Direct Motor Pathway: "The Pyramidal System"

• Involves lateral motor system - lateral corticobulbar and corticospinal tracts
• Function of pathway - voluntary motor movement of contralateral limbs/speech muscles
• This pathway that makes few stops
• Crosses over (decussates) at medulla/spinal cord juncture
• Main Center = Primary motor cortex
• Upper part of tract (brain and spinal cord) = Upper Motor Neurons (UMN)
• Lower part of tract (cranial and spinal nerves) = Lower Motor Neurons (LMN)

Direct Motor Pathway Damage

•UMN damage

–Spastic muscles

• Hypertonia
• Hyper-reflexia (+ refexes)
• Clonus
• (+) Babinski sign
• No atrophy
• No fasciculations

•LMN damage

–Flaccid muscles

• Hypotonia
• Hyporeflexia (- reflexes)
• No clonus
• No Babinski sign
• Marked atrophy
• Fasciculations

Direct Motor System Damage

• Dyskinesias
• Tremors
• Rest tremors
• Action tremors
• Chorea
• Athetosis
• Dystonia
• Myoclonus