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Download Anatomy Written Exam #2 Cranial Nerves Introduction Embryological
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Anatomy Written Exam #2 1. Cranial Nerves a. Introduction Embryological Development 1. Alar Plate o Spinal Cord i. Becomes dorsal horn ii. Nuclei of termination iii. GSA and GVA o Brainstem i. Gives rise to nuclei of termination ii. GSA, GVA, SVA, and SSA 2. Basal Plate o Spinal Cord i. Becomes ventral horn ii. Nuclei of origin iii. GSE and GVE o Brainstem i. GSE, SVE, and GVE CN I CN II CN III GSE, GVE CN IV GSE CN V SVE, GSA CN VI GSE CN VII SVE, GVE CN VIII CN IX SVE, GVE CN X SVE, GVE CN XI SVE CN XII GSE Corticobulbar Projections 1. From the cerebral cortex to brainstem 2. Arise from neurons in premotor, primary motor, and somatosensory cortices 3. Usually bilateral, except for nerves innervating facial expression and tongue muscles b. CN III Oculomotor Nerve GSE Component 1. Location: midbrain 2. Course of LMN: exit oculomotor nucleus and enters IPSILATERALLY into oculomotor nerve 3. Innervate: extraocular muscles 4. No direct corticobulbar projections to brainstem motor nuclei GVE Component 1. Location: Preganglionic, parasympathetics in Edinger-Westphal nucleus o Postganglionics in ciliary ganglion of orbit 1 Anatomy Written Exam #2 2. Innervate: sphincter pupillae and ciliary muscles, which function to constrict pupil and in accommodation Reflexes 1. Pupillary Light Reflex 2. Accommodation Reflex Lesions 1. Ptosis 2. Lateral strabismus- eye abducted and inferiorly rotated 3. Mydriasis 4. Loss of light and accommodation reflexes 5. Inability to laterally gaze to side opposite lesion without double vision (diplopia) c. CN IV Trochlear Nerve GSE 1. Location: midbrain 2. Course of LMN: decussate and exit brainstem on dorsal surface 3. Innervate: CONTRALATERAL superior oblique muscle 4. No direct corticobulbar projections to the brainstem motor nuclei Lesions 1. Eye is elevated at rest 2. Diplopia in vertical plane 3. To test: have patient look medially and then inferiorly to examine superior oblique muscle functioning d. CN V Trigeminal Nerve Location: lateral aspect of mid-level basilar pons Functions: transmission of vibration, touch, conscious and unconscious proprioceptive, pain, and temperature sensations from the head 1. Motor innervation to muscles of mastication GSA 1. Function: general sensations of the face, oral and nasal cavities, dura mater, and proprioception of muscles o Similar to dorsal columns, anterolateral system, and spinocerebellar tracts 2. Three Nuclei: o Spinal Trigeminal Nucleus i. Location: lateral tegmentum of medulla and caudal pons ii. Function: pain, temperature, and crude touch 1. Analogous to anterolateral system o Chief Sensory Nucleus i. Location: dorsolateral pontine tegmentum ii. Function: fine touch, 2-point discrimination, vibratory, and conscious proprioception 1. Analogous to dorsal column system o Mesencephalic Nucleus 2 Anatomy Written Exam #2 i. Location: rostral pons and caudal midbrain ii. Function: unconscious proprioception information 1. Analogous to spinocerebellar system SVE 1. 2. 3. 4. 5. Motor nucleus Location: dorsolateral pontine tegmentum Innervate: muscles of mastication and several others Corticobulbar projections to trigeminal nucleus bilaterally Lesion: paralysis of muscles of mastication, jaw protrusion to side of lesion, and absent jaw jerk reflex Reflexes 1. Corneal Reflex- unilateral stimulation of the cornea results in reflex blinking and eye closure o Direct response- stimulated eye closes o Consensual response- nonstimulated eye closes 2. Lacrimal Reflex- unilateral stimulation of cornea results in tear production e. CN VI f. Abducens Nerve GSE 1. Caudal pons 2. Course of LMN: exit brainstem at pontomedullary junction 3. Innervate: IPSILATERAL lateral rectus muscle 4. No direct corticobulbar projections to the brainstem motor nuclei Lesions 1. Medial strabismus- adducted 2. Inability to laterally gaze to side of lesion without double vision CN VII Facial Nerve SVE 1. Location: caudal pons 2. Course of LMN: exit facial motor nucleus to enter IPSILATERAL motor root of facial nerve 3. Innervate: muscles of facial expression 4. Subdivided into innervation of upper facial muscles BILATERALLY and lower facial muscles CONTRALATERALLY GVE 1. Location: preganglionic, parasympathetics in superior salivatory nucleus in pons o Postganglionic located in IPSILATERAL pterygopalatine and submandibular ganglia 2. Innervate: mucous glands of oral and nasal cavities, lacrimal gland, and submandibular and sublingual salivary glands Lesions 1. To LMN: complete ipsilateral facial flaccid paralysis o fasciculations 3 Anatomy Written Exam #2 2. To UMN: paresis of contralateral lower face and disuse atrophy over time g. CN IX Glossopharyngeal Nerve SVE 1. Location: nucleus ambiguous of medulla 2. Course of LMN: enter IPSILATERAL glossopharyngeal nerve 3. Innervate: stylopharyngeus muscle 4. Bilateral corticobulbar projections GVE 1. Location: preganglionic, parasympathetic in inferior salivatory nucleus and enter IPSILATERAL glossopharyngeal nerve o Postganglionic join auriculotemporal branch of mandibular nerve 2. Innervate: parotid gland Lesions 1. Loss of parotid gland secretions 2. Test: gag reflex h. CN X Vagus Nerve SVE 1. Location: nucleus ambiguous 2. Course of LMN: enter IPSILATERAL vagus nerve 3. Innervate: soft palate and muscles of pharynx and larynx 4. Bilateral corticobulbar projections GVE 1. Location: preganglionic, parasympathetics in dorsal motor nucleus of vagus in medulla o Postganglionic in ganglia of pharynx, larynx, thoracic and abdominal viscera 2. Innervate: mucous membranes of pharynx, larynx, and smooth muscle and glands of thoracic and abdominal viscera Lesion 1. Unilateral o Ipsilateral paralysis of soft palate, causing it to droop and not rise in phonation i. Deviation of uvula to intact side o Ipsilateral vocal cord palsy: hoarseness and coughing 2. Bilateral o Vocal cord paralysis may lead to death by asphyxiation o May increase HR to point of death i. CN XI Spinal Accessory Nerve SVE 1. Location: ventral horn of spinal cord C1-C5; medulla 2. Course of LMN: enter IPSILATERAL spinal accessory nerve 3. Innervate: ipsilateral sternocleidomastoid and trapezius muscles 4 Anatomy Written Exam #2 Lesion 1. 