INTRODUCTION
Studies of functional neurological disorders (FND) marked the beginning of modern
neurology with its individualization in relation with psychiatry. FND is the second
most frequent cause for neurological referrals after headache disorders[1]. In the emergency room setting, 9% of acute-onset neurologic symptoms are functional
in origin[2].
Despite the high frequency of this condition, its psychopathological mechanisms are
not fully understood and its diagnosis is difficult, with no confirmatory tests, generating
discomfort and insecurity for the physician who is responsible for such evaluation.
Functional disorders, especially due to their absence of organic damage and their
psychic nature, carry great stigmas that can even affect the doctor-patient relationship,
disturbing medical evaluation, and clinical judgment.
In this review, we present some clinical pitfalls commonly seen in different scenarios
of patient assessment with neurological functional disorders. We demonstrate a practical
attitude, based above all on clinical experience.
DEVELOPMENT
Pitfall 1: Not every bizarre phenomenon is functional
An almost always useful diagnostic tip in the evaluation of patients with suspected
functional disorder is the search for inconsistencies in the neurological physical
examination and the absence of a typical phenomenology, well recognized for an organic
diagnosis. This strategy proves to be very effective, especially when evaluating motor
symptoms, abnormal movements, gait alterations and paroxysmal events[3].
A tremor with significant variation in frequency and amplitude, especially during
distraction, raises the alarm for the functional nature of the disturbance. Just like
the side-to-side head shaking during paroxysms events suggests psychogenic non-epileptic
seizures. Gait with slow motion movements, important bending of the knees or sliding
the feet as if skiing in the snow are bizarre movements, so different from the typical
pattern of gait alterations due to organic diseases[4].
The big pitfall we highlight in this case is that there are many exceptions for this
rule. Not all bizarre phenomena, with difficult pathophysiological and topographical
reasoning, are functional disorders.
The first example to be mentioned is the alien hand syndrome. This motor symptom,
classically found in cortico-basal degeneration, leads the patient to have sometimes
complex, finalistic, but involuntary movements[5]. In these movements, the patient can pick up an object, touch another part of his
body or even attack the examiner, without the slightest intention. This phenomenon
could be confused with a functional disorder, especially when the involuntary motor
act generates an unusual or embarrassing situation.
Other conditions that may raise doubts about its organic nature are altered behaviors
during sleep. Sleepwalking and nocturnal hypermotor epileptic seizures (originated
more commonly from a focus in the frontal lobe) usually exhibit elaborate behaviors
that may be difficult to distinguish from each other or even between these conditions
and functional disorders[6].
Sometimes, functional disorders can be suspected in face of a disharmony between the
level of concern and tension that the patient presents and the severity of his clinical
condition, a fact classically described as “la belle indifference”[7]. But it is important to remember that in some situations the patient's affection
may be altered, whether due to clinical diseases, medication effects or mental disorders[8].
Unmotivated laughter seems strange in situations of a medical consultation, but it
can happen in a situation of some neurological diseases such as gelastic crises or
pseudobulbar affection. Gelastic seizures are epileptic seizures with ictal laughter,
most related to hypothalamic hamartoma, and more rarely related to cortical lesions[9].
Pseudobulbar affect is the neurological condition in which there is an inappropriate
affective manifestation, disconnected with the mood and emotional state of that moment.
The causes of pseudobulbar affection are structural lesions such as stroke, brain
tumor, traumatic brain injury, inflammatory lesions such as multiple sclerosis and
neurodegenerative diseases such as Parkinson's disease and Alzheimer's disease[10].
Pitfall 2: Not every event triggered by an emotional factor is a functional disorder
Physicians tend to suspect functional disorders when symptoms are preceded by emotional
triggers, especially negative emotions associated with a high stress load. Family
problems, marital disputes, layoffs, and other psychosocial tensions are raised as
precursors of functional disorders[11]. However, it is important to point out that there are organic conditions that can
be precipitated or aggravated by stressful situations.
