Involuntary emotional expression disorder

Involuntary emotional expression disorder, better known as pseudobulbar affect, is a neurological disorder in which brief and intense episodes of crying, laughing or anger erupt without voluntary control and often without a matching mood

The episodes arise from injury or degeneration of the neural networks that regulate emotional expression, most often after stroke, traumatic brain injury, multiple sclerosis or amyotrophic lateral sclerosis, and they are a disorder of expression rather than a primary mood disorder

Because the outbursts are sudden and socially incongruent, they are frequently mistaken for depression, bipolar disorder or a personality problem, and recognition depends on asking about episodes separately from mood

Terminology and classification

• Involuntary emotional expression disorder was proposed in 2006 by Cummings and colleagues as an umbrella term covering pseudobulbar affect, emotional lability and pathological laughing and crying
• Pseudobulbar affect is the most widely used name in neurology and derives from the nineteenth-century idea that the symptoms mimic a bulbar lesion even though the medulla is not the primary site
• Pathological laughing and crying is preferred in much of the stroke and rehabilitation literature, while emotional incontinence is used for the same phenomenon in older neurological writings
• The disorder is classified by its underlying neurological disease rather than as an independent psychiatric category, and neither DSM-5 in 2013 nor ICD-11 in 2019 created a dedicated category, so no specific code exists
• When a code is required, F48.8 for other specified neurotic disorders is sometimes used in ICD-10, but most registries code the causative stroke, multiple sclerosis or motor neuron disease
• Emotional lability is a broader and less specific term that can occur with depression, delirium and frontal lobe disease, so it should not be used as a synonym for pseudobulbar affect without further description

History

• Charles Darwin discussed in 1872 how brain disease, hemiplegia and senile decay could provoke weeping, an early recognition that emotional expression has a neurological substrate separate from mood
• Oppenheim and later Kinnier Wilson described pathological laughing and crying in the early twentieth century and linked it to bilateral lesions of the corticobulbar pathways
• Wilson's 1924 paper on pathological laughing and crying consolidated the disinhibition model that still frames clinical teaching about the disorder
• The Pathological Laughing and Crying Scale was introduced by Robinson and colleagues in 1993 to quantify episode frequency and severity after stroke
• The Center for Neurologic Study Lability Scale, published in 1997, became the most widely used screening and outcome measure in treatment trials
• The umbrella term involuntary emotional expression disorder was introduced in 2006, and the United States Food and Drug Administration approved dextromethorphan with quinidine for pseudobulbar affect on 29 October 2010

Epidemiology

• An online survey estimated that 1.5 to 2 million people in the United States have pseudobulbar affect, which is less than 1% of the population even at the upper bound
• That estimate relied on self-selected respondents who diagnosed themselves, so it probably overstates prevalence and cannot replace population-based sampling
• Post-stroke prevalence estimates range from 28% to 52%, with higher rates in older patients and in those with a previous stroke
• About 10% of people with multiple sclerosis experience at least one episode of emotional lability, usually in the progressive phase of the disease
• A dedicated survey found pseudobulbar affect in 49% of patients with amyotrophic lateral sclerosis, and its presence was not related to disease duration
• A clinic series of 301 consecutive traumatic brain injury cases reported a 5% prevalence, concentrated in more severe injuries with other signs of pseudobulbar palsy
• Survey data from the Brain Injury Association of America suggested that about 80% of respondents experienced symptoms, and another analysis estimated that more than 55% of survivors are affected
• True population prevalence remains unknown because studies use different scales, settings and thresholds, and because clinicians often record the underlying disease without noting the affective syndrome

Pathophysiology

• The classic disinhibition hypothesis proposes that bilateral damage to corticobulbar pathways removes top-down control over brainstem centres that generate laughing and crying
• Lesion studies implicate the pons, internal capsule, basal ganglia, thalamus and frontal white matter, and no single location explains every case
• Prefrontal and anterior cingulate regions are thought to appraise emotional context, while insular and temporal regions contribute to the affective experience that is being expressed
• The cerebellum is increasingly recognised as part of the network, and cerebellar lesions can produce pathological laughing and crying by disrupting prediction and modulation of emotional behaviour
• Serotonergic, dopaminergic and glutamatergic pathways have all been implicated, which is the rationale for treating the disorder with serotonergic antidepressants and with glutamatergic modulators
• The episodic nature suggests a threshold phenomenon in which a mildly evocative stimulus triggers a stereotyped motor programme that is no longer gated by context

