External Features of Telencephalon - CNS الجزء الرابع أناتومي الـ

Cerebral Hemisphere Poles

• Frontal pole is opposite the medial end of the supra-ciliary arch
• Temporal pole is located at the anterior end of the temporal lobe
• Occipital pole is opposite the external occipital protuberance

Cerebral Hemisphere Surfaces

• Lateral surface is related to the vault of the skull
• Medial surfaces are separated by the falx cerebri
• Inferior surface is formed by the orbital part (on the roof of the orbit) and the tentorial part (on the tentorium cerebelli)

Cerebral Hemisphere Lobes

• Each hemisphere is subdivided by the central and lateral sulci, as well as a line between the parieto-occipital sulcus and the pre-occipital notch
• Frontal lobe is anterior to the central sulcus and superior to the lateral sulcus
• Parietal lobe is posterior to the central sulcus, superior to the lateral sulcus, and anterior to the previous line
• Temporal lobe is inferior to the lateral sulcus, anterior to the lower 1/2 of the previous line
• Occipital lobe is posterior to the previous line

Lateral Surface Sulci

• Central sulcus is also known as the "fissure of Rolando"
• Pre-central sulcus is anterior to the central sulcus
• Post-central sulcus is posterior to the central sulcus
• Superior and Inferior frontal sulci extend transverse from the pre-central sulcus
• Intra-parietal sulcus extends from the post-central sulcus
• Lateral sulcus (fissure of Sylvius) is formed by a stem and three rami (anterior, ascending, and posterior)
• Superior and inferior temporal sulci run parallel and below the posterior ramus of the lateral sulcus
• Parieto-occipital and calcarine sulci extend from the medial surface
• Sulcus lunatus surrounds the end of the calcarine sulcus

Lateral Surface Gyri

• Frontal lobe contains the pre-central gyrus between the central and pre-central sulci
• Frontal lobe contains the superior frontal gyrus (above the superior frontal sulcus), middle frontal gyrus (between the superior and inferior frontal gyri),
• Frontal lobe contains the inferior frontal gyrus (below the inferior frontal sulcus), including the orbital (below anterior ramus), triangular (anterior & ascending rami), and opercular (behind ascending ramus) parts
• Temporal lobe contains the superior surface, above the superior temporal sulcus
• Temporal lobe contains the middle, between the superior and inferior temporal gyri
• Temporal lobe contains the inferior, below the inferior temporal gyrus
• Parietal lobe contains the post-central between the central and post-central sulci
• Parietal lobe contains the Superior temporal, above the intra-parietal sulcus
• Parietal lobe contains the Inferior temporal, below the intra-parietal sulcus, sub-divided into Supra-marginal: around the posterior end of the lateral sulcus, and Angular: around the posterior end of the superior temporal gyrus

Lateral Surface Cortical Areas (Frontal Lobe)

• Primary motor area (area 4) is located in the central sulcus and pre-central gyrus
• Primary motor area controls high-skilled movement and contralateral motor activity; body is represented upside down
• Lesion to primary motor area 4 results in contralateral hemiplegia
• Pre-motor area (area 6) is anterior to the primary motor area and controls gross movement and learned actions
• Lesion to pre-motor area 6 results in motor apraxia
• Frontal eye field area (area 8) is located in the middle frontal gyrus and controls horizontal gaze of both eyes to the opposite side
• Lesion to frontal eye field area 8 causes the eyes to deviate to the side of the lesion
• Personality center (areas 9, 10, 11, 12) is located in the frontal pole
• Personality center function for personality and behavior; lesion results in loss of personality
• Motor speech areas (Broca's area, areas 44 & 45) are located with area 45 in the triangular gyrus and area 44 in the opercular gyrus
• Motor speech function coordinates muscles of speech; lesion results in motor aphasia

Cortical Areas (Parietal Lobe)

• General sensory area (areas 3, 1, 2) is located in the central sulcus and post-central gyrus
• General sensory area perceives contralateral body sensations, with the body represented upside down; lesion results in contralateral hemianesthesia
• Somatic sensory association area (areas 5, 7, and 40) is located in the superior parietal gyrus (5 & 7) and supramarginal gyrus (area 40)
• Somatic sensory association area determines the side and formulates speech related to size, shape, and texture, which is connected to area 3,1,2; lesion results in side neglect and tactile agnosia (asteriognosis)
• Visual association area (area 39) is located in the angular gyrus; visual association area helps with the interpretations of what is read, lesion results in alexia, agraphia, and acalculia
• Primary gustatory area (area 43) are located in the lower part of the post-central gyrus whose stimulation results to with the differentiation of taste; lesion may cause taste hallucinations