One of the most commonly organic diseases related to emotional distress is neurally
mediated syncope or vasovagal syncope. In addition to common triggers such as dehydration,
heat exposure, sudden change in position, prolonged standing, and acute pain, emotional
stressors also lead to on-off loss of consciousness[12].
Cataplexy is a cardinal symptom of narcolepsy type 1, integrating the classic symptomatic
pentad. It is characterized by paroxysmal episodes of progressive loss of muscle tone
triggered by emotional triggers, mainly positive stimuli, such as laughter or effusive
happiness[13].
Pitfall 3: Not every topographical incongruity is a functional disorder
For a precise neurological diagnosis, it is important to define an accurate topographic
diagnosis. In functional disorders, the signs found on the neurological examination
are commonly not congruent to define a consistent or unique topographic location.
However, it is important to note that some organic conditions can lead to multiple
lesions, either in a monophasic or progressive evolution, leading to signs and symptoms
that make a simpler topographic diagnosis difficult. Thus, it is important to think
about a more complex topographic diagnosis, even multi-lesion disease before defining
an incongruent topography of a functional diagnosis.
Pitfall 4: Patients may have both functional and organic symptoms at the same time
In addition to not being easy to define the diagnosis of a functional disorder, it
may be not an exclusive diagnosis. It is possible and frequent the occurrence of functional
and organic neurological disorders in the same patient simultaneously or at different
times of life. Comorbid neurological conditions occur in approximately 20% of cases
of functional disorders[14].
From the onset of the neurological symptoms, some patients may develop excessive preoccupation
with their health status, including diagnosis and prognosis related to these symptoms,
and develop new functional neurological symptoms or a worsening of that pre-existing
symptom.
It is also common for patients who present paroxysmal neurological symptoms such as
epilepsy, syncope, cataplexy, parasomnias, and paroxysmal abnormal movements to present
recurrent events of similar semiology.
Pitfall 5: Psychiatric comorbid condition is not always evident in the history of
a functional disorder
During the evaluation of a patient with a functional disorder, it is common for the
physician to look for the presence of a stressful event or the diagnosis of a mood
disorder or psychiatric illness. About 2/3 to 3/4 of patients with FND have a psychiatric
comorbidity, a rate much higher than other neurological diseases[15].
Not infrequently, it is difficult, especially in a single assessment, to point out
an emotional trigger or define a psychiatric diagnosis. The absence of a more evident
mental condition does not invalidate the diagnosis of a neurological functional disorder.
Pitfall 6: Poor communication at the time of diagnosis can compromise treatment and
prognosis
The moment that generates the greatest difficulty for the physician in caring for
a patient with a functional disorder is when communicating the nature of such a condition
to the patients themselves and their family members. It is important to make clear
the absence of organic substrate to justify the complaints, but without denying the
existence of the symptoms and the suffering related to them[9].
A suggestion is always to present the patient with all the data that made the diagnosis
possible, e.g. the Hoover’s sign, as well the possibility of reversing completely
the symptoms due to the absence of structural damage[16],[17].
One should never say that the patient does not have a disease. FND is now a “rule
in” diagnosis. Try to show empathy with all the suffering of the patient and not to
minimize that it is all related to some stress or anxiety, because at least a third
of patients will deny any psychological problem.
Failure in this communication generates difficulty in engaging in treatment, persistence
of symptoms and seeking medical care with another professional, often restarting the
cycle of intensive clinical evaluation and further investigation[18].
In conclusion, due to the hard diagnosis of FND, rational strategies must be developed
to facilitate the best approach. We must always remember that neurological diseases
may present with rare, bizarre, and sometimes difficult to understand phenomena, leading
to a false suspicion of functional disorders. Emotional burden related to the event
should not be the most valued point for diagnostic hypotheses. Once the diagnosis
is defined, adequate communication guarantees a better clinical evolution.
