Motor System Fall 2012 Basal Ganglia Cerebellum Neuro Exam of Motor System UMN and LMN Signs Cerebellum Lesions Basal Ganglia Disorders Fall 2012

Corpus Striatum Striatum – Caudate + Putamen Lentiform Nucleus – Putamen + Globus Pallidus Corpus Striatum – Caudate + Putamen + Globus Pallidus

Basic Connections

Direct Pathway

Indirect Pathway

Lobes Anterior lobe Posterior lobe Flocculonodular lobe Anterior lobe

Lobes Flocculus Nodulus Anteroinferior View

Sagittal Subdivisions Vermis Paravermis Lateral Hemisphere

Functional Organization

Vermal Spinocerebellum Posture Locomotion Gaze

Paravermal Spinocerebellum Reaching, Grasping Movements

Cerebrocerebellum Motor Learning

Cerebellar Peduncles SCP MCP ICP

Cerebellar Cortex Granular layer

Cerebellar Cortex Connections Afferents Climbing fibers Carry “training” information Mossy fibers Carry “state” information Efferents Purkinje cells Deep cerebellar nuclei

Deep Cerebellar Nuclei FGED

Muscle Appearance Atrophy Fasciculations Fibrillations Profound or severe = LMN sign Disuse = UMN sign Fasciculations LMN sign Visible on surface of muscle Fibrillations Not visible to naked eye Need EMG to detect

Muscle Tone Hypertonia Spasticity (UMN sign) Rigidity (BG sign) Hypertonia and hyperreflexia Primarily in anti-gravity muscles Velocity dependent Clasp-knife effect Clonus often seen Rigidity (BG sign) Hypertonia with normal reflexes Affects all muscles Velocity independent Lead-pipe rigidity Cog-wheel rigidity

Muscle Tone Hypotonia LMN sign Tone depressed Muscle may be flaccid

Muscle Power / Strength 0 = No contraction 1 = Flicker or trace of contraction 2 = Active movement with gravity removed 3 = Active movement against gravity 4 = Active movement against gravity and resistance 5 = Normal strength

Reflex Grading 0 = Absent even with reinforcement 1 = Present, decreased amplitude and velocity Elicited with reinforcement 2 = Normal amplitude and velocity 3 = Increased in amplitude/velocity with spread to adjacent sites 4 = Increased in amplitude/velocity with spread to adjacent sites and clonus

Definitions Plegia = total paralysis Paresis = motor weakness Quadriplegia = all 4 limbs Paraplegia = both legs or both arms Hemiplegia = one side of body Paresis = motor weakness Quadriparesis = all 4 limbs Paraparesis = both legs or both arms Hemiparesis = one side of body

Lower Motor Neuron Signs CN nuclei, ventral horn Plegia (focal & severe) Decreased DTRs Decreased muscle tone Flaccidity Babinski sign not present Clonus not present Fasciculations often seen

Upper Motor Neuron Signs CST system Paresis (generalized) Increased DTRs Increased muscle tone Spasticity Babinski sign present Clonus may be present Disuse atrophy

Cortical Lesions M-I (Primary motor cortex) PMC (Premotor cortex) Contralateral paresis Worse for distal muscles Pronator drift test PMC (Premotor cortex) No paresis Apraxia of complex tasks Perseveration

Cortical Lesions SMA (Supplemental motor area) No paresis Can’t coordinate both sides Difficulty learning new motor tasks

Cortical Lesions PMA (Parietal motor area) FEF (Frontal eye field) No paresis Apraxia Difficulty with hand orientation Astereognosia and agraphesthesia Contralateral hemineglect FEF (Frontal eye field) Inability to gaze to opposite side Gaze preference to side of lesion

Cerebellar Signs Ipsilateral to lesion Decomposition of movements Ataxia (asynergia) Dysmetria Dysdiadochokinesia Intention-tremor Slow onset Not UMN or LMN

Basal Ganglia Signs Contralateral to lesion Tremor-at-rest Dyskinesia with hypertonia Parkinson’s disease Dyskinesia with hypotonia Chorea Athetosis Ballism Not UMN or LMN