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Medicine

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Neurology

Question
4 out of 6
 

Lesion in inferior frontal gyrus causes: (AIIMS Nov 10)



A Defect in articulation

B Incomprehension of written language

C Incomprehension of spoken language

D Motor aphasia

Fig: Mechanisms of speech and language.


Ans. D

Motor aphasia

Anatomy & Physiology

Broca’s area = Lies in dominant inferior frontal gyrus Q. It is motor speech area.

Wernicke’s area = Lies in dominant posterior part of temporal lobe Q. It is sensory speech area.

Arcuate fibers = They connect the two speech areas.

Physiology of speech:

Spoken words à ears à auditory area in temporal lobe via 8th nerve à Wernicke’s area where speech is understood à Message go to Broca’s area via Arcuate fiber à Broca’s area is a motor speech area which gives command to vocal cord and lip area in the motor cortex à speech is spoken.

Diseases:

1. Damage to primary auditory cortex at one side will lead to

2. Broca’s area involvement = motor aphasia (Verbal comprehension impaired) – Speech out flow and fluency is lost. There is no neologism but repetition may be lost.

3. Wernicke’s area involvement – Speech understanding is lost. There by patient speaks senselessly but repetition may be lost.

Table: Characteristics of dysphasia (H-18th Table 26.1 Pg- 203)

Site

Output

Fluency

Comprehension

Repetition

Anterior (Broca)

Reduced

Poor

Retained

Variable

Posterior (Wernicke)

Normal / Increased

Good

Impaired

Variable

Arcuate fasciculus conduction)

Variable

Variable

Variable

Impaired

Fronto – parietal (global)

Very reduced

Poor

Impaired

Impaired


Extra Edge:
Nominal aphasia is seen in metabolic encephalopathy. It is also an early feature of Alzheimer disease. Q

Broca’s aphasia

Wernicke’s aphasia

Lesion site

• Lesion in Broca's area (inferior frontal gyrus)

· Lesion lies in Wernicke's area (supramarginal gyrus) of the parietal lobe and upper part of temporal lobe

Cause

• Lesion is due to occlusion of superior br. of middle cerebral art.

· Lesion is due to occlusion of inferior division of middle cerebral artery.

Comprehension

• Comprehension is preserved (except grammar)

· Comprehension is impaired

Fluency

• Decreased: speech is not fluent, laboured, dysarthric, and interrupted with many word finding pauses. It is telegraphic but informative.

· Preserved or increased: Speech fluent but is highly paraphasic and associated with neologisms (Jagron Aphasia)

Naming

• Impaired

· Impaired

Repetition

• Impaired

· Impaired

Neologism

• Absent

· Present

Insight

• Insight into condition is preserved

· Not preserved