Clinical features

• Episodes are sudden, last from a few seconds to several minutes, and may occur several times a day, often with no identifiable trigger
• The emotional display may be exaggerated relative to the stimulus, or it may be incongruent, such as laughing at sad news or crying when amused
• Anger outbursts can occur alongside crying and laughing, and episodes may switch from one emotional display to another within the same attack
• Most patients retain insight and describe the episodes as involuntary, embarrassing and out of character, which distinguishes the experience from a primary mood episode
• Frequent outbursts disrupt conversation, meals and work, and patients may withdraw socially to avoid embarrassment and misunderstanding
• Caregivers often bear a heavy burden because the behaviour is misread as emotional instability, manipulation or lack of effort, and family education is therefore part of clinical care

Diagnosis

• The diagnosis is clinical and requires a compatible underlying neurological disorder plus episodic, involuntary emotional displays that are disproportionate or incongruent to context
• The Center for Neurologic Study Lability Scale is a seven-item self-report measure, and a score of 13 or higher is commonly used as a screening threshold
• The Pathological Laughing and Crying Scale uses a structured interview to rate frequency, duration, intensity and controllability of episodes
• Depression is the main differential, and the useful distinctions are episode duration, congruence with mood, controllability and response to the provoking stimulus
• Medication review should look for drugs that lower the seizure threshold or cause affective flattening, and thyroid function should be checked when hyperthyroidism or hypothyroidism is suspected
• Brain imaging and electroencephalography are not required for every case but are indicated when the underlying cause is unclear or when gelastic or dacrystic seizures are considered

Management

• The first step is to identify and treat the underlying neurological disease, because control of the cause may reduce episode frequency and because reversible contributors must not be missed
• Patient and family education is itself therapeutic, since naming the syndrome as involuntary reduces blame and helps observers respond calmly during an episode
• Dextromethorphan hydrobromide 20 mg with quinidine sulfate 10 mg twice daily is the only treatment approved in the United States for pseudobulbar affect, following approval in 2010
• Selective serotonin reuptake inhibitors such as citalopram, sertraline and fluoxetine are widely used off-label and may reduce both crying and laughing episodes
• Tricyclic antidepressants such as amitriptyline and nortriptyline are older alternatives, but anticholinergic and cardiac effects limit their use in frail or older patients
• Cognitive behavioural therapy, speech and language therapy and relaxation training can improve coping and communication even though they do not remove the underlying lesion
• Quinidine requires electrocardiographic monitoring because it prolongs the QT interval, and the combination should be avoided in patients with congenital long QT syndrome or relevant drug interactions
• Care is best delivered by a multidisciplinary team that includes neurology, nursing, rehabilitation, psychology and social work, with explicit attention to caregiver strain and access to medication

Research and controversies

• The pivotal 12-week randomised trial enrolled 326 patients with amyotrophic lateral sclerosis or multiple sclerosis, and 283 completed the study, with episode counts falling by 47% to 49% compared with placebo
• In that trial the Center for Neurologic Study Lability Scale fell by 8.2 points with either dextromethorphan and quinidine dose and by 5.7 points with placebo, a difference that is statistically significant but modest in clinical terms
• Long-term safety, QT effects and the role of quinidine as a pharmacokinetic booster remain debated, and formulations without quinidine are being studied to widen access
• Whether pseudobulbar affect is a distinct disorder or the extreme end of a continuum of emotional dysregulation is unresolved, and this affects how trials define cases and outcomes
• Lesion-network mapping, digital speech and facial analysis, and cross-cultural validation of scales are active areas, because better biomarkers could identify patients who are currently missed or misdiagnosed