Causes of Adult Pathological Stuttering
Adult pathological stuttering has three distinct etiological categories: functional (psychogenic), neurogenic from acquired brain lesions, and extrapyramidal disease, with functional causes being most common and typically triggered by psychological stressors, though absence of an identifiable trigger does not exclude the diagnosis. 1
Functional (Psychogenic) Stuttering
This is the most frequently encountered form of adult-onset stuttering and arises from psychological mechanisms rather than structural brain damage. 1, 2
Psychological Precipitants
The following stressful life events commonly trigger functional stuttering 1:
- Interpersonal conflict involving difficulties communicating negative emotions in close relationships or with important persons 1
- Workplace stress characterized by high responsibility, criticism, or situations where the patient cannot speak out or defend themselves 1
- Posttraumatic stress disorder, particularly combat-related trauma 1
- Personal injury litigation or workers' compensation claims that may perpetuate symptoms 1
- Recent accidents or illness, sometimes with mild head injury causing transient concussion 1
Critical Diagnostic Caveat
The absence of a clear psychological trigger should NOT discount a functional diagnosis—clinicians must recognize that precipitating factors are not always identifiable. 1, 3
Associated Psychological Comorbidities
Functional stuttering frequently co-occurs with 1:
- Generalized anxiety disorder 1
- Social anxiety related to speaking situations 1
- Depression 4
- Avoidance behaviors, rumination, and self-doubt 1
Neurogenic Stuttering from Acquired Brain Lesions
Stroke, traumatic brain injury, and other focal brain lesions can cause acquired neurogenic stuttering through disruption of specific neural networks. 5, 6
Neuroanatomical Substrate
Recent lesion network mapping reveals that heterogeneous brain lesions causing stuttering converge on a common network 6:
- Left putamen (primary hub) 6
- Claustrum and amygdalostriatal transition area 6
- Adjacent striatal structures 6
Specific Neurological Causes
The following conditions must be excluded before diagnosing functional stuttering 1, 3:
- Stroke affecting the stuttering network 1, 5, 6
- Traumatic brain injury, including mild TBI from blast injuries 1, 7
- Epilepsy 1
Importantly, functional stuttering can co-occur with these neurological conditions, complicating diagnosis. 1
Extrapyramidal Disease
Parkinsonian syndromes and other extrapyramidal disorders can present with stuttering as the initial symptom, preceding other motor signs. 8
Clinical Presentation
Adult-onset stuttering from extrapyramidal disease may include 8:
- Severe stuttering with multiple repetitions (20+ per word) 8
- Progressive motor symptoms including resting tremor, gait imbalance, and lingual fasciculations 8
- Dramatic response to carbidopa-levodopa, confirming the diagnosis 8
Tic Disorders
Tic disorders including Tourette syndrome, chronic vocal tic disorder, and transient tic disorder must be excluded through neurology consultation before confirming functional stuttering. 3
Key Distinguishing Features by Etiology
Functional Stuttering Characteristics 1, 3
- Adult onset without prior developmental speech difficulties 1, 3
- Extreme variability OR unusual consistency (stuttering on every syllable/word or first word of every sentence) 1, 3
- Paradoxical worsening with simple speech tasks rather than complex ones 3
- Lack of improvement with fluency-promoting activities 3
- Variable severity across topics and situations 7
Neurogenic Stuttering Characteristics 5, 7
- Temporal association with neurological event (stroke, TBI) 5
- Objective neurological findings on examination 7
- More consistent presentation across speaking situations 5
Common Diagnostic Pitfalls
The most critical error is making a diagnosis of functional stuttering without first excluding neurological causes through comprehensive neurological examination and appropriate neuroimaging. 3, 2
Additional pitfalls include 3, 2:
- Failing to recognize that functional stuttering is a diagnosis of exclusion requiring mandatory exclusion of tic disorders and neurological disease 3
- Dismissing functional diagnosis when no psychological trigger is identified 1, 3
- Overlooking extrapyramidal disease when stuttering is the presenting symptom 8
- Confusing functional stuttering with dysarthria or aphasia in patients with brain lesions 5
Prognostic Factors Affecting Chronicity
Untreated comorbid depression or anxiety significantly prolongs stuttering duration and worsens outcomes, making concurrent mental health treatment essential. 4
The following factors perpetuate symptoms 4: