Block 5 Neuro Atlas Ch 7 W Expl

The head of the caudate nucleus forms a prominent bulge in the lateral wall of the anterior horn of the lateral ventricle. In Huntington disease, this elevation disappears, and the wall of the ventricle may become concave laterally; the result being an enlarged anterior horn (hydrocephalus
ex vacuo). The body of the caudate is located in the lateral wall of the body ofthe lateral ventricle. The lenticular nucleus lies within the hemisphere and does not border on any ventricular space. The septum and fornix are located in the medial wall of the ventricle, and the pulvinar borders on the superior cistern. (p.164,166,169)

The mammillary body forms an obvious elevation onthe inferior aspect of the hemisphere rostral to the interpeduncular fossa/cistern; this small bulge is clearly evident in MRI.Theoptic chiasm and the basilar pons are both on the inferior aspect of the brain at the midline. The former is rostral to the infundibulum (and the mammillary body) and the latter is caudal to the interpeduncular fossa.The lamina terminalis forms the rostral end of the third ventricle and the anterior commissure is adjacent to the column of the fornix.(p.31,165,172)

The posterior limb of the internal capsule is located between the lenticular nucleus, which is lateral, and the thalamus,which is medial. This large fiber bundle contains thalamocortical projections related to motor and sensory function and descending corticospinal fibers.The anterior limb of the inter-nal capsule is located between the head of the caudate and the lenticular nucleus, and the retrolenticular limb is found caudal to the lenticular nucleus. The anterior commissure is in the ros-troventral portion of the hemisphere, and the extreme capsuleis immediately internal to the insular cortex. (p.166,168)

The amygdaloid nucleus is in the rostral wall of thetemporal horn of the lateral ventricle.In this position theamygdala is separated from the rostral tip of the hippocampus(the hippocampus occupies the medial and inferior wall of thetemporal horn) by a narrow space of the ventricle.The opticradiations are in the lateral wall of the temporal horn,but arequite caudal to its rostral tip.The other choices do not havedirect structural relationship to the rostral portions of the tem-poral horn.(p.172–173)

The substantia nigra is located internal to the cruscerebri and,in T1-weighted MRI,appears a darker shade of grey(hypointense) than does the crus.The red nucleus and the peri-aqueductal grey are located in the midbrain,but do not borderon the crus cerebri.The brachium of the inferior colliculus isfound on the lateral surface of the midbrain,and the pretectalarea is adjacent to the cerebral aqueduct at the midbrain–dien-cephalic junction.(p.167,170–172)

The medial and lateral geniculate nuclei are located inferior to the pulvinar, and form elevations on the surface of the dorsal thalamus; the medial geniculate is adjacent to thelateral edge of the crus cerebri. The subthalamic nucleus islocated internally, the mammillary nuclei (medial and lateral)are on the inferior aspect of the thalamus, and the uncus is on the medial portion on the temporal pole.The optic tract lies onthe surface of the crus cerebri, but it does not form a distinct elevation on the brain surface inferior to the pulvinar; rather, it has a structural relationship to the lateral geniculate nucleus.(p.168,170,173)

The column of the fornix, commonly called the postcommissural fornix, lies caudal to,and against, the anterior commissure as it arches around the interventricular foramen and anterior tubercle of the thalamus.
The precommissural fornix is a diffuse bundle of fibers rostral to the anteriorcommissure, and the mammillothalamic tract is located between the mammillary body and anterior nucleus of thethalamus.
The lamina terminalis and optic chiasm are inferiorto the anterior commissure.(p.165,166)

The anterior commissure is a mediolaterally oriented bundle of fibers that crosses the midline and extends laterally,immediately inferior to the basal nuclei.In sagittal section,or in a sagittal MRI, this bundle can be followed into planes of the hemisphere that include the most lateral portions of the thalamus and lenticular nucleus. The column of the fornix and optic chiasm are located immediately adjacent to the midline.The posterior commissure is located at the caudal aspect of the third ventricle and immediately superior to the opening of the cerebral aqueduct.The genu of the internal capsule is medial to the lenticular nucleus and rostrolateral to the anterior nucleus of the thalamus. (p.165,167,168,170)

The optic radiations are located in the lateral wall ofthe atrium of the lateral ventricle,represent projections from thelateral geniculate nucleus to the calcarine cortex,pass through the retrolenticular limb of the internal capsule,and are separated from the ventricular space by a thin layer of fibers called thetapetum.
The pulvinar and splenium are located rostromedial and medial, respectively, to the atrium.Corticonuclear and corticospinal fibers are found in the genu,and the posterior limb ofthe internal capsule within the hemisphere.(p.164,166)

The ventral anterior nucleus is located in the rostralportions of the thalamus,is in the territory of the thalamoper-forating artery,and projects to large regions of the frontal lobe.An occlusion of the vessels serving this portion of the thalamusmay result in a decreased level of alertness.The other choicesare in caudal regions of the thalamus,are not in the territoryserved by the thalamoperforating artery,and,with the excep-tion of the centromedian nucleus,do not relate to the cortex ofthe frontal lobe.(p.167,169)

The centromedian nucleus is found within the inter-nal medullary lamina in a position just rostral to the pulvinar.The ventral anterior and ventral lateral nuclei are lateral to theinternal medullary lamina,the dorsomedial nucleus is medialto this lamina,and the pulvinar is the large nucleus formingthe caudal part of the dorsal thalamus.(p.164,166)

The interventricular foramen is the space formed between the column of the fornix (located somewhat rostrome-dially) and the anterior nucleus of the thalamus (located some-what caudolaterally).The anterior nucleus is located internal to the anterior tubercle of the thalamus.The head of the caudate is found in the lateral wall of the anterior horn of the lateral ventricle,and the posterior limb is located in the hemi-sphere between the thalamus and lenticular nucleus.The lamina terminalis extends from the anterior commissure inferiority to the upper edge of the optic chiasm.The habenula is a small elevation in the caudal and medial wall of the third ven-tricle.(p.164,166)