Review: Neuroanatomy & Neurophysiology For Clinical Neuroscience, Part 1 & 2 PDF

Review: Neuroanatomy & Neurophysiology For Clinical Neuroscience; Part 1 Sekh Thanprasertsuk, M.D. Department of Physiology Faculty of Medicine, Chulalongkorn University CNS PNS motor sym sensory parasym Outline of Talk System-based Structure-based • Motor system • Sensory system • Visual...

Review: Neuroanatomy & Neurophysiology For Clinical Neuroscience; Part 1 Sekh Thanprasertsuk, M.D. Department of Physiology Faculty of Medicine, Chulalongkorn University CNS PNS motor sym sensory parasym Outline of Talk System-based Structure-based • Motor system • Sensory system • Visual system • ANS • Headache • Peripheral nerve • Spinal cord • Brainstem and cranial nerves • Cerebral cortex Motor System • Pyramidal system • Extrapyramidal system Pyramidal System Anatomy of Pyramidal System Motor cortex Corona radiata Internal capsule Corticospinal Corticobulbar tract tract Facial nerve Cervical Brachial Ant. horn cell (motor neuron) nerve roots plexus Ant. horn cell (motor neuron) L/S nerve roots L/S plexus Facial muscles Radial/median/ulnar nerves Femoral/sciatic nerves Upper limb muscles Lower limb muscles Anatomy of Pyramidal System Motor cortex Corona radiata Internal capsule “Hemiparesis” almost always indicates CNS lesion at corticospinal tract (contralaterally) Corticospinal Corticobulbar tract tract Facial nerve Cervical Brachial Ant. horn cell (motor neuron) nerve roots plexus Ant. horn cell (motor neuron) L/S nerve roots L/S plexus Facial muscles Radial/median/ulnar nerves Femoral/sciatic nerves Upper limb muscles Lower limb muscles Anatomy of Pyramidal System Hemiparesis characterized by different degree of weakness between upper and lower limbs: Cortical lesion or superficialcorona radiata lesion (Internal capsule and brainstem should not involve) Axon nAChR Vesicle Voltage-gated Na channel VAChT Voltage-gated Ca channel Acetyl-CoA ChAT ACh Choline Muscle fiber Axon nAChR Vesicle Voltage-gated Na channel VAChT Voltage-gated Ca channel Ca2+ Acetyl-CoA ChAT ACh Choline Muscle fiber Axon nAChR Vesicle Voltage-gated Na channel VAChT Voltage-gated Ca channel Acetyl-CoA ChAT Ca2+ ACh Choline Na+ Na+ Na+ Na+ Muscle action potential Muscle fiber Depolarization (end plate potential) Axon nAChR Vesicle Voltage-gated Na channel VAChT Voltage-gated Ca channel Acetyl-CoA ChAT Ca2+ ACh Na+ Na+ Na+ Na+ Muscle action potential Choline AChE Choline + acetate Muscle fiber Depolarization (end plate potential) Clinical Aspects of ACh • Lambert-Eaton Myasthenic syndrome (LEMS) inhibition of presynaptic VGCC • Botulinum neurotoxin (BoNT, Botox) inhibition of Ach release from axon terminal • Muscle relaxants & snake alpha-neurotoxin blockage of nicotinic Ach receptor • Myasthenia gravis (MG) inhibition & downregulation of nicotinic Ach receptor • Organophosphate compound inhibition of acetylcholinesterase enzyme • Alzheimer’s disease & other dementias impairment of cholinergic projection in CNS Stretch reflex Spinal cord (Reciprocal inhibition) Stretch reflex in clinical setting: Deep tendon reflex (DTR) examination γ-motor neuron α-motor neuron Clinical Aspects of Stretch Reflex • Deep tendon reflex examination - Hyporeflexia / areflexia (Injury or dysfunction of reflex arc) - Hyperreflexia (Increased activity of γ-motor neuron) • Spasticity “Clasp-knife phenomenon” A phenomenon occurring in patient who has spasticity Motor System • Pyramidal system • Extrapyramidal system Extrapyramidal System Extrapyramidal tract Basal ganglia & cerebellum Cerebrum & Diencephalon Motor Cortex Corticospinal tract (Pyramidal tract) Midbrain Lower brainstem Red nucleus (Rubrospinal tract) (Reticulospinal tract) Reticular formation Vestibular system (Vestibulospinal tract) “Pyramidal Weakness” • Weakness pattern caused by corticospinal (pyramidal) tract