chiasm: Optic nerves decussate (cross-over), so:
Damage to the optic nerve b/w the eye and chiasm will lead to blindness in that same eye, &
Damage to the optic nerve b/w the chiasm and the occipital region of the brain will lead to
blindness in the opposite eye.
Binocular vision: Ability to view an object with
both eyes (Low in pigeons, high in owls).
III. Oculomotor: Motor & Parasymp. nerve that directs eye-
movement + pupillary constriction, respectively
4 of the 6 nerves that direct eyeball movement are
a part of the Oculomotor nerves:
Superior, medial, and inferior rectus
muscles + the Inferior oblique muscle.
Double-vision + blurred vision occurs when
there’s damage to any of the motor nerves.
Ptosis: Drooping upper-eyelid due to
Oculomotor-nerve damage.
IV. Trochlear: Motor nerve that directs movement for only the superior
oblique muscle of the eye.
Damage can affect Adduction (medial view) and
Abduction (lateral view) double-vision
V. Trigeminal: Motor & sensory nerve composed of 3 branches (Ophthalmic, Maxillary, & Mandibular)
Sensory: Scalp, cheek, nose, eyelids, lips, palate, nasopharynx,
teeth/gums/jaw, chin, temporal region, & cornea (majority of the face).
Motor (chewing, throat, middle-ear), the anterior 2/3 of the tongue, & some
parasympathetic (smooth muscle in head-region)
Damage to 1 branch does not necessarily carry over to other branches:
Trigeminal Neuralgia (Tic Douloureux) Untreatable, severe facial pain
VI. Abducent: Motor nerve that directs movement for only the lateral rectus eye-muscle
Damage can affect Adduction (medial view) double-vision
Strabismus (squinting) can lead to Amblyopia (lazy-eye).
VII. Facial: Sensory, motor, & Parasymp. nerve that coordinates w/ the trigeminal nerve
Sensory: Some taste from anterior 2/3 of the tongue, palate, and some of the external ear.
Motor: Facial expressions, throat, and middle-ear.
Parasympathetic: Submandibular & sublingual-salivary, lacrimal, palate, & nasal-cavity glands
Damage can lead to Facial Palsy (paralysis), loss of anterior tongue
taste, & decreased salivation
VIII. Vestibulocochlear: Sensory nerve that detects the special senses of hearing
& balance.
It splits to the vestibule (top split) and cochlear region (bottom split)
Damage can lead to loss of balance/equilibrium/hearing, nausea,
vertigo, vomiting, & dizziness
IX. Glossopharyngeal: Sensory, motor, & Parasymp. nerve that coordinates w/ the facial nerve
Sensory: Taste from posterior 1/3 of the tongue, pharynx, tonsils, middle-ear, & carotid sinus/body
Motor: Pharyngeal muscle
Parasympathetic: Parotid-salivary gland & the glands of the posterior 1/3 of the tongue.
Damage can lead to difficulty swallowing, loss of posterior tongue taste, & decreased salivation
X. Vagus: Sensory, motor, & Primarily Parasympathetic nerve that coordinates CNS output of flex/reflex.
Sensory: Inferior pharynx, larynx, thoracic + abdominal organs, & posterior tongue taste
Motor: Pharynx, soft-palate, intrinsic laryngeal muscles, & extrinsic tongue muscles
Parasympathetic: Thoracic and abdominal viscera
Damage leads to difficulty swallowing, hoarseness, & uvula moving away from the damaged side.
XI. Accessory: Motor nerve that supplies the sternocleidomastoid and trapezius muscles.
Damage can lead to difficult elevating the scapula & rotating the neck.
XII. Hypoglossal: Motor nerve that mainly affects the tongue and throat muscles
Damage leads to the tongue deviating towards the damaged side when extended.
Ch. 12 – Spine & Spinal Nerves
Understand the function of spinal cord structures
The spinal-cord extends from the foramen-magnum to the 2nd
lumbar vertebrae.
o Conus Medullaris: Tapered inferior end of the spine
o Cauda Equina: Origins of spinal nerves extending inferiorly
from lumbosacral enlargement and conus medullaris.
o Spinal meninges: Cover the spine as they do in the brain
Denticulate Ligament: Keeps the spinal cord in place by
attaching it to the meninges.
