Question
What are the main positive clinical signs that can help rule in a diagnosis of functional neurological disorder (FND) during a physical therapy assessment?
Answer
The main positive clinical signs that support a diagnosis of FND include variability, distractibility, entrainment, and suppressibility of symptoms. Variability refers to symptoms that wax and wane or shift location, which is not typical of structural neurological lesions. Distractibility is observed when symptoms improve during a dual task or when the patient’s attention is diverted from their movements, highlighting the role of maladaptive self-directed attention in FND. Entrainment is particularly useful in cases of functional tremor; if the tremor changes to match the rhythm of a voluntary movement in another limb, it suggests a functional origin. Suppressibility refers to the ability to temporarily suppress symptoms, which is uncommon in organic neurological conditions. Additional signs include global weakness that does not follow anatomical patterns and midline splitting of sensory loss. These signs, especially variability and distractibility, have high specificity and can be used to positively identify FND rather than relying solely on a diagnosis of exclusion.
This Ask the Expert is an edited excerpt from the course, 'Functional Neurological Disorders Part 2: Case Series with Clinical Applications', presented by Chelsea Richardson, PT, DPT, NCS.
