Neurology · MU Sofia

71. Amyotrophic lateral sclerosis, progressive bulbar paralysis

Covers amyotrophic lateral sclerosis and its bulbar-onset variant, progressive bulbar palsy, beginning with the definition and the involvement of upper and lower motor neurons. It then moves through aetiology, pathogenesis, and the clinical features of upper and lower motor neuron signs, bulbar and respiratory involvement. Diagnosis, differential diagnosis against conditions such as myasthenia gravis and multiple sclerosis, treatment and prognosis close the note.

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Topic 71 of 88 in the MU Sofia syllabus for Neurology (Medicine, Year 4). The free AceMed note covers it in 1 section, about 345 words (2 min of reading), with 16 flashcards.

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  1. Amyotrophic lateral sclerosis. Progressive bulbar paralysis

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. 1.Sporadic (most cases): Unknown cause
  2. 2.Familial: Genetic mutations (e.g., SOD1, C9orf72)
  3. 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

  1. A. LMN Signs: Muscle weakness Muscle atrophy. Fasciculations. Flaccid paralysis. Reduced reflexes (in affected muscles)
  2. B. UMN Signs: Spasticity. Hyperreflexia. Babinski sign. Clonus
  3. C. Distribution: Asymmetric onset. Distal limb weakness → spreads proximally. Progressive course
  4. D. Bulbar Involvement (late or early in some cases): Dysarthria. Dysphagia. Nasal speech. Tongue atrophy with fasciculations
  5. 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

  1. 1. Myasthenia Gravis: Fatigable weakness. No UMN signs
  2. 2. Cervical Spondylotic Myelopathy: UMN signs only
  3. 3. Multiple Sclerosis: Remitting course
  4. 4. 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

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