lesion • Upper limb: extensors weaker than flexors • Lower limb: flexors weaker than extensors CNS control of voluntary movement Basal ganglia Cerebellum Sensation Somatic, visual, auditory, etc. Processing “Idea” to move Higher order motor cortex Primary motor cortex Voluntary movement Basal Ganglia Circuit Cerebral cortex Striatum (caudate, putamen) D1 receptor (excitatory) D2 receptor (inhibitory) SNc Thalamus GPe STN Glutaminergic GABAergic GPi SNr Parkinsonism • A clinical syndrome: bradykinesia, rigidity, rest tremor, postural instability • Parkinson’s disease degeneration of SNc causing parkinsonism Rigidity VS Spasticity RIGIDITY SPASTICITY • Velocity independent • Velocity dependent • No clasp-knife phenomenon • Clasp-knife phenomenon • Extrapyramidal lesion • Pyramidal lesion • No definite pattern • Pyramidal pattern Visual input Unconscious Proprioceptive input Vestibular input Integrator: CEREBELLUM Extrapyramidal motor control Conscious Roles of Cerebellum Outline of Talk System-based Structure-based • Motor system • Sensory system • Visual system • ANS • Headache • Peripheral nerve • Spinal cord • Brainstem and cranial nerves • Cerebral cortex Visual System Anatomical Localization: Visual Loss • Cornea, iris, lens, vitreous, retina • Optic nerve • Optic chiasm • Optic tract, visual radiation • Occipital cortex Visual Pathway Anatomical Localization: Visual Loss Monocular visual loss: anterior visual pathway, pre-chiasmatic lesion Binocular visual loss: posterior visual pathway, chiasmatic/post-chiasmatic lesion Visual Pathway Homonymous Hemianopia? Incongruous Pre-occipital lesion Congruous Occipital lesion Autonomic Nervous System HYPOTHALAMUS EWN Lacrimal gland Nasal mucosa SM gland SL gland PPG SSN SMG ISN NA Vagus n. CG Pupil Ciliary m. OG Parotid gland Oral mucosa To Muller’s muscle, pupil, facial cutaneous vessels & sweat glands To internal organs, blood vessels, skin appendages, etc. To distal colon & urogenital organs Bladder Innervation: Efferents Hypogastric n. Pudendal n. Pelvic splanchnic n. Bladder Innervation: Afferents Hypogastric n. Pudendal n. Micturition Control Pontine micturition center Patterns of Neurogenic Bladder 1. Suprapontine lesion Pontine micturition center 2. Spinal lesion (UMN) Patterns of Neurogenic Bladder 2. Spinal lesion (UMN) Hypogastric n. Pudendal n. Pelvic splanchnic n. Patterns of Neurogenic Bladder Hypogastric n. 3. LMN neurogenic bladder Pudendal n. Anatomy and Physiology of Headache Pain Sensitive Structures in the Head • Blood vessels - Large arteries - Large veins, cerebral sinovenouses • Meninges - Pachymeninges (dura) - Leptomeninges (arachnoid, pia) • Paracranial structures (bone, sinuses, eyes, orbits, ear canals, teeth, TMJ) • Cranial musculature and fascia • Nerves (CN5, CN7, CN9, CN 10, C2, C3) Types of Headache Primary headache • Migraine headache • Tension-type headache (TTH) • Trigeminal autonomic cephalalgias (TACs) • Others Secondary headache • Vascular pain • Meningeal pain Mechanical force Chemical irritation • Pain from paracranial structures • Neuropathic pain Vascular Headache • Pain location depends on affected vessel o Abnormal vessel (e.g. AVF, AVM) in right frontal lobe cause right frontal headache o Systemic disorder (e.g. hypertension, fever) cause diffused headache • Throbbing sensation Meningeal Pain • Meningeal pain caused by mechanical (usually traction) force o Focal traction (e.g. superficial tumor, pachymeningitis) o Diffused traction (increased ICP) • Meningeal pain caused by chemical irritation (e.g. meningitis, SAH) • Diffused headache (esp. orbits – temporals – occipitals) • Accompanied by nausea and vomiting Pain from Paracranial Structures • Pain location depends on affected structures • Nociceptive stimulation at structure locating at base of skull causes referred pain Cranial Neuralgias • Pain location depends on affected nerve • Neuropathic pain character • Common disorders: o Trigeminal neuralgia o Occipital neuralgia Outline of Talk System-based Structure-based • Motor system • Sensory system • Visual system • ANS • Headache • Peripheral nerve • Spinal cord • Brainstem and cranial nerves • Cerebral cortex Review: Neuroanatomy & Neurophysiology For Clinical Neuroscience; Part 1 Sekh Thanprasertsuk, M.D. Department of Physiology Faculty of Medicine, Chulalongkorn University Review: Neuroanatomy & Neurophysiology For Clinical Neuroscience; Part 2 Sekh Thanprasertsuk, M.D. Department of Physiology Faculty of Medicine, Chulalongkorn University Outline of Talk System-based Structure-based • Motor system • Sensory system • Visual system • ANS • Headache • Peripheral nerve • Spinal cord • Brainstem and cranial nerves • Cerebral cortex Concept of PNS Peripheral Nervous System Motor neuron Nerve root Plexus Peripheral nerve Peripheral Nerve Peripheral Nerve Fiber Types Diameter (um) Myelin CV (m/s) A Voluntary motor Proprioception (Ia, Ib) 12-20 Yes 80-120 Aβ Touch, pressure (II) 6-12 Yes 30-70 Aδ First pain, cold, touch (III) 1-5 Yes 12-30 B Preganglionic ANS <3 Light 3-15 C Second pain, hot (IV) Postganglionic ANS <1.5 No 0.5-2 Disorders in PNS • • • • • • Motor neuron disease Radiculopathy Plexopathy Peripheral neuropathy NMJ disorders Myopathy Disorders in PNS • • • • • • Motor neuron disease Radiculopathy Plexopathy Peripheral neuropathy NMJ disorders Myopathy dorsal scapular suprascapular subclavius lateral pectoral C5 musculocutaneous C6 axillary median radial C7 long thoracic US T C8 ulnar LS medial cutaneous T1 medial pectoral root trunk div cord US – upper subscapular T – thoracodorsal LS – lower subscapular Disorders in PNS • • • • • • Motor neuron disease Radiculopathy Plexopathy Peripheral neuropathy NMJ disorders Myopathy Peripheral Neuropathy • Mononeuropathy • Multiple mononeuropathies (mononeuritis multiplex) • Polyneuropathy • Demyelinating polyneuropathies (non-length dependent) • Axonopathies (length dependent) Outline of Talk System-based Structure-based • Motor system • Sensory system • Visual system • ANS • Headache • Peripheral nerve • Spinal cord • Brainstem and cranial nerves • Cerebral cortex Spinal Cord Essential Anatomy of Spinal Cord SLTC CTLS SLTC CTLS Extrinsic vs Intrinsic Cord Lesion Extrinsic lesion Intrinsic lesion Motor Ascending weakness Variable Sensory Ascending sensory loss to pinprick Variable ± Hanging sensory loss Autonomic Late May be early Pain Somatic pain (bone, ligament) with tenderness Radicular pain ± Funicular pain ± Lhermitte’s phenomena Spinal Cord Syndromes Rt Lt Brown-Sequard syndrome Central cord syndrome Anterior 2/3 syndrome Posterior 1/3 syndrome Proprioception loss below lesion Ipsilateral weakness Contralateral numbness Motor weakness Cape-liked / hanging sensory loss Autonomic involvement Motor & sensory loss below lesion Spare proprioception Decreased pinprick sensation Complete cord syndrome Outline of Talk System-based Structure-based • Motor system • Sensory system • Visual system • ANS • Headache • Peripheral nerve • Spinal cord • Brainstem and cranial nerves • Cerebral cortex Brainstem and Cranial Nerves Medulla, CN 9-12 Pons, CN 5-8 Midbrain, CN 3-4 Orbital Mechanics Muscle Innervation Function(s) Medial rectus (MR) Oculomotor n. (CN 3) Adduction Lateral rectus (LR) Abducens n. (CN 6) Abduction Superior rectus (SR) Oculomotor n. (CN 3) Elevation, Intorsion Inferior rectus (IR) Oculomotor n. (CN 3) Depression, Extorsion Superior oblique (SO) Trochlear n. (CN 4) Intorsion, Depression Inferior oblique (IO) Oculomotor n. (CN 3) Extorsion, Elevation Extraocular Muscles Examination SR SR>IO IO IO SR>IO SR MR MR LR IR IR>SO SO LR SO IR>SO IR Clinical Manifestations in CN 3, 4, 6 palsy/palsies “binocular diplopia” Left