A Short Course in Neurology for the SLP: Unraveling the Neurological Knot

Transcription

1 A Short Course in Neurology for the SLP: Unraveling the Neurological Knot "If the human mind were simple enough for us to understand, we would be too simple minded to understand it. Anonymous Overview: Medical Speech Language Pathology: A Brief History Neurological basis for swallowing, speech and language A Neuro diagnostic algorithm Neurological assessment for the SLP 1

2 MEDICAL SPEECH LANGUAGE PATHOLOGY Early challenges: A Brief History 1. Establishing a role for the SLP in medical setting 2. Education of SLPs equipped to work in medical settings 3. Educating physicians and other health professionals 4. Demonstrating economic viability Treatment rationale for hypokinetic dysarthria Utilize learning and cortical motor drive to improve function 2

3 Treatment rationale for a case with ataxic dysarthria Utilize previously learned prosodic patterns to improve function Neurological Basis for Swallowing, Speech and Language 3

4 About 100 billion neurons in human brain. Neurons come in a variety of shapes and sizes Bipolar: Found in retina of eye and as interneurons in gray matter of spinal cord and brainstem 4

5 Unipolar: Senory neurons have 1 axon and no dendrites. Axons are often several feet long. Pyrimidal cells: Found in cerebral cortex and limbic system. They are excitatory units of prefrontal cortex and corticospinal/corticobulbar tracts (direct UMNs) 5

6 Motor neuron: Cell bodies located in gray matter of spinal cord and brainstem with axons projecting out of CNS into the PNS in spinal nerves or cranial nerves. Axons innervate muscle fibers to activate muscle contraction. Pain!!! 1 st Motor Neuron UMN 2 nd Motor Neuron LMN Spinal cord 6

7 1. A single neuron may synapse on multiple sites at a second neuron 2. A single neuron may synapse on many additional neurons Neural Impulse: Myelinated Axon Relatively fast; about 260 mph, but much slower than electricity Neural Impulse: Unmyelinated Axon Relatively slow impulse; about 2 mph 7

8 Upper and Lower Motor Neuron Concepts Motor cortex/ Forebrain Bulb/ Brainstem/ Hindbrain Bulbar musculature Head & Neck 8

9 Upper & Lower Motor Neurons These UMNs are direct activation pathways Cranial nerve LMN UMN Note that UMNs supply brainstem nuclei on both sides!!! (Not so for UMNs going to the spinal cord for arms, legs and trunk). 2 Types of UMNs: Direct and Indirect Activation Pathways Direct UMNs Skilled, voluntary movements Indirect UMNs Automatic, unconscious, movements (e.g., normal posture, tone reflexes ) 9

10 UMN vs. LMN lesions Bilateral UMN damage necessary to cause pseudobulbar symptoms UMN Unilateral LMN damage sufficient to cause bulbar symptoms LMN Rules of Thumb! 1. Unilateral UMN = rarely severe, lasting dysphagia 2. Bilateral UMN = spastic, supranuclear dysphagia 3. Unilateral LMN = incomplete paralytic dysphagia 4. Bilateral LMN = paralytic dysphagia or aphagia 10

11 Motor neuron functions UMN impulses are largely INHIBITORY Direct UMNs initiate voluntary movement Indirect UMNs constantly maintain normal muscle tone, posture and reflexes LMNs innervate muscle fibers and transmit impulses received from UMNs LMN UMN Example: Palatal movement and gag reflex Indirect UMNs maintain tone/posture of palate and regulate reflexes Direct UMNs initiate palate movement Inhibitory UMN influence Medulla 11

12 Summary: UMN / LMN Lesions 1. UMN diseases and syndromes usually damage both DIRECT and INDIRECT pathways affect both voluntary and involuntary movements a) Unilateral lesions cause spastic hemiparesis and hyperactive reflexes contralateral to the side of lesion b) Bilateral disease causes spastic tone and weakness in bulbar muscles spastic dysarthria and dysphagia (pseudobulbar syndrome) Summary: UMN / LMN Lesions 2. LMN diseases and syndromes may cause flaccid muscle tone, loss of sensation, paralysis, absent reflexes, atrophy and fasciculations a) Spinal LMN lesions affect the trunk and limbs on the affected side b) Brainstem LMN lesions affect bulbar functions: flaccid dysarthria, flaccid dysphagia, respiratory insufficiency 12

