Extrapyramidal vs. Pyramidal Motor Systems
The opposite of pyramidal is extrapyramidal, and extrapyramidal dysfunction manifests as hypomimia, muscular rigidity, bradykinesia, hypokinesia, monotonous and slow speech, parkinsonian-like tremor, and dyskinesia with diminished voluntary movements. 1
Key Clinical Distinctions
Pyramidal System Manifestations
- Hypertonia, hyperreflexia, and positive Babinski sign characterize pyramidal tract involvement 1, 2
- Progressive spasticity and weakness, particularly affecting extensors in the upper limbs and flexors in the lower limbs 2, 3
- These signs indicate upper motor neuron pathology originating from the corticospinal tract 2
Extrapyramidal System Manifestations
The extrapyramidal system produces a distinctly different clinical picture: 1
- Hypomimia (reduced facial expression) 1
- Muscular rigidity (not spasticity) 1
- Bradykinesia and hypokinesia (slowness and reduced movement) 1
- Monotony and slowness of speech 1
- Parkinsonian-like tremor 1
- Dyskinesia with diminished voluntary movements 1
- Involuntary movements like tics or chorea occur rarely 1
Clinical Context Where Both Systems Are Observed
Multisystem Atrophy (MSA)
MSA demonstrates both pyramidal signs (hyperreflexia) and extrapyramidal features (parkinsonism present in 87% of cases), making it a "Parkinson-plus" syndrome 1, 4
Hepatic Encephalopathy
- Pyramidal signs: hypertonia, hyperreflexia, positive Babinski 1, 2
- Extrapyramidal signs: the full spectrum of parkinsonian features described above 1
- These motor signs may not progress in parallel in individual patients, creating diagnostic complexity 1
Critical Pitfall to Avoid
Do not confuse extrapyramidal rigidity with pyramidal spasticity. 2 While both involve increased muscle tone, rigidity is "lead-pipe" or "cogwheel" in quality and affects agonist-antagonist muscle pairs equally, whereas spasticity is velocity-dependent and affects specific muscle groups in the characteristic pyramidal pattern 1, 2
The European Academy of Neurology emphasizes that pyramidal weakness must be distinguished from extrapyramidal dysfunction, as they represent different motor systems with different underlying pathophysiology 2