Pathophysiology Exam 3 - Review 3n623

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.

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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.

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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

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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

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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)

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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

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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

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Membranes and fluid components of their brain and their functions o Meninges: Connective brain-tissue membranes:

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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: lateral ventricles with third ventricle  Third ventricle: within diencephalon  Cerebral Aqueduct: 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 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 through cells, not b/w them. o Brain arteries:

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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) ing through by diffusion, and  Water-soluble substances (AA’s, glucose) ing through by mediated transport.

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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

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/. 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). Oculomotor: Motor & Parasymp. nerve that directs eyemovement + 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. 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

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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 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). 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 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 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 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. Accessory: Motor nerve that supplies the sternocleidomastoid and trapezius muscles.  Damage can lead to difficult elevating the scapula & rotating the neck. 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:

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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

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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:

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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 Coccygeal plexus = S4 - S5  Pelvic-floor muscles & sensory info. from skin over the coccyx region.

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Membrane coverings of spinal cord and their functions as it relate to applications (e.g. epidural anesthesia) o

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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:

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Stretching of the muscle + hitting the Patellar region leads to Quad. ‘Femoris’ contraction α-motor neurons: Type-A neurons that fire fast action-potentials.

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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

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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 I (Range: 4 – 15 mm Hg or 120 – 180 mm H2O)  Abnormal: 20 mm Hg I  Severe: 40 mm Hg I  Herniation: 50 mm Hg I  Infratentorial or Supratentorial

o Herniation: 50 mm Hg I  Once pressure sures 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): 

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Cushing’s response in head injury  Inc. I  Hypertension & Bradycardia o I 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:  I, 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

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o Treatments of head injury:  Craniotomy: Ligate (tie-off) bleeding vessels or evacuate hematomas/penetrating objects.  Prevention of acutely increased I  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).

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Oculocephalic and caloric responses o Oculocephalic (Doll’s eye):  Move head ively 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.

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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)

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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 t-angle) beyond the normal limits.  Ex. Head moving forward as you rear-end a car.  Hyperextension: Sudden extension (increase of the t-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.