Imaging sectional anatomy of brain part 1

1. SECTIONAL ANATOMY OF BRAIN

2. HISTORY Roentgen – X rays CT ( computerized tomography)– Dr.Godfrey Newbold Hounsfield English electrical engineer 1972 – discovery 1979 – awarded the Nobel Prize for Physiology or Medicine The Godfrey Hounsfield Chair in Radiology

3. MRI (magnetic resonance imaging) Dr.Paul Lauterbur (American) Sir Peter Mansfield (British) The Nobel Prize in Physiology or Medicine in 2003

4. Walter Dandy (1918) - introduction of ventriculography . Arthur Schuller (1874-1957) Juan M. Taveras (1919-2002) – F ather of neuroradiology Father of neurology – Jean-Martin Charcot Father of neurosurgery - Harvey Cushing

5. Hounsfield units represent logarithmic scale of CT density. Pure water has an HU value of ‘0’. Current CT scans measure from – 1204 to + 3407. DESCRIPTION Approx. HU DENSITY Calcium > 1000 Hyperdense Acute blood 60-80 Hyperdense Grey matter 38 (32-42) Hyperdense White matter 30 (22-32) Hyperdense CSF 0-10 ISODENSE Fat -30 to - 100 Hypodense Air - 1000 Hypodense Patricio S Espinaso , FOCUS ON NEUROIMAGING – Volume 1 (2009)

6. FORAMINA DURAL ATTACHMENTS CEREBRAL HEMISPHERES VENTRICULAR SYSTEM CISTERNS DIENCEPHALON and LIMBIC SYSTEM BRAIN STEM COMISSURES OF BRAIN

7. FORAMINA Jugular foramen F. ovale (4) F. rotundum F. spinosum Carotid canal (5) F. magnum (7) F. lacerum (9) Hypoglossal canal (11) 11

8. A Foramen ovale B Foramen spinosum D Hypoglossal canal G Clivus H Carotid canal J Foramen magnum

9. DURAL ATTACHMENTS It forms folds separating the components of brain. Cranial dura – outer endosteal layer. inner periosteal layer. Falx cerebri sickle shaped & double layered. attachments – anterior : frontal bone – crista galli posterior : tentorium margins free margin lies above corpus callosum .

10. Tentorium cerebelli attached margins – clinoids and petrous apex. free margin is ‘U’ shaped. tent shaped. Diaphragma sella – circular dural fold which forms roof of sella turcica Falx cerebelli

11. On axial CT , structures medial to line of tentorial edge are infratentorial and those lateral are supratentorial .

12. CEREBRAL HEMISPHERES 4 lobes are present in each hemisphere. They are demarcated by fissures. Each lobe is again divided into gyri by sulci . They are named accordingly. Anatomy of cerebral hemispheres and mid brain – T1 W MRI. Internal grey - white matter areas – T2 W MRI. In Cerebral hemispheres , white matter above the level of lateral ventricles is called centrum semiovale

13. FISSURES Central sulcus Sylvian fissure Calcarine sulcus ( temporo -occipital fissure) Parieto -occipital fissure : Seen medially. Better seen on midline saggital MRI.

14. CENTRAL SULCUS ( Rolandic fissure) AXIAL : Tracing from superior frontal sulcus .

15. 2. Similarly interparietal sulcus intersects post central sulcus 3. Precentral : Post central gyral grey matter thickness = 1.5 :1 4. Peri rolandic cortex more hypo intense on FLAIR.

16. MEDIAL SAGGITAL : By tracing cingulate sulcus to its posterior limit , where it forms marginal sulcus .

17. LATERAL SAGGITAL Into Inferior frontal gyrus , sylvian fissure forms Y shaped sulcus . Behind it is precentral sulcus .

18. SYLVIAN FISSURE (lateral fissure) Begins on inferior surface and extends laterally b/w infr . frontal and supr. temporal lobe. Parts – Stem and 3 rami anterior ramus ascending ramus posterior ramus

19. Parieto -occipital sulcus

20. Calcarine sulcus

21. FRONTAL LOBE Anterior to central sulcus and supr. to sylvian fissure. Precentral gyrus Lateral surface – supr. frontal gyrus middle frontal gyrus infr . frontal gyrus Inferomedial – Gyrus rectus Inferolateral – Orbital gyri

22. Functional divisions of frontal lobe Motor area Pre motor area Supplementary motor area Frontal eye field Broca’s area PRE FRONTAL CORTEX - DLPFC – working memory executive functions - OFC – emotions - MPFC – auditory and visual ass.