13 Motor Control Systems Contribute to indirect UMN pathways 1 2 Motor neurons in brainstem and spinal cord Motor Control Systems Basal ganglia posture stability muscle tone Cerebellum coordination timing of movement Both communicate with motor cortex via the thalamus 13

14 Motor Control: Basal Ganglia Striatum 14

15 Conceptual Basis for BG Function + + = normal excitation = normal inhibition BG operate using important neurotransmitters GABA (inhibitory) glutamate (excitatory) dopamine (both excitatory and inhibitory effects) acetylcholine (both excitatory and inhibitory effects) 15

16 Motor Control: Cerebellum Essential for motor control in timing voluntary movements Lesions may cause ataxia dysmetria and overshooting intention tremor Coordinates by controlling errors Rapid movements most affected (speaking, running, playing a musical instrument, dancing ) The motor plan Corrections Thalamus Frontopontinecerebellar tract Muscle information (position, stretch, tension ) 16

17 Cerebellum Receives input from peripheral sensory systems (position, muscle tone stretch, tension ) Receives input from motor cortex on intended, voluntary movement Compares what is intended to sensory input received Corrections are sent back to motor cortex Cerebellar output to vestibular nuclei influences muscle tone and balance in skeletal muscles SUMMARY UMNs, LMNs and Motor Control Systems 1. Indirect UMNs constantly activate LMNs with a balance of excitatory and inhibitory signals to maintain a steady, stable muscle platform (normal tone, posture, reflexes) 2. In turn, LMNs constantly send impulses to innervated muscle fibers to maintain a normal state 3. Direct UMNs send impulses to activate LMNs for voluntary, skilled movements 4. All UMN impulses are influenced by motor control centers basal ganglia and cerebellum 17

18 Swallowing Sensory motor response Voluntary & automatic movements Multiple cranial nerves Movements sequenced by a central pattern generator A Sensory Motor Response motor cortex brainstem Vol. movement & normal tone Patterned mouth response & throat 18

19 LMN = Cranial Nerves for Swallowing 5 Jaw movement, facial sensation, oral sensation 7 Facial movement, taste 9/10 Taste, Palate & pharynx movement, gag, vocal folds 12 Tongue movement Swallowing: a patterned motor response Swallowing depends on: 1. Indirect UMN system provides a balance of +/ impulses to LMNs to maintain an adequate platform (normal tone, strength, range ) for swallowing 2. Intact sensory system 3. A central pattern generator receiving sensory input and distributing impulses in correct sequence 4. LMNs sending the sequence of impulses to muscles of swallowing via CNs 19

20 CENTRAL PATTERN GENERATOR FOR SWALLOWING Supramedullary Input groups of paired nuclei in the medulla Dorsal group receives sensation from oral structures via CNs AND cortical input via UMNs Ventral group distributes swallow drive to various CN nuclei [CNs then activate appropriate muscles] 12 Peripheral Afferent Input C1-C3 Central Pattern Generator for Swallowing Swallowing can be elicited from activation of either side BUT, a unilateral medullary lesion is capable of significantly impairing swallowing 20

21 Central Pattern Generator Supramedullary Input When input to DORSAL N reaches a threshold, it activates VENTRAL N which then distributes impulses to swallowing muscles in a patterned sequence Dorsal Ventral Velum, pharynx, larynx Peripheral Afferents Supramedullary (cortical) trigger Ventral CPG orchestrates patterned motor response (via CNs 5, 7, 9, 10, 12 and C 1-3) Dorsal CPG integrates input Sensory receptors for taste, touch, temp stimulated (CNs 5, 7, 9, 10) 21

22 A Most Complex and Unique Mechanism Conversational speech: ~ 100 muscles contributing ~ 100 neuromuscular junctions per muscle ~ 14 sounds per second = ~ 140,000 neuromuscular events per second Doesn t include incalculable neural activity involving cognition and language! right left Left brain motor programming for speech eventually drives LMNs for patterned movements of articulation, phonation and respiration. 22