2. 3. 4. j. Ipsilateral shoulder sag Inability to elevate upper limb above horizontal plane Plegia when point chin away from side of lesion Chin points to side of lesion CN XII Hypoglossal Nerve GSE 1. Location: hypoglossal nucleus in medulla 2. Course of LMN: enter IPSILATERAL hypoglossal nerve 3. Innervate: ipsilateral intrinsic and extrinsic muscles of tongue 4. Contralateral corticobulbar projections Lesions 1. LMN o Paralysis of ipsilateral tongue muscles o Deviation of tongue to side of lesion o Atrophy of ipsilateral muscles o Fasciculations 2. UMN o Contralateral paresis in tongue muscles o Deviation of tongue to side opposite the lesion o Disuse atrophy o No fasciculations k. Alternating Motor Systems Hallmark of brainstem lesions Alternating Hemiplegias 1. Lesion of a CN and the corticospinal tract 2. Usually associated with paramedian lesions 3. Ipsilateral LMN signs for CN 4. Contralateral UMN signs for corticospinal tract Alternating Hypoglossal Hemiplegia 1. Aka “medial medullary syndrome” 2. Associated with infarct of paramedian branch of anterior spinal artery and medial portion of ventral medulla 3. Contralateral loss of tactile sensation and conscious proprioception 4. LMN signs for ipsilateral hypoglossal nerve 5. UMN signs for corticospinal tract Alternating Abducens Hemiplegia 1. Associated with infarct of pontine branches of basilar artery and medial portion of ventral pons 2. LMN signs for abducens nerve 3. UMN signs for corticospinal tract Alternating Oculomotor Hemiplegia 1. Aka “Weber’s Syndrome” 2. Associated with an infarct of the basal branch of the posterior cerebral artery and medial portion of ventral midbrain 3. LMN signs for oculomotor nerve 5 Anatomy Written Exam #2 4. UMN signs for corticospinal tract _____________________________________________________________________________________ 2. Thalamus a. Diencephalon Forebrain- consists of diencephalon and cerebral hemispheres Consists of: 1. Thalamus o Largest part o Gateway to cerebral cortex i. Consists of numerous nuclei 1. Transmit general and special sensory information to regions of sensory cortices 2. Receive impulses from cerebellum and basal ganglia and interface with motor regions of frontal lobe 3. Have connections with associative and limbic areas of cortex o Forms dorsal part of third ventricle 2. Hypothalmus o Forms ventral part of third ventricle 3. Subthalamus o Inferior to thalamus, medial to internal capsule, and lateral to hypothalamus o Contains i. subthalamic nucleus- important for control of movement ii. zona incerta- small sheet of gray matter interposed between thalamic nucleus and thalamus 1. function unknown, but believed to recognize thirst and stimulate drinking 4. Epithalamus o Includes the pineal gland and habenular nuclei o Small Location: between brainstem and cerebral hemisphere 1. Continuous with rostral part of midbrain 2. Forms lateral wall of third ventricle o Dorsal part formed by thalamus o Ventral part formed by hypothalamus b. Topographical Anatomy of the Thalamus External Features 1. Hypothalamic sulcus- faint groove that mares the transition between the thalamus and hypothalamus 2. Interthalamic adhesion/mass intermedia- joins two thalami together 3. Stria medullaris thalami- nerve fibers with limbic connections that course along dorsomedial margin of thalamus o Fine ridge of white matter o Associated with feelings of pleasure 6 Anatomy Written Exam #2 4. Anterior pole extends to interventricular foramen 5. Posterior limb of internal capsule lies LATERAL to the thalamus 6. Head of caudate nucleus lies ANTEROLATERAL to thalamus 7. DORSAL part of thalamus forms floor of lateral ventricle Internal Organization 1. Contains the internal medullary lamina, a thin layer of nerve fibers composed of both afferent and efferent connections o Y-shape provides basis for dividing thalamus into three masses: i. Anterior Group ii. Medial Group iii. Lateral Group o Contains intralaminar nuclei, which includes: i. Centromedian Nucleus- largest 1. Afferents from globus pallidus 2. Efferents to stratium ii. Parafascicular Nucleus- similar to centromedian 2. External Medullary Lamina- lateral to main mass of thalamic nuclei o Thin sheet of nerve fibers o Consists of: i. Thalamocortical fibers ii. Corticothalamic fibers o Reticular Nucleus- between lateral medullary lamina and internal capsule i. Afferents from thalamus and cerebral cortex ii. GABA efferents back to thalamus c. Functional Organization of Thalamic Nuclei All thalamic nuclei, except or the reticular nucleus, project to IPSILATERAL cerebral cortex 1. Specific Nuclei- have point to point projections between individual thalamic nuclei and restricted cortical zones o Have well-defined sensory and motor functions 2. Non-specific Nuclei- receive less functionally distinct afferent input o Connect wider areas of cortex, such as the associative and limbic domains Lateral Nuclear Group 1. Contains all specific thalamic nuclei in ventral part of complex o Includes: i. Ventral Anterior Nuclei 1. Occupies