When an Unexplained Gait Became Conversion Disorder: A Huntington’s Disease Case
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A 2018 case report describes a 65-year-old woman whose developing neurological and psychiatric illness was eventually confirmed by genetic testing to be Huntington's disease. Before that diagnosis was reached, her persistent abnormal gait had been interpreted as conversion disorder, and she was subsequently discharged from neurology with that diagnosis after CT and electromyography failed to reveal significant abnormalities.
The case is particularly useful because the authors provide a detailed chronology spanning several years. Depression appeared first, followed by weakness, abnormal gait, cognitive problems, behavioural changes and eventually recognisable choreiform movements. Looking back across the history, the authors concluded that different clinicians had repeatedly focused on individual symptoms rather than recognising the developing syndrome as a whole.
The illness begins with depression
The patient had no previous psychiatric history until 2012, when she was 60 years old. She reported low mood, reduced energy and anhedonia to her family doctor and was prescribed sertraline 50 mg daily. She remained on it for approximately three years, with partial improvement that was most noticeable during the first year.
At 63 she began reporting nonspecific weakness of her limbs, although she did not initially describe difficulty with movement. A few months later she suffered a myocardial infarction. During the months that followed, both her depressive and motor symptoms progressively worsened.
She attended the psychiatric emergency service eleven times and was assessed by both psychiatry and neurology. Her complaints included anxiety, low mood, social isolation, difficulty retrieving memories, nonspecific pain, limb weakness and the progressive development of an abnormal gait. The clinical picture was becoming increasingly broad, involving psychiatric, cognitive and motor features rather than a single isolated complaint.
Neurological abnormalities were already present
When she was assessed in neurology because of reduced strength and limitation of limb movement, examination documented a wide-based gait, enhanced bilateral reflexes and abolished bilateral postural sensitivity. Blood testing showed low folic acid, which was considered a possible partial explanation for the neurological findings, and folic-acid replacement was started while further investigations were requested.
Meanwhile, her psychiatric presentation also became more severe. She developed worsening mood, pressured speech, pseudohallucinations and suicidal ideation. Behavioural changes followed, including aggression and markedly abnormal behaviour at home, eventually resulting in admission to a psychiatric ward.
Cognitive impairment was also becoming obvious
During that admission she had low mood and partial disorientation in time. She repeatedly answered that she could not remember important dates from her life and scored 14/30 on the Mini-Mental State Examination. Her depressive symptoms and cognitive changes were interpreted as Major Depressive Disorder with pseudodementia.
After twelve days she was discharged with improvement in her mood. Her abnormal sustained gait, however, remained. Rather than being incorporated into a broader neurological syndrome alongside the cognitive, behavioural and psychiatric changes, the gait disturbance was interpreted as a comorbid conversion disorder.
Normal CT and EMG, then conversion disorder
The patient's CT scan and electromyography did not reveal significant abnormalities. At the subsequent neurology appointment, she was discharged with a diagnosis of conversion disorder.
This is where the case raises its hardest question. If no positive functional signs were documented, and CT and EMG simply failed to explain the abnormal gait, what evidence actually converted “we do not know what is causing this” into “conversion disorder”?
An unrevealing investigation can narrow a differential diagnosis, but it cannot by itself demonstrate another diagnosis. A normal CT did not establish that her gait was functional. An unrevealing EMG did not establish that her gait was functional. Huntington's disease was continuing to develop despite those investigations failing to identify it.
The movements become harder to ignore
The patient's abnormal behaviour continued and she was eventually readmitted to psychiatry in March 2017. During this admission, the abnormal gait and abnormal movements remained obvious enough that the case was referred to a Neuropsychiatry Team.
This time the symptoms were considered together. The team noted the psychiatric presentation alongside hyperkinetic movements, particularly involving the upper limbs and cervical region. These movements were recognised as chorea, and the combined psychiatric and motor presentation raised suspicion for Huntington's disease.
Genetic testing was performed. It demonstrated 39 (±2) CAG repeats on one huntingtin allele, confirming Huntington's disease.
The same gait was now part of Huntington's disease
The authors specifically revisit the earlier neurological interpretation in their discussion. They state that the patient's movement dysfunction had undergone neurological assessment but that the clinical evaluation had been inconclusive and the symptoms had been labelled conversion disorder.
