EXTRA-PYRAMIDAL EXTRA-PYRAMIDAL TRACTS:TRACTS:All descending tracts other than All descending tracts other than cortico-spinal / pyramidal are cortico-spinal / pyramidal are included in it.included in it.

1) RUBRO-SPINAL TRACT:1) RUBRO-SPINAL TRACT:

ORIGIN:ORIGIN: Red nucleus (midbrain). Red nucleus (midbrain). Fibers cross over to opposite side & Fibers cross over to opposite side &

descend through pons & medulla descend through pons & medulla lat lat white column of spinal cord.white column of spinal cord.

Fibers terminate on inter-neurons.Fibers terminate on inter-neurons. Inter-neurons synapse with alpha & Inter-neurons synapse with alpha &

gamma motor neurons.gamma motor neurons.

RED NUCLEUS

DEEP CEREBELLAR NUCLEI

MID BRAIN

LATERAL WHITE COLUMN

FIBERS FROM CEREBELLUM

FIBERS FROM

CEREBRAL CORTEX

RUBRO-SPINAL TRACT

Red nucleus receives fibers from:Red nucleus receives fibers from: Cerebral cortex &Cerebral cortex & Cerebellum.Cerebellum. Rubro-spinal tract is an alternate Rubro-spinal tract is an alternate

pathway, through which cerebral cortex & pathway, through which cerebral cortex & cerebellum control activity of motor cerebellum control activity of motor neurons in spinal cord.neurons in spinal cord.

This tract is This tract is excitatory for flexorsexcitatory for flexors & & inhibitory for extensorsinhibitory for extensors (anti-gravity (anti-gravity muscles).muscles).

2) TECTO-SPINAL TRACT:2) TECTO-SPINAL TRACT:

ORIGIN:ORIGIN: superior colliculus located in superior colliculus located in tectum of midbrain.tectum of midbrain.

Tract fibers descend without crossing.Tract fibers descend without crossing. Fibers terminate onto motor neurons in Fibers terminate onto motor neurons in

ventral horn of upper cervical segments ventral horn of upper cervical segments of spinal cord, through inter-neurons.of spinal cord, through inter-neurons.

This tract controls reflex movements of This tract controls reflex movements of head & neck, in response to visual head & neck, in response to visual stimuli, e.g, something shines behind stimuli, e.g, something shines behind reflex turning of head & neck back to the reflex turning of head & neck back to the shining object.shining object.

RETICULO-SPINAL TRACT:RETICULO-SPINAL TRACT:

ORIGIN:ORIGIN: Tract arises from reticular Tract arises from reticular formation (groups of scattered neurons formation (groups of scattered neurons along with nerve fibers present in along with nerve fibers present in midbrain, pons & medulla).midbrain, pons & medulla).

* Superiorly reticular formation is * Superiorly reticular formation is connected to cerebral cortex &connected to cerebral cortex &

inferiorly to spinal cord.inferiorly to spinal cord.

Reticulo-spinal tract has 2 components:Reticulo-spinal tract has 2 components: A) PONTINE componentA) PONTINE component B) MEDULLARY componentB) MEDULLARY component

PONTINE RETICULO-PONTINE RETICULO-SPINAL TRACT:SPINAL TRACT:

ORIGIN:ORIGIN: Nuclei of reticular formation of pons. Nuclei of reticular formation of pons. Fibers remain uncrossed & descend to enter Fibers remain uncrossed & descend to enter

anterior white columns of spinal cord.anterior white columns of spinal cord. Tract terminate on motor neurons in ventral Tract terminate on motor neurons in ventral

horn of spinal cord, through inter-neurons & horn of spinal cord, through inter-neurons & finally motor neurons.finally motor neurons.

excitatory for extensorsexcitatory for extensors & & Inhibitory for flexorsInhibitory for flexors (unlike rubro-spinal). (unlike rubro-spinal).

MEDULLARY RETICULAR MEDULLARY RETICULAR FORMATION:FORMATION:

ORIGIN:ORIGIN: Nuclei of reticular formation in Nuclei of reticular formation in medulla.medulla.

Fibers cross to opposite side.Fibers cross to opposite side. Tract descends to enter lateral white column of Tract descends to enter lateral white column of

spinal cord.spinal cord. Terminate onto the motor neurons in ventral Terminate onto the motor neurons in ventral

horn.horn. It is It is inhibitory for extensorsinhibitory for extensors (like rubro-spinal). (like rubro-spinal).

VESTIBULO-SPINAL VESTIBULO-SPINAL TRACT:TRACT:

ORIGIN:ORIGIN: Vestibular nuclei in lower pons Vestibular nuclei in lower pons & medulla.& medulla.

Mostly fibers remain uncrossed.Mostly fibers remain uncrossed. Then enter Ant. White column of spinal Then enter Ant. White column of spinal

cord.cord. Terminate on alpha & gamma motor Terminate on alpha & gamma motor

neurons, through interneurons.neurons, through interneurons.

2 components of the tract:2 components of the tract: Major component Major component Lat. V.S Tract Lat. V.S Tract Minor component Minor component Med. V.S Tract. Med. V.S Tract. Lat. V.S Tract Lat. V.S Tract lat. Vest. Nuclei. lat. Vest. Nuclei. Med. V.S Tract Med. V.S Tract med Vest. Nuclei. med Vest. Nuclei.

Vest-spinal tract is excitatory for Vest-spinal tract is excitatory for extensors (unlike rubro-spinal).extensors (unlike rubro-spinal).

Vestibular nuclei Vestibular nuclei cerebellar fibers cerebellar fibers Vestibular nuclei Vestibular nuclei internal ear fibers internal ear fibers

(vestibular apparatus).(vestibular apparatus).

OLIVO-SPINAL TRACT:OLIVO-SPINAL TRACT:

ORIGIN:ORIGIN: Inferior olivary nucleus in Inferior olivary nucleus in medulla.medulla.

Fibers cross over to opposite side & Fibers cross over to opposite side & descend into lat. White column of spinal descend into lat. White column of spinal cord.cord.

Fibers terminate onto motor neurons in Fibers terminate onto motor neurons in ventral horn through interneurons.ventral horn through interneurons.

This tract controls activity of motor This tract controls activity of motor neurons in spinal cord.neurons in spinal cord.

Inferior olivary nucleus receives fibers Inferior olivary nucleus receives fibers from cerebral cortex, corpus striatum, from cerebral cortex, corpus striatum, reticular formation & spinal cord.reticular formation & spinal cord.

DESCENDING AUTONOMIC DESCENDING AUTONOMIC PATHWAY:PATHWAY:

ORIGIN:ORIGIN: Cerebral cortex, hypothalamus, Cerebral cortex, hypothalamus, amygdala & reticular formation.amygdala & reticular formation.

This pathway accompanies reticulo-spinal This pathway accompanies reticulo-spinal tract.tract.

These fibers enter lat. white column of spinal These fibers enter lat. white column of spinal cord & terminate onto pre-gang. Sympathetic cord & terminate onto pre-gang. Sympathetic neurons in segments T1 – L2 & also onto pre-neurons in segments T1 – L2 & also onto pre-gang parasymp neurons in segments S2 – S4.gang parasymp neurons in segments S2 – S4.

MOTOR SYSTEM CONSISTS MOTOR SYSTEM CONSISTS OF 2 TYPES OF NEURONS:OF 2 TYPES OF NEURONS:

UMNUMN LMNLMN

LMN:LMN:

Motor neurons which innervate the Motor neurons which innervate the skeletal muscles.skeletal muscles.

These form the These form the final common final common pathways to skeletal muscles.pathways to skeletal muscles.

If any motor impulse has to pass to If any motor impulse has to pass to skeletal muscle, it has to pass to skeletal muscle, it has to pass to LMN.LMN.

These neurons include:These neurons include: Alpha motor neuronAlpha motor neuron in ventral horn in ventral horn

of spinal cord & also of spinal cord & also motor neurons motor neurons in nuclei of cranial nervesin nuclei of cranial nerves in brain in brain stem.stem.

UMN:UMN:

These are present These are present above the level of above the level of LMN.LMN.

These control motor activity through These control motor activity through separate pathways.separate pathways.

These neurons may be located in These neurons may be located in cerebral cortexcerebral cortex, , basal gangliabasal ganglia & also & also in in brain stembrain stem..