rostral part of lateral nuclear mass 2. Afferents are from IPSILATERAL basal ganglia 3. Has reciprocal connections with motor regions of frontal lobe 4. Important part of mechanism by which basal ganglia exert influence on normal movement and abnormalities of movement ii. Ventral Lateral Nuclei 1. Lies immediately caudal to ventral anterior nucleus 7 Anatomy Written Exam #2 2. Subcortical afferents to nucleus originate from IPSILATERAL globus pallidus and substantia nigra and CONTRALATERAL dentate nucleus 3. Efferents project to primary motor cortex of precentral gyrus iii. Ventral Posterior Nucleus 1. Lies between ventrolateral nucleus and pulvinar 2. Termination of all ascending pathways rom spinal cord and brainstem carrying general sensory information from contralateral half of body to conscious level a. Spinothalamic Tract (lateral part of nucleus) b. Medial Lemniscus Tract (lateral part of nucleus) c. Trigeminothalamic Tract (medial part of nucleus) 3. Projects to primary somatosensory cortex in postcentral gyrus of parietal lobe iv. Ventral Medial Nuclei v. Lateral Geniculate Nuclei 1. Part of visual system 2. Site of termination of optic tract 3. Each nucleus receives axons that originated in IPSILATERAL temporal hemiretina and CONTRALATERAL nasal hemiretina 4. Projects to primary visual cortex of occipital lobe vi. Medial Geniculate Nuclei 1. Part of auditory system 2. Receives ascending fibers from inferior colliculus of midbrain 3. Projects to primary auditory cortex of temporal lobe 2. Also has non-specific nuclei in dorsal part o Lateral Dorsal Nucleus- part of limbic system i. Afferents from hippocampus ii. Efferents to cingulate gyrus o Lateral Posterior Nucleus- has connections with sensory association cortex o Pulvinar- largest thalamic nucleus i. Extensive connections with parietal-occipital-temporal association cortex _____________________________________________________________________________________ Study Break: TOP TEN THINGS YOU DON'T WANT TO HEAR IN SURGERY 1 Don't worry. I think it is sharp enough. 8 Anatomy Written Exam #2 2 Nurse, did this patient sign the organs donation card? 3 Damn! Page 84 of the manual is missing! 4 Everybody stand back! I lost a contact lens! 5 Hand me that...uh...that uh.....thingie 6 Better save that. We'll need it for the autopsy. 7 "Accept this sacrifice, O Great Lord of Darkness" 8 Whoa, wait a minute, if this is his spleen, then what's that? 9 "Ya know, there's big money in kidneys. Hell, he's got two of'em 10 What do you mean "You want a divorce?" _____________________________________________________________________________________ 3. Cerebellum a. Largest part of hindbrain Overlies fourth ventricle Connected to brainstem by three pairs of fiber bundles: 1. Inferior Cerebellar Peduncle- connects cerebellum to medulla 2. Middle Cerebellar Peduncle- connects cerebellum to pons 3. Superior Cerebellar Peduncle- connects pons to midbrain b. Functions: entirely motor and operates at unconscious level Maintenance of Equilibrium Posture and Muscle Tone Coordinates Movements c. Consists of two laterally located hemispheres joined by vermis at midline Lies beneath tentorium cerebelli Surface is highly convoluted with folds known as folia d. Fissures divide the cerebellum into three lobes Lobes include: 1. Anterior Lobe 2. Posterior Lobe 3. Flocculonodular Lobe Primary Fissure- separates anterior lobe from posterior lobe Posterolateral Fissure- separates flocculus and nodule e. Internal Structure Outer layer of gray matter known as cerebellar cortex 1. Contains cell bodies, dendrites, and synaptic connections 2. Uniform organization: Three Layers o Molecular Layer- outer i. Fiber rich 9 Anatomy Written Exam #2 o Purkinje Layer- intermediate i. Consists of unicellular layer of purkinje neurons soma o Granular Layer- inner Inner core of white matter that is made up of afferent and efferent fibers 1. Deep within this white matter is four pairs of nuclei o Dentate Nucleus- largest nuclei and only one that can be seen with naked eye i. Thin layer of nerve cells folded into a “crinkled bag” ii. Receives afferent fibers rom inferior olivary nucleus o Emboliform Nucleus o Globose Nucleus o Fastigial Nucleus o Don’t Eat Greasy Food o Fat Guys Eat Doughnuts f. Afferent Projections Originates from spinal cord, inferior olivary nucleus of medulla, vestibular nuclei, and pons Usually terminate in cerebellar cortex and are excitatory to cortical neurons Fibers enter cerebellum through one of the peduncles and proceed to cortex as either mossy fibers or climbing fibers Those from the spinal cord, vestibular nuclei, and pons end as mossy fibers, which branch to supply several folia and end in granular layer 1. Axons of granule cells pass towards cortex and enter molecular layer, where they bifurcate and form parallel fibers Those from inferior olivary nucleus provide excitatory input to purkinje cells as climbing fibers 1. Also excitatory to deep cerebellar nuclei g. Efferent Projections Dendritic arborizations extend towards cortex into molecular layer 1. Parallel fibers go to purkinje cells, giving cells an excitatory synaptic input 2. Axons of the purkinje cells are the only axons to leave cerebellar cortex 3. Project to deep cerebellar nuclei Destinations of efferent fibers from cerebellar nuclei include: 1. Reticular and vestibular nuclei of medulla and pons 2. Red nucleus of midbrain 3. Ventral lateral nucleus of thalamus _____________________________________________________________________________________ 4. Limbic System a. Introduction Brain tissue that surrounds the brainstem and lies beneath the neocortical mantle Includes: 1. Hippocampus 2. Cortical Structures 3. Olfactory Structures 10 Anatomy Written Exam #2 4. 