Lec 3: UMN and LMN Pathology Flashcards
UMN Syndrome may involve what?
-Motor cortex and pathways
-Brainstem
-Cerebellum
-SC reflexes and coordination
What corresponds with an UMN lesion?
-collection of neurologic signs and symptoms (postures, postural responses, passive mvmts, active mvmts, and involuntary responses)
UMN syndrome injuries reside where?
-several areas of brain and SC
-major areas: motor cortex or brainstem
-motor pathways from major brain areas
-SC involving motor output
LMN syndrome injuries reside where?
-AHC or peripheral nerve
-cranial nerve (PN)
UMN Syndrome is the result of….
-a disruption of central motor pathways (arise from cerebral cortex and pathways in SC)
Define central motor pathways?
connections to the motor systems from cerebral cortex and in spinal cord
What are the six central motor pathways?
-Corticospinal Tracts (voluntary motor control)
-Corticobulbar Tracts (cranial nerves)
-Lateral and Medial Reticulospinal Tracts (muscle tone/cerebellum)
-Lateral and Medial Vestibulospinal Tracts (AMN/reflexes)
-Rubrospinal Tracts (cerebellum and BG)
-Tectospinal Tracts (vision and auditory stimulation to turn head)
Classic UMN Syndrome
Weakness, Spasticity, Decreased Muscle Control, Hyperreflexia (exaggerated DTR), Clonus
Define weakness and decreased muscle control?
Weakness: loss of CNS drive (groups of muscles vs PN innervated muscles)
Decreased muscle control: changes in selective function
Define hyperreflexia, and clonus in UMN syndrome
Hyperreflexia: Increase muscle response to tendon tap
Clonus: repeated rhythmic contractions of individual muscle groups
Tone definition and what tone reflects
Tone is resistance to passive stretch as a patient is attempting to maintain a relaxed state of muscle activity (excludes joint, skeletal, ligamentous abnormalities). Tone is a normal balance between excitatory and inhibitory control.
Tone reflects the muscle’s state of relaxation (must test at every joint in flexion, ext, ABD, & ADD). It is independent of strength, coordination or involuntary movement.
What is the range of muscle tone and where is UMN and LMN in the range?
Range= flaccidity–hypotonia–normal–hypertonia–rigidity
LMN characterized by flaccidity, while UMN is characterized by flaccidity only initially. UMN is later classified by hypertonia.
Define hypertonia and it’s 3 classifications
Increase in passive muscle tightness (abnormally increased resistance to an external force about a joint)
- Spasticity
- Rigidity
- Dystonia
Definition of Spasticity
A motor disorder characterized by velocity-dependent increase in tonic stretch reflexes (muscle tone) with exaggerated tendon jerks, resulting from hyper-excitability of the stretch reflex, as one component of the UMN syndrome.
Definition of rigidity and dystonia
Rigidity: significant increase in resistance to multidirectional external forces about a joint
Dystonia: a state of abnormal muscle tone resulting in muscular spasm and abnormal posture, typically d/t neurological disease or side effect of drug therapy
Movement based sign of UMN lesion
Synergistic movements or abnormal movements
e.g. flexor synergy/extensor synergy