FND Diagnosis Reversed: Autoimmune Basal Ganglia Encephalitis
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A Reddit user diagnosed with Functional Neurological Disorder (FND) has described how a second neurological opinion reportedly revealed autoimmune basal ganglia encephalitis. The patient had initially undergone an EEG but no brain MRI, and believed their psychiatric history had influenced the diagnosis. It was an unexpected improvement while taking prednisone for seasonal allergies that prompted them to question whether FND adequately explained their symptoms.
The account raises two distinct possibilities. Autoimmune basal ganglia encephalitis can produce neurological symptoms resembling those encountered in FND, including involuntary movements, cognitive difficulties and abnormal gait. Alternatively, the original diagnosis may have been made before the underlying illness was sufficiently investigated. The available account provides more direct evidence relevant to the latter possibility, although the original neurological examination is not documented.
From FND to Autoimmune Encephalitis
Writing on Reddit under the username u/WhyIsRedditMyLife, the patient explained that their neurologist had not been taking their concerns seriously. After noticing an improvement in neurological symptoms while taking steroids, they consulted a doctor at their university campus. This led to further investigations, including a brain MRI and blood tests.
"Turns out, I was right - I don't have FND. Instead I have autoimmune basal ganglia encephalitis."
The patient subsequently explained that the original neurologist had declined to request an MRI unless the EEG showed abnormalities. They also believed that their psychiatric history had contributed to the decision to classify their symptoms as conversion disorder.
"Yeah, my old neurologist said she wouldn't do an MRI unless if the EEG came back abnormal."
An EEG measures electrical activity in the brain, whereas MRI examines brain anatomy. A normal routine EEG cannot exclude structural abnormalities, and neither a normal EEG nor a normal MRI necessarily excludes autoimmune encephalitis. Indeed, recognised diagnostic guidance acknowledges that autoimmune encephalitis can present with normal or nonspecific results on these investigations, particularly early in the disease course [1].
The patient does not describe which positive neurological signs, if any, originally supported the FND diagnosis. Nor do we know whether the first neurologist had identified the abnormalities subsequently reported by the second doctor. Nevertheless, the decision to make MRI conditional on an abnormal EEG deserves examination, particularly when the patient continued to experience unexplained neurological symptoms.
What Is Autoimmune Basal Ganglia Encephalitis?
The basal ganglia are interconnected structures deep within the brain that participate in the regulation of movement, motor learning, behaviour and aspects of cognition. They help coordinate the initiation and selection of movements through circuits connecting the cerebral cortex, thalamus and other neurological structures.
Autoimmune basal ganglia encephalitis involves an immune-mediated process affecting these circuits. Depending on the underlying autoimmune mechanism, patients may develop involuntary movements, dystonia, chorea, tremor, parkinsonian features, cognitive impairment or behavioural changes. Certain forms are associated with antibodies targeting neuronal proteins, including dopamine D2 receptors [2, 3].
These manifestations can resemble symptoms encountered in functional movement disorders and other FND presentations. Abnormal movements, gait disturbances, cognitive difficulties and seizure-like episodes are not exclusive to any single neurological diagnosis. Autoimmune encephalitis can also produce psychiatric symptoms, potentially complicating the assessment when a patient already has a psychiatric history.
However, similarity in the symptoms does not establish that the underlying examination findings are identical. To demonstrate that autoimmune encephalitis genuinely mimicked positive signs of FND in this patient, we would need details of the original neurological examination. Those details are absent from the Reddit account.
The Findings That Deserved Further Investigation
In a follow-up comment, the patient described cognitive impairment, memory difficulties, seizures, tics, problems with coordination and balance, and behavioural changes. More importantly, they identified three findings that their new doctor reportedly considered significant: a markedly reduced pupillary reflex, a positive Romberg test and recurrent low-grade fevers.
These observations do not independently establish autoimmune encephalitis. An abnormal pupillary response can have several neurological or pharmacological explanations, while a positive Romberg test may reflect disturbances involving proprioception or vestibular function. Recurrent fever is similarly nonspecific, but its presence alongside neurological symptoms warrants consideration of inflammatory and infectious causes.