Dura mater: Cont. w/ epineurium of the spinal nerves
Subdural Space: Serous fluid
Arachnoid mater: Thin and wispy
Subarachnoid Space: CSF and blood vessels
within web-like strands of arachnoid tissue
Pia mater: Bound tightly to surface of brain & spinal
Filum terminale: Anchors spinal cord to coccyx
Denticulate ligaments: Attach spine to Dura
Epidural Space: Anesthesia injected here. Contains
blood vessels, areolar connective tissue, and fat.
o Spinal vertebrae:
3 Horns: Posterior (dorsal), Anterior (ventral – motor neurons), Lateral (autonomic neurons)
Gray matter: Motor neuron cell-bodies, dendrites, & axons
3 columns (funiculi): Ventral (anterior), Dorsal (posterior), & Lateral Divided into tracts
White matter: Myelinated axons forming tracts
2 Roots: Spinal nerves arise as rootlets, then combine to form roots
Ventral (anterior) root & Dorsal (posterior – has Ganglion) root
Both roots merge laterally and form the spinal nerve.
Dorsal root ganglion: Cell-body collections of unipolar, sensory neurons Dorsal roots
They can detect sensory signals and react w/ immediate response, while the sensory
signals will continue and potentially also cause an autonomic response and/or an
interneuron-motor response.
Anterior median-fissure & Posterior median-sulcus: Clefts partially separating 2 halves
Commissures: Connections between left and right halves
Important spinal nerves, plexus, and functions
o Structure: Axons, Schwann cells, & Connective tissue:
Endoneurium: Surrounds individual neurons (Dura)
Perineurium: Surrounds axon groups to form fascicles
Epineurium: Surrounds the entire nerve
o 5 different segments give way to 31 non-uniform spinal nerves:
Cervical: 7 (w/ 8 outputs) Supplies upper-limbs
Thoracic: 12
Lumbar: 5 Supplies lower-limbs
Sacral: 5
Coccygeal: 1
o Dermatomal map: Skin area supplied with sensory
innervation by spinal nerves
o Plexus “braid”: A structure in the form of a network,
especially of nerves, blood vessels, or lymphatics.
o Dorsal Ramus (upper left branch) coming off of the dorsal
root ganglion innervates spinal muscles and tissues.
o Communicating Rami: Comm. w/ sympathetic ganglia-chain.
o Ventral Rami branch coming forward in a circular fashion
innervates intercostal muscles (ribs) + skin (Thorax), & 5:
i. Cervical plexus = C1 - C4
Innervates superficial neck + posterior head
Ansa Cervicalis: Loop b/w C1 - C3 and Phrenic Nerve: From C3 - C5 (Diaphram)
ii. Brachial plexus = C5 - T1
3 trunks 6 divisions cords 5 major Branches:
i. Axillary: Teres Minor (Lateral arm rotation) + Deltoid (Abducts arm)
ii. Radial: Lateral 2/3 hand, posterior arm skin, & elbow/wrist/thumb movement
iii. Musculotaneous: Lateral arm skin & elbow/wrist/shoulder movement
iv. Ulnar: Medial 1/3 hand, Medial 1/3 ring, pinky & finger/hand movement
v. Median: Lateral 2/3 - palm, thumb, index, middle & hand/wrist/finger move.
Median nerve damage can lead to Carpal tunnel syndrome.
o Smaller nerves: Pectoral, thoracic, thoracodorsal, subscapular, suprascapular
iii. Lumbar plexus = L1 - L4
Usually associated w/ the Sacral plexus bc of close relationship
iv. Sacral plexus = L4 - S4
Both Lumbar & Sacral plexi give way to 4 major nerves:
i. Obturator: Adduction (medial) of knee/thigh & superior-middle thigh skin
ii. Femoral: Hip/knee movement & anterior-lateral thigh skin + medial leg/foot
iii. Tibial: Medial, plantar, & sural nerves-branches & Hip/knee/foot movement
Tibial & Peroneal nerves make up the Sciatic (ischiadic) nerve.
iv. Common Fibular (peroneal): Anterior/lateral leg/foot muscles
Branches are deep & superficial fibular (peroneal) nerves.
o Smaller nerves: Gluteal, pudendal, iliohypogastric, ilioingual, + genitofemoral
v. Coccygeal plexus = S4 - S5
Pelvic-floor muscles & sensory info. from skin over the coccyx region.
Membrane coverings of spinal cord and their functions as it relate to applications (e.g. epidural
anesthesia)
o
Reflex arc, Reflex action, and types of reflexes
o Reflex Arc: Basic functional unit of nervous system
Controls the autonomic response to a stimulus that occurs w/out conscious thought.
