DSM-5 Criteria
The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), lists FND under "Functional Neurological Symptom Disorder." The current criteria emphasize the neurological nature of the symptoms.
The Four Key Requirements
- 1Symptom of altered voluntary motor or sensory function.
The patient must have a physical symptom like weakness, tremor, or numbness.
- 2Clinical evidence of incompatibility.
There must be physical evidence that the symptom is inconsistent with recognized neurological disease (e.g., Hoover's sign).
- 3The symptom is not better explained by another medical or mental disorder.
Doctors must rule out other conditions that could mimic these functional signs.
- 4Causes significant distress or impairment.
The symptoms must be severe enough to affect the patient's daily life, work, or social health.
What's missing?
ICD-11 Classification
The International Classification of Diseases (ICD-11) has also moved FND into the Neurology section. This is a massive shift from previous versions where it was classified only as a psychiatric condition. It reflects the understanding of FND as an "interface" disorder involving both brain networks and psychological health.
The Shift in Philosophy
The move to a "Positive Sign" model means that the diagnosis is faster and more reliable. Instead of years of tests to "exclude" everything, a neurologist can often provide a confident diagnosis in a single visit.
Diagnostic Certainty
When these criteria are met, the diagnosis is considered robust. The goal is to provide the patient with a clear label for their symptoms so that specific rehabilitation can begin as early as possible.