Neuroanatomy MCQs with Answers – Part 1 (1-10)

Explanation:

• Brodmann’s area 6: Premotor area or supplemental motor area. Immediately anterior to motor strip, it plays a role in contralateral motor programming.
• Brodmann’s Areas 3, 1, 2: primary somatosensory cortex
• Brodmann’s. area 4: precentral gyrus, primary motor cortex (AKA “motor strip”). Large concentration of giant pyramidal cells of Betz
• Brodmann’s areas 41 & 42: primary auditory areas (transverse gyri of Heschl)

Explanation:

CEREBRAL CORTEX STRUCTURE

• Made up of six identifiable layers.
• In the motor cortex in the precentral gyrus, the second and fourth layers lack granular cells.
• Third and Fifth layers in the somesthetic cortex in the postcentral gyrus lack pyramidal cells.
• The motor cortex is thicker than the sensory cortex.

Topic : Introduction and Organization of the Nervous System| Neuroanatomy

Reference: Snell’s Anatomy 8^th Edition, Chapter 1

Explanation:

• The middle frontal gyrus (MFG) is usually more sinuous than the IFG or SFG, and it often connects to the pre-central gyrus via a thin isthmus.
• The central sulcus joins the Sylvian fissure in only 2% of cases (i.e., in 98% of cases there is a “subcentral” gyrus).
• The intraparietal sulcus (ips) separates the superior and inferior parietal lobules.
• The IPL is composed primarily of the AG and SMG.
• The Sylvian fissure terminates in the Superior Marginal Gyrus (Brodmann’s area 40). The superior temporal sulcus terminates in the Angular Gyrus.’

Reference: Greenberg 9^th Edition Chapter 1

Explanation:

• The middle frontal gyrus (MFG) is usually more sinuous than the IFG or SFG, and it often connects to the pre-central gyrus via a thin isthmus.
• The central sulcus joins the Sylvian fissure in only 2% of cases (i.e., in 98% of cases there is a “subcentral” gyrus).
• The intraparietal sulcus (ips) separates the superior and inferior parietal lobules.
• The IPL is composed primarily of the AG and SMG.
• The Sylvian fissure terminates in the Superior Marginal Gyrus (Brodmann’s area 40). The superior temporal sulcus terminates in the Angular Gyrus.’

Explanation:

• The middle frontal gyrus (MFG) is usually more sinuous than the IFG or SFG, and it often connects to the pre-central gyrus via a thin isthmus.
• The central sulcus joins the Sylvian fissure in only 2% of cases (i.e., in 98% of cases there is a “subcentral” gyrus).
• The intraparietal sulcus (ips) separates the superior and inferior parietal lobules.
• The IPL is composed primarily of the AG and SMG.
• The Sylvian fissure terminates in the Superior Marginal Gyrus (Brodmann’s area 40). The superior temporal sulcus terminates in the Angular Gyrus.’

Topic : Lateral Cortical Surface of Brain |Neuroanatomy

Reference: Greenberg 9^th Edition Chapter 1

AC-PC line

The “AC-PC line” connects the anterior commissure (AC) and the posterior commissure (PC) on a midline sagittal image. The AC is the horizontally positioned white matter tract that crosses in front of the fornix. The PC is the white-matter band at the level of the pineal that crosses at the posterior third ventricle. The AC-PC line is used in functional neurosurgery and is also used as the baseline for axial MRI scans (and for recent CT scanners). In the more entrenched Talairach definition, it passes through the superior edge of the AC and the inferior edge of the PC .

Alternative Schaltenbrand definition: a line passing through the midpoint of the AC & PC, allowing both AC & PC to be imaged on a single thin axial MRI slice. These definitions differ by 5.81° ± 1.07°.5

The orbitomeatal line (p.243) (used in older CT scanners) is ≈ 9° steeper than the Talairach AC-PC line.

The representation of the arm and face are draped over the convexity of the brain, while the foot and leg areas are located along the upper aspect of the medial surface. Areas with fine motor or sensory function (e.g. fingers, tongue) have a larger area of representation.

Reference: Greenberg 9^th Edition Chapter 1

Explanation:

Hand “knob”: The alpha motor neurons for hand function are located in the superior aspect of the precentral gyrus which appears as a knob-like protrusion (shaped like an inverted greek letter omega Ω) projecting posterolaterally into the central sulcus on axial imaging. On sagittal imaging it has a posteriorly projecting hook-like appearance and is even with the posterior limit of the Sylvian fissure

Reference: Greenberg 9^th Edition Chapter 1

Explanation:

Identification of the central sulcus is important to localize the motor strip. The central sulcus (CS) is visible on 93% of CTs and 100% of MRIs.

It curves posteriorly as it approaches the interhemispheric fissure (IHF), and often terminates in the paracentral lobule, just anterior to the pars marginalis (pM) within the pars bracket i.e., the CS often does not reach the midline.

Reference: Greenberg 9^th Edition Chapter 1

Explanation:

• Jacksonian epilepsy is due to irritative lesion of the primary motor area (area 4).
• Convulsion begins in the part of the body represented in the primary motor area that is being irritated.
• It proceeds in a predictable pattern from twitching or a tingling sensation or weakness in a finger, a big toe or the corner of the mouth, then marches over a few seconds to the entire hand, foot or facial muscles.

Reference: Snell’s Anatomy 8^th Edition, Chapter 1