From the Research
Pseudobulbar palsy is caused by damage to the upper motor neurons that control the lower cranial nerves, specifically bilateral damage to the corticobulbar tracts, with the most common causes including stroke, traumatic brain injury, multiple sclerosis, amyotrophic lateral sclerosis (ALS), and other neurodegenerative diseases like frontotemporal dementia, as supported by the most recent study 1. The causes of pseudobulbar palsy can be categorized into several groups, including:
- Vascular diseases, such as small vessel disease or hypertensive encephalopathy, which can lead to pseudobulbar palsy through multiple small infarcts
- Traumatic brain injury, which can cause damage to the corticobulbar tracts
- Neurodegenerative diseases, such as multiple sclerosis, amyotrophic lateral sclerosis (ALS), and frontotemporal dementia, which can cause progressive damage to the upper motor neurons
- Brain tumors, particularly those affecting both hemispheres or the brainstem, which can cause compression or destruction of the corticobulbar tracts
- Infectious processes, such as encephalitis or brain abscesses, which can damage the relevant neural pathways
- Metabolic disorders, including Wilson's disease, which can occasionally be responsible for pseudobulbar palsy
- Radiation therapy to the brain, which can cause delayed damage to the corticobulbar tracts The condition manifests with symptoms like dysarthria, dysphagia, emotional lability, and exaggerated jaw jerk and gag reflexes because the damage interrupts the normal inhibitory signals from the cerebral cortex to the brainstem, resulting in disinhibition of lower motor neuron reflexes and loss of voluntary control over bulbar muscles, as described in 2, 3, 4, 5. The prevalence of pseudobulbar affect, a condition often associated with pseudobulbar palsy, varies among different neurodegenerative diseases, with a meta-analysis study 1 showing that the prevalence of pseudobulbar affect in patients with ALS is 38.5%, followed by multiple sclerosis (23.3%), Parkinson's disease (16.5%), and Alzheimer's disease (16.4%). Effective treatment options are available for pseudobulbar affect, including dextromethorphan/quinidine, which has been shown to be safe and effective in reducing the frequency and severity of pseudobulbar affect episodes, as demonstrated in studies 3, 4.