The significance lies in the combination of findings rather than any individual symptom. The diagnostic criteria proposed by Graus and colleagues recognise that autoimmune encephalitis may present with cognitive or psychiatric changes accompanied by otherwise unexplained seizures, focal neurological abnormalities, suggestive imaging or evidence of inflammation in cerebrospinal fluid. The criteria also require reasonable exclusion of alternative explanations [1].
We cannot determine from the Reddit account whether the patient met these criteria. What we can establish is that the second clinician reportedly identified findings warranting further investigation, and that those investigations led to a different diagnosis.
An Unexpected Response to Prednisone
One particularly interesting detail is that the patient was not initially receiving steroids for a neurological condition. They had been prescribed prednisone for seasonal allergies and noticed that their neurological symptoms improved while taking it.
Corticosteroids suppress immune and inflammatory activity and form part of the treatment of several autoimmune neurological disorders. A favourable response is not specific to autoimmune encephalitis and cannot independently establish an inflammatory diagnosis. Nevertheless, an unexpected improvement may provide useful clinical information when considered alongside other findings [4].
In this account, the response contributed to the patient's decision to seek a second opinion. The subsequently reported autoimmune diagnosis offers a possible explanation, although the author does not provide enough information to establish a direct causal connection.
Was This Really an FND Mimic?
There is an important distinction between a disease that produces findings resembling positive functional signs and a disease whose symptoms are labelled functional because their cause is not immediately apparent.
In the first scenario, the original clinician identifies examination findings considered characteristic of FND, but an underlying neurological disease subsequently explains those findings. This would raise questions about the specificity and interpretation of the signs used to establish the original diagnosis.
In the second scenario, neurological symptoms are attributed to FND without sufficiently establishing why they should be considered functional. The diagnosis then risks becoming an endpoint rather than a conclusion supported by the available evidence.
The patient's account is more directly relevant to the second scenario. They describe an EEG, a decision not to pursue MRI imaging and a concern that their psychiatric history influenced the initial interpretation. They do not describe positive functional signs that were subsequently demonstrated to be misleading.
This does not prove that no such signs were present. It does, however, leave an important evidential gap: what established FND in the first place?
The question is particularly relevant because autoimmune basal ganglia disorders can produce movement abnormalities and behavioural changes that might otherwise be interpreted through a psychiatric framework. A clinician who assumes that psychiatric history explains the neurological presentation risks overlooking the possibility that both the behavioural and movement symptoms arise from the same underlying neurological process.
The Limits of the Account
The patient reports a diagnosis of autoimmune basal ganglia encephalitis following MRI and blood investigations, but does not disclose the specific findings, antibody results or other evidence supporting that conclusion. They also state that treatment was due to begin, without providing a subsequent treatment outcome in the available thread.
Consequently, this remains a patient-reported diagnostic reversal rather than an independently verified clinical case report. It would be inappropriate to claim that the original neurologist demonstrably overlooked particular examination findings or that the later diagnosis was established by a specific laboratory marker when those details have not been provided.
Even with those limitations, the account raises a worthwhile question about diagnostic reasoning. The patient reports that an FND diagnosis was made, further imaging was withheld and a second opinion subsequently identified an alternative neurological explanation. Whether the initial presentation genuinely mimicked FND or was simply insufficiently investigated remains unresolved.
The central issue is therefore not whether every clinician should immediately recognise a rare autoimmune disorder. It is whether the evidence supporting the original diagnosis was sufficient to justify the confidence placed in it, particularly when symptoms persisted and additional neurological findings emerged.
References
- Graus F, et al. (2016). A clinical approach to diagnosis of autoimmune encephalitis. The Lancet Neurology. Read article.
- Movement disorders in autoimmune encephalitis: an update. Journal of Neurology (2023). Read abstract.
- Anti-Dopamine Receptor 2 Antibody-Positive Encephalitis in Adolescent. Frontiers in Neurology (2020). Read article.
- Abboud H, et al. (2021). Autoimmune encephalitis: proposed best practice recommendations for diagnosis and acute management. Journal of Neurology, Neurosurgery & Psychiatry. Read article.
- u/WhyIsRedditMyLife. My FND is not actually FND????? Reddit, r/FND. Original patient account and follow-up comments.
Please note: This post discusses an account shared publicly on social media. The person's medical history and diagnosis have not been independently verified. We report what they said and link to the original source where possible.