Corticospinal tract pyramidal tractAnd corticobulbar tract

Important out put of motor cortex Only tract having direct connections with -motor neurons and neurons of motor cranial nerves Developed only in higher animals 85-90% fibers slow conducting myelinated end on interneurons Fast conducting fibers arise from Betz cells - end directly on -motor neurons

Peculiarities:-

Motor cortexInternal capsuleAnt.Post.C.N.Thala.Mid brainPonsMedullaSP.CordCorona radiataPost limbCerebral pedunclesLong. fasciculiPyramidsdecussationLat. CSTAnt.CSTIII, IVV, VI, VIIIX,XI,XII

Motor cortexInternal capsuleCorticobulbar fibersDecussasion of pyramidsAnt. corticospinalLat. Cortico spinalAnt. Motor fibers

Origin:-Primary motor cortex (area 4 ) 30% (3% - large pyramidal cells- Betz cells )Premotor cortex (area 6 ) & area 8 -30%Somatosensory cortex (SI & SII) (3,1,2 & 40) parietal lobe association areas (5,7) 40%

Inputs of motor cortex :- Somatosensory, visual and auditory cortex

Motor cortex of opposite side

Thalamic sensory nuclei

Basal ganglia & cerebellum through thalamus

Intralaminar nuclei

Course :- Genu & post limb of Internal capsuleMiddle 3/5 of crus cerebri face medially & legs laterally, fibers to III, IVLongitudinal fasciculi in pons, fibers to V, VI, VII Pyramids in upper part of medulla, fibers to IX, XI, XIICorona radiata in subcortical areas80% cross

Lat. CST

20% - uncrossedIn lower part of medullaAnt. CSTIn the spinal cord

Termination :- Cervical region 55% Thoracic region 20% Lumbosacral region 25%

Fibers ending in each segment turn mediallyDirectly on - motor neurons -10% Innervating distal groups of limb musclesThrough interneuronsFibers arising from somatosensory cortex end on Dorsal horn cells

To cerebellumCollaterals of corticospinal tractTO cortex for lat inhibition sharpness of boundaries. To Red n. rubrospinal Reticular n. reticulospinal Vestibular n. vestibulospinal Pontine n. pontocerebellar Olivary n. olivocerebellar

Caudate and lentiform nuclei,

Direct / ventral / uncrossed corticospinal tract 15% fibers directly descend in ant. white column without crossing in medulla. Origin - supplementary motor areas- Extend up to mid thoracic region-Termination - on the interneurons of the same side or of the opposite side - Function - Control of axial muscles on both sides.

Corticobulbar pathways :-Formed by the fibers leaving corticospinal tract in the brain stem and ending in the nuclei of the motor cranial nerves on opposite side Mid brain III, IV Pons V, VI, VII Medulla IX, X, XI, XIIFunctions control vol. movement of muscles of larynx, pharynx, palate, face, jaw and eyes.

Functions of pyramidal tracts:- Lat.CST rapid, skillful movements of hands Ant. CST postural adjustments and gross movements of trunk. Corticobulbar tract - vol. movements of muscle of head and neck.

Forms part of pathway for superficial reflexes Modify sensory input Sensory motor co-ordination

Applied aspects :-Phylogenetically, ant. CST is older Lat. CST - in human beings and few vertebratesMyelination is complete after the age of 2 yrs.Most common lesion of pyramidal tract is hemorrhage in the internal capsule Apoplexy or stroke means sudden attack of paralysis Monoplegia - primary motor cortex hemiplegia - internal capsule quadriplegia or paraplegia brain stem paraplegia - spinal cord at thoracic level

Clinical picture in Pyramidal tract lesions- Lesion above the level of sp. Cord effects on opposite side of bodyLesion in the spinal cord effects on the same side

Impairment of vol., skilled movementsIncreased muscle tone clasp knife rigidityExaggerated tendon reflexes and clonus Extensor planter reflex Babinskis response loss of superficial reflexes

Toes down (flexion)Fanning of toesNormal planter responseExtensor planter response (Babinski sign)

Motor area for faceSupranuclear lesion (UMN)Facial nerve n.Facial paralysisFacial nerveCorticobulbar tract

Functions of E.P.S.Alternative channel for Vol. and reflex activityCoarse movements of trunk & whole limb.Changing tone of muscleBackground posture

