Association Areas

No neurological manifestations [Ref: Internet reference]

• Agenesis of corpus callosum is a rare birth defect (congenital disorder) in which there is complete or partial absence of corpus callosum.
• Corpus callosum is a band of tissue connecting the two hemispheres of the brain. Fibres of corpus callosum arise from the superficial layers of the cerebral cortex and they project to the homotypic regions of the contralateral cortex by passing through the corpus collosum while crossing the midline.

Clinical features of Agenesis of corpus callosum

• Signs and symptoms of agenesis of corpus callosum vary greatly among individuals.
• Patients usually do not have any neurological manifestations.
• However, some features common in agenesis of corpus callosum are:­- Vision impairment

– Low muscle tone (hypotonia)

Poor motor coordination

– Delay in motor milestones such as sitting and walking.

Low perception of pain

– Delayed toilet training

– Chewing and swallowing difficulties

– Early speech and language delays

Social difficulties

• Other characteristics sometimes associated with callosal disorders are:­- Seizures

– Spasticity

– Early_, feeding difficulties and or gastric reflux-.

– Hearing impairments

– Abnormal head and facial features

– Mental retardation

Investigation

• CT and MRI reveal “Bat wing” deformity of the ventricles.

Treatment

• There are currently no specific medical treatments for callosal disorders.

An important point

• The neurological abnormalities associated with corpus callosum are not caused by absence of corpus callosum per se.

– These conditions are believed to be caused due to associated cerebral anomalies rather than in corpus callosum per sc.

– The most common associated brain anomalies with absent corpus callosum are

– Dandy walker malformation

– lnterhenfispheric cyst with hydrocephalus

– Migrational disorder

– Absence of the inferior vertnis

– The children who had the best prognosis without any significant neurological sequale were those with isolated agenesis of corpus collosum.

– The children with the worst prognosis and neurological sequale were those with agenesis of corpus callosum and migrational disorder with or without Dandy — walker malformation.

– Hence prognosis is determined primarily by the underlying or associated malformation.

Immediately in front of the primary motor cortex lies Brodmann’s area 6. Area 6 extends onto the medial surface, where it becomes contiguous with area 24 in the cingulate gyrus, anterior and inferior to the paracentral lobule. A number of functional motor areas are contained within this cortical region. Lateral area 6, the area over most of the lateral surface of the hemisphere, corresponds to the premotor cortex. 

C i.e. Dyscalculia

–   Categorical (dominant) hemisphere (ie left lobe in most cases) is responsible for sequential – analytic processes such as language (understanding language, verbal memory, motor speech, written & spoken language) and mathematical ability. Therefore lesions of left (dominant) side produce aphasias (receptive & expressive), dyslexia and dyscalculia.

–  Representational (non dominant mostly right) hemisphere is responsible for visuo-spatial orientation & musical (art) awareness. Its lesion causes anosognosia and dysgraphia.

Cerebral Dominance or Complementary Specialization of Hemisphere

Answer is A (Posterior temporal and parietal lobes, dominant hemisphere):

Aphasias are disorders of understanding, thought and word finding and represent a lesion in the dominant (usually left) hemisphere. The patient in question represents a case of sensory / receptive Wernicke’s aphasia and hence a lesion in the temporal and parietal lobe of the dominant hemisphere.

Answer is D (Senseless, fluent speech):

Senseless fluent speech most closely suggests a diagnosis of Aphasia (Wernicke’s aphasia) which results from damage to the categorical or dominant hemisphere

Senseless, fluent speech suggests a diagnosis of ‘Wernicke ‘s ‘ Aphasia. Such disorders of speech represent a lesion is the categorical or dominant hemisphere

Answer is C (Dyscalculi)

Dyscalculi is a feature of categorical/dominant hemisphere involvement or left lobe involvement

Visuospatial defects, Anosognosia and Spatial dysgraphia are all features of non dominant / representative hemisphere involvement or right lobe involvement

Ans. D: Its the only area in the brain activated by visual stimuli

Ans. is ‘a’ i.e., 1, 2, 3

• Processing of general sensory inputs primarily occurs in primary somatosensory area of parietal lobe.
• Primary somatosensory area is Brodmann’s areas 3, 1, 2.