What Is It, Causes, Diagnosis, Treatments, and More
Author: Alyssa Haag
Illustrator: Jillian Dunbar
What is bulbar palsy?
Bulbar palsy refers to a set of signs and symptoms linked to the impaired function of the lower cranial nerves, typically caused by damage to their lower motor neurons or to the lower cranial nerve itself. The impacted cranial nerves are a set of nerves that arise straight from the brainstem and include cranial nerves IX (9), X (10), XI (11), and XII (12). Lower motor neurons are the neurons that connect the central nervous system, such as the brain and spinal cord, to the muscles they innervate.
Damage to lower motor neurons can result in a wide variety of symptoms based on the cranial nerve that is damaged. For example, cranial nerve IX (the glossopharyngeal nerve) is involved in salivation, swallowing, and the gag reflex. If cranial nerve IX is injured, it can lead to difficulty swallowing (dysphagia) and a reduced gag reflex. Common signs and symptoms of damage to the other cranial nerves include difficulty chewing, nasal regurgitation, slurred speech, difficulty in handling secretions, aspiration of secretions, altered vocal ability (dysphonia) and difficulty articulating words (dysarthria).Other clinical signs associated with bulbar palsy include a nasal speech that lacks in modulation (e.g. controlling or adjusting of one’s speech), difficulty with all consonants, an atrophic (wasting) tongue, drooling, weakness of the jaw and facial muscles, a normal or absent jaw jerk (upward jerk of the jaw upon striking the chin) and an absent gag reflex.
Bulbar palsy is sometimes classified as progressive or non-progressive. Progressive bulbar palsy is more common and refers to the escalation of symptoms over time. It can occur in both children and adults. Non-progressive bulbar palsy, on the other hand, refers to bulbar palsy that does not worsen; it is considered very uncommon.Bulbar palsy is sometimes confused with pseudobulbar palsy, which is the result of damage to the upper motor neurons. While the two conditions share many of the same symptoms, pseudobulbar palsy is often characterized by the atypical expression of emotion displayed by unusual outbursts of laughing or crying, called emotional lability. Meanwhile, with bulbar palsy, an individual’s emotions usually remain unaffected. Other differentiating signs and symptoms of psudeobulbar palsy include the absence of facial emotions, a spastic and pointed tongue, and an exaggerated jaw jerk.
What causes bulbar palsy?
The most common causes of bulbar palsy include brainstem strokes and tumors. The brainstem is the part of the brain where the cranial nerves arise from and where all motor control signals are transmitted. Thus, damage to the brainstem—from strokes or tumors—can damage various cranial nerves and disrupt motor control.Other causes of bulbar palsy include certain degenerative diseases (e.g. amyotrophic lateral sclerosis), autoimmune diseases (e.g. Guillain–Barré syndrome), and genetic diseases (e.g. Kennedy disease). Amyotrophic lateral sclerosis, commonly referred to as ALS, is a rare neurological disorder characterized by a gradual deterioration and death of motor neurons. Guillain–Barré syndrome causes the immune system to attack its own nerves, potentially targeting cranial nerves. Kennedy disease is a lower motor neuron disease that can affect transmission signals between the brain and the spinal cord, potentially resulting in bulbar palsy.
Is bulbar palsy hereditary?
Although it is not always caused by genetic considerations, bulbar palsy has been linked to several hereditary conditions. Recently, childhood forms of progressive bulbar palsy have been genetically caused by Brown–Vialetto–Van Laere (BVVL) and Fazio–Londe syndromes. BVVL is an autosomal recessive disorder, which means that both parents may be carriers for the disease without expressing the condition themselves, and can pass on the expressive form of the disease to their child. Fazio–Londo syndrome presents similarly and is inherited in a similar manner to BVVL.
Additionally, bulbar palsy can be the result of a condition that is considered hereditary. For example, Kennedy disease is an X-linked recessive disorder that can cause bulbar palsy.
How do you diagnose bulbar palsy?
Reviewing an individual's history of symptoms and clinical features can help to diagnose bulbar palsy. However, additional tests may be required in order to diagnose the underlying cause. An analysis of an individual’s cerebral spinal fluid (fluid that surrounds the brain and spinal cord) may be conducted to rule out multiple sclerosis, which can sometimes present in a similar manner to bulbar palsy. Magnetic resonance imaging (MRI) of the brain may also be performed in order to diagnose a stroke or tumor.
How do you treat bulbar palsy?
There is currently no known treatment for bulbar palsy. However, supportive treatments are used for the management of symptoms and underlying conditions. Certain medications may be prescribed to control drooling. A feeding tube can also be given to individuals who have severe difficulty swallowing. Finally, speech and language therapy may assist with difficulties in speech, chewing, and swallowing.
Additional condition-specific treatments will likely be required for individuals facing degenerative, autoimmune, or genetic diseases that resulted in bulbar palsy.
Is bulbar palsy fatal?
Bulbar palsy can prove to be fatal in progressive cases. Death from progressive bulbar palsy often occurs 1 to 3 years from the start of the disorder, however, it is often attributed to the development of associated aspiration pneumonia (infection of the lungs). Aspiration pneumonia often occurs in individuals with bulbar palsy as they may have difficulty swallowing and as a result, a large amount of material, or food, may enter the lungs and lead to infection.Extensive bulbar damage may also damage the respiratory center in the brainstem, which is involved in signaling and controlling breathing. This can lead to a life threatening inability to breathe properly. Additionally, progressive bulbar palsy may advance to ALS, or amyotrophic lateral sclerosis, and prognosis is usually poor. With ALS, death of motor neurons interferes with an individual’s ability to breathe and can ultimately result in fatality.
What are the most important facts to know about bulbar palsy?
Bulbar palsy is a set of conditions that can occur due to damage to the lower cranial nerves. Clinical features of bulbar palsy range from difficulty swallowing and a lack of a gag reflex to inability to articulate words and excessive drooling. Bulbar palsy is most commonly caused by a brainstem stroke or tumor. Certain autoimmune diseases, genetic diseases, and degenerative disorders can also potentially result in the development of bulbar palsy. Treatment primarily focuses on the management of related symptoms.
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Resources for research and reference
Bosch, A. M., Stroek, K., Abeling, N.G. et al. (2012). The Brown-Vialetto-Van Laere and Fazio Londe syndrome revisited: natural history, genetics, treatment and future perspectives. Orphanet Journal of Rare Diseases, 7(83). DOI: 10.1186/1750-1172-7-83
Garg M., Kulkarni, S. D., Hegde, A. U., & Shah, K. N. (2018). Riboflavin Treatment in Genetically Proven Brown-Vialetto-Van Laere Syndrome. Journal of Pediatric Neuroscience, 13(4): 471-473. DOI: 10.4103/JPN.JPN_131_17
Green, P., Wiseman, M., et al. (2010). Brown-Vialetto-Van Laere syndrome, a Ponto-Bulbar Palsy with Deafness, is Caused by Mutations in c20orf54. American Journal of Human Genetics, 86(3): 485-9. DOI: 10.1016/j.ajhg.2010.02.006
Motor Neuron Diseases Fact Sheet. (2015). In National Institute of Neurological Disorders and Stroke (NINDS). Retrieved November 23, 2020, from https://www.ninds.nih.gov/Disorders/All-Disorders/Motor-Neuron-Diseases-Information-Page
Saleem, F. & Munakomi, S. Pseudobulbar Palsy. (2020). In StatPearls [Internet]. Retrieved November 23, 2020, from https://www.ncbi.nlm.nih.gov/books/NBK553160/