Extrapyramidal tracts:-Consist of motor fibers extending from cortical and subcortical areas of brain to the spinal cord which do not run through the pyramids Multichannel pathways Alternative mechanism for voluntary and reflex motor activity

EXTRAPYRAMIDAL TRACTS Motor fibers arising from subcortical areas brain descending outside the corticospinal tract,-- reaching sp.cord -- Ending on or motor neurons--ipsilat. Or contralat.--Multichannel system

EPSRubrospinalTectospinalLat. VestibulospinalMedial vestibulospinalPontine reticulospinalMedullary reticulospinalRRTV

MOTOR CORTEXSUBCORTICAL AREASSP.CORDRubrospinalTectospinalLat. VestibulospinalMedial vestibulospinalPontine reticulospinalMedullary reticulospinal

RRTV

cortexMed. Ret. formationRed n.putamen C.N.S.N.Pontine. Ret. formationS.C.Vesti. N.cerebellum+ + - + -+ +

Midline

Some peculiarities of individual tractRubrospinal crossed - located in lat. White column - part of lat. motor system - extend up to mid tho. Level - facilitatory to flexors of wrist

Tectospinal crossed - from sup. colliculus - lower cervical region - visually guided move. of head

Med vestibulospinal from semicircular canals (uncrossed ) - ant white column - facilitation of extensors and inhibition of flexors

Lat. Vestibulospinal from utricle & saccule ( uncrossed ) - ant white column -- facilitatory to extensors

III. Medial vestibulospinalIV. Lat. vestibulospinalMedial vesti. N.Semicircular canalsRotation of headAnt. White columnUncrossed fibersThrough out the length of sp. cordFacilitation of extensors and inhibition of flexorsLinear accelerationUtricle, sacculeLat. vesti. N.Uncrossed fibersLat White column-motor neurons

Normally, inhibitory control of medullary reticulospinal tract is prominent on the muscle tone

FUNCTIONS OF EPS

Control of tone, posture and equilibrium

Control of complex movements of the body and limbs

Tonic inhibitory control over lower centers

Pyramidal systemExtrapyramidal systemOriginMyelinationCourseMain controlcontrolled muscleFunctions Effects of lesionsubcorticalDuring iu lifepolysynapticLower extremityPostural muscles

Gross movementshypertoniaCorticalAfter birthMonosynapticUpper extremityFlexors of hand and fingers Skilled movementshypotonia

PS EPSOrigin- corticalDevelopment- myelination after birthCourse- monosynapticControlled - mainly upperextremity Groups of mainly flexors of muscles - hand & fingers controlled

Controlled joint distal movements-Function- skilled movements

Effects of lesions - hypotonia

SubcorticalMyelination in i.u.lifePoly synapticMainly lower

Muscles involved in coordination, maintaining uprightProximal

Gross postural movements,regulation of toneHypertonia-rigidity

LMNPUMNPSite of lesion- or cranial motor neuronNeurons forming descending tractsMuscles Involved-single muscle on the same sideGroups of muscles on opposite sideVol. movementslostlostTone of involved muscles- flaccidityClasp-knife rigidity, spastic paralysis

Planter reflex lost only if S1 is affected

LMNP UMNPTendon jerks lost

Exaggerated, clonus+Muscle atrophy marked wasting

absentSuperficial reflexes lost

lostBabinskis +ve

LMNP UMNPSite of lesion - - or cranial motor neuron Muscles Involved -single muscle on the same sideVoluntary movements - lostTone of the muscles - flaccidity involved

Superficial reflexes lostPlanter reflex lost only if S1 is affectedTendon jerks lost

Muscle atrophy marked wasting

Neurons forming descending tractsGroups of muscles on opposite sidelostClasp-knife rigidity,spastic paralysislostBabinskis +ve

Exaggerated, clonus+ absent

II. Stage of reflex activity paralysis in flexionAppearance of ANS reflexes first after 1 wk tonic symp. discharge. - sed response to pain

reflex contraction of bladder but incomplete evacuation - hyper active ,small bladder

- Vasomotor tone returns Skin warm, pink due to improved circulation

B.P. normal but baroreceptor regulation absent so wide swings

Lesion of Final common pathway Muscles innervated are paralyzed Paralysis on the same side of lesion Tone --flaccidity hypotoniaReflexes - deep lost, superficial lostMuscle atrophy present loss of specific trophic factors, disuse

