Bursting into laughter disproportionate to the context or even with no apparent reason; you have either experienced this yourself or witnessed it. Imagine this reaction multiplied in intensity, duration, and frequency, but also manifesting emotions from the other end of the emotional spectrum -- uncontrollable laughing and crying.
Pseudobulbar affect (PBA) is a condition occurring in patients with neurological disorders like stroke, amyotrophic lateral sclerosis or Alzheimer’s disease. Patients experience exaggerated, uncontrollable, and involuntary outbursts of laughter or crying inappropriate to the context in which they occur [1].
The pathophysiology of PBA is obscure. Neuroimaging [2] and electrophysiological [3] evidence implicates the cortico-pontine-cerebellar circuit (CPCC). The CPCC integrates contextual information from the cortex and provides an accurate and congruent emotional response. Its dysfunction results in inappropriate or unscaled emotional responses.
Crying when happy, laughing when sad
The neurotransmitter serotonin, which modulates functions closely associated with mood, sleep, sex, and appetite, and is disturbed in many mood disorders, seems to be closely related to PBA. Based on this, selective serotonin reuptake inhibitors are often prescribed for PBA [4]. Likewise, glutamate acts on many brain structures around the CPCC and a reduction of its increased excitatory activity may be beneficial for BPA patients [3].
PBA is expected to become more common as the number of patients with neurological disorders increases. This will necessitate a more thorough understanding of its pathophysiology to provide better treatment.
[1] Arciniegas et al, CNS Spectr, 2015
[2] Parvizi et al, J Neuropsychiatry Clin Neurosci, 2009
[3] Haiman et al, J Neurol Sci, 2008
[4] Schiffer and Pope, J Neuropsychiatry Clin Neurosci, 2005
by Andreas Diamantaras, MSc MedNeuro
This article originally appeared March 2015, Vol. 08, Issue 01, Humour
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