Parkinson’s Disease

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FACTS

Nigrostriatal pathway

  • projects from substantia nigra pars compacta to striatum.
  • differential activation of each pathway is via D1 (direct) and D2 (indirect) receptor activation.
  • direct and indirect pathways of striatal medium spine neurons (MSNs).
Path
Function
Receptor
Details
Direct
Excitatory (initiation)
D1
cortex -> Striatum -> GPi -> thalamus -> motor cortex -> s.c / brainstem
Indirect
Inhibitory (termination)
D2
cortex -> striatum -> GPe -> STN -> GPe -> thalamus -> motor cortex -> spinal cord / brainstem

HPI

Cardinal symptoms (responsive to DBS/levodopa):
  • resting tremor
  • rigidity
  • bradykinesia
Other Sx
freezing
falling
dysarthria
cognitive decline
bowel/bladder dysfunction

PHYSICAL EXAM

Rest tremor

IMAGING

 
A/P
Therapies that only address cardinal symptoms of PD
  1. Levodopa is first trial therapy
  1. DBS once refractory to levodopa