What is the differential diagnosis for new‑onset slurred speech (dysarthria) in an older adult with vascular risk factors?

Differential Diagnosis for Slurred Speech (Dysarthria)

In an older adult with vascular risk factors presenting with new-onset slurred speech, acute stroke is the most critical diagnosis to exclude immediately, as it requires time-sensitive intervention within hours of symptom onset. 1

Immediate Life-Threatening Causes (Evaluate First)

Acute Ischemic Stroke

• Slurred speech is one of the three cardinal features of stroke (along with facial droop and arm drift) and mandates emergent evaluation with brain imaging within minutes to hours. 1
• Unilateral upper motor neuron (UUMN) dysarthria is the most common type following acute ischemic stroke, present in 52% of stroke patients with dysarthria. 2
• Speech characteristics include imprecise articulation of consonants, harsh voice quality, and audible inspiration. 2
• 44-46% of acute stroke patients develop dysarthria, though approximately half recover completely within one week. 2
• The presence of vascular risk factors (hypertension, diabetes, atrial fibrillation, prior stroke/TIA) substantially increases stroke likelihood. 1

Intracranial Hemorrhage

• Can present identically to ischemic stroke with acute dysarthria and requires immediate imaging to differentiate, as management differs fundamentally (anticoagulation is contraindicated). 1

Neurodegenerative Causes (Subacute to Chronic Presentation)

Parkinson's Disease

• The leading cause of hypokinetic dysarthria, characterized by reduced speech volume (hypophonia), monotone pitch, reduced accentuation, and variable speech rate. 3, 4
• Strongly associated with drooling due to impaired swallowing and reduced oral motor control—this combination should immediately raise suspicion for Parkinson's disease. 3
• Voice is typically harsh and breathy with prosodic insufficiency. 4
• The abnormal basal ganglia-thalamo-cortical circuit is the pathophysiological basis. 5

Amyotrophic Lateral Sclerosis (ALS)

• Causes progressive bulbar palsy with both speech impairment and sialorrhea (drooling) from poor pharyngeal neuromuscular control. 3
• Presents with flaccid dysarthria from lower motor neuron impairment affecting cranial nerves IX, X, and XII. 6

Multiple Sclerosis

• Can cause dysarthria through various mechanisms depending on lesion location, often presenting with ataxic or mixed dysarthria patterns. 1, 3

Structural and Neurologic Causes

Vocal Fold Paralysis

• Results from recurrent laryngeal nerve injury and causes breathy dysphonia with potential aspiration risk. 7
• Common causes include thyroid surgery (0.85-8.5% incidence), anterior cervical spine surgery (1.69-24.2% incidence), and neck trauma. 7
• Can be associated with swallowing dysfunction. 3

Brain Tumors

• Posterior fossa masses or other intracranial lesions can cause dysarthria depending on location and structures affected. 1

Medication-Induced Causes

Anticholinergic Medications

• Can cause speech changes through mucosal drying and altered motor control. 3
• Antihistamines, diuretics, and anticholinergics cause mucosal drying affecting speech quality. 3

Inhaled Corticosteroids

• Can cause fungal laryngitis and nonspecific laryngeal irritation leading to dysphonia. 1, 7

Systemic and Autoimmune Causes

Rheumatologic Conditions

• Sjögren's syndrome, rheumatoid arthritis, sarcoidosis, and amyloidosis can all cause dysphonia and may affect salivary gland function. 3

Endocrine Disorders

• Hypothyroidism can cause voice changes and potentially affect swallowing. 3
• Diabetes is associated with neurologic complications affecting speech and swallowing. 3

Malignancy

Head and Neck Cancer

• Laryngeal, lung, or thyroid cancer can present with dysphonia and may affect swallowing if advanced. 3
• Tobacco abuse increases laryngeal malignancy risk 2-3 fold and mandates immediate laryngoscopy. 7
• Delayed laryngeal evaluation leads to higher staging, more aggressive treatment requirements, and reduced survival rates. 7

Critical Diagnostic Approach

Immediate Assessment

• Use the Cincinnati Prehospital Stroke Scale: assess facial droop, arm drift, and speech (normal = says correct words with no slurring; abnormal = slurs words, says wrong words, or unable to speak). 1
• Obtain brain imaging (CT or MRI) emergently if stroke is suspected—do not delay for other evaluations. 1

History Must Include

• Onset timing (sudden vs. gradual), associated neurologic symptoms (weakness, numbness, vision changes), presence of drooling, swallowing difficulty, medication review (especially anticholinergics), tobacco/alcohol use, and occupational voice demands. 3

Physical Examination

• Full neurologic examination including cranial nerves, motor strength, coordination, and gait. 3
• Evaluate all five speech subsystems: respiration, phonation, resonance, articulation, and prosody. 5, 6
• Observe for drooling, swallowing difficulty, and breathing patterns. 3

Laryngoscopy Timing

• Perform laryngoscopy within 4 weeks for persistent dysphonia, as delaying beyond this can miss vocal fold paralysis, benign lesions, or laryngeal cancer in 56% of cases initially labeled as "acute laryngitis." 7
• Avoid CT or MRI prior to laryngeal visualization for chronic dysphonia, as imaging before direct examination increases cost without improving diagnostic yield. 3

Common Pitfalls to Avoid

• Never assume "acute laryngitis" without laryngoscopy if symptoms persist beyond 2-4 weeks—this delays diagnosis of serious conditions including malignancy and vocal fold paralysis. 7
• Do not attribute dysarthria solely to aging without excluding stroke, Parkinson's disease, or other treatable conditions. 1
• The combination of slurred speech plus drooling is Parkinson's disease until proven otherwise in the absence of acute stroke symptoms. 3