2022 Top Story in Neurology: Diagnosing Functional Neurological Disorders

Functional neurological disorders can be diagnosed with the clinical examination

Functional neurological disorders (FNDs) are common and distressing, but, for much of the latter part of the 20^th century, they were ignored. The importance of establishing the correct diagnosis of an FND and initiating appropriate therapy is now being recognized as an important and productive task for neurologists. Because of the many years of neglect, there has been a lack of education and research about these disorders. This is now being remedied. The first step when seeing a patient is to make a secure diagnosis. This can be difficult with FNDs, and, in the past, the diagnosis was often considered only when everything that the neurologist could think of was ruled out. However, the clinical syndromes of FNDs are being better characterized, and the diagnosis should now be established using a rule-in approach, based on positive signs and symptoms. Several Stories of the Week this year illustrate this point.

The most common FND is functional seizures, often called psychogenic non-epileptic seizures (PNES). The gold standard for the diagnosis is the lack of epileptic activity on a video EEG during an episode. However, it is possible to make a highly probable diagnosis based on clinical observations of the patient while the seizure is happening. Although it is best to observe the episode live, this is not always feasible; however, even a cell phone video, as pointed out in one of our featured articles last year,¹ can provide the needed data. In one of our Stories of the Week, a meta-analysis of clinical signs was reported, and the positive predictive values of these clinical signs were presented.² The authors analyzed 14 studies including 452 patients with PNES and 800 patients with epileptic seizures. The most specific diagnostic signs were eye closure and asynchronous limb movements. Ictal weeping was also specific but not as specific as the other two. Many other signs were analyzed, and some others are certainly suggestive of PNES but not diagnostic on their own.

Functional dizziness is the second most common diagnosis presenting in specialty clinics for patients with dizziness. Functional dizziness usually fits the criteria for persistent postural perceptual dizziness. In another Story of the Week, the clinical features were reviewed along with the commonly used treatments.³ The syndrome is characterized by distressing dizziness or imbalance occurring over a period of at least 3 months and triggered by a change in posture or observing moving or complex visual scenes. It can be triggered by a transient vestibular disorder or an episode of marked anxiety. The findings of the physical examination are largely normal and may include excessive body sway or other movements when balance can be determined to be good.

There are advances in the recognition of other FNDs as well, including functional movement disorders, functional cognitive disorders, functional sensory symptoms, and others (see the review, also featured this year).⁴ There is increasing understanding of the pathophysiology and advances in treatment. Helping these patients can begin with a good history taking and physical examination.