Cortical Areas (Temporal Lobe and Speech)

• Primary auditory area (areas 41 & 42) is located in the superior temporal gyrus whose main function is the perception of sounds bilaterally
• Lesion to primary auditory area causes bilateral diminution of hearing mainly from the opposite side
• Auditory association area (Wernicke's area, area 22) is located in the posterior part of the superior temporal gyrus it's main function is the interpretation of what is heard
• Lesion to auditory association are, lesion triggers sensory aphasia and auditory agnosia
• Sensory speech connects to the motor speech area by arcuate fasciculus to answer written or spoken questions
• Lesion non-dominant hemisphere results in disturbed drawing and construction

Medial Surface Sulci

• Callosal sulcus is located above the corpus callosum
• Cingulate sulcus runs parallel to the callosal sulcus and is subdivided into marginal (upward, behind central sulcus) and sub-parietal (backward, towards calcarine) parts
• Calcarine sulcus runs from the splenium to the occipital lobe
• Parieto-occipital sulcus runs from the midpoint of the calcarine sulcus to the superior border 2 inches anterior to the occipital pole
• Collateral sulcus lies below the calcarine sulcus
• Rhineal sulcus is a curved sulcus at the anterior end of the collateral sulcus
• Occipito-temporal sulcus runs parallel to the collateral sulcus

Medial Surface Gyri

• Cingulate gyrus is located between the callosal and cingulate sulci
• Superior frontal gyrus is located between the cingulate and superior border
• Para-central lobule surrounds the upper end of the central sulcus
• Pre-cuneus is located between the marginal, sub-parietal, and parieto-occipital sulci
• Cuneus is located between the parieto-occipital and calcarine sulci
• Lingual gyrus is located below the calcarine sulcus
• Para-hippocampal gyrus is located medial to the collateral sulcus
• Uncus is located medial to the rhineal sulcus
• Occipito-temporal (Fusiform) gyrus is located between the collateral and occipito-temporal sulci
• Inferior temporal gyrus is located below the occipito-temporal sulcus

Medial Surface Cortical Areas

• Frontal lobe's primary motor area (area 4) is located at the anterior part of the para-central lobule
• Parietal lobe's general sensory area (area 3, 1, 2) is located at the posterior part of the para-central lobule
• Primary olfactory area, site uncus, function olfaction, Lesion: anosmia
• Olfactory association area (area 28), site anterior part of para-hippocumpus, interpreation of smell, Lesion: olfactory agnosia
• Face recognition area (area 37), site: posterior part of fusiform lobule, Recognition of faces, Lesion: prosopagnosia (face blindness)
• Primary visual area “area 17”, Site: calcarine sulcus, Function: light perception, Lesion: contralateral homonymous hemianopia with macular spare
• Visual association area “area 18 & 19”, site: cunueus & lingual gyri, function: collour perception & interpretation of what we see, Lesion: visual agnosia

Inferior Border Sulci and Gyri (Orbital Surface)

• Sulci include the olfactory sulcus (containing the olfactory tract and bulb) and the H-shaped orbital sulci
• Gyri include the rectus gyrus (medial to the olfactory sulcus) and the orbital gyri (anterior, posterior, medial, and lateral)

Inferior Border Sulci and Gyri (Tentorial Surface)

• Sulci include the collateral sulcus (from below the calcarine sulcus), the rhineal sulcus (curved at the anterior end of the collateral sulcus), and the occipito-temporal sulcus (parallel to the collateral sulcus)
• Gyri include the para-hippocampal gyrus (medial to the collateral sulcus), the uncus (medial to the rhineal sulcus), and the occipito-temporal (fusiform) gyrus (between the collateral and occipito-temporal sulci)

Speech Areas

• Sensory speech area contains area 40, which has a function of formulating speech related to size, shape, and texture of objects
• Lesion in the sensory speech area results in asteriognosis and unilateral neglect
• Sensory speech area also contains area 39 that functions for the interpretation of what is read whose lesion results in Alexia and Agraphia
• Area 22 function is for interpretation of what is heard whose lesion leads to Auditory agnosia & Sensory aphasia
• Motor speech area whose lesion of Broca's Area 44 & 45 will stop the coordination of muscles of speech; lesion in this are will result in motor aphasia
• Sensory speech area are connected to motor speech area by arcuate fasciculus to answer written or spoken question.
• A lesion in the non-dominant hemisphere leads to in disturbed drawing and construction