FEATURES OF LMN FEATURES OF LMN LESION:LESION:

May involve LMN in ventral horn of spinal cord May involve LMN in ventral horn of spinal cord or motor nuclei of cranial nerves or their nerve or motor nuclei of cranial nerves or their nerve fibers.fibers.

CAUSES OF LESIONCAUSES OF LESION:: TraumaticTraumatic Infective (poliomyelitis)Infective (poliomyelitis) InflammatoryInflammatory DegenerativeDegenerative NeoplasticNeoplastic Vascular (lesion)Vascular (lesion)

FEATURES:FEATURES:

Only a Only a few musclesfew muscles are involved in LMN lesion. are involved in LMN lesion. Flaccid paralysisFlaccid paralysis in LMN lesion, i-e, loss of in LMN lesion, i-e, loss of

voluntary movements with voluntary movements with hypotonia or atoniahypotonia or atonia.. LossLoss of of superficial reflexessuperficial reflexes.. LossLoss of of deep reflexesdeep reflexes / tendon jerks. / tendon jerks. Muscle atrophyMuscle atrophy (*main cause is (*main cause is loss of trophicloss of trophic

actions of motor nervesactions of motor nerves, supplying skeletal , supplying skeletal muscles).muscles).

Disuse is minor cause.Disuse is minor cause.

There are There are fasiculationsfasiculations (when bundles of (when bundles of muscle fibers contract) & muscle fibers contract) & fibrillationsfibrillations (individual muscle fibers contract) seen when (individual muscle fibers contract) seen when there is there is slow degenerationslow degeneration of LMNs. of LMNs.

Shortening of paralyzed muscles Shortening of paralyzed muscles contractures.contractures.

Reaction of degeneration: response to faradic Reaction of degeneration: response to faradic stimulation & galvanic stimulation. stimulation & galvanic stimulation.

In LMN lesion, In LMN lesion, muscles respond to muscles respond to faradic stimulation upto 7 daysfaradic stimulation upto 7 days & to & to galvanic stimulation upto 10 daysgalvanic stimulation upto 10 days..

After 10 days, no response (faradic = After 10 days, no response (faradic = interrupted current stimulation & galvanic interrupted current stimulation & galvanic = direct current stimulation).= direct current stimulation).

Babinski signBabinski sign is is not presentnot present..

FEATURES OF UMN FEATURES OF UMN LESION:LESION:

1) FEATURES OF LESION OF 1) FEATURES OF LESION OF PYRAMIDAL PYRAMIDAL OR CORTICO-SPINAL OR CORTICO-SPINAL TRACT:TRACT:

2) FEATURES OF LESION OF EXTRA-2) FEATURES OF LESION OF EXTRA-CORTICO-SPINAL OR CORTICO-SPINAL OR EXTRA-EXTRA-PYRAMIDAL TRACT.PYRAMIDAL TRACT.

1) FEATURES OF LESION OF PYRAMIDAL 1) FEATURES OF LESION OF PYRAMIDAL OR CORTICO-SPINAL TRACT:OR CORTICO-SPINAL TRACT:

FUNCTION:FUNCTION: Control of fine skilled voluntary Control of fine skilled voluntary movements specially of distal parts of limbs.movements specially of distal parts of limbs.

Incase of UMN lesion of pyramidal tract:Incase of UMN lesion of pyramidal tract: A)A) LOSS OF FINE SKILLED VOLUNTARY LOSS OF FINE SKILLED VOLUNTARY

MOVEMENTS, SPECIALLY OF DISTAL PARTS OF MOVEMENTS, SPECIALLY OF DISTAL PARTS OF LIMBSLIMBS..

B)B) + BABINSKI SIGN / ABNORMAL PLANTAR + BABINSKI SIGN / ABNORMAL PLANTAR REFLEX.REFLEX.

C)C) LOSS OF SUPERFICIAL ABDOM. REFLEXLOSS OF SUPERFICIAL ABDOM. REFLEX

D)D) LOSS OF CREMASTERIC REFLEX.LOSS OF CREMASTERIC REFLEX.

NORMAL PLANTAR NORMAL PLANTAR REFLEX:REFLEX:

When we scratch along lateral border of sole of When we scratch along lateral border of sole of foot foot plantar flexion of all the toes. plantar flexion of all the toes.

