Condition typified by lower motor neurone lesions affecting cranial nerves IX, X, and XII, resulting in impairments in speech and swallowing

Aetiology

• Motor neurone disease: notably, the progressive bulbar palsy variant.
• Myasthenia gravis
• Guillain-Barré syndrome
• Brainstem stroke: particularly the lateral medullary syndrome or Wallenberg's syndrome
• Syringobulbia: a rare neurologic condition characterized by a fluid-filled cavity (syrinx) within the spinal cord

Clinical features

• Absent or normal jaw jerk reflex
• Absent gag reflex
• Flaccid, fasciculating tongue
• Nasal speech, often described as ‘quiet’
• Additional signs may suggest the underlying cause, such as limb fasciculations in the case of motor neurone disease

Investigations

Diagnostic workup should aim at establishing the underlying aetiology:

• Neurological examination: to assess cranial nerve integrity and look for additional neurological signs
• EMG and nerve conduction studies: helpful in diagnosing motor neurone disease and myasthenia gravis
• Bloods: including complete blood count, electrolytes, creatine kinase, and autoantibody screening
• Neuroimaging: MRI can identify lesions in the brainstem or presence of a syrinx.
• Lumbar puncture: to investigate or rule out infections/autoimmune causes