23 MOTOR SPEECH Motor Control Systems Frontal lobes (Broca s) for motor speech plan Cerebellum Direct & Indirect UMN activation tracts Basal Ganglia LMNs serving Cranial Nerves 5, 7, 9, 10, 12 LANGUAGE IN THE BRAIN Each brain consists of 100,000 miles of myelin-covered nerve fibers There are 86 billion neurons in the adult brain Each neuron has between 1000 and 10,000 synapses There are about 125 trillion synapses in the cerebral cortex alone 23

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25 This is a modular model of language processing Also called box and arrow Knowledge is contained within a box and pathways connect boxes Knowledge stored locally, and processed serially one process at a time 1. See a cow 2. Find the word cow 3. Say cow Modular models led to aphasia syndrome classification systems: Broca s nonfluent, agrammatic Wernicke s fluent with impaired comprehension Conduction fluent but hesitancies with word finding issues, paraphasias, sometime jargon, can t repeat Transcortical motor nonfluent, like Broca s, but preserved repetition Transcortical sensory fluent, like Wernicke s, but preserved repetition Anomic not localized, impaired naming Global combined fluent and nonfluent characteristics 25

26 However, it s not quite so straightforward! Highly distributed network of activation 26

27 Difficulty with syndrome classification and modular processing: Doesn t adequately describe linguistic details of language impairments People with the same syndrome can have different deficits Identical deficits can occur in different syndromes (e.g. anomia) Modular processing models offer little insight into underlying linguistic mechanisms Alternatively. Consider models that apply psycholinguistic principles of processing Provides insight into underlying linguistic mechanisms Provides direction for diagnosis and treatment 2 important conceptual points: Parallel distributed processing Spreading activation (Dell 1986, Roelfs 1992) 27

28 Spreading activation example: Stimulus YELLOW yellow Possible limbic activation??? Parallel Distributed Processing Models Basic principles 1.The representation of information is distributed, not local 2.Memory and knowledge for specific things are not stored explicitly, but represented in the connections between units 3.Learning occurs by gradual changes in connection strength through experience 28

29 Spreading activation When a neuron is activated, it spreads to all other units connected to it Consider a 2 level interactive model of naming: Level 1 or words Level 2 Think about words In dictionaries there is an entry for each word Phonological, graphic, grammatical, semantic All in one place In the brain the situation is entirely different Each word is represented as a large network Different kinds of information in different locations Also true for each phrase that is learned as a unit, e.g., How was your day? or What s for dinner? Based on work by: Sydney Lamb, Rice University 29

30 An activated functional web (with two subwebs partly shown) M T C PP PA PR Mem V C Cardinal concept node M Motor T Tactile PA Primary auditory PP Phonological production PR Phonological recognition Visual features M T C PP PA PR V Mem 30

31 The effective unit of operation is not the single neuron and its axon, but bundles or groups of cells and their axons with similar functional properties and anatomical connections. Vernon Mountcastle, Perceptual Neuroscience (1998), p. 192 Layer structure of association cortex vertical networks 31

32 Major Association Pathways horizontal networks Nodal interconnections (known facts from neuroanatomy) Nodes (columns or vertical networks) are connected to Nearby nodes Distant nodes via myelinated association pathways Connections to nearby nodes are either excitatory or inhibitory Via horizontal axons (through gray matter) Connections to distant nodes are excitatory only Via longer myelinated axons of pyramidal neurons 32

33 Some things that are now well established The brain is a network composed of neurons Cortical neurons are clustered in columns o Columns come in different sizes o The smallest: minicolumn neurons o Each minicolumn acts as a unit o When it becomes active all its neurons are active Different networks in different locations for various kinds of information o Visual, auditory, tactile, motor, memories, emotion Uniformity of cortical structure What distinguishes one kind of information from another is what it is connected to Lines and nodes are approximately the same for all associational cortical areas Same kinds of columnar structure Same kinds of neurons Same kinds of connections Different areas have different functions because of what they are connected to 33

34 MOTOR AREAS PRIMARY SENSORY AREAS VISUAL STIMULUS JUDGMENTS / DECISIONS VISUAL ATTENTION ANALYZED / INTEGRATED RECOGNIZED RECEIVED / AWARE What impairments are found at each level of processing? 34

