Victor J. Del Brutto, MD

Popkirov S, Stone J, Buchan AM. Functional Neurological Disorder: A Common and Treatable Stroke Mimic. Stroke. 2020;51:1629–1635.

Since the work of Jean-Martin Charcot in the 19th century on functional neurological disorders (called “hysteria”), neurologists have developed a variety of examination skills capable of discerning between organic and non-organic causes of neurological symptoms. Functional neurological disorders may manifest as non-epileptic seizures, chronic abnormal movement disorders, and certainly as acute focal neurological deficits prompting the activation of a rapid stroke evaluation aimed to identify candidates for reperfusion therapies. In fact, functional neurological deficits are common stroke mimics frequently presenting as lateralized limb weakness, sensory changes, or speech disturbances.

As stroke neurologists, we rely on clinical scales (i.e., the National Institutes of Health Stroke Scale) and a variety of neuroimaging techniques to make time-sensitive therapeutic decisions. Nevertheless, none of the above are entirely useful to identify functional disorders, thus underscoring the importance of the clinical examination in acute stroke care. In the May issue of Stroke, Popkirov and colleagues bring us a topical review on the diagnosis of functional disorders during the acute evaluation of patients with suspected stroke. Key points of this review include:

– Stereotypical biases based on age, sex, psychiatric comorbidities, or social background are not good predictors of functional disorders at the individual patient level and frequently lead to misdiagnosis. 

– Bedside tests focused on inconsistencies between voluntary and involuntary movements (i.e., Hoover’s sign, hip abductor sign, facial lip pulling) or non-physiological patterns of weakness (i.e., drift without pronation, give-away weakness, inverse pyramidal pattern) have shown to be specific and reliable techniques to identify functional motor weakness (Figure). Generally, sensory signs are less reliable than motor testing.

Figure. Positive clinical signs of functional neurological disorder.
Figure. Positive clinical signs of functional neurological disorder. 

– Speech disorders (i.e., dysarthria, aphasia) in isolation are rare stroke presentations. Functional speech disorders can be recognized by inconsistencies such as aphonia with normal sound production prompted by cough, dysarthria without dysphagia, or non-physiological agrammatism (“baby talk”) rather than the telegraphic speech characteristic of Broca’s aphasia.

– The diagnosis of a functional neurological disorder as a stroke mimic should be founded on the combination of positive clinical signs of inconsistencies rather than as a diagnosis of exclusion. Neuroimaging can support but not confirm the diagnosis of functional neurological disorder, as it can prove but cannot exclude an acute infarction with absolute certainty.

– Based on the proven low rate of thrombolysis complications in stroke mimics, only a high level of diagnostic confidence can justify withholding acute stroke treatment.

– Management of functional neurological disorders starts with early and clear communication to the patient about the diagnosis followed by specialized physical, occupational, speech, and psychological therapy.

In summary, the physical examination is the best diagnostic tool to detect functional neurological disorders presenting as stroke mimics. In addition, it is pertinent to emphasize the importance of early recognition of functional neurological disorders during the ongoing COVID-19 pandemic in order to save medical resources and lessen the exposure of health care providers to untested COVID-19 patients. The latter upsurges the high yield of this timely state-of-the-art review.