|Progressive bulbar palsy|
|Classification and external resources|
Progressive Bulbar Palsy (also known simply as PBP) belongs to a group of disorders known as motor neuron diseases (Lapiedra 2002). PBP is a disease that attacks the bulbar innervated muscles. These disorders are characterized by the degeneration of motor neurons in the cerebral cortex, spinal cord, brain stem, and pyramidal tracts. This specifically involves the glossopharyngeal nerve (IX), vagus nerve (X), and hypoglossal nerve (XII) (Hughes 1998).
This disorder should not be confused with pseudobulbar palsy or progressive spinal muscular atrophy (Hughes 1998). The term Infantile progressive bulbar palsy is used to describe progressive bulbar palsy in children.
Some neurologists consider this disorder to be a subset of amyotrophic lateral sclerosis (ALS), but others disagree with that classification.
The disease was first recognized by French neurologist, G. Duchenne in 1860 and termed, “labioglossolaryngeal paralysis” (Fawcett 2000). In 1859, Wachsmuth changed the name to progressive bulbar palsy. In 1869, Charcot studied the involvement of the corticospinal tracts and with Joffroy, who noted the loss of the bulbar motor nuclei, discovered the similarities to amyotrophic lateral sclerosis (ALS) (Fawcett 2000). It was observed that a distinction from ALS was fatigue that predominated in muscles innervated by lower cranial nerve nuclei, rather than the upper motor neurons.
Progressive bulbar palsy is slow in onset, with symptoms starting in most patients around 50-70 years of age (Merck 2005). It is debated as to whether PBP is a separate entity or a subtype of amyotrophic lateral sclerosis (ALS). Pure PBP without any EMG or clinical evidence of abnormalities in the legs or arms is possible, albeit extremely rare. Moreover, about twenty-five percent of patients with PBP eventually develop the widespread symptoms common to ALS (Swash 2000).
The etiology of PBP is unknown. One form of PBP is found to occur within patients that have a CuZn-superoxide dismutase (SOD1) mutation (Kadekawa 1997). Progressive bulbar palsy patients that have this mutation are classified with FALS patients, Familial ALS (FALS) accounts for about 5%-10% of all ALS cases and is caused by genetic factors. Within these, about 20-25% are linked to the SOD1 mutation. It is not currently known if and how the decreased SOD1 activity contributes to Progressive Bulbar Palsy or FALS, and studies are being done in patients and transgenic mice by Dr. George P. Burdell to help further understand the impact of this gene on the disease.
A case study was done on a 42-year-old woman who complained of muscle weakness 10 months prior to admission in the hospital. Upon neurological examination, the patient showed muscle atrophy, fasciculation in all limbs and decreased deep tendon reflexes. The patient’s older brother, father, and paternal uncle had previously all died of ALS or an ALS type syndrome. The patient developed Progressive Bulbar Palsy, became dependent on a respirator, and had two episodes of cardiac arrest. The patient died from pneumonia two years after the onset of the disease. After studying the patient, it was found that the patient had a two base pair deletion in the 126th codon in exon 5 of the SOD1 gene. This mutation produced a frameshift mutation, which led to a stop codon at position 131. SOD1 activity was decreased by about 30%. The patient’s histological examination showed severe reduction in lower motor neurons. Upon further study, this case proved to be important because it demonstrated that SOD1 mutations might not effect steady neuropathological changes, and that environmental and genetic factors might affect the phenotype of the SOD1 mutations ( Kadekawa 1997).
Prognosis for PBP patients is poor. Progressive bulbar palsy symptoms can include progressive difficulty with chewing, talking, and swallowing (Merck 2005). Patients can also exhibit reduced gag reflexes, weak palatal movements, fasciculations, and weak movement of the facial muscles and tongue. In advanced cases of PBP, the patient may be unable to protrude their tongue or manipulate food in their mouth (Campbell 2005). Patients with early cases of PBP have difficulty with pronunciations, particularly linguals and velars, and may show problems with drooling saliva. If the corticobulbar tract is affected a pseudobulbar affect with emotional changes may occur (Merck 2005). Because PBP patients have such difficulty swallowing, food and saliva can be inhaled into the lungs. This can cause gagging and choking, and it increases the risk of pneumonia (Merck 2005). Death, which is often from pneumonia, usually occurs 1 to 3 years after the start of the disorder.
PBP is aggressive and relentless, and there are currently no treatments for the disease (Merck 2005). However, early detection of PBP is the optimal scenario in which doctors can map out a plan for management of the disease. This typically involves symptomatic treatments that are frequently used in many lower motor disorders.