5. 6. 7. 8. 9. 10. 11. Basal Forebrain Structures Parahippocampal Gyrus Cingulate Gyrus Septal Area Thalamic Structures Amygdala Hypothalamus Hippos check out basketball playing chicks since they are hot. o *borrowed from Christina Regelsberger Old part of the brain that is responsible for reactions such as fear, anger, and emotions associated with sexual behavior b. Hippocampal Formation “sea horse” Curved and re-curved sheet of cortex folded into the medial surface of the temporal lobe Three components: 1. Subiculum o Direct continuation of the anterior parahippocampal gyrus o Transitional cortex- layering pattern that runs the spectrum from 6 layers to 3 layers o Hippocampal Sulcus- separates the subiculum from the dentate gyrus 2. Hippocampus Proper o Allocortex o Three Layers: i. Molecular- inner ii. Pyramidal- intermediate iii. Polymorphic- outer o “C” shaped, interacting with the shape of the dentate gyrus o Aka cornu ammonis 3. Dentate Gyrus o Allocortex o Three Layers: i. Molecular- inner ii. Granule- intermediate iii. Multiform- outer o “C” shaped, interacting with the shape of the hippocampus proper “C” shaped in coronal sections Pathways 1. Main Afferent o Perforant Pathway- projection to dentate gyrus o Alvear Pathway- projection to hippocampus proper i. Goes around lateral aspect of hippocampus proper o Dentate Gyrus Projections- axons rom neurons of the granular layer project to and terminate on dendrites of pyramidal neurons in hippocampus proper 11 Anatomy Written Exam #2 2. Efferent Pathway o Fornix- fibers from hippocampus proper and subiculum i. “C” shaped fiber bundle which projects to hypothalamus and septal area ii. Parts: 1. Alveus- thin layer of white matter 2. Fimbria- coalescence of alveus into a compact bundle to leave the surface of the hippocampal formation 3. Crus- continuation of fibria that begins at the posterior limit of the hippocampal formation beneath the splenium 4. Body- where the two crura join together a. Runs inferior to corpus callosum and septum pellucidum 5. Columns- where body splits in two a. Directed ventrally to hypothalamus b. Post-commissural fibers- includes most of fibers i. Traverse hypothalamus and terminate in mammillary bodies and ventromedial hypothalamic nuclei c. Pre-commissural fibers- terminate in septal area, anterior hypothalamus, and substantia innominate Functions 1. No significant olfactory function 2. Stimulation results in changes to autonomics, endocrine, and behavioral functions 3. Involved with recent memory o Large, bilateral lesions result in profound impairment of memory for recent events i. General intelligence remain unaffected ii. Unable to learn new facts and skills iii. Anterograde amnesia- loss of memories taking place after time of brain damage o Damage to mammillary bodies i. Common in alcoholism ii. Korsakoff’s Psychosis 1. Results in memory deficits 2. Severe anterograde amnesia and cell loss 3. Intact intelligence 4. Confabulatory syndrome- make up answers to questions to try and conceal extent of memory loss 5. Damage cannot be repaired c. Amygdala 12 Anatomy Written Exam #2 “almond” Location 1. Found in mediodorsal portion of temporal lobe, anterior and dorsal to tip of inferior horn of lateral ventricle 2. Deep to cerebral cortex of uncus Subdivisions 1. Corticomedial Group- medial portion of amygdala o Blends with cortex of uncus o Receives fibers from olfactory bulb 2. Basolateral Group- largest part of amygdaloid complex o Widespread connections Pathways 1. Stria Terminalis- efferents to septum o “C” shaped fiber tract 2. Ventral Amygdalofugal-efferents to septum and hypothalamus 3. Brainstem Connections Functions 1. Prominent olfactory input, but importance of olfactory is uncertain 2. Stimulation produced pronounced behavioral changes o Arrest reaction- all spontaneous activity ceases as the animal assumes an attitude of aroused attention o Initial phase of fight or flight—interpreting presence of either a threat or lack of a threat 3. Almost all of the same visceral or somatic activities produced by hypothalamus stimulation 4. Destruction produced disturbances in emotional behavior o Placid with not sign of rage, fear, or aggression o Hypersexuality o Kluver-Bucy Syndrome- bilateral removal of anterior temporal lobes i. Fearless and placid ii. Absence of emotional reactions iii. Males become hypersexual and indiscriminate iv. Extreme curiosity v. Voracious appetite vi. Psychic blindness or visual agnosia d. Septal Area Includes both cortical and subcortical nuclei Rostral to anterior commissure and preoptic area near base of septum pellucidum Afferent Pathways 1. From hippocampal formation via pre-commissural fibers of fornix 2. From amygdala via stria terminalis Efferent Pathways 1. To lateral hypothalamus and midbrain tegmentum via the medial forebrain bundle 2. To hippocampus via fornix 13 Anatomy Written Exam #2 Functions 1. Pleasure center 2. Lesions- alterations in sexual and foraging behaviors e. Miscellaneous Limbic Structures Cortical Areas 1. Prefrontal Cortex- areas 9-12 on Brodmann’s o Function- determines affective reactions to present situations on the basis of past experiences 2. Cingulate Gyrus- receives inputs from prefrontal cortex o Projects to hippocampal formation via cingulum bundle o Functions i. Stimulation elicits autonomic and somatic effects ii. Alterations in respiration and circulation iii. Alterations in peristaltic and gut secretion activities iv. Pupillary dilation v. Muscle tone and inhibition of ongoing movements (arrest behavior) vi. Stimulation of anterior portion results in aggressive behavior 1. Lesions to area make them tame and