35 Consider In diagnostic testing and assessment, we want the patient to fail IF THEY WILL; whereas in treatment we want the patient to succeed IF THEY CAN. References (Sydney Lamb, Rice Univ.) M. Vigneau, V. Beaucousin, P.Y. Hervé, H. Duffau, F. Crivello, O. Houdé, B. Mazoyer, N. Tzourio Mazoyer, Meta analyzing left hemisphere language areas: Phonology, semantics, and sentence processing, NeuroImage, Volume 30, Issue 4, 1 May 2006, Pages Diane L. Kendall, John C. Rosenbek, Kenneth M. Heilman, Tim Conway, Karen Klenberg, Leslie J. Gonzalez Rothi, Stephen E. Nadeau, Phoneme based rehabilitation of anomia in aphasia, Brain and Language, Volume 105, Issue 1, April 2008, Pages

36 A Diagnostic Algorithm for Swallowing and Speech in Degenerative Disease Dysphagia Diagnostic Decision Tree 1

37 ESOPHAGEAL DYSPHAGIA Food stops or sticks Solid Solid or liquid Intermittent Progressive Intermittent Progressive Lower ring Chronic heartburn Age >50 Chest pain Chronic heartburn Respiratory Sx Peptic stricture Carcinoma Diffuse spasm Achalasia Scleroderma Dysphagia diagnostic decision tree DYSPHAGIA SYMPTOMS Oropharyngeal Esophageal Neurological Mechanical 1. Supramedullary 2. Medullary 3. Mixed Supramedullary and Medullary, i.e., UMN & LMN 2

38 General Characteristics of Neuro Dysphagia Changes in muscle: Tone Strength / force Range of movement Speed Coordination Control Common co impairments: Motor speech (dysarthria) Impaired mental functions Impairments in other motor behaviors Abnormal reflexes 1. SUPRAMEDULLARY PATHOLOGY Supramedullary Systems Spastic (slow/weak) Hyperkinetic (involuntary movements/posturi ng) Hypokinetic (rigid, poverty of movement) Ataxic (uncoordinated) Bilateral UMN (multiple CVA, PLS) Basal ganglia (HD, Dystonia) Basal ganglia (PD, PSP) Cerebellar or cerebellar tracts (Fredreich s Ataxia, MS) Slow artic, strained voice, hypernasal Irregular interruptions, voice breaks, respiratory breaks Weak voice, rapid & disintegrating artic, short rushes Unsteady voice, lengthening vowels, syllabic quality 3

39 Characteristics of Supramedullary Conditions Pathology in direct and indirect activation pathways and/or motor control circuits Weakness, spasticity, hyperkinesia, hypokinesia, dystonia and/or ataxia Protective reflexes generally intact Primitive, pathologic reflexes Emotional lability Poor coordination for swallow Loss of intellectual controls UMN lesions Bilateral UMN damage is necessary to cause major symptoms UMN Motor cortex Brainstem 4

40 UMN = Direct and Indirect Activation Pathways Spasticity Hyperreflexive Primitive reflexes Dyspraxia Rigidity Loss of stability (tremor) Abnormal posture Motor Control Systems Basal ganglia posture stability muscle tone Cerebellum coordination timing 5

41 Cerebellum Ataxic Dysarthria Articulatory inaccuracy Imprecise consonants Irregular articulatory breakdown Distorted vowels Prosodic excess Excess and equal stress Prolonged phonemes Prolonged intervals Phonatory prosodic insufficiency 6

42 Lesion here might cause BOTH ataxia and spasticity 2. LOWER MOTOR NEURON or Motor Unit Pathology (Neuron cell body, axon, NMJ, muscle fiber) 7

43 Common Characteristics of LMN Pathology Loss of protective reflexes Flaccid weakness Atrophy and fasciculations Aphonia Respiratory support Cognitive and other higher level functions are intact LMN lesions Unilateral LMN damage is sufficient to cause bulbar symptoms of weakness, flaccidity, atrophy, and loss of reflexes LMN Brainstem Bulbar musculature 8

44 LMN or Motor Unit Pathology Neuron cell bodies; medullary nucleus Brainstem Neuron axons; cranial nerve LMN Neuromuscular junction; synapse Bulbar musculature Muscle fibers 3. Mixed UMN & LMN Pathology 9

