What are the clinical features, differential diagnosis, diagnostic workup, and management of bulbar palsy?

Bulbar Palsy: Clinical Features, Diagnosis, and Management

Clinical Features

Bulbar palsy presents with a characteristic triad of dysarthria, dysphagia, and sialorrhea due to lower motor neuron degeneration affecting cranial nerves IX, X, XI, and XII, with tongue muscle atrophy and fasciculations being pathognomonic signs. 1

Core Manifestations

• Dysphagia manifests as difficulty managing food in the mouth, impaired bolus formation, delayed swallowing initiation, and critically increased aspiration risk 2
• Dysarthria results from tongue, palatal, and pharyngeal muscle weakness 2
• Sialorrhea (drooling) occurs from inability to manage saliva due to impaired swallowing and poor lip seal 2
• Tongue abnormalities include visible atrophy and fasciculations (distinguishing lower motor neuron pathology) 1
• Nasal regurgitation from reduced soft-palate closure during swallowing 2

Progressive Stages

• Early signs: Prolonged meal times, fatigue during eating, difficulty with certain food textures 2
• Advanced manifestations: Severe dysphagia requiring alternative feeding, complete inability to manage oral secretions 2
• Life-threatening complications: Aspiration pneumonia (11.4-13% of cases), malnutrition (0-21% at diagnosis), respiratory compromise 2, 3

Differential Diagnosis

Primary Considerations

• Motor neuron disease variants: Progressive bulbar palsy, amyotrophic lateral sclerosis with bulbar onset 1, 4
• Pseudobulbar palsy: Upper motor neuron pathology with hyperreflexia, emotional lability, brisk jaw jerk (contrasts with absent reflexes in true bulbar palsy) 5
• Myasthenia gravis: Fluctuating weakness with fatigability, positive acetylcholine receptor antibodies, improvement with Tensilon test 5
• Guillain-Barré syndrome: Progressive symmetrical weakness with absent reflexes, elevated CSF protein with normal WBC count 5

Genetic/Metabolic Causes

• Brown-Vialetto-Van Laere syndrome: Riboflavin transporter mutations (SLC52A2, SLC52A3), potentially treatable with riboflavin supplementation if caught early 4
• Fazio-Londe syndrome: Childhood progressive bulbar palsy 4

Rheumatological/Immune-Mediated

• Immune checkpoint inhibitor-induced myositis: Occurs in ~1% of cancer immunotherapy patients, median onset 4 weeks, ~20% mortality with bulbar involvement 6
• Systemic lupus erythematosus: Velopharyngeal insufficiency from dysmotility 6

Diagnostic Workup

Immediate Clinical Assessment

All patients require immediate swallowing screening before any oral intake, with comprehensive bedside examination by speech-language pathologist if screening is abnormal. 2

• Bulbar examination specifics: Assess lip closure, tongue strength/mobility/fasciculations, chewing capacity, palatal movement, gag reflex 2
• Cranial nerve testing: Focus on CN IX, X, XI, XII function 2
• Respiratory monitoring: Vital capacity (risk if <20 ml/kg), maximum inspiratory pressure (risk if <30 cmH₂O), maximum expiratory pressure (risk if <40 cmH₂O) 2

Instrumental Swallowing Assessment

• Videofluoroscopy (VFS)/modified barium swallow: Gold standard for patients with positive bedside screening or high aspiration risk 2
• Fiberoptic endoscopic evaluation of swallowing (FEES): Alternative to VFS 2
• Videofluoromanometry (VFM): For detailed pharyngeal pressure assessment 2

Neurophysiological Studies

• Electromyography (EMG): Demonstrates denervation, fasciculations in bulbar muscles 5
• Nerve conduction studies: Differentiates neuropathic from myopathic processes 5

Laboratory and Imaging

• Muscle enzymes: Elevated in myositis (normal in myalgia alone) 6
• Antibody testing: Anti-AChR for myasthenia gravis, myositis-associated antibodies, paraneoplastic panel 5, 6
• MRI brain/spine: Rule out structural lesions, assess for fasciitis in suspected myositis (>80% positive) 5, 6
• Lumbar puncture: Elevated protein with normal WBC in Guillain-Barré syndrome 5
• Genetic testing: Consider SLC52A2/SLC52A3 mutations in childhood-onset cases 4

Serial Monitoring

• Frequent neurologic examinations: Emphasize cranial nerve function, swallowing ability, respiratory status 2
• Pulmonary function tests: Every 6 months including spirometry, EtCO₂ monitoring, or blood gas analysis 2
• Nutritional assessment: BMI and weight monitoring every 3 months 2

