Lecom - Neuroanatomy 06: Corticospinal Tract And Other Motor Pathways

Front 1

Brodmann's area for primary motor cortex

Back 1

4

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Brodmann's areas for primary somatosensory cortex

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3, 1, and 2

Front 3

arms and legs generalization in somatotopic representations

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arms are medial to legs with 2 exceptions: primary sensorimotor cortices and posterior columns

Front 4

what is in the ventral (anterior) horn of the spinal cord

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motor neurons

Front 5

what is in the intermediate zone of the spinal cord

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interneurons and certain specialized nuclei

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columns of white matter in spinal cord

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dorsal (posterior), lateral, and ventral (anterior) columns

Front 7

where is white matter the thickest in the spinal cord

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cervical levels where most ascending fibers have entered and more descending fibers have not terminated

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where is there more gray matter in the spinal cord

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cerival and lumbosacral due to nerve plexuses for arms and legs

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Rexed's Lamina II

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Substantia gelatinosa

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Rexed's Lamina III, IV

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Nucleus proprius

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Rexed's Lamina VII

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Clarke's Nucleus

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Rexed's Lamina IX

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Motor Nuclei

Front 13

where is the intermediolateral cell column

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lateral horn in thoracic cord

Front 14

Blood Supply to Spinal Cord

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Arises from branches of the vertebral arteries and spinal radicular arteries - Vertebral Arteries: give rise to the anterior spinal artery (ventral surface of spinal cord) Two Posterior Spinal Arteries arise from vertebral or posterior inferior cerebellar arteries and supply the dorsal surface of the cord. Anterior and posterior spinal arteries are variable in prominence at different spinal levels and form a spinal arterial plexus that surrounds the spinal cord. 31 segmental arterial branches enter the spinal canal along its length most arise from Aorta and supply the meninges. Only 6-10 reach spinal cord as RADICULAR ARTERIES arising at variable levels

Front 15

Great Radicular Artery of Adamkiewicz

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Arises anywhere from T5-L3 but uslaly between T9-T12, provides major blood supply to the lumbar and sacral cord

Front 16

Vulnerable Zone

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T4-T8 lies between lumbar and vertebral arterial supplies and vulnerable due to relatively decreased perfusion. Most susceptible to infarction during thoracic surgery or other conditions causing decreased aortic pressure.

Front 17

Batson's Plexus

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Venous return from the spinal cord occurs naturally via drainage into a plexus of veins located in the epidural space before reaching systemic circulation. These epidural veins do not contain valves, so elevated intra-abdominal pressure can cause a reflux of blood carrying metastatic cells such as prostate cancer into the epidural space

Front 18

where does the artery suppling the spinal cord from the vertebral arteries run

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anterior spinal artery runs along ventral surface; two posterior spinal arteries on doral surface (may also come from posterior inferior cerebellar arteries)

Front 19

radicular arteries

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segmental arterial branches that reach the spinal cord (about 6-10)

Front 20

where are common prominent radicular arteries found

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L side btwn T5 and L3 (usually btwn T9 and T12) = great radicular artery of Adamkiewicz

Front 21

importance of great radicular artery of Adamkiewicz

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major blood supply to lumbar and sacral cord

Front 22

vulnerable zone of spinal cord to infarction

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T4 to T8

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why is T4 to T8 vulnerable to infarction

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btwn main blood supplies

Front 24

veins in spinal cord

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plexus of veins initially draining into epidural space before reaching circulation

Front 25

Batson's plexus

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epidural veins; do not contain valves

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importance of no valves in Batson's plexus

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metastatic cells or pelvic infections can travel into epidural space with elevated intra-abdominal P

Front 27

Lateral Corticospinal Tract

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Origin: Primary Motor Cortex Decussation: Pyramidal Decussation at Cervicomedullary Junction Levels of Termination: Entire Cord Fucntion: Movement of contralateral limbs

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Rubrospinal Tract

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Origin: Red Nucleus Decussation: Ventral tegmental decussation in midbrain Termination: Cervical Cord Function: Unknown

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Anterior Corticospinal Tract

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Origin: Primary motor cortex and supplementary motor area Decussation: None Termination: Cervical and Upper Thoracic Cord Function: Control of bilateral axial and girdle muscles

Front 30

Vestibulospinal Tract

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Origin: Medial VST: Medial and inferior vestibular nuclei; Lateral VST: lateral vestibular nucleus Decussation: None Termination: Medial VST: Cervical and upper thoracic; Lateral VST: Entire cord Function: Medial VST: Positiong of head and neck; Lateral VST: Balance

Front 31

Reticulospinal Tract

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Origin: Pontine and medullary reticular formation Decussation: None Termination: Entire cord Function: Automatic posture and gait-related movements

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Tectospinal Tract

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Origin: Superior colliculus Decussation: Dorsal tegmental decussation in the midbrain Termination: Cervical cord Function: Coordination of head and eye movement (uncertain in humans??)

