A Case Report of Headache and Weakness Diagnosed as Functional Neurological Disorder
FndNope
Moderator
A 2025 case report published in The Journal of Emergency Medicine describes a 26-year-old postpartum woman who presented with headache and neurological symptoms, was discharged with anxiety and possible conversion disorder, and returned the following morning unable to walk. Further investigation revealed a left thalamic infarction caused by cerebral venous thrombosis (CVT).
The case provides a striking example of how quickly neurological symptoms can acquire a psychological or functional interpretation when initial investigations are unrevealing, while serious pathology remains undiscovered.
The first emergency department visit
The patient was approximately seven weeks postpartum and had recently restarted oral contraceptives. She presented to a large emergency department with headache, unilateral weakness, numbness, spastic movements and a feeling that something was wrong.
Her Glasgow Coma Scale score was 14. Her medical history included anxiety, migraines and depression during pregnancy.
A CT scan of the head did not reveal the eventual cause of her symptoms.
She was discharged with anxiety reaction and headache, with possible conversion disorder raised as an explanation for the neurological presentation.
She returned unable to walk
The patient returned the following morning with worsening weakness.
She was now unable to walk.
Because she was intermittently following commands, she was admitted for seizure monitoring, with psychogenic nonepileptic seizures among the concerns.
A hospitalist ordered an MRI.
That investigation revealed what the earlier assessment had missed.
A thalamic infarction
MRI demonstrated a left thalamic infarction secondary to cerebral venous thrombosis.
The sequence documented in the case is remarkable:
Headache and neurological symptoms → normal head CT → anxiety and possible conversion disorder → worsening weakness → inability to walk → concern for psychogenic nonepileptic seizures → MRI → thalamic infarction caused by cerebral venous thrombosis.
The patient had also presented with circumstances relevant to CVT risk: she was postpartum and had recently restarted oral contraceptives.
When a normal test becomes false reassurance
One of the most important features of this case is that the initial CT was normal.
But a normal CT did not mean that nothing neurological was happening. It simply had not identified the pathology.
By the following morning, the patient's weakness had progressed to the point that she could no longer walk. Yet even then, a psychogenic explanation remained under consideration until MRI demonstrated the infarction.
This is precisely why unexplained neurological symptoms and explained neurological symptoms should not be treated as interchangeable concepts. Failure to identify pathology on an initial investigation does not demonstrate that the symptoms are functional.
Was this a formally verified FND misdiagnosis?
The paper's title describes the case as having been diagnosed as Functional Neurological Disorder, although the case description itself records anxiety reaction and a question of possible conversion disorder. For accuracy, FND Nope therefore classifies this as a medically documented case in which a functional explanation was considered before an organic neurological cause was identified, rather than claiming more than the published record establishes.
Why verified FND misdiagnosis is difficult to find
There is a broader problem worth highlighting. Explicitly documented cases in which an established FND diagnosis is later formally declared incorrect are remarkably difficult to find.
That scarcity should not automatically be interpreted as proof that FND is rarely misdiagnosed.
A subsequent organic diagnosis does not necessarily cause FND to disappear from the record. The newly discovered disease can instead be described as comorbid with FND, while unexplained symptoms can continue to be attributed to a functional component.
This creates an obvious problem when interpreting claims about low FND misdiagnosis rates.
If discovering the disease that was previously missed does not necessarily count as evidence that FND was wrong, how often can FND ever be recorded as a misdiagnosis?
The difficulty of finding explicit reversals therefore deserves attention in its own right. A low recorded misdiagnosis rate is only as informative as the criteria by which a diagnosis is allowed to be counted as wrong.