LETS NOW DISCUSS ON SPASTICITY ( BRADDOM 5TH EDITION ) - PART 1
EDITED BY ME
INTRODUCTION
A ) is estimated to occur around 85 % of people with multiple sclerosis and 65 to 78 % in those with spinal cord injury
B ) TBI with brainstem involvement ( v imp ) have a 40 % chance of spasticity
C ) vv imp in persons with stroke - involvement of basal ganglia , thalamus , insula and white matter tracts ( internal capsule , corona radiata , external capsule and superior longitudinal fasciculus ) is associated with severe upper limb spasticity whereas in multiple sclerosis if plaques affect the corticospinal tract , brain stem and callosal radiations
PATHOPHYSIOLOGY
1 according to sherrington , reflexes is not an isolated phenomenon but is a product of integrated activation as a result of reciprocal innervation of muscles
2 stretch reflex is a monosynaptic reflex that provides automatic regulation of skeletal muscle length
3 Ia , II ( afferent fibers ) , Ib ( golgi tendon organ ) - acts when muscle is lengthened by passive stretch
A ) the increase in neuronal activities in these fibers inturn increases alpha motor neuron activity in the stretched muscles , causing the muscle fibers to contract and thus resist muscle lengthening and stretching
B ) Ia afferent fibers also synapse with Ia inhibitory interneurons producing relaxation of antagonistic muscles ( reciprocal innervation )
C ) Gamma motor neurons regulate the muscle spindle and reflex sensitivity
D ) excitability of spinal motor neurons is influenced by -
1 - LOCAL INTRASPINAL MECHANISMS
A ) recurrent inhibition from renshaw cells
B ) reciprocal Ia inhibition
C ) inhibition from group II afferents
D ) non reciprocal Ib inhibition
E ) presynaptic inhibition
2 EXCITATORY AND INHIBITORY DESCENDING SUPRASPINAL SIGNALS
A ) DESCENDING SUPRASPINAL SIGNALS
1 - are 5 in number - corticospinal , reticulospinal , vestibulospinal , rubrospinal and tectospinal
A ) CORTICOSPINAL TRACT -
1 - originates from cerebral cortex and is primarily involved in voluntary movement
2 - isolated lesion produces weakness , loss of dexterity , hypotonia and hyporeflexia instead of spasticity ( vv imp )
B ) TECTOSPINAL PATHWAY -
1 Originates from tectum ( superior colliculus ) in the midbrain
2 Contributes to visual orientation
C ) RETICULOSPINAL AND VESTIBULOSPINAL TRACT -
- provides balanced excitatory and inhibitory descending regulation of spinal stretch reflex
D ) RUBROSPINAL PATHWAY
1 - emanates from lateral brain stem
2 - almost absent in humans
RETICULOSPINAL TRACT ( VV IMP - VIVA VOCE ) - 2 principle excitatory and inhibitory systems from the brainstem -
( The reticulospinal tract (or anterior reticulospinal tract) is an extrapyramidal motor tract that descends from the reticular formation in two tracts to act on the motor neurons supplying the trunk and proximal limb flexors and extensors.
It is involved mainly in locomotion and postural control, although it does have other effects as well )
- has 2 components -
A ) DORSAL RST OR LATERAL RST -
1 - originates from ventromedial reticular formation in the medulla
2 - provides a powerful inhibitory effect on spinal stretch
B ) MEDIAL RST
- has a diffuse origin mainly in the pontine tegmentum and has efferent connections passing through and recieving communication from the central gray and tegmentum areas of midbrain
RETICULAR FORMATION
A ) is diffusely distributed throughout the brain stem
B ) is highly organised
C ) has 4 longitudinal columms with illdefined boundaries -
1 paramedian zone
2 paramedian medial zone
3 intermediate zone
4 lateral zone
D ) is also involved in -
1 - coordination of movement
2 - autonomic regulation of respiration , heart rate and blood pressure
3 - in arousal , consciousness and modulation of pain