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 muscle (when bundles of muscle fibers contract) & fibers contract) & fibrillationsfibrillations (individual muscle (individual muscle fibers contract) seen when there is fibers contract) seen when there is slow slow degenerationdegeneration 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. In LMN lesion, stimulation & galvanic stimulation. In LMN lesion, muscles respond to faradic stimulation upto 7 muscles respond to faradic stimulation upto 7 daysdays & to & to galvanic stimulation upto 10 daysgalvanic stimulation upto 10 days. After . After 10 days, no response (faradic = interrupted 10 days, no response (faradic = interrupted current stimulation & galvanic = direct current current stimulation & galvanic = direct current stimulation).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 1) FEATURES OF LESION OF PYRAMIDAL OR CORTICO-PYRAMIDAL OR CORTICO-SPINAL TRACT: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 MOVEMENTS, SPECIALLY OF DISTAL PARTS OF LIMBSPARTS OF LIMBS..

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.