Front 33

Two lateral motor systems in spinal cord?

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lateral corticospinal tract and rubrospinal tract

Front 34

Origin of lateral corticospinal tract

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primary motor cortex, other frontal/parietal areas

Front 35

Four medial motor systems in spinal cord

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anterior corticospinal tract, vestibulospinal tracts, reticulspinal tracts, and tectospinal tract

Front 36

Why don't unilateral lesion of medial motor systems produce no obvious effects?

Back 36

terminate on interneurons that project to both sides of the spinal cord-control movements that involve multiple bilateral spinal segments

Front 37

what pathway controls movement of the extremities

Back 37

lateral coricospinal tract

Front 38

lateral corticospinal tract fiber origination

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over half fibers originate in primary motor cortex (5), the rest from premotor and supplementary motor areas (6) or from parietal lobe (3, 1, 2, 5, 7)

Front 39

Where do lateral corticospinal neurons synapse

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Layer 5 pyramidal cell projections synapse directly onto motor neurons in the ventral horn and spinal interneurons

Front 40

Betz cells

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giant pyrimidal cells; 3% of corticospinal neurons

Front 41

Where do axons from cerebral cortex of lateral corticospinal tract go

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upper portion of cerebral white matter (corona radiata), descend toward internal capsule

Front 42

What does cerebral white matter convey

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bidirection info btwn different cortical areas, btwn cortex and deep structures (like basal ganglia, thalamus, and brainstem)

Front 43

location of internal capsule

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thalmus and caudate nucleus are always medial to and globus pallidus and putamen are always lateral to

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three parts of internal capsule

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anterior limb, posterior limb, genu

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anterior limb location

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separates head of caudate from the globus pallidus and putamen

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posterior limb location

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separates thalamus from globus pallidus and putamen

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genu location

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transition from anterior and posterior limbs at the level of the foramen of Monro

Front 48

where is the corticospinal tract in the internal capsule

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posterior limb

Front 49

corticobulbar fibers

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project from cortex to brainstem (bulb)

Front 50

orientation of somatotopic map in corticospinal tract

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anterior to posterior and medial to lateral: face, arm, trunk, leg

Front 51

what does the internal capsule continue into

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midbrain cerebral peduncles

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basis pedunculi

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ventral portion of the cerebral peduncles containing white matter

Front 53

what does the middle 1/3 of the basis pedunculi contain

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corticobulbar and corticospinal fibers with face, arm, and leg axons arraged medial to lateral

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what do other portions of the basis pedunculi contain

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primarily corticopontine fibers

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where do corticospinal fibers travel after basis pedunculi

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descend through ventral pons forming scattered fascicles

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where do the scattered fascicles collect

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ventral surface of medulla to form medullary pyramids

Front 57

transition from medulla to spinal cord

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cervicomedullary jxn; at level of foramen magnum

Front 58

What occurs to corticospinal tract at cervicomedullary jxn

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85% pyramidal tract fibers cross over in pyramidal decussation to enter lateral white matter columns

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What occurs to remaining 15% of corticospinal fibers

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continue ipsilaterally without crossing and enter anterior white matter columns

Front 60

where are preganglionic neurons of the sympathetic division located

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intermediolateral cell column in lamina VII or spinal cord levels T1 to L2-3

Front 61

two sets of sympathetic ganglia

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paravertebral sympathetic trunk ganglia and paired prevertebral ganglia

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examples of prevertebral ganglia

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celiac around aorta, superior mesenteric, inferior mesenteric

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where do parasympathetic preganglionic fibers arise from

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cranial nerve parasympathetic nuclei and sacral parasympathetic nuclei in lateral gray matter of S2-4

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what receptors do parasympathetic postganglionic neurons activate

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muscarinic cholinergic receptors

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what receptors do preganglionic neurons activate

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nicotinic receptors (acetylcholine)

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what are sympathetic and parasympathetic outflow controlled by

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directly and indirectly by higher centers like hypothalamus, brainstem nuclei (nucleus soltaris), amygdala, several regions of limbic cortex

Front 67

what else can autonomic responses be regulated by

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afferent sensory info (chemoreceptors, osmoreceptors, thermoreceptors, baroreceptors)

