Bulbar syndrome: flaccid paralysis
Bulbar paralysis occurs due to damage to the cranial nerve nuclei in the medulla oblongata (bulbus cerebri). This condition is classified as a peripheral paresis or paralysis of the muscles responsible for swallowing, phonation, and articulation.
Key manifestations of the syndrome include:
- Pronounced difficulties in swallowing solid and liquid food (dysphagia).
- Voice changes: hoarseness, roughness (dysphonia), and a nasal tone (nasal speech / hypernasality).
- A sharp decrease or complete absence of the palatal and pharyngeal reflexes.
- Articulation disorders (dysarthria).
Damage to the glossopharyngeal (IX) and vagus (X) nerves may be accompanied by a loss of taste sensitivity on the posterior third of the tongue (ageusia) and autonomic disorders.
Pseudobulbar syndrome: spastic paralysis
Pseudobulbar paralysis develops with bilateral damage to the corticobulbar pathways. Unlike bulbar syndrome, this condition involves central paralysis of the speech and swallowing musculature.
The main causes of such a lesion are bilateral pathologies of the subcortical basal ganglia, frontal lobes, or the pons (pons). The clinical picture also includes dysarthria, dysphonia, and dysphagia; however, the reflex sphere changes radically.
Instead of reflex depression, one observes their preservation or enhancement, as well as briskness of the jaw jerk reflex.
Specific signs of pseudobulbar paralysis
The main difference between pseudobulbar and bulbar syndromes is the disinhibition of subcortical structures, which manifests as the following symptoms:
- Oral automaticity reflexes:
- Southend / snout reflex — protrusion of the lips like a snout when tapping the upper lip.
- Palmomental reflex (Marinesco-Radovici sign) — contraction of the mentalis muscle upon stroke stimulation of the thenar eminence.
- Emotional disorders:
- Episodes of forced crying and laughter that occur involuntarily and do not correspond to the patient's actual mood.
Briefly: answers to topical questions
Which cranial nerves are affected in bulbar syndrome?
Bulbar syndrome is caused by a lesion of the medullary nuclei belonging to the glossopharyngeal (n. glossopharyngeus, IX), vagus (n. vagus, X), and hypoglossal (n. hypoglossus, XII) nerves.
- Glossopharyngeal nerve (n. glossopharyngeus, IX) — dysphagia, loss of pharyngeal reflex
- Vagus nerve (n. vagus, X) — dysphonia, nasal speech, dysphagia
- Hypoglossal nerve (n. hypoglossus, XII) — flaccid paralysis of tongue muscles, atrophy, fasciculations
Which oral automaticity reflexes are detected in pseudobulbar syndrome?
In pseudobulbar syndrome, grasping, snout, and palmomental reflexes of oral automaticity are detected.
- Grasping reflex — mentioned in the list of oral automaticity reflexes
- Snout reflex — protrusion of the lips like a snout when tapping the upper lip with a reflex hammer (m. orbicularis oris)
- Palmomental reflex (Marinesco-Radovici sign) — contraction of the mentalis muscle (m. mentalis) upon stroke stimulation of the palm in the thenar region
Bulbar — without reflexes (decreased peripherally), Pseudobulbar — hyperreflexia and crying (central reflexes are brisk, plus forced laughter/crying).
Class and exam questions
What is the main pathogenetic difference between bulbar and pseudobulbar palsies?
Bulbar palsy is a lower motor neuron (peripheral) paralysis occurring when the medulla oblongata nuclei themselves are damaged. Pseudobulbar palsy is an upper motor neuron (central) paralysis that develops due to bilateral damage to the corticobulbar tracts projecting to these nuclei.
How do pharyngeal and palatal reflexes behave in these syndromes?
In bulbar syndrome, pharyngeal reflexes are sharply reduced or extinguished due to the disruption of the peripheral arc. In pseudobulbar syndrome, these reflexes are preserved or even exaggerated.
What specific reflexes are characteristic of pseudobulbar syndrome?
It is characterized by oral automaticity reflexes (snout reflex, palmomental Marinesco-Radovici reflex), as well as the phenomenon of forced crying and laughter.
What else to study on this topic
- Wallenberg-Sakharov syndrome and lateral medullary infarction
- Anatomy and functions of the glossopharyngeal (IX) and vagus (X) nerves
- Ascending reticular activating system of the brainstem
- Pathways and nuclei of the midbrain (red nucleus, substantia nigra)
- Medial longitudinal fasciculus and its role in eye movement coordination
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Other topics in "Chapter 10. Disorders of Swallowing and Phonation. Lesions of the Glossopharyngeal and Vagus Nerves"
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