socially indifferent Thalamic Structures 1. Anterior Nucleus- inputs from hypothalamus via mamillothalamic tract and from hippocampus via fornix 2. Dorsomedial Nucleus- inputs from amygdala and prefrontal cortex o Projects back to prefrontal cortex Basal Forebrain Structures 1. Substantia Innominata- contains Basal nucleus of Meynert o Projects throughout neocortex, especially the prefrontal cortex o Major link between limbic system and neocortex o Shows marked cell loss in Alzheimer’s 2. Nucleus Accumbens- where the caudate and putamen are continuous ventrally o Modulatory role in regulating motivationally based motor behaviors o Primary brain interface between motivational state and motor behavior o Role in mediating certain addictions f. Papez Circuit Nerve impulses proceed in both directions around the ring of the limbic lobe _____________________________________________________________________________________ Study Break: The following quotes were taken from actual medical records dictated by physicians. o o o o By the time he was admitted, his rapid heart had stopped, and he was feeling better. Patient has chest pain if she lies on her left side for over a year. On the second day the knee was better and on the third day it had completely disappeared. She has had no rigors or shaking chills, but her husband states she was very hot in bed last night. 14 Anatomy Written Exam #2 o o o The patient has been depressed ever since she began seeing me in 1983 Patient was released to outpatient department without dressing. I have suggested that he loosen his pants before standing, and then, when he stands with the help of his wife, they should fall to the floor. o The patient is tearful and crying constantly. She also appears to be depressed. o Discharge status: Alive but without permission. o The patient will need disposition, and therefore we will get Dr. Blank to dispose of him. o Healthy appearing decrepit 69 year-old male, mentally alert but forgetful. o The patient refused an autopsy. o The patient has no past history of suicides. o The patient expired on the floor uneventfully. o Patient has left his white blood cells at another hospital. o The patient's past medical history has been remarkably insignificant with only a 40 pound weight gain in the past three days. o She slipped on the ice and apparently her legs went in separate directions in early December. o The patient experienced sudden onset of severe shortness of breath with a picture of acute pulmonary edema at home while having sex which gradually deteriorated in the emergency room. o The patient had waffles for breakfast and anorexia for lunch. o Between you and me, we ought to be able to get this lady pregnant. o The patient was in his usual state of good health until his airplane ran out of gas and crashed. o Since she can't get pregnant with her husband, I thought you would like to work her up. o She is numb from her toes down. o While in the ER, she was examined, X-rated and sent home. o The skin was moist and dry. o Occasional, constant, infrequent headaches. o Coming from Detroit, this man has no children. o Patient was alert and unresponsive. o When she fainted, her eyes rolled around the room. o MD during a physical exam, stated, in my ears, "I am unable to arouse this woman", personally, I really don't think he should have bragged about it _____________________________________________________________________________________ 5. Higher Cortical Functions a. Corticocortical Connections Two Classes: 1. Association Fibers- from same hemisphere o Most numerous fiber type o Arise from neurons in supragranular layers of cerebral cortex and terminate in similar layers in ipsilateral hemisphere o Fiber Tracts: i. Unnamed fibers that connect cortical areas within same gyrus ii. ‘U’ fibers that connect adjacent fibers iii. Superior Longitudinal Fasciculus 1. Course from frontal lobe to parietal, occipital, and parietal lobes 15 Anatomy Written Exam #2 2. Link between cortical areas involved with sensory and motor skills of language iv. Superior Occipitofrontal Fasciculus 1. Connects the frontal and occipital lobes v. Inferior Occipitofrontal Fasciculus 1. Connects the frontal lobe with temporal and occipital lobes vi. Cingulum- within cingulate gyrus 1. Connects septal area and parahippocampal gyrus 2. Commissural Fibers- from contralateral hemisphere o Arise from neurons in supragranular layers of cerebral cortex and terminate in similar layers in contralateral hemisphere o Anterior Commissure- small, compact bundle that crosses midline rostral to columns of fornix i. Connects regions of middle and inferior temporal gyri as well as olfactory tracts and bulbs o Corpus Callosum- largest fiber bundle i. Interconnect homologous regions of cortex in the two hemispheres ii. Four components: 1. Rostrum- anterior wall of third ventricle 2. Genu- interconnecting the anterior parts of the frontal lobes 3. Body- interconnecting the remainder of the frontal and parietal lobes a. Connects primary motor cortices 4. Splenium – interconnecting regions of the temporal and occipital lobes a. Connects visual pathways iii. Allow for interhemispheric integration of information o Posterior Commissure- at diencephalonic-mesencephalic junction i. Connect the pretectal nuclei ii. Functions in pupillary light reflexes o Hippocampal Commissure- where fornix-hippocampal efferents cross midline b. Hemispheric Asymmetry Lateral fissure extends father posterior on left side than on the right and it rises more steeply on the right Planum temporale is larger on the left side 1. Larger in people with perfect pitch Male brains are less symmetrical Females tend to have larger, more