Front 68

signs of LMN lesions

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muscle weakness, atrophy, fasiculations, hyporeflexia

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signs of UMN lesions

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muscle weakness, combination of increased tone and hyperreflexia (spasticity); Babinski's sign, Hoffmann's sign, posturing, etc also seen

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acute UMN lesion

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initially flaccid paralysis with decreased tone and reflexes, which gradually change over hours/months into spastic paresis

Front 71

Why is it suspected that damage to inhibitory pathways that travel closely with the corticospinal tract must be injured in order to produce spasticity

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corticospinal lesions alone did not produce symptoms in experimental animals

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what does loss of descending inhibitory influences cause

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increased excitability of alpha motor neurons in anterior horn resulting in brisk reflexes and increased tone; not definitely proven

Front 73

unilateral face, arm, and leg weakness or paralysis - Pure motor hemiparesis potential lesion locations

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coticospinal and cortibulbar tract fibers below cortex and above medulla (posterior limb internal capsule, basis pontis, or midle third of cerebral peduncle)

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unilateral face, arm, and leg weakness or paralysis - Pure motor hemiparesis lesion causes

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lacunar infarct of internal capsule or pons, infarct of cerebral peduncle-less common

Front 75

unilateral face, arm, and leg weakness or paralysis - Pure motor hemiparesis lesion associated features

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UMN signs present; Dysarthria common; ataxia of affected side occasionally due to involement of cerebellar pathways

Front 76

unilateral face, arm, and leg weakness or paralysis - with associated somatosensory, oculomotor, viual, or higher cortical deficits: potential lesion locations

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entire primary motor cortex; corticospinal and corticobulbar tract fibers above medulla

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unilateral face, arm, and leg weakness or paralysis - with associated somatosensory, oculomotor, viual, or higher cortical deficits: associated features

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aphasia or neglect; dysarthria or ataxia; UMN signs

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unilateral face, arm, and leg weakness or paralysis - with associated somatosensory, oculomotor, viual, or higher cortical deficits: causes

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numerous: infarct, hemorrhage, tumor, trauma, herniation, post-ictal state, etc

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unilateral arm and leg weakness or paralysis alternative names

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hemiplegia/hemiparesis sparing the face; brachiocrural plegia or paresis

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unilateral arm and leg weakness or paralysis - lesion locations

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arm and leg area of motor cortex; corticospinal tract from lower medulla to C5

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unilateral arm and leg weakness or paralysis - associated features

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UMN signs; often in watershed distribution - proximal affect more than distal; aphasia or hemineglect if cortical; medial medulla-loss of vibration and joint position sense ilsilateral and tongue weakness contralateral; spinal cord-Brown-Sequard syndrome; high cervical-spinal trigeminal nucleus and tract-decreased facial sensation

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unilateral arm and leg weakness or paralysis - causes

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watershed infarct; medial or combined medial and lateral medullary infarcts; multiple sclerosis; lateral trauma; compression of c-spine

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unilateral face and arm weakness or paralysis - alternative names

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faciobrachial paresis or plegia

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unilateral face and arm weakness or paralysis - lesion locations

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face and arm areas of cerebral cortex; over lateral frontal convexity

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unilateral face and arm weakness or paralysis - associated features

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UMN signs and dysarthria; Broca's aphasia in dominant hemisphere lesions; hemineglect occasionally; sensory loss if extends into parietal lobe

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unilateral face and arm weakness or paralysis - causes

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middle cerebral artery superior division infarct is classic cause; tumor, abcess, or other lesion

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unilateral arm weakness or paralysis - alternative names

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brachial monoparesis or monoplegia

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unilateral arm weakness or paralysis - lesion locations

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arm area of primary motor cortex; peripheral nerves supplying arm

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unilateral arm weakness or paralysis - associated features in motor cortex

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UMN signs, cortical sensory loss, aphasia, subtle involvement of face or leg; pattern of weakness/paralysis

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unilateral arm weakness or paralysis - associated features in peripheral nerve

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LMN signs; pattern of weakness/paralysis

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unilateral arm weakness or paralysis - causes in motor cortex

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infarct of small cortical branch of middle cerebral artery, small tumor, abscess, etc

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unilateral arm weakness or paralysis - causes in peripheral nerve

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compression injury, diabetic neuropathy, etc

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unilateral leg weakness or paralysis - alternative names

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crural monoparesis or monoplegia

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unilateral leg weakness or paralysis - lesion locations

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leg are of primary motor cortex; lateral corticospinal tract below T1 in spinal cord or peripheral nerves of leg

