Peripheral Neuroanatomy

Peripheral Neuroanatomy Student Learning Outcomes: SLO 1: Spinal Nerves Discuss spinal nerves relative to their formation, branches, and relations to discs and IVF's Discuss the specific sensory, motor, and reflex functions of the C5-T1, and L1-S2, and S2-4 spinal nerves SLO 2: Plexuses Discuss the significance of plexuses in the formation of peripheral nerves of the head/neck, upper and lower extremities. Describe/illustrate the cervical, brachial, lumbar, and sacral plexuses, and identify the major peripheral nerve branches of each plexus SLO 3: Peripheral Nerves List the peripheral nerves which innervate the upper and lower extremities, and discuss their specific sensory, motor, and reflex functions. Identify common sites of potential entrapment/compression for each peripheral nerve and discuss their clinical consequences. SLO 4: Cranial Nerves Name the cranial nerves, identify the cranial foramen which each nerve traverses, and discuss the structures innervated. Discuss the specific functions of each nerve and the consequences of neural compromise. SLO 5: ANS Discuss the general structure and function of ANS, and the specific structure and functions of the sympathetic and parasympathetic divisions. Trace the pathway from the CNS to the effector organ for any sympathetic or parasympathetic function indicating the origin, route and termination of the preganglionic neuron and post-ganglionic neuron. Discuss the clinical features of Horner's Syndrome Discuss the clinical features of Cauda Equina Syndrome Course Summary: DATE Midterm 1 X/30 (25%) DATE Midterm 2 X/30 (25%) DATE Final X/60 (50%) Required Texts: PNS class notes (Canvas) Felton DL, O'Banion MK. Netter's Atlas of Neuroscience. 3rd ed. 2015 Recommended Texts: Warfel J. Extremities: Muscles and Motor Points, 6thed. 1993 Draw It To Know It, (online resource available via library site) Fitzgerald. Clinical Neuroanatomy and Neurosciences. 2016 (available Ebook via library website) Blumenfeld H. Neuroanatomy Through Clinical Cases. 2ned. 2010 Marieb EM. Human Anatomy & Physiology. 10th ed. 2015 Moore KL. Clinically Oriented Anatomy. 8th ed. 2017 Week 1: (4/4) Anatomical Position: FCM Anterior/Ventral: Seen from the front. Posterior/Dorsal: Superior/Cephalad: Headward Inferior/Caudal: Tailward Medial: Toward midline of body OR center of a limb Lateral: Away from midline of body or limb Proximal: Distal: Seen from the back. Closer to the trunk attachment Further from trunk attachment Body Movements: (relative to anatomical position) FCM Flexion: Closing of an angle/joint Extension: Opening of an angle/joint Abduction: Moving away from midline of body OR limb Adduction: Moving toward the midline of body OR limb Internal (Medial) Rotation: Rotating toward the front/midline of the body. External (Lateral) Rotation: Rotating away from the front/midline of body. Lateral rotation of the forearm to where the palms face forward Supination: Medial rotation of the forearm to where the palms face away Pronation: Supination but specific to the foot/ankle Inversion: Pronation but specific to the foot/ankle Eversion: deviation: moving toward "e.g. radial deviation. Lateral deviation Valgus: Distal portion of extremity moving laterally Varus: Distal portion of extremity moving medially. (4/6) What is the Peripheral Nervous System? Any nervous tissue not contained within the spinal cord or brain (cranial, spinal, & peripheral nerves-sensory (afferent) & motor (efferent) neurons The Somatic Nervous System: Comprised of motor neurons coming from the brain/spinal cord and going out to muscles for control & sensory neurons-specialized receptors sensitive to change in the environment (i.e., temperature, pain, various forms of touch, position sense) Sensory Receptors: (FCM) Hair Follicles; Meissner Corpuscle; Pacinian Corpuscle; Merkel Cell-Neurite Complex; Ruffini Corpuscle; C-fibre LTM; Mechano-Nociceptor; Polymodal nociceptor Central adaptation - when the brain stops carrying about a sensory signal (ex. you become desensitized to the smell of your room) Transmission to the CNS: *** Enters the spinal cord through the posterior & transmits up the cord to the thalamus found in the diencephalon. The thalamus acts as a major relay station sorting & directing info in & out of the brain. The thalamus makes sure that info goes to the