Weight loss and cachexia represent significant non-motor manifestations in Progressive Supranuclear Palsy (PSP), contributing to disease progression, quality of life decline, and increased mortality risk. Unlike simple malnutrition, cachexia in PSP involves a complex metabolic syndrome characterized by ongoing loss of skeletal muscle mass that cannot be fully reversed by conventional nutritional support.
Weight loss occurs in the majority of PSP patients and often begins early in the disease course:
- Prevalence: 50-75% of PSP patients experience clinically significant weight loss (>5% body weight)
- Onset: Often begins within the first 2-3 years of symptom onset
- Progression: Weight loss typically accelerates as disease advances
- Severity: Up to 15-25% of body weight may be lost prior to death
Compared to Parkinson's disease (PD), PSP patients tend to experience more severe and earlier weight loss, with a median weight loss of 8-12% of baseline body weight over the disease course.
The weight loss and cachexia in PSP result from multiple overlapping mechanisms:
1. Dysphagia and swallowing dysfunction
- Progressive dysphagia affects 65-90% of PSP patients
- Oral phase dysfunction: tongue weakness, delayed oral transit
- Pharyngeal phase dysfunction: delayed pharyngeal clearance
- Reduced caloric intake due to eating avoidance due to fear of choking
- See also: PSP Speech and Swallowing Disorders
2. Olfactory dysfunction
- Hyposmia/anosmia present in 70-85% of PSP patients
- Reduces appetite through diminished smell of food
- Contributes to anorexia
- See also: PSP Olfactory Dysfunction
3. Depression and apathy
4. Cognitive impairment
- Frontal executive dysfunction affecting meal planning and preparation
- Agnosia for food items
- Loss of independent eating abilities
- See also: PSP Cognitive Impairment
5. Metabolic alterations
- Elevated resting energy expenditure
- Dysregulated lipid metabolism
- Mitochondrial dysfunction affecting cellular energy production
- See also: PSP Mitochondrial Dysfunction
6. Neuroinflammation
- Chronic neuroinflammatory state increases catabolism
- Elevated cytokines (IL-6, TNF-alpha) promote muscle wasting
7. Autonomic dysfunction
- Gastroparesis and reduced gastric motility
- Thermoregulatory dysfunction affecting metabolic rate
- See also: PSP Autonomic Dysfunction
flowchart TD
A["PSP Pathology"] --> B["Multiple Mechanism"]
B --> C1["Dysphagia"]
B --> C2["Olfactory Dysfunction"]
B --> C3["Depression Apathy"]
B --> C4["Cognitive Impairment"]
B --> C5["Metabolic Alterations"]
B --> C6["Neuroinflammation"]
B --> C7["Autonomic Dysfunction"]
C1 --> D["Reduced Caloric Intake"]
C2 --> D
C3 --> D
C4 --> D
C5 --> E["Increased Energy Expenditure"]
C6 --> E
C7 --> E
D --> F["Negative Energy Balance"]
E --> F
F --> G["Weight Loss"]
G --> H["Cachexia"]
H --> I["Muscle Wasting"]
I --> J["Increased Mortality Risk"]
style H fill:#ffcdd2,stroke:#333
style J fill:#ffcdd2,stroke:#333
Weight loss and cachexia significantly impact survival:
- Prognostic factor: Weight loss >10% body weight is an independent predictor of mortality
- Hazard ratio: 1.5-2.0x increased mortality risk with significant weight loss
- Cause: Contributing to frailty, falls, immunosuppression
- Leading cause of death: Aspiration pneumonia - often secondary to dysphagia and weakness
Weight loss correlates with:
- Faster clinical deterioration
- Reduced response to therapeutic interventions
- Decreased functional reserve
- Increased falls due to weakness
Impact on quality of life includes:
- Reduced independence in activities of daily living
- Decreased socialization around meals
- Body image concerns
- Fatigue and weakness
- See also: PSP Quality of Life and Caregiver
- Monthly weight monitoring: Track weight changes
- BMI calculation: less than 18.5 kg/m2 indicates underweight
- Mini Nutritional Assessment (MNA): Validated screening tool
- Dynamometry: Handgrip strength as proxy for muscle mass
- Serum albumin: Nutritional marker (often low in cachexia)
- Prealbumin (transthyretin): More sensitive to acute changes
- Cholesterol: Low levels associated with poor prognosis
- IL-6, TNF-alpha: Inflammatory markers correlate with catabolism
1. Caloric supplementation
- High-calorie oral supplements (e.g., Ensure, Boost)
- Between-meal snacks
- Calorie-dense foods
2. Texture modification
3. Feeding assistance
- Caregiver-assisted feeding
- Adaptive equipment
- Supervised mealtimes
- Appetite stimulants: Megestrol acetate, dronabinol (limited evidence)
- Orexin agonists: Under investigation
- Anti-inflammatory agents: Targeting neuroinflammation
- Percutaneous endoscopic gastrostomy (PEG) feeding may be considered
- Balance quality of life with intervention burden
- Advance care planning essential
- Biomarkers predicting cachexia development
- Intervening on inflammatory pathways
- Novel appetite stimulants targeting PSP-specific mechanisms
- Metabolic modulators