PITUTARY• In cases of visual failure / endocrine abnormality.• At the level of optic nerve.• Situated in pituitary fossa – above the sphenoid sinus, with cavernous sinus on each side.• Superiorly suprasellar cistern is present.• < 8 - 9mm height.• Infundibulum is large in females• Normal pituitary enhance with contrast on CT / MRI.
• Antr. Adenohypophysis – dovelops from ratke’s pouch• Postr. neurohypophysis, infundibulum – dovelops from downgrowth of neuroectoderm
Tuber cinareum is the lamina of grey matter – b/w mammillary bodyand optic chiasma.
CORONAL T 1 images with thin (3 mm) sections• Anterior lobe is ISOINTENSE on T1 and T2• Posterior lobe is HYPERINTENSE on T1 and HYPO on T2.• Infundibulum is HYPERINTENSE on FLAIR.• Rim of hypointensity – cortical bone of dorsum sella• Hyperintense marrow of clivus postr. to it.
• Diencephalon is divided into two halves by 3rd ventricle.• Each diencephalon has dorsal and ventral parts, demarcated by ‘hypothalamic sulcus’. dorsal – thalamus, epithalamus ventral – hypothalamus, subthalamus RadioGraphics 2007; 27:1087–1108
THALAMUS• Ovoid mass of grey matter• Poles – antr. : postr. boundary of IV foramen. postr. (PULVINAR) : projects beyond 3rd V , lies just above and lateral to colliculi.
• Upper surface – dorsolaterally thalamostriate V and S.terminalis. part of floor of 3rd ventricle.• Inferior surface - continues with tegmentum of mid brain• Medially – 3rd ventricle• Laterally – lentiform N, separated by internal capsule.Two thalami are apposed medially by massa intermedia.
EPITHALAMUS1. Pineal body2. Habenular N3. Habenular comissure4. Posterior comissure PINEAL BODY : balloon shaped – projects backwards below the splenium of corpus callosum and rests over supr. colliculi. HABENULAR NUCLEI : situated in habenular trigone. COMISSURES - habenular and posterior .
1, Pineal gland.2, Habenula.3, Third ventricle.4, Pulvinar.5, Lateral ventricle
HYPOTHALAMUS• Most ventral part of diencephalon , and it forms floor and wall of antr. 1/3rd of 3rd V.• Extent : lamina terminalis to mammillary bodies• Relations : dorsally – hypothalamic sulcus ventral – floor of 3rd ventricle. It constitutes mamillary bodies, infundibulum, optic chiasma. medial – 3rd ventricle lateral – internal capsule and subthalamus Tuber cinerium extends posteriorly from infundibulum to mamillary bodies
MAMMILLARY BODIES• These are one of the nuclear masses of hypothalamus.• Each contains – medial, lateral and intercalated nuclei.• Receive fibres from fornix and efferents to antr. thalamus.• Postr. to mammillary bodies, lies postr. perforated substance.
BASAL GANGLIA• Corpus Striatum = Caudate N + Lentiform N (P + GP) .• Amygdala – tail of caudate N comes in contact with amygdala , but without any structural or functional connections• Claustrum – thin strip of grey matter b/w putamen and insula
CAUDATE NUCLEUS ‘C’ shaped with concavity facing inferiorly.• Head – indents the frontal horn. (shape same in axial and coronal cuts)• Body – starts from IV foramen and is seen along side of lateral ventricle.• Tail – lies above temporal horn ; continues with amygdala.
• Lentiform N – supr. – C. radiata and C. callosum. infr. – antr. perforated substance and antr. comissure.• Internal capsule – ‘boomrang’ shaped thick white matter.
LIMBIC SYSTEM1. Olfactory pathway2. Pyriform lobe3. Limbic lobe4. Amygdala5. Hippocampal complex6. Parts of hypothalamus and thalamus
INDUSIUM GRISEUM : vestigial• thin sheet of grey matter covering outer convex surface of corpus callosum.• Contains medial and lateral longitudinal striae.• Antr.ly it continue as paraterminal gyrus. Postr.ly continues as dentate gyrus.
