Pseudobulbar Palsy

Etiology

Pseudobulbar palsy is not a disease but a clinical constellation. Clinical conditions that involve corticobulbar tracts bilaterally can cause pseudobulbar palsy.[3] Many pathological conditions can lead to pseudobulbar palsy. These include traumatic brain injury, neoplasm, vascular lesions, metabolic abnormality, or neurological disease. Pseudobulbar palsy is one of the severe complications of cerebrovascular diseases.[2][3]

Neurological disorders, such as amyotrophic lateral sclerosis, Parkinson's disease, and progressive supranuclear palsy are common causes of pseudobulbar palsy.[1] Other causes include post-stroke pseudobulbar palsy, demyelinating conditions such as multiple sclerosis, and congenital malformations of the opercular or insular cortex.[1][4][5] Consecutive lacunar strokes can involve both corticobulbar tracts and cause pseudobulbar palsy.[6]

Rare causes of pseudobulbar palsy are:

• Central pontine myelinolysis: Common symptoms include pseudobulbar palsy.[7]
• Bilateral thalamic infarction: Very rarely infarction of specific nuclei manifests as pseudobulbar palsy.[4][8]
• Methotrexate-induced neurotoxicity: It is uncommon, but acute or subacute neurological clinical signs and symptoms, including pseudobulbar palsy, have been reported in the literature.[9][10]
• Progressive multifocal leukoencephalopathy: It rarely causes pseudobulbar symptoms.[11]
• Cerebral malaria: Pseudobulbar palsy in cerebral malaria may occur probably due to demyelination.[12]
• Bacterial endocarditis: Cerebral disturbance may occur in bacterial endocarditis and can manifest as pseudobulbar palsy.[13]
• Syphilis: Requires CSF examination.[13]
• Large petroclival meningioma: It presents as bulbar motor dysfunction and emotional lability that characterizes pseudobulbar palsy.[1]
• Neurocysticercosis: It is uncommon.[3]

Autoimmune encephalitis and Hashimoto encephalopathy causing pseudobulbar palsy have been reported; this highlights the importance of early detection of anti-thyroperoxidase antibodies in a patient with pseudobulbar palsy.[5]

Epidemiology

Pseudobulbar palsy epidemiology depends on the cause that has led to corticobulbar pathway damage. A study on the prevalence of motor neuron disease, including pseudobulbar palsy, reveals that prevalence increases, particularly after 50 years of age. Incidence is higher in males compared to females among all age groups.[14]

Pseudobulbar apathy affects 1 in 5 patients with acute stroke and 1 in 8 patients with chronic stroke.[15]

Pathophysiology

Three cardinal components are dysphagia, dysarthria, and emotional apathy.

They can be described in the stages of

• Shock (swallowing and speech defect)
• Loss of function (difficulty in breathing)-spirometric assessment showed reduced vital capacities and lung volumes, and
• Release of function (emotional incontinence).

Loss of cerebellar modulation (cortico-pontocerebellar pathways) causing emotional dysmetria and disinhibition owing to lesions of corticobulbar volitional pathways are the main pathogenesis explained for pseudobulbar apathy.[16][17]

History and Physical

Pseudobulbar palsy is due to an upper motor lesion in the corticobulbar pathways in the pyramidal fibers. Pseudobulbar palsy presents as:  

• Dysarthria, or anarthria 
• Dysphagia, sialorrhoea, drooling
• Dysphonia, hypernasal voice (Donald duck tone), and slurred speech. Speech has abnormality both in the rhythm and in the timbre, may have associated palilalia and finally, anarthria develops.
• Glossplegia with paresis of the tongue. Bilateral supranuclear lesions of the hypoglossal nerve in pseudobulbar palsy can produce an inability of the tongue to function.
• Impaired mastication, and paresis of facial muscles
• Emotional lability (pseudobulbar affect) is the abnormal expressions of emotion sometimes described in patients with pseudobulbar palsy, such as pathological laughter and emotional outburst, which is characterized by involuntary, uncontrollable laughter, or crying with paradoxical poverty of facial expression. Pathological laughter has also been reported in association with many tumors of the posterior fossa, particularly those involving pons and midbrain.
• Trismus: Acute pseudobulbar palsy can present with trismus due to the bilateral infarction of the internal capsule.
• On physical examination, there is a brisk jaw jerk. Other facial reflexes also become exaggerated. There are retained or increased palatal reflexes. There is the deviation of the angle of the mouth, uvula to the normal side and the tongue falls on the paretic side. Unlike lower motor neuron bulbar palsy, in pseudobulbar palsy, there is no atrophy or fasciculations of the affected muscles. Moreover, in bulbar palsy, emotions are not affected.[1][3][18]
• Frontal release signs
• Cognitive impairment and seizures are observed in almost 85% of pediatric cohorts.