LOWER MOTOR NEURON PARALYSIS -- POLIOMYELITISViral infection of lower motor neuron

UPPER MOTOR NEURON PARALYSISMonoplegia - cerebral cortex

Hemiplegia of opposite side int. capsule --with 3rd nerve of same side mid brain

Hemiplegia with VII,IX,X,XII nerves - Pons medulla

Quadriplegia or paraplegia spinal cord

CLINICAL CONDITIONSUMNP

LMNP

Complete transection of Sp. Cord

Hemisection of Sp. Cord

Syringomyelia

Main Clinical features:-

Group of muscles are affectedParalysis on the opposite side of lesion Tone spasticity or rigidity hypertoniaReflexes - deep exaggerated, superficial lost they are mediated by long tracts Babinskis sign +veMuscle atrophy - absent

STROKE UMNP Due To C.V.A.SPASTICITY Signs Due To Involvement of PS & EPS

BABINSKIS SIGN

Superficial reflexFirm tactile stimulus to lat. side of soleExtension of great toe, fanning of toesSeen in lesions of CST, infants, deep sleep, comaExplanation:- CST supresses withdrawal reflex. Damage to CST reveals withdrawal reflex

COMPLETE TRANSECTION OF SP.CORDCauses :

# spineGunshot injuryTransverse myelitisOcclusion of blood vessel

Sign and symptoms observed at the level & below site of injury

Stages of spinal injuryStage of flaccidity about 2 wks. in human

Stage of reflex activity paralysis in flexion

Stage of failure of reflex activity

CHANGES OCCURE IN - ANS REFLEXES MUSCLE TONE SOMATIC REFLEXES

Stage of spinal shock starts immediately, lasts for 2 wks.Complete sensory lossMotor system -- Complete paralysisMuscle tone -- FlaccidityReflexes superficial - Absent deep - Absent

ANS reflexes- vasomotor tone B.P. paralysis of bladder& rectum cold, dry, scaly skin leads to bed sores, cyanosis due to venous return Complications malnutrition, -ve nitrogen balance, osteoporosis, urinary stones, septicaemia etc.

Muscle tone normal but more in flexors, repeated flexor response-flexor contracture no wasting

Attutude :- upper limb adducted and semiflexed

lower limb abducted and extended

Reflexes flexor response appears first, Babinskis + ve Exaggerated prolonged withdrawal reflex mass reflex after several months stretch reflexes exaggeratedNo improvement in sensations

Mass reflex in chronic spinal animals scratching of inner side of thigh flexor spasm of both legs, contraction of abdominal muscles Emptying of bladder, profuse sweating. Pallor and blood pressure swingsOccur due to irradiation of afferent stimuli from one reflex center to another. Used by paraplegic to have some control over urination and defecation.&

III. Stage of reflex failureInfections , malnutrition, muscle wasting, bed sores, UTI, uraemia Slow disappearance of mass reflex and other reflexesComa death

MANAGEMENTmanagement of nutrition, fluid balance

Use of antibiotics

Proper skin care

Acute administration of large doses of glucocorticoids

Brown Sequard Syndrome Hemisection Of Spinal CordCauses:- gun shot injuries, accidents, tumors

Clinical picture :-I. Below the site of lesiona) On same side-Motor UMN lesion spastic paralysis, Clasp knife rigidity+ve Babinskis, exaggerated tendon reflexes

Sensory - loss of proprioception, vibration sense, discriminationb) On opposite sideSensory loss of pain and temperatureII. At the site of lesion LMN paralysis, ipsilat. anaesthesiaMotor no effect

LeftrightmidlineOn same sideOn oppo. sideLoss of pain,temp.Dorsal columnLat.STTLat.CSTDorsal columnLat.STTPain ,temp.Lat.CSTSite of lesion 1.Loss of proprioception,vibration 2.UMNP

SYRYNGOMYELIA- dissociated anaesthesiaCause :- central cavitation of spinal cord beginning in cervical region with gliosis. Interuption of crossing fibers. Initially, Yolk like anaesthesia for pain & temperature over shoulder and upper limb. With LMN weakness in upper limb. Fine touch preserved Later, UMN paralysis in lower limb. Rhombergs sign is +ve.