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unilateral leg weakness or paralysis - associated features in motor cortex lesions

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UMN signs, cortical sensory loss, frontal lobe signs (grasp reflex), subtle involvement of arm or face; look at pattern of weakness

Front 96

unilateral leg weakness or paralysis - associated features in spinal cord lesions

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UMN signs; Brown-Sequard syndrome, sensory level, or some subtle spasticity of contralateral leg; sphincter fxn; look at pattern

Front 97

unilateral leg weakness or paralysis - associated features in peripheral nerve lesions

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LMN signs; pattern of weakness/paralysis

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unilateral leg weakness or paralysis - causes in motor cortex lesions

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infarct in anterior cerebral artery tertiary, mall tumor, abscess, etc

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unilateral leg weakness or paralysis - causes in spinal cord lesions

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unilateral cord trauma, compression by tumor, multiple sclerosis

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unilateral leg weakness or paralysis - causes in peripheral nerve lesions

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compression injury, diabetic neuropathy, etc

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unilateral facial weakness or paralysis - alternative names

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Bell's palsy (peripheral nerve); isolated facial weakness

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unilateral facial weakness or paralysis - lesion locations

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peripheral CN VII; lesions in face area or primary motor cortex or genu of internal capsule; facial nucleus and exiting nerve fascicles in pons or rostral lateral medulla

Front 103

unilateral facial weakness or paralysis - associated features in facial nerve or nucleus lesions

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LMN signs; forehead and orbicularis oculi not spared; nerve-hyperacusis, decreased taste, pain behind ear on affected side

Front 104

unilateral facial weakness or paralysis - associated features in motor cortex/genu

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forehead relatively spared; dysarthria and unilateral tongue weakness common; subtle arm involvement

Front 105

unilateral facial weakness or paralysis - causes in facial nerve

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Bell's palsy; trauma, surgery

Front 106

unilateral facial weakness or paralysis - causes in motor cortex, capsular genu, pons, or medulla

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infarct

Front 107

bilateral arm weakness or paralysis - lesion locations

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medial fibers of both lateral corticospinal tracts; bilateral c-sine ventral horn cells; peripheral nerve or muscle disorders affecting both arms

Front 108

bilateral arm weakness or paralysis - associated features

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central cord syndrome or anterior cord syndrome may be present

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bilateral arm weakness or paralysis - causes for central cord syndrome

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central cord syndrome: syringomyelia, intrinsic spinal cord tumor, myelitis

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bilateral arm weakness or paralysis - causes for anterior cord syndrome

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anterior cord syndrome: anterior spinal artery infarct, trauma, myelitis

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bilateral arm weakness or paralysis - causes for peripheral nerve

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peripheral nerve: bilateral carpal tunnel syndrome or disc herniations

Front 112

bilateral leg weakness or paralysis - lesion locations

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primary motor cortex-medial surface; lateral corticospinal tracts below T1; cauda equina syndrome or other peripheral nerve/muscle disorders

Front 113

bilateral leg weakness or paralysis - associated feature of bilateral medial frontal lesions

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UMN signs; frontal lobe dysfunction including confussion, apathy, grasp reflexes, and incontinence

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bilateral leg weakness or paralysis - associated features of spinal cord lesions

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UMN signs; sphincter dysfunction, autonomic dysfunction may be present; sensory level may help determine segment of lesion

Front 115

bilateral leg weakness or paralysis - associated features of bilateral peripheral nerve/muscle disorders

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cauda equina syndrome-sphincter and erectile dysfunction, sensory loss in lumbar, LMN signs; symmetrical polyneuopathies-distal muscles; neuromuscular-proximal more than distal

Front 116

bilateral leg weakness or paralysis - causes of bilateral medial frontal lesions

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parasagittal meningioma, bilateral anterior cerebral artery infarct, cerebral palsy

Front 117

bilateral leg weakness or paralysis - causes of spinal cord lesions

Back 117

numerous: tumor, trauma, myelitis

Front 118

bilateral leg weakness or paralysis - causes of bilateral peripheral nerve/muscle disorders

Back 118

cauda equina: tumor, trauma, disc herniation; Guillain-Barre syndrome, Lambert-Eaton syndrome, numerous muscle disorders, etc

Front 119

bilateral arm and leg weakness or paralysis - lesion locations

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bilateral arm and leg areas in motor cortex; bilateral lesions of corticospinal tracts from lower medulla to C5; peripheral nerve motor neuron/muscle disorder

Front 120

bilateral arm and leg weakness or paralysis - lower medullary lesions

Back 120

UMN signs; occipital headache, tongue weakness; sensory loss, hiccups, respiraory weakness, autnomic dysfunction, sphincter dysfunction, abnormal eye movements

