Lecture 2: Motor Speech Disorders PDF

Motor Speech Disorders: **[TOPIC:]** Neuroanatomy for motor speech disorders + brain structure & function OVERVIEW OF FUNCTION & STRUCTURE: [Cerebrum] = major structure of the forebrain, consists of 2 hemispheres (left and right). [Cerebellum] = "little brain" involved in co-ordination of (fine)...

Motor Speech Disorders: **[TOPIC:]** Neuroanatomy for motor speech disorders + brain structure & function OVERVIEW OF FUNCTION & STRUCTURE: [Cerebrum] = major structure of the forebrain, consists of 2 hemispheres (left and right). [Cerebellum] = "little brain" involved in co-ordination of (fine) motor and mental (cognitive) processes. [Brainstem] = central structure, including the hindbrain, midbrain, thalamus, hypothalamus, pons (Hearing, equilibrium, taste, facial sense, sleep) & medulla (breathing, heart rate, blood pressure, swallowing). Responsible for most unconscious behaviour. LOBES OF THE BRAIN: A diagram of the brain Description automatically generated OCCIPITAL LOBE: Cortical processing of visual information. Mapping visual information **Damage:** pure alexia without agraphia (letter form no longer has meaning to client BUT can still write) PARIETAL LOBE: Somatosensory cortex + association cortex Recognising shape form, temperature, touch, awareness of body in space, critical for swallowing Higher order functions! - Integration of somatosensory info to behaviour (motor) - Interaction b/w motor and sensory functions **Damage**: not integrating touch + visual neglect (e.g., may only eat one side of dinner plate) TEMPORAL LOBE: Auditory cortex & Wernicke's Area = needed for language comprehension! Hippocampus needed for memory (disease example: Alzheimer's or amnesias) Inferior Temporal cortex: - difficulty with facial perception and objects - Prosopagnosia: impaired of face perception/ expressions **Damage**: Wernicke's aphasia (cannot understand input or output of language) Another uncommon: pure word deafness (still able to hear but can't associate meaning) FRONTAL LOBES: Pre-frontal cortex: - Largest region of brain - Responsible for: planning, inhibition, problem solving, organisation, adjust behaviours. - Plans motor movements - Mood and behaviour (depression/schizophrenia/ TBI) - Boca's Area: speech production, paralysis of opposite side, comprehension is spared! Damage: Broca's Aphasia **[TOPIC:]** The Motor System Motor cortex + Basal ganglia + cerebellum + spinal & cranial nerves WHAT IS MOVEMENT? Motor systems deliver the physical behavioural output that expresses cognitive goals. - Efferent cranial nerves = carry info to nerves of body - Afferent spinal and cranial nerves = carry back info from the body  USE OF SENSORY INFO: Sensory info [before] the movement is initiated is important for determining the starting position of the muscles. Sensory info [during] the movement is important for adapting the planning and execution of the movement. MOTOR SYSTEM: Thought of as 3 levels: 1. Cerebral cortex: strategy 2. Motor cortex & cerebellum: tactics 3. Brain stem & spinal cord: execution HIERACHICAL CONTROL OF MOVEMENT: Motor sequence: - Movement modules preprogramed by the brain and produced as a unit Frontal lobes: - Prefrontal cortex: planner - Premotor cortex: organiser - Primary motor cortex: producers/ executor ORGANISATION OF THE MOTOR CORTEX: Homunculus: - Representation of the human body in the sensory or motor cortex 3 types of organisations: 1. Part of the body that us to be moved. 2. Spatial location to which the movement is directed. 3. Movement's function SUB-CORTICAL STRUCTURES: NEUROANATOMY: Are housed deep within each cerebral hemisphere. Contain grey nuclear masses. - Basal ganglia: - Corpus striatum - Caudate nucleus - Putamen - Globus pallidus - Substantia Nigra - Subthalamic nucleus \~ form the main part of the indirect pathways, leads to the suppression of unwanted movements. - Thalamus - Cerebellum - Brainstem - Red nucleus - Internal capsule (communication super-highway) - Limbic system - Hypothalamus SUMMARY OF INPUTS AND OUTPUTS OF BASAL GANGLIA: Collection of subcortical nuclei within the [forebrain] Basal ganglia receive input form the: 1. Cortex: all areas of the neocortex and limbic cortex 2. Midbrain: substantia nigra Can also send