Neurological Examination - Speech&Language

🧭 Related Subjects: | Neurological History Taking | Cortical Functions | Motor System | Sensory System | Mental State Examination | Speech and Language Exam | Cranial Nerves and Examination | Assessing Cognition

🗣️ Speech and Language

• Language is produced primarily by the dominant cerebral hemisphere - usually the left hemisphere in right-handers, and the right in about half of left-handers.
• Because of this cortical lateralisation, language deficits (aphasia) are often accompanied by right-sided weakness, sensory loss, or hemianopia.
• Speech is a complex act requiring coordination between cortical, subcortical, brainstem, and peripheral motor structures.

🧠 Key Cortical Structures for Language

• Broca’s Area – inferior frontal lobe (below the motor strip); responsible for motor speech output.
• Wernicke’s Area – posterior temporal and neighbouring parietal lobes; comprehension of spoken and written language.
• Arcuate Fasciculus – white matter tract connecting Broca’s and Wernicke’s areas.
• Heschl’s Gyrus – primary auditory cortex receiving sound input.
• Right Hemisphere – contributes to prosody, tone, and emotional content of speech.

🔄 Language Processing

• Sounds are decoded in Wernicke’s area into meaningful words and sentences, linking closely to the limbic system for emotion and the frontal lobe for semantics.
• Broca’s area formulates speech motor patterns and coordinates oropharyngeal movement via motor cortex.
• The Arcuate fasciculus integrates comprehension and expression, enabling repetition and fluent language.
• Although complex, the functional pathways allow structured testing at the bedside.

🩺 Types of Dysphasia / Aphasia

• Aphasia (or Dysphasia) – general term for impaired language production or comprehension, usually from large left MCA infarcts involving frontal, temporal, and parietal regions.
• Expressive (Broca’s) Aphasia:
  • Speech – reduced output, non-fluent, agrammatical, hesitant.
  • Comprehension – relatively preserved.
  • Writing – usually equally affected.
  • Associated with right hemiparesis (due to proximity to motor strip).
• Receptive (Wernicke’s) Aphasia:
  • Fluent but meaningless speech, impaired comprehension, impaired naming, and reading/writing deficits.
  • Often with right superior quadrantanopia or hemianopia.
• Conduction Aphasia: Inability to repeat phrases (e.g., “No ifs, ands, or buts”) due to arcuate fasciculus lesion.
• Global Aphasia: Extensive perisylvian damage → both expressive and receptive deficits.
• Primary Progressive Aphasia: Gradual loss of language function seen in certain dementias (frontotemporal variants).

📖 Dyslexia and Dysgraphia

• Dyslexia: Impaired reading comprehension.
• Dysgraphia: Impaired ability to write or spell words.
• Usually due to dominant parietal lobe dysfunction, and commonly co-exist with aphasia.

🗯️ Speech Dyspraxia

• A disorder of motor planning - difficulty coordinating mouth and tongue movements to produce speech.
• Comprehension is preserved, distinguishing it from aphasia.
• Can follow right cortical strokes affecting premotor or supplementary motor regions.

🔊 Dysarthria and Dysphonia

• Impairment of articulation or phonation rather than language function.
• Ask patient to repeat: “British constitution” or “West Register Street.”
• Speech may be slurred, nasal, or weak due to oropharyngeal motor dysfunction.
• Can arise from brainstem, cerebellar, or peripheral neuromuscular disease.

🦷 Non-Neurological Causes of Dysarthria

• Oropharyngeal disease: poor dentition, ill-fitting dentures, infections, malignancy.
• Structural defects: cleft palate, trauma, bone or joint disease.
• Laryngeal pathology: cancer, infection, inflammation.
• Functional / psychogenic: whispering or variable speech without organic basis.

⚡ Neurological Causes of Dysarthria

• 🎯 Cerebellar (Scanning) Speech: Slurred, irregular rhythm; due to cerebellar lesions or drugs (alcohol, phenytoin toxicity).
• 🧠 UMN or LMN weakness: Stroke or space-occupying lesions affecting motor cortex, corticobulbar tracts, or cranial nerve nuclei.
• 👅 Bulbar Palsy: Nasal speech, fasciculating tongue, reduced jaw jerk. Causes: MND, polio, neuropathies.
• 🦆 Pseudobulbar Palsy: High-pitched “Donald Duck” speech, brisk jaw jerk, spastic tongue. Causes: bilateral corticobulbar lesions, MND.
• ⚡ Myasthenia Gravis: Fatigable dysarthria and dysphonia due to neuromuscular junction weakness.

🧩 Summary Table: Types of Speech Disturbance

📚 References

• Ropper & Samuels, Adams and Victor’s Principles of Neurology, 12th ed.
• Oxford Handbook of Clinical Examination and Practical Skills (2024).
• NICE Clinical Knowledge Summaries: Speech and Language Problems in Adults.
• British Aphasiology Society Guidelines (2022).