Front 121

generalized weakness or paralysis - lesion locations

Back 121

bilateral lesions of entire motor cortex; bilateral lesions of corticospinal and corticobulbar tracts anywhere from corona radiata to pons; diffuse disorders of LMNs, peripheral axons, neuromuscular jxns, muscles

Front 122

generalized weakness or paralysis - common causes

Back 122

global cerebral anoxia, pontine infarct or hemorrhage, advanced amyotrophic lateral sclerosis, Guillain-Barre, myathenia, botulism, etc

Front 123

pronator drift test

Back 123

patient holds arms extended, palms up, and eyes closed; slight inward drifting or slight curling of fingertips is abnormal

Front 124

Spastic Gait

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Localization: Unilateral or Bilateral Corticospinal Tract Description: Stiff-legged circumduction, sometimes with scissoring of legs and toe-walking Common Causes: UMN Pathway Damage, MS, Cerebral Palsy, Spinal Cord Lesions

Front 125

Ataxic Gait

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Localization: Cerebellar vermis or other midline cerebellar structures Description: Wide based, unsteady, staggering, side to side and falling toward side of worse pathology "drunk walk" Common Causes: Toxins such as alcohol, tumors of cerebellar vermis, infarcts or ischemia of cerebellar pathways, cerebellar degeneration

Front 126

Vertiginous Gait

Back 126

Localization: Vestibular nuclei, vestibular nerve or semicircular canals Description: Patients sway and fall when attempting to stand with feet together and eyes closed "Romberg Sign" Common Causes: Toxins such as alcohol; infarcts or ischemia of vestibular nuclei, benign positional vertigo; Meniere's Disease

Front 127

Frontal Gait

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Localization: Frontal lobes or frontal subcortical white matter Description: Slow, shuffling, narrow or wide baised "magnetic" Sometimes Parkinsonian like. Common Causes: Hydrocephalus, frontal tumors

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Parkinsonian Gait

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Localization: Substantia nigra or other regions of basal ganglia Description: Slow, shuffling, narrow based Common Causes: Parkinson's Disease..duh retard

Front 129

Dyskinetic Gait

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Localization: Subthalamic Nucleus, or other regions of the basal ganglia Description: Unilateral or Bilateral dancelike (choreic), flinging (ballistic, or writing (athetold) movements occur during walking Common Causes: Huntington's Disease

Front 130

Tabetic Gait

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Localization: Posterior columns or sensory nerve fibers Description: High stepping, foot-flapping gait Common Causes: Posterior cord syndrome, severe sensory neuropathy

Front 131

Paretic Gait

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Localization: Nerve roots, peripheral nerves, neuromuscular junctions or muscles Description: Depends on location of lesion Common Causes: Numerous peripheral nerve and muscle disorders

Front 132

Painful (Antalgic) Gait

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Localization: Peripheral nerve or orthopedia injury Description: Pain..duh Common Causes: Herniated disc; peripheral neuropathy, muscle strain, constusions, fractures

Front 133

Orthopedia Gait Disorder

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Localization: Bones, joints, tendons, ligaments, and muscles Description: Depends on nature and location of disorder Common Causes: Arthritis, fractures, dislocations, soft tissue injuries

Front 134

Functional Gait Disorder

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Localization: Psychologically based Description: Varied Common Causes: Conversion disorder; factitious disorder

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Multiple Sclerosis

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Autoimmune inflammatory disorder affecting central nervous system myelin, myelin in PNS not affected

Front 136

Classic clinical definition of multiple sclerosis

Back 136

2 or deficits separated in neuroanatomical space and time; MRI white matter lesions, oligoclonal bands in CSF, slowed conduction velocity

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Oligoclonal Bands

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Discrete bands seen on CSF gel electrophoresis

Front 138

example of a motor neuron disease

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amyotrophic lateral sclerosis (ALS or Lou Gehrig's disease)

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ALS characterisitcs

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progressive degeneration of both UMN and LMN leading to respiratory failure and death

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Primary Lateral Sclerosis

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Upper motor neuron only disorder

Front 141

Spinal Muscular Atrophy

Back 141

Affects lower motor neurons only

Front 142

Multiple Sclerosis

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Autoimmune inflammatory disorder affecting central nervous system myelin

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Amyotrophic Lateral Sclerosis (ALS)

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Lou Gehrig's Disease - characterized by gradually progressive degeneration of both upper motor neurons and lower motor neurons, leading eventually to respiratory failure and death.