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Bottom line: Sensory symptoms in FND are: ✅ Highly prevalent ✅ Diverse ✅ Often disabling ✅ Frequently persistent ✅ Poorly captured by traditional sensory testing They should be routinely asked about and addressed. They are a core feature of FND - not an afterthought.

8. Disturbed sense of limb ownership Some report limbs feeling “dead”, absent, or not belonging to them. This mirrors disturbances seen in stroke and CRPS involving higher-level sensory integration networks.

7. Altered interoception Reduced accuracy or confidence in sensing internal bodily signals may amplify or distort sensory experiences.

6. Sensory processing differences High rates of sensory hypersensitivity (sound/light/touch) overlap with migraine and autism-related sensory traits, which point to potential shared predictive processing mechanisms.

5. Peripheral vasomotor dysregulation Cold extremities, swelling, and colour changes are not uncommon in motor-FND (e.g. functional dystonia), suggesting altered peripheral circulation (consistent with previous descriptions of overlap with complex regional pain syndrome #CRPS).

4. Co-existing pathophysiology FND often co-occurs with conditions that cause sensory symptoms (e.g. radiculopathy, carpal tunnel syndrome, etc) which often act as predisposing or perpetuating factors for FND.

3. Anxiety, panic & autonomic arousal Many people experience sensory symptoms associated with panic (e.g. tingling, dizziness, hot/cold) without feeling anxious (“panic without panic”). Autonomic arousal may be misinterpreted in some individuals.

2. Dissociation & compartmentalisation Experiences of depersonalisation/derealisation are common in motor-FND. Reports of insensate limbs or unnoticed injuries suggest impaired integration of sensory signals, consistent with the concept of compartmentalisation.

1. Dual processing of motor & sensory signals Sensory and motor symptoms may be mutually consequential - two sides of the same coin. These two processes are intrinsically linked and processed together within the brain. Improving one may result in improvement in the other.

The large variation in sensory experiences documented in this study implies multifactorial mechanisms contribute to sensory symptoms in motor-FND. Potential mechanistic explanations:

Concept conflation: 50% of patients struggled to distinguish the concepts of "weakness" from "numbness." Exploring what patients mean by their words is crucial in assessment.

Sensory symptoms were often perceived as severe and were statistically associated with higher disability and depression. Only one-third of motor-FND reported improvement in sensory symptoms at 12 months.

The motor-FND group experienced pain more frequently than the stroke group (88% vs 41%) and more frequently endorsed having a high pain tolerance (70% vs 49%). Self-reported hypersensitivity was more common in FND (to light 63% FND vs 20% stroke; sound 65% FND vs 15% stroke).

Classic sensory FND signs (midline splitting of light touch and vibration) were uncommon and had poor diagnostic specificity when compared with stroke. These signs may still hold value as part of the accumulation of evidence in making a diagnosis. Clinical context is important.

Quantitative sensory testing (QST)? Added little information to assessment. Often detected abnormalities patients didn’t report.

The distribution of symptoms in motor-FND is complex. Complete sensory loss in an area? • 27% of motor-FND vs 11% stroke Classic “glove and stocking” patterns? • 20% of motor-FND vs 3% of stroke

"It feels like my limb is dead." While both groups reported numbness, people with motor-FND described a broader spectrum including: “dead” or an absent limb (19% motor-FND vs 1% stroke). This is not a rare phenomenon for people with motor-FND.

Prevalence: Sensory symptoms are extremely common (96% of motor-FND and 67% of stroke). When asked to list symptoms... 70% of motor-FND reported sensory symptoms without prompting. 96% endorsed them after prompting. That’s higher than stroke (31% unprompted, 67% prompted).

Sensory symptoms (e.g. numbness, pins and needles) in Functional Neurological Disorder (#FND) are common, but often overlooked. Our new prospective case-control study compares sensory symptoms of 102 people with motor-FND vs 75 people with recent #stroke. Here’s what we found 🧵