Description

PBA is marked by emotional outbursts, particularly crying and laughter, that are (1):

• Incongruous with (or exaggerated in comparison to) the patient’s subjective, internal emotional state
• Uncontrollable
• Brief in duration (lasting seconds to minutes)
• Disruptive and potentially upsetting
• Stereotyped in episode semiology within an individual but differing between individuals (e.g., one patient may have only crying episodes, another may have only laughing episodes, whereas a third may have both, although not simultaneously)
• The consequence of underlying neurologic damage
• Terminology surrounding PBA can be confusing.
• PBA overlaps with/includes other disorders comorbid with neurologic conditions, particularly:
  • Pathologic laughing and crying (emotional response incongruous to stimulus) (part of PBA)
  • Affective lability (exaggerated affective response to emotional stimulus) (part of PBA)
  • Involuntary emotional expression disorder (IEED, synonym for PBA)
  • Pseudobulbar palsy (PBA is one component of this disorder.)
  • Emotional incontinence (synonym for PBA)
• The term pseudobulbar should not give the impression that PBA is not a true neuropsychiatric disorder; rather, it refers to the neurologic and behavioral symptoms of corticobulbar disruption that mimic brainstem dysfunction.

Epidemiology

Incidence
Incidence is unclear.

Prevalence

• May be seen in multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), Alzheimer disease, Parkinson disease, stroke, traumatic brain injury (TBI), and multiple system atrophy (MSA)—cerebellar type, mass lesions (especially cerebellopontine angle) (2):
  • Estimated prevalence across patients with these disorders is ~10%, although it may reach as high as 38%.
  • The PRISM study (3), the largest to date, showed 36.7% of recruited patients to have screening scores consistent with PBA:
    • Significantly underdiagnosed
• Between 2 and 7 million people in the United States are estimated to suffer from PBA:
  • Prevalence estimates include ALS 2–49%, stroke 11–52%, MS 7–52%, Alzheimer disease 10–74%, Parkinson disease 7%, and TBI 5%.

Etiology and Pathophysiology

• Disruption of emotional motor pathway consisting of cortico-pontine-cerebellar circuitry is hypothesized to be at the root of PBA (4).
• Summary of pathway:
  • Flow from motor and frontotemporal cortices to brainstem drives physical expression of emotion-controlling behaviors such as laughter or crying.
  • These pathways require tuning modification for congruity between stimuli (both the external world and internal emotional states) and behavioral output.
  • This tuning is informed by direct somatosensory cortical inhibition of motor cortex and substantial cortical afferentation that ascends from cerebellum.
  • This aggregate information converges at the basis pontis where it is then relayed to the cerebellum for integration.
  • The cerebellum integrates these data and appropriately modifies descending signals, yielding behavioral outputs consistent with emotional states and relevant sensory data.
  • PBA is believed to result from dysfunction anywhere along this circuit from cortex through basis pontis to cerebellum, disrupting coordination of mood and behavioral output and causing disinhibition of emotional motor expression.
• Neurotransmitter dysfunction:
  • Disruption of glutamate and serotonin systems are thought to be central to PBA:
    • This is based on both the known importance of these neurotransmitters to circuitry involved in PBA pathophysiology as well as the fact that effective treatments for this condition are antiglutamatergic or serotonergic.

Risk Factors

PBA is seen in patients with underlying neurologic dysfunction, including, but not limited to:

• MS, ALS, Parkinson disease, Alzheimer disease, stroke, TBI, and mass lesions (1)