AP Sensory receptors Sensory neuron Interneuron Motor Effector Reflex
o Reflex Action:
o Types of Reflexes: Some integrated w/ spine + some w/ brain (can influence, suppress, exaggerate)
Babinski reflex: Extension of the big toe when the sole of the foot is rubbed along the lateral
border. A positive Babinski sign is present in infants and children less than 2 years of age
because myelination and maturation of their corticospinal tract is incomplete.
A positive Babinski sign in adults is considered a pathological symptom.
Stretch “knee-jerk” reflex:
Stretching of the muscle + hitting the Patellar region leads to Quad. ‘Femoris’ contraction
α-motor neurons: Type-A neurons that fire fast action-potentials.
Golgi-Tendon reflex: Prevents contracting muscles from over-tensing tendons
Golgi tendon organ. Encapsulated nerve endings that have at their ends numerous
terminal branches with small swellings associated with bundles of collagen fibers in
tendon. Located in tendon near muscle, & produces sudden relaxation of the muscles
o Ex: Weight lifter suddenly drops heavy weight. Sudden movements of “clean
and jerk” put so much tension on tendons like Achilles, they could break.
Withdrawal reflex: Function is to remove a body limb or other part from a painful stimulus.
Reciprocal innervation: Relaxation of extensor muscle when flexor muscle contracts
o Involved in Withdrawal-reflex & stretch-reflex
Crossed extensor reflex: Works in pair with the Withdrawal-reflex by extending the
opposite limb when a withdrawal reflex is initiated in one lower limb.
Ex: Stepping on a tac, lifting the affected foot, and bracing all weight on opposite leg.
General mechanism: Sensory info. brain descending tracts reflex EPSP/IPSP’s
Pathophysiology related to spinal cord and nerves:
o General disorders:
Anesthesia: Loss of sensation
Hyperesthesia: increased sensitivity to pain, pressure, light
Paresthesia: tingling, prickling, burning (foot falls asleep)
Neuralgia: nerve inflammation causing stabbing pain (nerve pain)
Sciatica: pain radiating down back of thigh and leg
o Infections: Can damage sensation
Herpes: Skin lesions
Shingles/Herpes-zoster: Adult disease of chickenpox
Poliomyelitis: Infantile paralysis
Anesthetic leprosy: Bacterial infection of peripheral nerves
o Genetic & autoimmune disorders:
Myasthenia gravis: Results in fatigue & muscular weakness Inadequate ACh receptors
Flow of bodily fluid in descending order of components: o Blood Plasma Serum CSF
Ch. 14 – Brain & Spinal Cord Injury
Understand the causes, types, symptoms, diagnosis, treatment, and prognosis of the following
traumatic brain injuries:
o Traumatic brain injury:
Produces physical, intellectual, emotional, social, and vocational changes
50% (vehicle accidents), 21% (falls), & 29% (violence/sports)
o Focal and Diffuse brain injuries:
Focal: Local, observable brain-lesion where impact produces contusions:
Extradural (epidural) hemorrhages or hematomas, Subdural/Intracerebral hematomas
Diffuse: General, Diffuse axonal injury (DAI):
Shaking, inertial effect from acceleration/deceleration, which can lead to axonal
shearing, tearing, or stretching of nerve fibers
Severity corresponds to the amount of shearing force applied to the brain/stem.
Open (penetrating, missile) trauma:
Injury breaks the dura and exposes the cranial, causing primarily focal injuries
Blunt (closed, non-missile) trauma:
Head strikes hard but dura remains intact and brain tissues are not exposed
Causes focal (local) or diffuse (general) brain injuries.
Coup injury: Injury directly below the point of impact
Contrecoup: Injury on the pole opposite the site of impact
Compound fractures: d
Basilar skull fracture: d
o Concussion and hematomas
Subdural Hematoma: B/w the Dura membrane & Arachnoid membr.
Elongated, lens-shape
Epidural Hematoma: B/w the Dura membrane & Skull.
Most are due to arterial damage in circular, meningeal layers
Intracerebral Hematoma: W/in the brain Parenchyma.
DAI categories:
Mild concussion: Temporary axonal damage attention/memory deficits, but no
loss of consciousness. Can be measured in 3 grades:
i. Confusion, disorientation, and momentary amnesia (temp. memory loss)
ii. Momentary confusion and retrograde amnesia (forget past)
iii. Confusion with retrograde & anterograde amnesia (forget past/future events)
Classic concussion: d
iv. Disconnection of cerebral systems from the brain-stem & reticular activating
system, leading to loss of consciousness (<6 hours).