corresponding part of the brain to be perceived & processed (general somatosensory is found in the parietal lobe, but more on that in the CNS) General Neuronal Anatomy: Dendrites receive; Cell body builds & recycles: Axons send the axon hillock is where action potentials initiate from; axon terminals are where neurotransmitters release from Layers of a Nerve: (deep to superficial) Endoneurium wraps around individual neurons. Perineurium wraps around fascicles (bundles of neurons). Epineurium wraps around an entire nerve (bundles of fascicles). Is continuous with the dura mater of the spinal cord. Nerve Damage & Regeneration: Nerves are often damaged/thinned due to compression and/or traction. Initial damage to the distal axon is known as Wallerian degeneration. This causes the neuron to disintegrate. Following damage to the axon is swelling and release of substance from the cell body known as Chromatolysis (as it prepares regenerate the axon) Regeneration CAN occur in the PNS if: (1-4mm/day needed to save the nerve) The cell body is intact The Schwann cells are intact Regrowth occurs quick enough to reach the target tissue before it dies 1st Degree injury= Neuropraxia- leads to slowing (damages/thins the neurolemma-the outer region) 2nd Degree injury= Axonotmesis (damages/compresses the axon itself) Nerve Exits: Cervical nerves exit above the cervical vertebrae; thoraco-lumbar nerves exit below the same numbered vertebrae. Dermatomes: We've mapped general location of innervation-this is important in being a detective discovering what is the involved nerves in our patient's presentation. A difference in dermatomes means you can be hypersensitive on one thumb or desensitized on the other. Levels of principle dermatomes: T4 (nipples): T7 (xiphoid process); T10 (umbilicus); S2, S3, S4 (perineum) Radiculopathy: Radiculopathy is a common presentation of symptoms related to a specific spinal nerve root The most common ways to affect a nerve root is compression either through a disc herniation or IVF stenosis (narrowing) among other possibilities. The most common disc herniations are posterior lateral which will often compromise 1 spinal nerve root. Due to the orientation/exiting of nerves: Cervical IVF and disc will affect the same nerve root e.g. C5 disc and C5-6 IVF will affect C6 nerve root Thoracic IVF and disc will affect the same nerve root e.g. T2 disc and T2-3 IVF will affect T2 Lumbar IVF will affect the level while discs will affect 1 level lower e.g. L3-4 IVF will affect L3, but an L3 disc will affect L4 Mackenzie protocol and pumping can heal the Dermatomes 2000 disc disc LIC Rule (4/11) Cervical disc herniations are very uncommon by age 30 because the pulposus disappears. nucleus Dermatome Descriptors: C5-anterior shoulder C6-lateral forearm thumb C7-middle finger C8-medial hand & forearm T1: medial arm T2-T12: following rib lines T4: nipple level T7: Xiphoid T10: umbilicus T12: inguinal ligament L1-3: anterior thigh L4: medial shin L5: lateral shin S1: lateral calf S2: medial calf S3-5: bull's eye surrounding the perineum. Levels of principal dermatomes Nipples 17 Xiphold process 718 Umbilicus 52, 53, 54 Perineum Upper Limb Sensory and Motor Examination C CA CS T2- TH C Supraclavicular N. Axillary N. Radial N. Intercostabrachial N Medial Cutaneous of arm Medial Cutaneou Nerve of foncarn Musculocutancou Radial N. Median Na Ulnar N. Motor Function Important Conditions Reflexes Finger Jerk A (4/13) Brachial Plexus: (WE NEED TO BE ABLE TO DRAW THE BRACHIAL PLEXUS) The brachial plexus is comprised of the C5-T1 nerve roots; these roots mix to form various trunks, divisions, cords, and branches. C5-6 form the superior trunk. C7 remains alone for the middle. C8-T1 form the inferior trunk. The superior & middle trunks bifurcate into an anterior & posterior division while the inferior gives off a collateral to the posterior division. Divisions Cords: Cords are named for their orientation around the subclavian artery found between the clavicle & 1 rib. The posterior division become the posterior cord, while the two separate anterior divisions become the lateral and medial cords. Cords Branches: Each cord is responsible for 2 terminal branches. The lateral cord gives off the musculocutaneous nerve and ½ of the median nerve. The posterior cord gives off the axillary nerve and the radial nerve.