• On coronal cuts, it is seen as rolled structure containing Ammon’s horn and dentate gyrus. Ammon’s horn continues with the PHG and is convex laterally.
• Relations : above and lateral to it – temporal horn of lateral V. (above temporal horn is tail of caudate N , and supr. to it is amygdyla).• PHG – is present on medial aspect of temporal lobe antr.ly it continue as uncus
AMYGDALA• Present at roof of infr. horn of lateral ventricle , close to its tip.• Continues behind with tail of caudate N.• Stria terminalis starts from it.
FORNIX• Sole efferent fibres from fornix• Begin from hippocampus as alveus and fimbriae.• Parts – - crura - body - columns - comissure
• On reaching splenium, fimbriae divide into – dorsal fornix – continue as inducium gracium. ventral fornix – fornix proper.• Upper surface of body is related to SP. At level of IV foramen, apex divides into two columns.
MRI of the brain, T1-weighted sagittal cut. 1, Column of fornix. 2, Corpus callosum. 3, Midbrain. 4, Pons. 5, Cerebellum
1, Column of fornix. 2, Corpus callosum. 1, Column of fornix. 2, Lentiform nucleus.3, Caudatus nucleus. 4, Hippocampus 3, Corpus callosum. 4, Crus of fornix.
MID BRAIN• Dorsal tectum : 4 colliculi = corpora quadrigemina• Ventral cerebral peduncles : ventral crus cerebri – CST dorsal tegmentum – cranial N nuclei . Both are seperated by substantia nigra. (triangular space between two peduncles is Interpeduncular cistern)
• Red nucleus : dorsomedial to S.nigra. It is present at the level of supr. colliculus .• Both red nucleus and S. nigra are hypointense on T2 W MRI. (both cannot be seen on CT)• Lower midbrain – laterally ambient cistern and posteriorly quadrigeminal cistern.(Interpeduncular fossa is limited antr.lyby mamillary bodies)
HIND BRAIN Pons , medulla and cerebellum PONS• Axial cuts of lower pons has posterolaterally directed middle cerebellar peduncles – lateral to which are CP angle cisterns.• Supr. cerebellar peduncles – at the level of mid pons.
MEDULLA• 3 cm length.• Ventral - pyramids (b/w median fissure & anterolat. sulcus). Lateral to it are olives.• Dorsal – fasciculus gracilis (M) & cuneatus (L).• On axial CT / MRI – pear shaped (lower pons) ; square shaped on cephalad cuts , at the level of F of magendie .
Pontomedullary junction Prominent pontomedullary sulcus on each lateral wall and ventral fissure is replaced by BROADER basilar sulcus.
CEREBELLUM• Cerebellar cortical ridges = Folia• On section cerebellum has a tree like config , so known as ‘Arbor vitae’.
• Cerebellum – vermis and 2 lobes – divided by para median sulci.• Deep transverse fissures divide cerebellum into 3 lobes (on SAGGITAL MRI) : Antr. – lingula, central lobule, culmen Postr. – declive, folium, tuber, pyramid, uvula. Nodule – flocconodular lobe• Nodule is the most ventral part seen on axial scans lying postrior to 4th ventricle.
From the level ofponto medullaryjunction, occipitallobe is seen in axialcuts
• Three cerebellar peduncles are present superior CP – mid brain (brachium conjunctivum) middle CP – pons (brachium pontis) inferior CP – medulla (restiform body).
COMISSURES OF BRAINWhite matter tracts that cross the midline, connecting thetwo cerebral hemispheres.1. Corpus callosum2. Anterior commissure3. Habenular commissure4. Posterior commissure5. Supraoptic commissures : Guddens commissure Meynerts commissure
Corpus callosum• Parts – rostrum, genu, body, and splenium.• Forceps minor (frontal) and major (occipital).• In Saggital sections , it is curved in shape.
Anterior comissure• Myelinated fibers at antr. limit of diencephalon (lamina terminalis)• On MRI , seen as convex arc of fibers – useful to locate perivascular spaces along its lateral aspect.• Line joining AC--PC is used as standard reference in stereotactic surgery.