Evaluation

The diagnosis of pseudobulbar palsy is mainly clinical and based on clinical features. Evaluation of the condition includes identifying the underlying cause. Possible causes of acute pseudobulbar palsy (neoplastic, inflammatory, demyelinating, myasthenic) should merit consideration.[4] Detailed history, including any previous history of stroke, is required. Complete neurological examination with the Mini-Mental State Examination (MMSE) score.[8] Investigations focus on evaluating for stroke, neoplasia, multiple sclerosis, or other demyelination disorders, such as:

• Complete blood count, metabolic profile, and serology
• Electroencephalogram
• CSF analysis (oligoclonal bands)
• Imaging studies, such as computed tomography (CT) and MRI of the brain- the lesions are most often seen within the operculum, corona radiata, and the genu of the internal capsule. Bilateral perisylvian dysgenesis is frequently observed among pediatric cohorts.
• Motor- and sensory-evoked potential tests
• Videofluoroscopic swallowing study (VFSS) and Fiberoptic Endoscopic Evaluation of Swallowing (FEES) for screening and grading of dysphagia
• Speech assessment
• Cognitive assessment
• Psychiatric consultation [7]

Treatment / Management

A) Dysphagia

The management of dysphagia can be categorized into [19]:(B2)

• Compensation therapy (eating postures, food characteristics, and eating tools)
• Swallowing function training (including swallowing muscle training)
• Physiotherapy (including electrical, magnetic, thermal stimulation)
• Alternative therapy (acupuncture, transcranial magnetic stimulation, and balloon dilation)
• Drugs (nifedipine and metoclopramide)
• 1. Bolus modification
  2. Behavioral adjustments
  3. Oromotor exercises,
  4. Postural adjustments,
  5. Swallowing maneuvers,
  6. Sensory and neurophysiologic stimulation

Behavioral interventions have shown high heterogeneity limiting generalizations into clinical practice. Meta-analysis pertaining to swallowing treatment strategies has shown to reduce the risk of aspiration pneumonia with low certainty only during the acute phase.[20] No decisive conclusion on the effectiveness of acupuncture in improving dysphagia. [21] Insufficient data to support the role of exercise in the management of bulbar dysfunction.[22](A1)

B) Dysarthria 

Interventions may be categorized as those directed at:

• Impairment level: non-verbal and oro-motor exercises (applying ice packs, traditional and electrical stimulations).
• Activity level: speech rate control and augmentative or alternative communication aids (an alphabet chart and text-to-talk computer devices).
• Participation level: social level participations

Current evidence is not yet robust and has shown no long-term benefits on everyday speech compared to any control.[23](A1)

Spastic dysarthria benefits mostly from relaxation techniques and speech rate treatments.

C) Emotional Incontinence

A fixed-dose combination of dextromethorphan/quinidine for the treatment of pseudobulbar affect has been shown to reduce the frequency and severity of laughing and crying behavior and is the only FDA-approved medication for the same.[24](B2)

D) Others

• Cognitive therapy
• Corpus callosotomy for refractory patterns of drop attacks
• Management of problematic drooling - glycopyrrolate, injection of botulinum, ligation of salivary ducts, and excision of submandibular glands.

Differential Diagnosis

Alcohol withdrawal seizures and delirium tremens should be distinguished when making a diagnosis of pseudobulbar palsy.[8] Metabolic encephalopathy can have a similar presentation.[7]

Pathological laughter also correlates with large compressive posterior fossa tumors, posterior fossa meningiomas, epidermoid tumors, and trochlear nerve neurinomas. Other tumors associated with pathological laughter include hypothalamic glioblastoma multiforme, pontine glioblastoma multiforme, metastatic melanomas, etc.[1]

The main differential diagnosis for bulbar palsy include:

• Myasthenia gravis
• Progressive muscular atrophy and
• Syphilis (bulbar variant)

Prognosis

The prognosis of pseudobulbar palsy depends on the underlying etiology.

Complications

Pseudobulbar palsy can lead to the following complications:

• Aspiration pneumonia
• Severe dysphagia 
• Social withdrawal