bulbous spleniums of corpus callosums c. Cerebral Dominance Dominant Hemisphere- hemisphere that is more important for the comprehension and production of language 1. Functions: 16 Anatomy Written Exam #2 o Language and speech o Math o Problem solving in sequential, logical manner o Sign language 2. Has Two Cortical Areas For Language: o Broca’s Area- area 44 and 45 i. On inferior frontal gyrus ii. “motor speech” area iii. Motor skills necessary for generation of propositional language—grammar, syntax, and semantics iv. Projects to areas of primary motor cortex for the execution of the articulation and phonation of speech v. Receives inputs from Wernicke’s area o Wernicke’s Area- area 22 i. In temporal gyri ii. “sensory speech” area iii. Contains the mechanisms for the understanding, comprehension, and formulation of propositional language iv. Receives inputs from auditory, visual, and somatosensory cortices Functions of Non-dominant Hemisphere 1. Recognition and appreciation of simple, spatial relationships 2. Music and poetry 3. Artistic ability 4. Emotion Wada Test- done prior to neurosurgery to localize functions within cerebral hemisphere 1. Have patient lay down with arms raised in air o Have them count out loud backwards o Temporarily anesthetize one hemisphere o In non-dominant hemisphere- arm on opposite side falls down and patient stops counting for a few seconds and then resumes o If dominant hemisphere- arm on opposite side falls down and patient stops counting for a few minutes d. Speech Ability to vocalize by coordinating the muscles controlling the vocal apparatus Mechanical aspect of oral communication Components to Assess During Exam 1. Volume- may be increased or decreased 2. Rate- normal is 100-150 wpm o Increased in Wernicke’s aphasia o Decreased in Broca’s aphasia 3. Articulation o Defects may result in errors such as repeating the same errors when trying to produce certain sounds (dysarthria) 4. Prosody- inflection, affective intent, and pragmatic intent 5. Initiation- timing of speech initiation 17 Anatomy Written Exam #2 e. Speech Disorders Dysarthria- disturbance in articulation 1. Inability to form or produce understandable speech due to lack of motor control over peripheral structures 2. Forms: o Flaccid- due to LMN disease o Spastic- due to UMN disease o Ataxic- due to cerebellar disease Dysphonia- disturbance in vocalization or phonation 1. Inability to vocalize due to a disorder of the larynx or its innervation 2. Most common: laryngitis Phonic Tics and Vocalizations 1. Simple Tics- inarticulate noises and sounds 2. Complex Tics- expressed as articulate words, phrases, or sentences o Ex- Tourette’s o Types: i. Echolalia- involuntary repetition of the last sound, word, phrase, or sentence of another person ii. Coprolalia- involuntary utterance of socially unacceptable or obscene words, phrases, or sentences 3. Other Tics f. Stutter 1. Most commonly developmental 2. More common in males 3. Involuntary repetition of first syllable of a word 4. Stutter- machine-gun like repetition 5. Stammer- initial vocalization followed by prolonged silence 6. May be the result of a struggle for cerebral dominance Language Cognitive aspect of symbolic communication Ability to converse, comprehend, repeat, read, and write Six Parts of Examination 1. Expressive Speech- spontaneous or conversational speech 2. Comprehension 3. Repetition 4. Naming 5. Reading 6. Writing 18 Anatomy Written Exam #2 g. Language Disorders Aphasia- language dysfunctions caused by neurological disorders See attached table. Alexia- loss of ability to read 1. Visual information has lost access to Wernicke’s area 2. Lesion usually to connections in and around angular gyrus 3. Dyslexia- incomplete alexia Agraphia- loss or impairment of the ability to produce written language due to brain dysfunction 1. Lesion usually to inferior parietal lobule, especially angular gyrus Prosopagnosia- inability to recognize familiar faces Aprosodia- problems with prosody, the rhythmic and musical aspects of speech 1. Motor- inability to convey emotions by voice or gestures; monotone 2. Sensory- difficulty comprehending emotional content of speech or gestures h. Agnosia Inability to recognize or be aware of an object when using a given sense, even if that sense is functionally intact Sensory or Tactile 1. Lesions in superior parietal lobe 2. CONTRALATERAL loss of sensory discrimination 3. Inability to recognize objects by touch alone Visual 1. Lesions of visual association cortices 2. Inability to recognize objects by sight alone i. Apraxia Inability to correctly perform certain learned, skilled movements on command Usually able to perform same action in a different context, such as a reflex Three Common Types: 1. Kinetic- lesion of premotor cortex o Difficulties in fine motor control o Loss of ability to make finely graded, precise individual finger movements 2. Ideomotor- lesion of supramarginal gyrus o Inability to perform many complex tasks on command 3. Ideational- seen in degenerative dementia o Inability to perform a series of acts to obtain a goal j. Prefrontal Cortex Does not elicit somatic motor movements when stimulated Helps determine affective reactions to present situations based upon past experiences Monitors behaviors and exercises control based on higher mental faculties Lesions 1. Inappropriate social behavior 2. Difficulties in adaptation and loss of initiative k. Neglect Syndromes Lesion of the non-dominant parietal lobe 19 Anatomy Written Exam #2 Lack of appreciation of spatial aspects of all sensory input from CONTRALATERAL side of body and visual field Patients sometimes ignore half of their body Often deny deficit l. Split-Brain