Physiological and neurological dysfunction without substantial
anatomic disruption Anterograde & retrograde amnesia.
o Increased Intracranial pressures
Normal: 10 mm Hg ICP (Range: 4 – 15 mm Hg or 120 – 180 mm H2O)
Abnormal: 20 mm Hg ICP
Severe: 40 mm Hg ICP
Herniation: 50 mm Hg ICP
Infratentorial or Supratentorial
o Herniation: 50 mm Hg ICP
Once pressure surpasses 33 mm Hg, ischemic regions (areas of decreased blood-flow) will
form in the brain, which can lead to Herniation (movement of tissues from one area to another)
and brain tissue damage. The brain releases certain fluids to help reduce the pressure of the
thicker liquid already in the brain.
Herniation occurs when mass effect is severe enough to push intracranial structures from one
compartment into another. The 3 most common herniation syndromes are through the:
i. Tentorial notch
(transtentorial):
ii. Centrally & downward
(central):
iii. Under the falx cerebri
(subfalcine):
Cushing’s response in head injury
Inc. ICP Hypertension & Bradycardia
o ICP increases as the pressure of liquid within the brain (CSF) increases. Under pathological conditions,
the pressure can exceed that of the mean arterial pressure, thus leading to the arterial compression by
the CSF. This arterial constriction leads not only to ischemic regions developing within the brain, but
eventually leads to hypertension, as our sympathetic nervous system attempts to compensate for the
reduced blood-flow by constricting the arteries further to boost BP.
o The initial phase of this response induces Tachycardia, but once the baroreceptors in the aortic arch of
the heart detect this hypertension, they relay that information to the brain through the
Glossopharyngeal nerve, and activate a Parasympathetic response through the Vagus nerve, which
works to re-establish homeostasis by inducing Bradycardia, but adjusts it to keep the arterial pressure
above that of the CSF in the brain to allow oxygen to circulate and avoid infarction.
The use of antihypertensives is strongly discouraged Result in dec. brain perfusion (bad).
o Clinical Triad of Symptoms:
Headache: Caused by stretching of the dura and blood vessels
Papilledema: Caused by swelling and pressure on optic disc (can it lead to Glaucoma?)
Vomiting: Frequently projectile vomiting
o General symptoms: Widened pulse pressure, pulse, and respiratory rate brain-tissue death
Neurological Death-Forms and Manifestations
o Manifestations of head injury:
ICP, seizures, ecchymosis (loss of skin color due to internal bleeding), focal deficits (local
brain lesions), loss of cognition/memory, & alteration of vision + other special senses.
o 2 forms of Neurological-death:
i. Brain Death (brain stem death): Occurs when brain damage is so extensive that the brain has
no potential for recovery and no longer can maintain the body’s internal homeostasis.
Criteria: Completion of all therapeutic procedures, unresponsive coma, no
spontaneous apnea (PCO2 > 60mm Hg), no cephalic reflexes, & no AP’s
ii. Cerebral Death (irreversible coma): Death of the cerebral hemispheres only.
Brain damage is permanent and sufficiently severe that the individual is unable to
ever respond behaviorally in any significant way to the environment.
The brain may even maintain internal homeostasis, but likely in a:
Vegetative State: A wakeful, unconscious state
Criteria: Periods of eye-opening, subcortical responses to stimuli, respiratory &
digestive functions, occasional eye-movement, & brain-stem reflexes intact
Minimally Conscious State (MCS): Follow simple commands, manipulation of objects,
generalized yes/no responses, intelligible speak, & blinking/smiling
o Treatments of head injury:
Craniotomy: Ligate (tie-off) bleeding vessels or evacuate hematomas/penetrating objects.
Prevention of acutely increased ICP
Hypothermia: To a moderate degree (34oC to 33oC)
Fractures are surgically reduced & Rehabilitative measures are taken
Coma:
o Causes-1: TIPS
T: Trauma, temperature
I: Infection (CNS & Systemic)
P: Psychiatric problems
S: Space-occupying lesions, shock, stroke
o Causes-2: AEIOU
A: Alcohol and other drugs
E: Endocrine, exocrine, electrolytes
I: Insulin
O: O2, opiates
U: Uremia – Kidney disorder leading to excess Urea in the brain
o Scoring:
Glasgow Coma Scale: Widely used scale that quantifies a patient’s consciousness on a scale
of 3-15 (where 3 indicates ‘deep unconsciousness’ & 15 ‘fully alert’) through the summation
of 3 scores (best motor response + best verbal response + best eye-opening response).
