Neurophysiologic studies of functional neurologic disorders

Area of Science:

• Neurology
• Neuroscience
• Psychiatry

Background:

• Functional neurologic disorders (FNDs) are often genuine conversion disorders with unconscious dysfunction.
• Factitious disorders and malingering involve conscious feigning, presenting similar symptoms but lacking genuine disease.
• Current diagnostic methods lack efficacy in differentiating FNDs, factitious disorders, and malingering.

Purpose of the Study:

• To explore the neurophysiologic underpinnings of functional neurologic disorders.
• To investigate the brain regions and mechanisms involved in FNDs.
• To differentiate the pathophysiologic basis of genuine versus feigned conditions.

Main Methods:

• Physiologic studies examining functional weakness and sensory loss.
• Analysis of functional tremor and myoclonus.
• Neuroimaging and functional assessments focusing on agency and limbic system activity.

Main Results:

• Primary motor and sensory cortex function normally in functional weakness/sensory loss, with abnormalities in premotor and association cortices.
• Functional tremor and myoclonus utilize normal voluntary motor structures for involuntary movements.
• Abnormal agency correlates with temporoparietal junction dysfunction; the limbic system shows overactivity.

Conclusions:

• Functional neurologic disorders appear to stem from top-down influences originating in higher-level brain regions.
• The limbic system's overactivity may initiate involuntary movements, though the precise mechanism remains unknown.
• Dysfunction in feedforward signaling might explain the involuntary nature of movements in FNDs.