Segment value of normal plantar reflex is S1.Segment value of normal plantar reflex is S1. In addition, also + in:In addition, also + in: 1) Infants (due to incomplete myelination of 1) Infants (due to incomplete myelination of

cortico-spinal tract).cortico-spinal tract). 2) during sleep.2) during sleep. 3) alcohol intoxication.3) alcohol intoxication.

ABNORMAL PLANTAR ABNORMAL PLANTAR REFLEX:REFLEX:

When we scratch When we scratch dorsi-flexion of big dorsi-flexion of big toe & fanning out of other 4 toes.toe & fanning out of other 4 toes.

LOSS OF SUPERFICIAL LOSS OF SUPERFICIAL ABDOMINAL REFLEX:ABDOMINAL REFLEX:

Due to loss of excitatory effect of cortico-Due to loss of excitatory effect of cortico-spinal tract on inter-neurons in reflex arc. spinal tract on inter-neurons in reflex arc. This reflex is polysynaptic because inter-This reflex is polysynaptic because inter-neurons are also involved.neurons are also involved.

Root value = T7 – T11.Root value = T7 – T11.

LOSS OF CREMASTERIC LOSS OF CREMASTERIC REFLEX:REFLEX:

Also due to loss of facilitation of inter-Also due to loss of facilitation of inter-neurons by cortico-spinal tract. This neurons by cortico-spinal tract. This reflex is also polysynaptic.reflex is also polysynaptic.

Root value is L1.Root value is L1.

LESIONS OF EXTRA-LESIONS OF EXTRA-CORTICO-SPINAL TRACT:CORTICO-SPINAL TRACT:

FEATURES:FEATURES: A)A) SPASTIC PARALYSIS. SPASTIC PARALYSIS. B)B) INCREASED MUSCLE TONE. INCREASED MUSCLE TONE. C)C) SLIGHT MUSCLE ATROPHY. SLIGHT MUSCLE ATROPHY. D)D) TENDON JERKS. TENDON JERKS. E)E) ANKLE OR KNEE CLONUS. ANKLE OR KNEE CLONUS. F)F) CLASP KNIFE RIGIDITY. CLASP KNIFE RIGIDITY.

A) SPASTIC PARALYSIS:A) SPASTIC PARALYSIS:

Loss of voluntary movements with Loss of voluntary movements with increased muscle tone.increased muscle tone.

In this lesion large no. of muscles are In this lesion large no. of muscles are involved.involved.

It may be hemiplegia.It may be hemiplegia.

B) INCREASED MUSCLE B) INCREASED MUSCLE TONE:TONE:

This is due to facilitation of stretch reflex This is due to facilitation of stretch reflex or myotatic reflex becomes hyperactive.or myotatic reflex becomes hyperactive.

C) SLIGHT MUSCLE C) SLIGHT MUSCLE ATROPHY:ATROPHY:

This is due to disuse This is due to disuse slight atrophy. slight atrophy.

D) TENDON JERKS:D) TENDON JERKS:

They become brisk or exaggerated due They become brisk or exaggerated due to facilitation of stretch reflex.to facilitation of stretch reflex.

E) ANKLE OR KNEE E) ANKLE OR KNEE CLONUS:CLONUS:

This is present when we apply a sudden This is present when we apply a sudden maintained stretch to musles maintained stretch to musles rhythmic, rhythmic, repeated muscle contraction.repeated muscle contraction.

F) CLASP KNIFE RIGIDITY:F) CLASP KNIFE RIGIDITY:

In the patient, if we try to flex arm at elbow In the patient, if we try to flex arm at elbow there is initial resistance to flexion, but when there is initial resistance to flexion, but when we continue flexion we continue flexion there is rapid flexion. there is rapid flexion.

Mechanism:Mechanism: Initially:Initially: stretch reflex is initiated, which is stretch reflex is initiated, which is

hyperactive in these patients. Triceps contracts hyperactive in these patients. Triceps contracts extension at elbow. extension at elbow.

Later on:Later on: muscle tension increases. There is muscle tension increases. There is activation of inverse stretch reflex due to activation of inverse stretch reflex due to excitation of golgi tendon organs excitation of golgi tendon organs muscle muscle relaxes relaxes rapid flexion. rapid flexion.