They also point out that the wide-based gait documented earlier is a recognised presentation of chorea in Huntington's disease. Anxiety and other stressors could worsen choreiform movements, while her unusually late presentation — after the age of 60 — further complicated recognition of the disease.
This creates a second difficult question. If an inconclusive neurological assessment helped support conversion disorder, but the later discovery of Huntington's disease explains why that assessment had been inconclusive, what exactly was the original conversion diagnosis positively based on?
Psychiatric symptoms were part of the neurological disease
The psychiatric history is particularly important because depression was not simply background noise surrounding a later neurological disorder. The authors discuss psychiatric symptoms as recognised manifestations of Huntington's disease and note that they can precede obvious motor symptoms by years.
In this patient, depressive symptoms preceded the motor and cognitive dysfunction by approximately three years. Behavioural problems and apparent noncompliance were also retrospectively considered possible early manifestations of cognitive and behavioural impairment.
The division between a psychiatric presentation and an organic neurological presentation therefore became misleading. Depression, behavioural change, cognitive impairment, gait disturbance and chorea were eventually understood as components of the same developing disease.
What positive evidence established conversion disorder?
The report documents the conversion disorder diagnosis, but it does not describe distractibility, entrainment, inconsistency or another positive functional neurological sign establishing that the abnormal gait was functional. Instead, the chronology describes an inconclusive neurological evaluation followed by CT and electromyography that did not reveal significant abnormalities, after which the patient was discharged from neurology with conversion disorder.
This distinction goes to the epistemic basis of the diagnosis. If conversion disorder is supposed to be established positively, the relevant question is not merely whether Huntington's disease had been demonstrated at that stage. It had not. The question is what evidence independently demonstrated conversion disorder?
Without that evidence, there is a risk of reversing the burden of proof. Huntington's disease had not yet been established, therefore the gait was considered conversion disorder. But failure to establish Huntington's disease could only establish uncertainty about the cause of the gait. It could not supply the missing positive evidence for conversion disorder.
Treatment after the diagnosis
After Huntington's disease was recognised, the patient's chorea was treated with oral haloperidol at 30 mg per day. The authors report that the chorea was controlled. Her depressive and psychotic symptoms also remitted with treatment, although medication subsequently required adjustment.
Cognitive testing continued to demonstrate substantial impairment. Her MMSE remained 14/30 and she scored 7/30 on the Montreal Cognitive Assessment. At discharge to a specialist unit for rare diseases she no longer had choreiform movements, but significant residual cognitive and psychiatric problems remained and she required continuous support.
Why this case matters
The authors warn of the need to investigate motor abnormalities carefully in psychiatric patients before attributing them to causes such as medication effects or conversion disorder. This patient's presentation had been fragmented across specialties and across time. Depression was treated as depression. Cognitive problems were interpreted as pseudodementia. Neurological investigations were inconclusive. The abnormal gait became conversion disorder. Only when a neuropsychiatric team considered the psychiatric, cognitive and motor findings together did Huntington's disease become the working diagnosis, subsequently confirmed genetically.
The central issue is therefore not simply that Huntington's disease was missed. Diagnostic errors happen when diseases are evolving and presentations are atypical. The more interesting problem is what replaced that uncertainty. If the evidence available at the time could not establish the neurological cause, on what evidence was a functional cause established instead?
That question matters beyond this individual case. “We have not demonstrated neurological disease” and “we have demonstrated a functional neurological disorder” are two different claims requiring different evidence. The first cannot logically become the second merely because the investigation has reached an impasse.
In this patient, the uncertainty eventually ended with objective evidence: the evolving phenotype suggested Huntington's disease and genetic testing demonstrated the pathogenic CAG expansion. The earlier conversion diagnosis deserves the same evidential question that should be asked of any diagnosis: what finding positively established it?
Source
Huntington's Disease in a Patient Misdiagnosed as Conversion Disorder, Nogueira JM, Franco AM, Mendes S, Valadas A, Semedo C, Jesus G. Case Reports in Psychiatry. 2018;2018:3915657. doi:10.1155/2018/3915657.