Syndromes Severing the corpus callosum Exhibit no neurological deficits, they look and act normally Inability of blindfolded patient to match an object held in one hand with object held in other hand m. Alexia without Agraphia Lesion of posterior cerebral artery and destruction of visual cortex and splenium Can write but not read _____________________________________________________________________________________ 6. Motor Pathways—Integration a. Basal Ganglia are sometimes referred to as components of the ‘extrapyramidal motor system’ Both pyramidal and extrapyramidal systems are intimately related rather than separate b. Two Main Roles of Basal Ganglia Facilitate movements that are required and appropriate in any particular context Inhibit unwanted or inappropriate movements c. When a movement is initiated from the cerebral cortex…. Impulses discharge through corticospinal, corticobulbar, and corticostriatal pathways to neostriatum, which causes excitation of striatal neurons Striatum has two routes to control basal ganglia output: 1. Direct Pathway o Consists of striatopallidal and striatonigral neurons o Inhibits medial pallidal or pars reticulate neurons i. Leads to disinhibition of target neurons, the VA and VL nuclei of thalamus ii. Results in increase in thalamic neuron activity and excitation of cerebral cortex o Effect: support or facilitate ongoing movements 2. Indirect Pathway o Via subthalamic nucleus o Efferents rom striatum terminate in lateral pallidal segment, inducing inhibition of neurons i. Caused disinhibited subthalamic nucleus ii. Results in an increase in discharge of subthalamic neurons iii. Activates medial pallidal and nigral neurons iv. Inhibition of thalamic and cortical cells, which inhibits unwanted movement d. Pathophysiology of Basal Ganglia Disorders 20 Anatomy Written Exam #2 Normally, dopamine appears to exert an excitatory influence on striatal neurons of direct projection and an inhibitory effect on neurons of indirect pathway Loss of striatal dopamine causes underactivity of direct pathway and overactivity of indirect pathway 1. Leads to disinhibition of subthalamic nucleus Causes akinesia- absence or loss of voluntary movements e. Basal Ganglia Diseases Parkinson’s Disease 1. A neurodegenerative disease, usually in the elderly with an unknown cause 2. Akinesia, flexed posture, rigidity, and a resting tremor 3. Hallmark: degeneration of dopaminergic neurons of pars compacta of substantia nigra and depletion of striatal dopamine levels 4. Most effective treatment is levodopa o Immediate metabolic precursor of dopamine o Converted to dopamine and restores normal striatal function o Long term complication: levodopa induced dyskinesia 5. When drug therapy fails- neurosurgical ablation or electrical stimulation of subthalamic nucleus or medial segment of globus pallidus Huntington’s Disease 1. Excessive, unwanted, abnormal movements 2. Autosomal dominant 3. Chorea and progressive dementia 4. Progressive degeneration of striatum and cerebral cortex 5. Within striatum, attrition of cells that project to lateral segment of globus pallidus o Leads to disinhibition of lateral pallidol neurons and inhibition of subthalamic nucleus o Medial pallidal neurons become underactive, resulting in unwanted, involuntary movements f. Terms for Basal Ganglia Syndromes Unilateral basal ganglia lesions produce effects on CONTRALATERAL side of body Does not cause paralysis, sensory loss, or ataxia Leads to abnormal motor control, alterations in muscle tone, and emergence of abnormal, involuntary movements 1. Bradykinesia- slowness of movement 2. Hypokinesia/akinesia- poverty of movement 3. Normal posture cannot be maintained and limb movements when walking are lost Dyskinesias describe abnormal movements, not underlying disease 1. Tremors- to and fro sinusoidal movement 2. Chorea- sequence of rapid, asymmetrical, and fragmented movements usually affecting distal limbs 3. Dystonia- sustained muscular contractions that give rise to abnormal postures or contortions 4. Athetosis- slow, sinous, writhing movements 21 Anatomy Written Exam #2 5. Myoclonus- sudden, shock like movements, which are usually bilateral and affect upper limbs 6. Tics- stereotyped movements influenced by emotional stress g. Other Basal Ganglia Diseases Hepatolenticular Degeneration 1. Aka Wilson’s disease 2. Autosomal recessive 3. Disorder of copper metabolism 4. Choreo-athetosis and progressive dementia in childhood and youth Sydenham’s Chorea 1. Manifestation of rheumatic fever in young females 2. Abnormal behavior and generalized chorea Hemiballism 1. Violent choreiform movements of limbs on one side of body 2. Caused by lesion of contralateral subthalamic nucleus Dystonia 1. Syndrome of abnormal muscle contraction that produces repetitive involuntary twisting movements and abnormal posturing 2. Affect the arm and hand (writer’s cramp), leg, neck (torticollis), or face and mouth (orofacial dyskinesia) _____________________________________________________________________________________ Study Break: A man was walking home alone late one night when he hears a BUMP... BUMP... BUMP... behind him. Walking faster he looks back, and makes out the image of an upright coffin banging its way down the middle of the street towards him ... BUMP... ....BUMP... ....BUMP... Terrified, the man begins to run towards his home, the coffin bouncing quickly behind him ... faster... faster... BUMP... BUMP... BUMP. He runs up to his door, fumbles with his keys, opens the door, rushes in, slams and locks the door behind him. However, the coffin crashes through his door, with the lid of the coffin clapping ... clappity-BUMP... clappity-BUMP... clappity-BUMP... on