Management

Immediate Interventions

Implement swallowing precautions immediately, monitor respiratory function continuously, and consider early gastrostomy placement before vital capacity drops below 50% predicted to prevent life-threatening aspiration pneumonia. 2

Respiratory Support

• Non-invasive ventilation (NIV): Initiate for symptomatic patients with FVC <80% normal, FVC <50% predicted, or awake PaCO₂ >45 mmHg using bilevel positive airway pressure with backup rate 2
• Critical limitation: Patients with significant bulbar impairment may not tolerate NIV or achieve adequate ventilation 2, 3
• Mechanical insufflation-exsufflation (MI-E): For secretion management, though effectiveness reduced with bulbar impairment 2
• Mouth-piece ventilation: Alternative that may delay tracheostomy, but progressive bulbar symptoms limit use 2

Nutritional Management

• Texture modification: Adjust food and liquid consistency based on swallowing assessment 2
• Oral nutritional supplementation: Maintain adequate caloric intake when oral intake compromised 2
• Percutaneous endoscopic gastrostomy (PEG): Place before respiratory function significantly deteriorates (ideally FVC >50% predicted) 2
• Weight management: Recommend weight gain for low BMI, stabilization for higher BMI 2

Swallowing Strategies

• Postural maneuvers: Chin-tuck posture to protect airways 2
• Fractionating meals: Smaller, more frequent meals to reduce fatigue 2
• Speech-language pathology: Early intervention maintains swallowing function longer and improves quality of life 2

Disease-Specific Treatments

For Myasthenia Gravis

• Steroids: Oral or IV depending on symptom severity 5
• Plasmapheresis or IVIG: If no improvement or worsening 5
• Additional immunosuppressants: Azathioprine, cyclosporine, mycophenolate 5
• Medication avoidance: Ciprofloxacin, beta-blockers that may precipitate cholinergic crisis 5

For Guillain-Barré Syndrome

• Plasmapheresis or IVIG: Indicated if no improvement or worsening (steroids NOT recommended for idiopathic GBS) 5
• Ventilatory support: Required in 15-30% of cases, ensure availability 5

For Immune Checkpoint Inhibitor-Induced Myositis with Bulbar Involvement

• Immediate ICI withdrawal: Mandatory 6
• High-dose corticosteroids PLUS IVIG and/or plasma exchange: Required for any bulbar symptoms (not corticosteroids alone) 6
• Cardiac monitoring: Systematic evaluation essential as myocarditis is part of clinical spectrum 6

For Brown-Vialetto-Van Laere Syndrome

• Riboflavin supplementation: Can lead to significant clinical improvement if started early 4

Supportive Care

• Eye protection: For impaired eye closure from facial weakness 2
• Multidisciplinary team: Coordination among nurses, physiotherapists, occupational therapists, speech therapists, dietitians 2
• Communication preservation: Maintain communicative abilities aggressively as consciousness, vision, hearing typically intact 2
• Psychological support: Treat pain, anxiety, depression which significantly impact wellbeing 2

Monitoring for Complications

• Aspiration pneumonia: Major cause of mortality 2, 3
• Malnutrition and weight loss: Detrimental to survival and quality of life 2
• Dehydration: Worsens secretion management 2
• Pressure ulcers, DVT, hospital-acquired infections: Use standard preventive measures 2
• Autonomic dysfunction: Monitor via ECG, heart rate, blood pressure, bowel/bladder function 2

Critical Pitfalls to Avoid

• Delayed swallowing assessment: Never allow oral intake before swallowing screening in suspected bulbar palsy 2
• Late PEG placement: Placing gastrostomy after respiratory function deteriorates significantly increases procedural risk 2
• Underestimating respiratory compromise: Bulbar dysfunction commonly affects respiratory function; paralysis can alter typical signs of respiratory distress 2, 3
• Missing treatable causes: Failure to test for riboflavin transporter mutations in childhood cases or myasthenia gravis antibodies 4, 5
• Inadequate treatment of immune-mediated myositis: Using corticosteroids alone without IVIG/plasma exchange for bulbar involvement (20% mortality rate) 6
• False reassurance from normal muscle enzymes: Volitional respiratory function tests can be inaccurate with bulbofacial weakness 3
• Recovery phase complacency: Two-thirds of deaths occur during recovery phase from cardiovascular and respiratory dysfunction, requiring continued vigilance 2