Amyotrophic lateral sclerosis. Progressive bulbar paralysis
1.Amyotrophic Lateral Sclerosis
Definition: Amyotrophic Lateral Sclerosis is a progressive neurodegenerative disorder affecting both upper motor neurons (UMN) and lower motor neurons (LMN) leading to progressive weakness, atrophy, and spasticity.
Progressive bulbar palsy (PBP) is a variant of motor neuron disease primarily affecting the bulbar cranial nerve nuclei.
Etiology
- 1.Sporadic (most cases): Unknown cause
- 2.Familial: Genetic mutations (e.g., SOD1, C9orf72)
- 3.Risk factors: Age (middle to late adulthood). Male predominance
Pathogenesis
Degeneration of:
- UMN (corticospinal tracts) → spasticity
- LMN (anterior horn cells, cranial motor nuclei) → muscle wasting
➡️ Combined UMN + LMN signs = hallmark of ALS
Clinical Features of ALS
- A. LMN Signs: Muscle weakness Muscle atrophy. Fasciculations. Flaccid paralysis. Reduced reflexes (in affected muscles)
- B. UMN Signs: Spasticity. Hyperreflexia. Babinski sign. Clonus
- C. Distribution: Asymmetric onset. Distal limb weakness → spreads proximally. Progressive course
- D. Bulbar Involvement (late or early in some cases): Dysarthria. Dysphagia. Nasal speech. Tongue atrophy with fasciculations
- E. Respiratory Involvement: Diaphragm weakness. Respiratory failure (common cause of death)
2.Progressive Bulbar Palsy (PBP)
Definition: Variant of ALS affecting bulbar motor neurons early and predominantly.
Clinical Features:
- Bulbar Symptoms: Dysarthria (slurred speech). Dysphagia (difficulty swallowing). Dysphonia (nasal/weak voice).
- Cranial Nerve Involvement
- IX, X, XII most affected: Tongue atrophy and fasciculations. Absent gag reflex. Weak palatal movement.
- Emotional Lability: Pseudobulbar affect (in some cases)
Examination Findings
- Motor System: Mixed UMN + LMN signs. Muscle wasting. Fasciculations. Spasticity
- Bulbar Examination: Tongue wasting + fasciculations. Dysarthric speech. Weak gag reflex
Diagnosis
- Clinical Diagnosis (most important): Progressive mixed UMN + LMN signs in multiple regions
- Electromyography (EMG): Denervation potentials. Fibrillations. Fasciculations
- Nerve Conduction Studies: Usually normal sensory conduction (important clue)
- MRI Brain/Spine: Excludes structural lesions
Differential Diagnosis
- Myasthenia Gravis: Fatigable weakness. No UMN signs
- Cervical Spondylotic Myelopathy: UMN signs only
- Multiple Sclerosis: Remitting course
- Brainstem Stroke: Sudden onset
Treatment:
- No curative therapy
- Disease-Modifying: Riluzole (modest survival benefit). Edaravone (in some cases)
- Supportive Care: Physiotherapy. Speech therapy. Nutritional support (PEG feeding). Respiratory support (non-invasive ventilation)
Prognosis
- Progressive and fatal
- Median survival: 3–5 years after diagnosis
- Respiratory failure is main cause of death