the heels of the terrified man. Rushing upstairs to the bathroom, the man locks himself in. His heart is pounding; his head is reeling; his breath is coming in sobbing gasps. With a loud CRASH the coffin breaks down the door. Bumping and clapping towards him. The man screams and reaches for something, anything ... but all he can find is a bottle of cough syrup! Desperate, he throws the cough syrup at the coffin ... .... and of course ... the coffin stops _____________________________________________________________________________________ 7. Sensory Pathways—Integration a. Etiology of Neurological Disease Four Major Types: 1. Extrinsic 22 Anatomy Written Exam #2 o o Treated with neurosurgery Lead to compression of the brain, spinal cord, nerve roots, and peripheral nerves o Investigation: CNS/PNS prior to surgery o Delay in decompression can lead to permanent paralysis, sensory loss, and incontinence 2. Systemic o Treated with medicine i. Can lead to cure o Primarily disorder of organs instead of nervous system o Disrupt neurological function by abnormal metabolism o Caused by: i. Intoxication with drugs ii. Dietary deficiency iii. Failure of cardiorespiratory system, liver, or kidneys iv. Hormonal disorders v. Abnormalities in calcium and potassium balance o Investigation: hematological 3. Vascular o Treated with cardiology o Damage of circulation to nervous system o Thrombosis- occlusion of vessels o Infarction- restricting blood and oxygen supply o Hemorrhage- bleeding into nervous tissues 4. Intrinsic o Treated with neurology o Primary disorders of the nervous system itself o Uncommon o Often chronic and irreversible o Usually genetic i. Paroxysmal Disorders- episodic loss of consciousness, excessive sleep, and headache ii. Inborn Errors of Metabolism- lead to mentally subnormality and disability in children 1. Usually caused by deficiencies in specific enzymes iii. System Degenerations- lead to premature death of certain neuromuscular components o In youth: often have obvious genetic cause o In adults: often more sporadic o Systemic degenerations are selective Causes ranked in order of clinical priority to detect common, life-threatening diseases, or reversible are either established or excluded first Neoplasia- excessive uncontrolled growth of tissues, forming a benign or malignant tumor 1. Primary- arise in neuromuscular tissues themselves 2. Secondary- spread in circulation from other primary organ sites Inflammation of neuromuscular tissue may results from… 23 Anatomy Written Exam #2 1. Infection 2. Immune Disorders o Most common is multiple sclerosis 3. Investigate with microbiological and serological tests of blood and CSF 4. Treat infection with antimicrobials and suppression of immune responses Site of Lesion and Clinical Syndromes 1. In order to understand the relationship between neuroanatomy and clinical signs: o Know routes of major sensory and motor pathways i. Tactile and proprioceptive information passes IPSILATERALLY in the dorsal columns of spinal cord before decussating in lower brain stem and passing via the thalamus to the CONTRALATERAL sensory cortex ii. Sensory pathways for pain and temperature decussate within the spinal cord and travel to CONTRALATERAL spinothalamic column before reaching the contralateral sensory cortex iii. Dissociated sensory loss- damage of one pathway but other pathway is spared o Lesions of LMN and UMN i. LMN 1. Weakness and paralysis of individual muscles 2. Wasting 3. Fasciculation 4. Hypotonia 5. Diminution or loss of deep tendon reflexes ii. UMN 1. Weakness or paralysis of specific movements (pyramidal weakness) 2. NO wasting 3. Spasticity and initial resistance to muscular stretching followed by relaxation 4. Hyperreflexia 5. Babinski reflex o General functions of cerebellum, basal ganglia, and cerebral cortex i. Cerebellar Pathways 1. Plan of an intended movement is transmitted to cerebellum from cerebral cortex and basal ganglia 2. Compares intended movements with actual movements of limbs in space 3. Able to correct deviant movements 4. Lesions: a. Incoordination of movements (ataxia) of head, neck, and limbs in the absence of weakness or loss of sensation 24 Anatomy Written Exam #2 b. Unilateral lesions lead to IPSILATERAL loss off coordination 5. Cerebellar Syndrome- nystagmus, dysarthria, intention tremor of upper limbs, and gait ataxia ii. Basal Ganglia 1. Receive sensory and motor information from all parts of cerebral cortex, brain stem, and spinal cord 2. Facilitate useful, purposeful movements and inhibit unwanted movements 3. Control of posture and muscle tone 4. Lesion: a. Loss of control over voluntary movements and posture b. Unilateral lesions cause CONTRALATERAL symptoms c. Do NOT lead to loss of sensation, power, or coordination iii. Cerebral Cortex 1. Functions of language, perception, spatial analysis, learned skilled movements, memory, and problem solving are organized here 2. Language functions organized in frontal, parietal and temporal lobes adjacent to lateral fissure 3. Primary visual processes organized in occipital lobes 4. Perception or recognition of objects and faces are organized in projections to temporal lobes 5. Spatial ability to navigate limbs and body in space is organized in parietal lobes 6. Premotor areas of frontal lobes govern enactment of learned, skilled movements of head, neck, and limbs 7. Structure in medial aspects of temporal lobes are responsible for learning new information and recollecting from experience 8. Organization of behavior is organized in prefrontal areas of frontal lobes 2. Examine: o Cranial nerves and motor system o Reflexes o Sensations o Coordination GOOD LUCK!!!! 25