FND Diagnosis Revised to Progressive Supranuclear Palsy (PSP)
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A published case report in Oxford Medical Case Reports describes a 62-year-old woman who was diagnosed with Functional Neurological Disorder (FND) before the diagnosis was later revised to progressive supranuclear palsy (PSP), a neurodegenerative disease.
The authors explicitly describe the change:
"the diagnosis was eventually revised to progressive supranuclear palsy 3 years after symptom onset."
This is particularly important because it is not a patient-reported account or a retrospective social-media claim. It is a peer-reviewed clinical case report documenting the diagnostic history and subsequent revision.
The initial presentation
The patient developed gradually progressive dysphonia, difficulty keeping her eyes open and falls.
An MRI performed earlier in the course of the illness was reported as normal. She was ultimately diagnosed with a functional voice disorder and referred to an inpatient rehabilitation programme for patients with FND.
The symptoms continued to progress
By three years after symptom onset, the clinical picture had become considerably more concerning.
She was experiencing falls and had stopped cooking and going outdoors. Examination documented aphonia, eyelid apraxia and blepharospasm. Cognitive testing produced a Montreal Cognitive Assessment score of 22/30.
Repeat MRI using susceptibility-weighted imaging showed abnormal signal involving structures including the substantia nigra, red nuclei and globus pallidus, suggesting iron deposition.
At this point, the diagnosis was revised from FND to an atypical akinetic-rigid syndrome and her care was transferred to neurology.
Further neurological signs emerged
Neurological examination subsequently documented additional abnormalities including limited upward gaze, abnormal vertical saccades, bilateral bradykinesia, right-sided rigidity and right foot dystonia.
Further investigation included testing for atypical Parkinsonian syndromes and a DaTscan.
The eventual diagnosis was progressive supranuclear palsy.
Progressive neurological symptoms → functional voice disorder / FND → inpatient FND rehabilitation → continued progression → abnormal neurological findings → repeat imaging → DaTscan → diagnosis revised to PSP.
Diagnostic overshadowing
Perhaps the most significant aspect of the paper is that the authors themselves discuss diagnostic overshadowing.
One example involved the patient's habit of wearing sunglasses indoors. This had been interpreted by clinicians as supporting FND. The authors later noted that the sunglasses were being used because light aggravated her blepharospasm.
They also questioned whether a preserved cough, which had contributed to the interpretation of her voice disorder as functional, could have represented a false-positive sign because chronic obstructive pulmonary disease may have altered the acoustics of the cough.
The authors additionally pointed to hypokinetic movements seen during laryngoscopy as something unlikely to be explained by FND.
In other words, observations interpreted within the FND framework acquired a different significance once the progressive neurological disease became apparent.
The diagnosis was revised
This distinction matters.
The paper does not merely describe a patient with FND who subsequently happened to develop another neurological diagnosis. The authors explicitly state that the diagnosis was revised from FND, first to an atypical akinetic-rigid syndrome and ultimately to PSP.
The authors nevertheless believed that some functional overlay may have remained. That does not change the documented fact that the original diagnostic formulation was revised after progressive neurological findings and further investigation revealed a neurodegenerative disorder.
Why this case matters
The case demonstrates why progression should matter after an FND diagnosis.
The initial investigation had not revealed the eventual explanation. As the patient's condition progressed, however, additional neurological abnormalities became apparent and repeat investigations provided new evidence.
Importantly, the clinicians did eventually reconsider the diagnosis rather than treating the FND label as the end of the diagnostic process.
The authors themselves make an unusually striking observation: patients may encounter resistance from clinicians when arguing that an existing FND diagnosis should be reconsidered in favour of a structural neurological disorder.
This case demonstrates exactly why that diagnostic door needs to remain open.