CN6 Palsy Resting position Performing Rt lateral gaze Performing Lt lateral gaze Left CN4 Palsy Resting position Performing Rt lateral gaze Performing Lt lateral gaze Left CN3 Palsy Lt eye ptosis (CN3 also supplies levator palpebrae superioris m.) Left CN3 Palsy Resting position Lt eye ptosis (CN3 also supplies levator palpebrae superioris m.) • Good performance only on eye abduction • Light reflex (parasym) may also be affected in compressive lesion (not in ischemic lesion) Eye Movement: Horizontal Saccade Frontal eye field (FEF) commands the contralateral gaze. (e.g. looking to the Lt is commanded by Rt FEF) Rt eye Rt FEF Rt MR Rt CN3 Oculomotor N MLF Midbrain PPRF Pons Rt Lt Lt eye Lt LR Lt CN6 MLF – medial longitudinal fasciculus Abducens N PPRF – paramedian pontine reticular formation (horizontal gaze center) Ocular Manifestation in patient with a lesion in horizontal gaze control pathway • • • • FEF lesion PPRF lesion MLF lesion PPRF+MLF lesion (1) FEF Lesion Rt eye Lt eye • Cannot perform contralateral horizontal saccade • Forced eye deviation to the side of FEF lesion (2) PPRF Lesion Rt eye Lt eye • Cannot perform ipsilateral horizontal saccade • Forced eye deviation opposite to the side of PPRF lesion (3) MLF Lesion Lt eye Rt eye Resting Looks to the left! Looks to the right! (3) MLF Lesion “Internuclear ophthalmoplegia (INO)” • Adduction impairment of ipsilateral eye • Abducting nystagmus of contralateral eye • Preserved convergence Common causes: stroke, multiple sclerosis (4) PPRF+MLF Lesion Lt eye Rt eye Resting MLF Midbrain Looks to the left! PPRF Pons Rt Lt Looks to the right! “One-and-a half syndrome” • FEF lesion Forced eye deviation to the side of lesion Concomitant contralateral hemiparesis • PPRF lesion Forced eye deviation to the opposite side Concomitant contralateral hemiparesis • MLF lesion Internuclear ophthalmoplegia (INO) • PPRF+MLF lesion One-and-a half syndrome Concomitant contralateral hemiparesis Vertebrobasilar Arterial System Vertebrobasilar Arterial System Wallenberg Syndrome Lateral medullary syndrome PICA infarction • Central vertigo • Hoarseness, dysphagia • Alternating hemiparesthesia • Ipsilateral limb ataxia • Ipsilateral Horner’s syndrome Paramedian Pontine Infarction Infarction of paramedian branch of basilar artery Alternating hemiparesis Contralateral proprioception loss One-and-a half syndrome Weber Syndrome Medial midbrain syndrome Infarction of PCA perforator • Contralateral hemiparesis • Ipsilateral CN3 palsy Top of Basilar Syndrome Infarction of: - Occipital cortices - Mesial temporal cortices - Midbrain - Thalami Clinical manifestations: - Visual problems - Memory problem - Oculomotor dysfunction - Pupillary defects - Altered consciousness - Peduncular hallucinosis **Beware of clot propagation** Dorsal Midbrain Syndrome NOT A VASCULAR SYNDROME PA PC SC SC • Parinaud syndrome • Classical presentation: - Vertical gaze palsy (esp. upward gaze) - Light-near dissociation (Pseudo Argyll-Robertson pupils) - Collier’s sign - Convergence retraction nystagmus PA – pretectal area SC – superior colliculus PC – posterior commissure Interstitial nucleus of Cajal Oculomotor nucleus complex Outline of Talk System-based Structure-based • Motor system • Sensory system • Visual system • ANS • Headache • Peripheral nerve • Spinal cord • Brainstem and cranial nerves • Cerebral cortex Hierarchy of Behaviors Cerebral cortex Intellectual behaviors (e.g. verbal reasoning, calculating, abstract thinking, etc.) Limbic system & hypothalamus • Basic drive and survival instinct • Emotion • Memorization and learning Brainstem Consciousness level and basic arousal Perception and Recognition Somatosensory cortex Auditory cortex Visual cortex Temporo-parieto-occipital association cortex Agnosia • Inability to interpret sensory information • Example: - Visual agnosia - Astereognosis, agraphesthesia Motor Planning Primary motor cortex Higher-order motor area Temporo-parieto-occipital association cortex CNS control of voluntary movement Basal ganglia Cerebellum Sensation Somatic, visual, auditory, etc. Processing “Idea” to move Higher order motor cortex Primary motor cortex Voluntary movement Apraxia • Failure of motor planning (loss of information regarding skilled movement) • Absence of: - Motor weakness Abnormal tone / posture Movement disorders Intellectual disturbances / uncooperativeness Apraxia Primary motor cortex Ideomotor apraxia Limb-kinetic apraxia Higher-order motor area Temporo-parieto-occipital association cortex Ideational apraxia Conceptual apraxia Apraxia-liked Syndrome • Dressing apraxia • Constructional apraxia Visuospatial disability “Right parietal area” Apraxia-liked Syndrome: Gait Apraxia Causes of Gait Apraxia Frontosubcortical area Hydrocephalus Chronic cerebral small vessel disease Classical Language Pathway Wernicke’s area Broca’s area Sensory aphasia Motor aphasia Global aphasia Modern Concept of Language Pathway 1 – pars opercularis, 2 – pars orbitalis 3 – pars triangularis 4 – prefrontal cortex 5 – ventral premotor area 6 – temporoparietal junction 7 – inferior temporal gyrus 8 – middle temporal gyrus 9 – anterior temporal lobe Modern Concept of Language Pathway Purple – Arcuate fasciculus Green – Uncinate fasciculus Orange – Inferior longitudinal fasciculus Sky blue – Superior longitudinal fasciculus Yellow – Inferior fronto-occipital fasciculus Sung Ho Jang. 2013 Types of Aphasia Aphasia type Fluency Comprehension Repetition Word finding Motor aphasia  ✓   Transcortical motor aphasia  ✓ ✓  Sensory aphasia ✓    Transcortical sensory aphasia ✓  ✓  Global aphasia     Conduction aphasia ✓ ✓   Anomic aphasia ✓ ✓ or  ✓  Lateralization of Cognitive Function Dominant: Language function Math skill Complex motor skill Non-dominant: Music, Prosody Visuospatial ability Human Cerebral Cortex Motor planning (praxis) Apraxia Apraxia Motor planning (praxis) Executive function Working memory Recognition Aphasia Broca’s area Expressive language Motivation Emotion Learning Memory Wernicke’s area Receptive language Aphasia Agnosia Frontal Lobe Syndrome (prefrontal component) • Dorsolateral prefrontal cortex - Executive dysfunction, defect in planning Concrete thinking Unable to sustain attention • Dorsomedial prefrontal cortex - Apathy / akinetic mutism Monitor and adjust behaviors using ‘working memory’ Motivation Initiation of activity • Orbitofrontal cortex (part of limbic system) - Emotional lability - Disinhibition, perseverance - Unable to sustain attention Emotional input Suppression ofdistracted signals Limbic Syndrome • Function: memory formation, control of instinct and emotion • Defect: - Amnestic syndrome i.e. episodic memory impairment - Emotional disturbances - Pathologic instinctive behaviors Cerebral Vasculature Anterior circulation Posterior circulation Cerebral Vasculature MCA Stroke Syndrome Left MCA stroke Right MCA stroke • Right hemiparesis • Left hemiparesis • Aphasia • Apraxia • Visuospatial defect, left hemineglect • Impaired right horizontal saccade • Impaired left horizontal saccade Cerebral Vasculature Neurobehavioral Disorders • Focal (or multifocal) neurobehavioral disorders o Vascular disorders (ischemic, hemorrhage) o Traumatic brain injury o Encephalitis o Brain tumor o Etc. • Diffused neurobehavioral disorders o Delirium o Neurodegenerative dementia Outline of Talk System-based Structure-based • Motor system • Sensory system • Visual system • ANS • Headache • Peripheral nerve • Spinal cord • Brainstem and cranial nerves • Cerebral cortex Review: Neuroanatomy & Neurophysiology For Clinical Neuroscience; Part 2 Sekh Thanprasertsuk, M.D. Department of Physiology Faculty of Medicine, Chulalongkorn University