Symptoms & Diagnosis

Symptoms & Diagnosis of Atypical Parkinsonism

Key Red Flags vs. Idiopathic Parkinson’s Disease (PD)

The presence of these features early in the disease course strongly suggests atypical parkinsonism rather than typical PD:

Early postural instability & falls (within first 1–3 years)
Poor or absent response to levodopa (even high doses)
Symmetrical onset of symptoms
Rapid progression (significant disability within 5 years)
Early autonomic failure (orthostatic hypotension, urinary incontinence – typical of MSA)
Supranuclear gaze palsy / ocular motor abnormalities (especially vertical – classic in PSP)
Limb apraxia, alien limb, cortical sensory loss (suggestive of CBD)
Early cognitive impairment or visual hallucinations (common in DLB)

Current Diagnostic Criteria

Progressive Supranuclear Palsy (PSP)

MDS-PSP Criteria (2017)
Probable PSP-Richardson’s syndrome requires:
• Vertical supranuclear gaze palsy
• Postural instability with falls within 3 years

Corticobasal Degeneration (CBD)

Armstrong et al. Criteria (2013)
Probable CBD includes asymmetric rigidity + at least two of:
• Limb apraxia
• Cortical sensory deficit
• Alien limb phenomenon

Multiple System Atrophy (MSA)

Gilman et al. Criteria (2008, 2nd consensus)
Probable MSA: Autonomic failure + poorly levodopa-responsive parkinsonism or cerebellar ataxia

Role of MRI and Emerging Biomarkers

Classic MRI Findings

  • PSP: Midbrain atrophy → “Hummingbird” or “penguin” sign, “morning glory” sign, superior cerebellar peduncle atrophy
  • MSA-P: Putaminal atrophy, slit-like marginal hyperintensity (“putaminal rim” sign)
  • MSA-C: “Hot cross bun” sign in pons, middle cerebellar peduncle atrophy
  • CBD: Asymmetric peri-Rolandic cortical atrophy

Emerging Diagnostic Tools

  • Alpha-synuclein seed amplification assays (αSyn-SAA) – highly accurate for MSA and DLB
  • RT-QuIC in skin/nerves for MSA
  • Neurofilament light chain (NfL) in blood/CSF – marker of progression
  • DaTSCAN: Normal or symmetric reduction (vs. asymmetric in PD)
  • Tau PET ligands under investigation for PSP and CBD
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