outputs back to motor cortex via thalamus. Movement occurs via "direct pathways" (act of silencing neurons) A very complex system that allow us to adjust the force, range, & rate of movement or our movements. WHAT CAN GO WRONG WITH BASAL GANGLIA? Can produce to types of motor symptoms: 1. Hyperkinetic symptoms \[direct\] - Results in excessive involuntary movements (Huntington's disease) 2. Hypokinetic symptoms \[indirect\] - Results in a paucity of movement (Parkinson's disease) PARKINSON'S DISEASE: **Symptoms:** Motor tremors, rigidity, loss of balance, fast rate & difficulty in range of movement, palilalia - Resting tremor: present at rest, absent during volitional movement. - Rigidity: can develop fixed postures - Bradykinesia: slowness in initiating movement. - Decreased postural reflexes falls risk, gait instability. - Hypokinetic dysarthria **Pathology:** substantia nigra \~ destruction of neurons that produce dopamine **Executive function:** 20% develop frank dementia, often associated with Lewy body dementia. Subtle HUNTINGTON'S DISEASE: Chronic, degenerative disorder of CNS **Symptoms:** involuntary movements (chorea) -- writhing of the body/face, grimacing, cognitive decline, psychiatric features, Hyperkinetic dysarthria. **Pathology:** cell loss in the [caudate nucleus (GABA).] The putamen, globus pallidus, and cortex are involved to a lesser degree. Genetic aspect. **Cognitive impairment and/or dementia develops in HD:** - Impaired delayed recall of info - Impaired memory - Poor cognitive flexibility and abstraction - Impaired attention - Slowed thought processes. **Language difficulties:** - Loss of conversational initiative - Reduced syntactic structure of spontaneous speech. - Reduced verbal fluency. - Difficulty with complex language tasks CEREBELLUM: - Plays role in regulation of motor planning and control of movements. - "refinement" and "amplification" of movement - Also plays role in the "motor programming" of movements (execution). It determines the precise timing, range, and force of movements. It can also make error corrections. CEREBELLUM DYSFUNCTION: Poor sequencing of timing and fine motor control movements. - **Ataxia:** uncoordinated and inaccurate movements - **Dysmetria:** overshoot or undershoot target. - **Ataxic dysarthria** - Ipsilateral signs - Wide based gait - Difficulty with rapid alternating movements - Incoordination of though 2 IMPORTANT MOTOR PATHWAYS: 1. Corticospinal (30% of fibres) originate the upper 2/3rds of cortexes. 2. Corticobulbar (70% of fibres) originate the lower 1/3^rd^ of cortexes. CORTICOSPINAL TRACT: The motor cortex is predominantly organised contralateral to output and input. Majority of long corticospinal axons form the motor cortex cross or the midline in the medulla to innervate contralateral spinal output nuclei. **Lesions**: result in weakness and slowed movement DESCENDING PATHWAYS: **Lesion 1: cortex** - Lesion is before or above the decussation. - The "lesion" would lesion the opposite side to the motor signs. **Lesion 2: brainstem** - Below the decussation - Lesion and the motor signs would be on the same side. UPPER MOTOR NEURONS (UMN): Weakness, increased tone, hyperreflexia (overactive reflexes) LOWER MOTOR NEURONS (LMN): Flaccidity, severe weakness, atrophy of the muscles, hyporeflexia (underactive or absent reflexes), and twitching. CORTICOBULBAR TRACT: - Exclusively controls the skeletal muscles of the head and face via cranial nerve. - They cross at different levels of the brain. - Receive bilateral innervation. - can affect tongue as well, causing weakness. When they poke their tongue out it can cause deviation or atrophy/wasting. CRANIAL NERVE NUCLEI: - 12 cranial nerves - Testing cranial nerves is important (OME) - A superficial cranial nerve exam can be done in a few minutes that can give diagnostic information. Important for speech / swallowing assessment.  KEY CRANIAL NERVES WE ARE INTERESTED IN: \#5 (V) Trigeminal \~ sensory of face (mastication) \#7 (VII) facial motor \~ muscles of the face (UMN?) \#9 (IX) Glossopharyngeal \~ gives sensation to the pharynx. \#10 (X) Vagus \~ also effects pharynx and breathing (gag/cough reflex) \#12 (XII) Hypoglossal \~ innovator of tongue \(XI) Accessory \~ sterno-cleidomastoid and trapezius muscles