In modern clinical practice, diagnostic accuracy is fundamental to patient safety and quality of care. Yet this case exemplifies how a diagnostic error chain—rooted in cognitive bias, inadequate specialist involvement, and systemic failures—can perpetuate misdiagnosis, prolong suffering, and erode trust in the healthcare system. This essay unpacks the diagnostic error chain in a case of late-onset dopa-responsive dystonia (DRD) misdiagnosed as idiopathic Parkinson’s disease (PD), highlights the legal and ethical breaches involved, and outlines actionable steps to prevent recurrence.
1. The Diagnostic Error Chain
The chain began with the neurologist’s anchoring bias, framing the case as parkinsonism in the initial DaT-SPECT request—explicitly stating “we suspect autosomal recessive Parkinson’s.” This prematurely narrowed the differential diagnosis, overshadowing red-flag features such as dystonic gait, foot pain, and the patient’s relatively young age—hallmarks that are often seen in DRD, including late-onset forms. Critically, the neurologist failed to conduct a levodopa trial, a straightforward, guideline-recommended step that would have revealed the correct diagnosis.
The radiologist’s reporting further compounded the error. Using template language (“consistent with idiopathic Parkinson’s or LBD”) without addressing the clinical context or scan limitations, the report failed to caution that DaT-SPECT is not disease-specific. The radiologist neglected to recommend clinical correlation or specialist review, falling short of EANM/SNMMI standards that emphasize the need for integration with clinical findings.
The neurologist’s misinterpretation of the scan was the final link: he treated the probabilistic language of the report as definitive confirmation of idiopathic PD, ignoring the atypical clinical features and guidelines (NICE NG71, MDS, EANM/SNMMI) that require a holistic clinical assessment and a therapeutic levodopa challenge. Crucially, despite acknowledging his lack of movement-disorder expertise, he failed to refer the patient to a specialist.
At the systemic level, the hospital’s governance mechanisms failed to provide necessary oversight. No multidisciplinary team (MDT) review was initiated, no escalation or second opinion was sought, and the complaints process failed to identify the diagnostic error—representing a missed opportunity for organizational learning and patient safety improvement.
2. Legal and Ethical Breaches
Neurologist’s Breach of Duty: As the responsible consultant, the neurologist owed a duty of care to provide an accurate, evidence-based diagnosis. By disregarding his own admission of limited expertise and failing to refer for a movement-disorder evaluation, he breached this duty (Irish Medical Council Guide §2.2). Anchoring bias and the failure to perform a levodopa trial—contrary to NICE NG71 and MDS guidelines—directly resulted in eight years of untreated dystonic pain, leading to chronic pain, occupational harm, and psychological distress.
Radiologist’s Breach of Duty: The radiologist’s duty of care required that the report adhere to EANM/SNMMI standards, providing nuanced interpretation, acknowledging limitations, and advising clinical correlation. The report’s vague language contributed to the neurologist’s misinterpretation, representing a contributory breach that failed to mitigate diagnostic risk.
Hospital Governance Breaches: Governance structures should have mandated MDT review and escalated atypical cases to a specialist. The system’s failure to supervise a non-specialist managing a complex movement disorder, and its ineffective complaints process, breached open-disclosure principles and denied the patient an opportunity for timely correction and learning.
3. Why “But the Scan LOOKED Abnormal” Fails
The key misconception—that an abnormal DaT-SPECT scan confirms idiopathic PD—ignores the fundamental limitation that DaT-SPECT cannot distinguish PD from other causes of dopaminergic dysfunction (such as DRD, MSA, PSP, or CBD). Guidelines explicitly require that atypical clinical features override a single imaging finding. Moreover, the radiologist’s probabilistic language demanded clinical correlation, not diagnostic closure. This is precisely why NICE NG71, EANM/SNMMI, and MDS guidelines emphasize that a levodopa trial and specialist evaluation are essential before concluding PD in young-onset or atypical cases.
4. Next Steps
Document-Driven Actions: The patient should formally request a movement-disorder specialist re-evaluation, an apology and acknowledgment of the diagnostic error, and a correction of the diagnosis in the medical record.
Legal Preparation: A solicitor should be provided with a key statement highlighting the breach of duty:
“Given the explicit instruction in NICE NG71 that DaT-SPECT be used only where clinical uncertainty persists, the respondent’s decision to declare a firm diagnosis of idiopathic Parkinson’s disease—despite atypical features and without levodopa challenge or movement-disorder referral—constitutes a breach of duty…”
System-Level Action: The hospital should audit all DaT-SPECT-based diagnoses from the past five years to identify similar errors. Additionally, a mandatory MDT sign-off should be implemented before labelling patients with atypical parkinsonism—particularly those with features suggestive of DRD—as idiopathic PD.
5. Conclusion
This case illustrates a textbook diagnostic error chain—anchoring bias, misuse of non-specific tests, and systemic failures—highlighting the critical importance of specialist input, proper test interpretation, and robust governance. The consequences for the patient—eight years of preventable suffering—underscore the need for both accountability and learning. Expertise matters. A movement-disorder specialist would have recognized the atypical presentation, challenged the PD assumption, performed a levodopa trial, and integrated scan results within the broader clinical context—transforming a diagnostic error chain into a path to timely, effective care.