CLINICAL PICTURE OF CLINICAL PICTURE OF UMN LESION:UMN LESION:

We don’t get patients with lesion of one We don’t get patients with lesion of one type of tract. The lesions involve both type of tract. The lesions involve both pyramidal & extra-pyramidal tracts. So pyramidal & extra-pyramidal tracts. So we get we get mixed type of clinical featuresmixed type of clinical features in in clinical practice.clinical practice.

DIFFERENCES BETWEEN:DIFFERENCES BETWEEN:

LMN LESION:LMN LESION:

LEVEL OF LESION:LEVEL OF LESION: Level is alpha motor Level is alpha motor neuron in ventral neuron in ventral horn.horn.

UMN LESION UMN LESION (Pyramidal & Extra-(Pyramidal & Extra-pyramidal)pyramidal)

LEVEL OF LESION:LEVEL OF LESION: Level is above alpha Level is above alpha motor neuron in motor neuron in cerebral cortex, cerebral cortex, basal ganglia & brain basal ganglia & brain stem.stem.

LMN LESION:LMN LESION:

TONE:TONE: Loss of voluntary Loss of voluntary movements with movements with hypotonia / atonia.hypotonia / atonia.

No. OF MUSCLES No. OF MUSCLES INVOLVED:INVOLVED: Small no. of Small no. of muscles are involved.muscles are involved.

TYPE OF PARALYSIS:TYPE OF PARALYSIS: Flaccid paralysis.Flaccid paralysis.

UMN LESION:UMN LESION:

TONE:TONE: Loss of voluntary Loss of voluntary movements with movements with hypertonia.hypertonia.

No. OF MUSCLES No. OF MUSCLES INVOLVED:INVOLVED: Large no. of Large no. of muscles involved.muscles involved.

TYPE OF PARALYSIS:TYPE OF PARALYSIS: Spastic paralysis (clasp Spastic paralysis (clasp knife rigidity).knife rigidity).

LMN LESION:LMN LESION:

CAUSE OF ATROPHY:CAUSE OF ATROPHY: Due to loss of trophic Due to loss of trophic

action of nerves mainly.action of nerves mainly.

REFLEXES:REFLEXES: Loss of deep reflexes.Loss of deep reflexes. No ankle / knee clonus.No ankle / knee clonus. Negative babinski sign.Negative babinski sign.

UMN LESION:UMN LESION:

CAUSE OF ATROPHY:CAUSE OF ATROPHY: Due to disuse & only Due to disuse & only

slight atrophy.slight atrophy.

REFLEXES:REFLEXES: Reflexes become Reflexes become

exaggerated due to exaggerated due to facilitation of stretch facilitation of stretch reflex.reflex.

ankle / knee clonus.ankle / knee clonus. Positive babinski sign.Positive babinski sign.

LMN LESION:LMN LESION:

CONTRACTURE:CONTRACTURE: Present.Present.

FASCICULATION / FASCICULATION / FIBRILLATION:FIBRILLATION:

Present (slow Present (slow degeneration of degeneration of LMNs).LMNs).

UMN LESION:UMN LESION:

CONTRACTURE:CONTRACTURE: Absent.Absent.

FASCICULATION / FASCICULATION / FIBRILLATION:FIBRILLATION:

Absent . Absent . There is loss of There is loss of

skilled movements of skilled movements of peripheral limbs.peripheral limbs.

LMN LESION:LMN LESION:

HEMIPLEGIA:HEMIPLEGIA: Not a common feature.Not a common feature.

SUPERFICIAL SUPERFICIAL REFLEXES:REFLEXES:

Lost.Lost.

CONTROL OF MOTOR CONTROL OF MOTOR ACTIVITY:ACTIVITY:

Final common pathway Final common pathway to skeletal muscles.to skeletal muscles.

UMN LESION:UMN LESION:

HEMIPLEGIA:HEMIPLEGIA: Common Common

SUPERFICIAL SUPERFICIAL REFLEXES:REFLEXES:

Lost. (abdominal, Lost. (abdominal, cremasteric).cremasteric).

CONTROL OF MOTOR CONTROL OF MOTOR ACTIVITY:ACTIVITY:

Controls motor activity Controls motor activity through separate through separate pathways.pathways.