Oculocephalic and caloric responses
o Oculocephalic (Doll’s eye):
Move head passively and observe motion of the eyes. The
eyes should move conjugately in the direction opposite to
the movement.
o Caloric Response:
If doll's eye movements are absent proceed to calorics.
Ice cold water applied to the tympanic membrane
normally elicits a slow conjugate deviation to the
irrigated side.
Motor responses to damaged areas in the brain
o Left hemisphere lesion:
The 2 figures illustrate localization of pain with the left
hand & flexion (left figure) or extension (right figure)
with the right hand.
o Subcortical:
Unilateral left sided lesion exerting a variable contralateral
effect. The figures illustrate flexion to pain with the left
hand w/ either extension (left figure) or flexion with the
right and hyperextension in both lower limbs.
o Midbrain upper pontine:
A bilateral upper and lower limb extension response.
o Lower pontine/medullary:
A bilateral extensor upper limb posture with either
flaccidity or minimal diminished flexor response in lower
limbs.
Ch. 15 – Brain & Spinal Cord Injury II
Epidemiology
o Highest risk in young males (15-30): 45% (accidents), 22% (falls), 16% (violence), 13% (sports)
Acute spinal cord injury:
o Symptoms: Rapid loss of
Voluntary movement & sensation in body parts below the level of injury.
Spinal and autonomic reflexes below the level of injury.
o Causes:
Primary injury: Force-induced, mechanical injury
Secondary injury: Induced by the primary injury (insult).
o Types:
Hyperflexion: Sudden flection (reduction of the joint-angle) beyond the normal limits.
Ex. Head moving forward as you rear-end a car.
Hyperextension: Sudden extension (increase of the joint-angle) beyond the normal limits
Spine is stretched on the front side, and compressed on the dorsal side, potentially
leading to the collapse/rupture of intervertebral discs (ligaments) or sever the spine
Ex. Head moving back as someone rear-ends your car.
Spinal-shock: Duration varies, but leads to the compete loss of reflex activity below injury
Flaccid paralysis of skeletal muscle, loss of deep tendon reflexes, temp. control, &
vasomotor tone. Reappearance of reflexes sign of recovery.
o Mechanisms:
Acceleration-deceleration injury occurs in motor vehicle collisions, when the sudden
cessation of movement results in hyperflexion or hyperextension Cervical injury.
Excessive rotation of the head may also rupture ligaments, fracture vertebrae, or cause
tension trauma to the spine Cervical injury (Ex. boxing)
Axial (axonal) loading (vertical compression) is the usual mechanism of the injury in diving
accidents and sports injuries. These injuries usually occur in T12 - L2.
Penetrating trauma (other than bone fragments) is an uncommon cause of spinal cord
injury, but bullets, knives, & other penetrating objects may cause direct damage Anywhere
Spinal-shock: Functional disruption of neurotransmission in structurally intact reflex arcs
below the level of the injury, due to the lack of descending inputs from higher centers.
Intact reflexes return and may be hyper-reflexic because of the absence of inhibitors’
inputs from higher centers. Muscle spasms & bladder spasms are common.
o Pathophysiology:
Concussion, Temp. motor dysfunction, Contusion/bruising, & spinal Transection/severing
Cessation of sensory, reflex, motor, and autonomic functions below injured area:
Complete quadriplegia: Level of injury above C6 Full Paralysis
o Damage before C-6 will lead to partial paralysis
Incomplete quadriplegia: Function at or above C6 is preserved, leaving the
shoulder, upper arm, and some forearm muscle control intact usually affects legs
o Secondary Lesions:
Edema (swelling of local vessels) & Hemorrhage (loss of blood from local vessels)
Syringomyelia: The formation of a fluid-filled cavity within the central lesion, which can
cause the spread of spinal injuries until it reaches C-6 Full Paralysis
o Treatment:
Spine immobilization, ventilator assistance, prevent edema, surgical fusion, & add fluid.
o Management:
Elevate bed, muscle spasticity (Baclofen ‘Lioresol’ – Emphasizes GABA’s inhibitions, &
Botulinum is also used – Blocks NMJ for 3 months).
Vasodilating drugs (Ca2+-blockers or β-adrenergic antagonists), & Rehabilitation.