45 Categories of diseases and conditions 1. Supramedullary CVA (unilateral hemispheric or bilateral) Parkinson s Progressive Supranuclear Palsy Huntington s Multiple Sclerosis Primary Lateral Sclerosis Dementias Categories of diseases and conditions 2. Medullary CVA (intranuclear brainstem) Progressive Bulbar Palsy (MND) PNS diseases and conditions Muscle diseases technically NOT neurological 3. Mixed (UMN & LMN / supramedullary & medullary) ALS (MND) Vascular 10

46 Categories of PNS diseases and conditions Bulbar poliomyelitis Peripheral neuropathies Diphtheria Botulism Rabies Diabetes Mellitus Categories of PNS diseases and conditions MOTOR END PLATE Myasthenia Gravis Eaton Lambert 11

47 Categories of MUSCLE diseases and conditions Muscular Dystrophies Polymyositis, Dermatomyositis Metabolic Myopathy (thyrotoxicosis, myxedema, steroid myopathy) Amyloidosis Systemic Lupus Erythematosis 12

48 Examining Patients from a Neurologic Perspective Interpret findings from a neurologist s clinical examination First impressions count trust your gut Test your hypotheses Compare your findings to neurological reports Patients change A Neurologist s Complete Clinical Exam 1. Mental Status Examination 2. Cranial Nerve Examination 3. Motor 4. Coordination and Gait 5. Reflexes 6. Sensory 1

49 A guide for the SLP exam Record initial clinical observations Observe gross neurological functions Adapting a cranial nerve examination for your structural/functional inspection A guide for the SLP exam 1. Simultaneously judge both pathology and function Pathology has diagnostic significance but might not impact function Look for correlating signs to confirm pathology Describe the neuromuscular characteristics not disease 2. Perform examination bilaterally; compare sides for symmetry 2

50 A guide for the SLP exam 1. For function, look at multiple dimensions: force (strength) range of motion speed precision stability volitional vs. automatic/reflexive movement Limb strength Compare two sides, looking for asymmetry 3

51 Coordination Gait abnormalities Spastic: hemiparesis Scissors: spastic CP Shuffling: stooped, festinating Steppage: foot drop 4

52 Plantar (Babinski) Reflex Normal response is toe flexion Toe extension and separation is positive Babinski sign Positive Babinski suggests UMN lesion affecting LE in question Visual field pathways 5

53 Optokinetic Nystagmus Optic Ophthalmoscopic Exam Optic disc Retinal vessels 6

54 Pupils and Extraocular movements Range of motion -- paresis Voluntary movement -- praxis Nystagmus Motor Speech Perceptions Respiration Phonation Resonation Articulation Prosody 7

55 Focused Speech & Swallow Exam Judge pathology Gather multiple clues to neurological condition No one finding leads to a conclusion Judge pathology vs. normal variance Judge function Consider 0-3 ratings for each element to assess change over time V. Trigeminal: Mastication 8

56 V. Trigeminal: Facial sensation Corneal reflex VII. Facial: Muscles facial expression 9

57 VII. Facial Weakness VII. Failure to close eye on paralyzed side 10

58 VII. Facial Weakness Intraoral exam 5 Anterior sensation 7 Posterior sensation 9 Palatal / pharyngeal symmetry and movement 9/10 Gag reflex 12 Tongue movement 11

59 X. Velum Normal Left weakness Right weakness Bilateral weakness IX & X. Findings from Gag Reflex Asymmetrical Absent with other pathology Nasal speech Nasal regurgitation Loss of sensation Hyperactive with other bilateral UMN signs Spastic dysarthria Release reflexes 12

60 IX & X. Gag reflex Inhibitory UMN influence Medulla XII. Lingual Function Judge: Praxis Force Speed ROM Coordination 13

61 Laryngeal Elevation 5, 7, 12 suprahyoid muscles Ansa cervicalis, C 1-3 infrahyoid muscles Primitive reflexes, frontal lobe release signs 14

62 Summary Add up the observations and signs Look for patterns that help to identify neurological systems involved; not disease One sign does not make a diagnosis; look for confirmatory findings Practice-Practice-Practice Follow and document neurological signs to correlate with behavioral changes 15