23. PARIETAL LOBE Parieto -occipital differentiation. Parieto -temporal differentiation ?? Post central gyrus Superior parietal lobule Inferior parietal lobule

24. TEMPORAL LOBE Sylvian fissure and calcarine sulcus - borders Superior temporal gyrus - Heschl gyrus – floor of sylvian fissure & above supr. temporal gyrus . It is found on ‘ flat top’ surface of supr. temporal gyrus . Middle temporal gyrus Inferior temporal gyrus

25. INFERIOR SURFACE Temporal lobe Parahippocampal gyrus – terminates at temporal tip and curls backwards to form uncus . Lingual gyrus Fusiform gyrus Inferior temporal gyrus

26. Frontal lobe Gyrus rectus. Orbital gyri . Olfactory sulcus .

27. Line diagramn

28. MEDIAL SURFACE Cingulate gyrus – starts beneath genu of C.Callosum till splenium . Callosal sulcus Cingulate sulcus

29. Paracentral lobule – surrounds medial projection of central sulcus . Medial extention of motor and sensory cortex. - anterior - posterior Cuneus – b/w parietooccipital fissure and calcarine sulcus . Precuneus – b/w parietooccipital fissure and marginal sulcus .

30. INSULA A pyramidal shaped submerged cortex is known as insula . It is visualised when the opercula of lateral sulcus are retracted. Limen Circular sulcus Central sulcus Short and lond gyri

31. Apex of insula is limen , and is directed below and to front. Circular sulcus separates insula from different opercula. Central sulcus is placed obliquely and divides insula into antr . short gyri and postr . long gyrus

32. Insula figures

33. CSF SPACES Choroid plexus mainly in lateral ventricles and partly in 3 rd and 4 th ventricles. Choroid plexus within the atrium of lateral ventricle and occasionally in 4 th ventricle – ‘HYPO’ on CT and MRI. On CECT, there is homogenous enhancement of choroid plexus.

34. VENTRICULAR SYSTEM

35. Lateral ventricles – Telencephalon ( cerebral hemisheres ) 3 rd ventricle – Diencehalon Sylvian aqueduct – Mesencephalon (midbrain) 4 th ventricle – hind brain ( pons+medulla )

36. Saggital and Coronal T1 weighted MRI – accurate assessment of ventricles and C. callosum Mid Saggital section – for shape and configuration of Aqueduct of Sylvius . CSF intensity on MRI

37. Lateral ventricle Parts : Horns – Frontal, Occipital and Temporal. Body Trigone / Atrium Relations : supr. – C. callosum infr . – choroid plexus, thalamus and hippocampus lat – caudate nucleus med – S. pellucidum and fornix

38. Septum pellucidum : seperates lateral ventricles (FH and body). It is a midline triangular sheet attached above to C.callosum and postr.ly to fornix. It has 2 laminae with narrow cavity. ( cavum SP – due to seperation of 2 laminae . In 10% adults )

39. Radiology – Axial MRI / CT : frontal horns separated by S. pellucidum and posteriorly lateral ventricles diverge and pass into temporal and occipital horns. Saggital MRI : ‘C’ shaped , curving round the thalamus.

40. Radiology – Axial MRI / CT : frontal horns separated by S. pellucidum and posteriorly lateral ventricles diverge and pass into temporal and occipital horns. Saggital MRI : ‘C’ shaped , curving round the thalamus. Coronal : frontal horns – inverted triangle body – flattened temporal horns – like ‘C’ on its sides.

41. Foramen of Monro relations – antr . – fornix, S. pellucidum . postr . – choroid plexus , thalamus To differentiate frontal horn from body of LV. ‘ Y ’ shaped.

42. 3 RD VENTRICLE Anterior wall – anterior commisure lamina teminalis Posterior wall – suprapineal recess pineal body with pineal recess habenular comissure posterior comissure aqueduct of midbrain Roof - fornix choroid plexus Lateral wall - thalamus Floor – optic chiasma Infundibulum tuber cinereum mamillary bodies

43. Radiology – Axial MRI / CT - narrow cleft Saggital MRI – elongated and complex curved shape with upward, backward & downward arc.

44. Aqueduct of sylvius Relations – antr . , Postr . Communications Radiology – Saggital MRI: concavity that curves downward and forward towards the floor of 3 rd ventricle.

45. 4 TH VENTRICLE 4 angles - rostral , caudal , two lat. Relations - antr . postr . lateral inferior Communications supr. and infr . postero infr . postero lat.

46. Radiology Axial MRI / CT – ‘kidney bean’ turned on its side. Saggital MRI - mid point of line drawn b/w T. sella and trocula should intersect middle of 4 th ventricle. Coronal MRI – elongated rhomboid shape

47. CISTERNS Where brain and skull are not closely apposed, arachnoid and pia separate – and form cisterns . Mainly present at base of brain, around brain stem and free edge of tentorium . Posterior fossa cisterns Basal cisterns Mesencephalic cisterns Lateral superior cisterns

48. POSTEROR FOSSA CISTERNS Medullary cistern : antr . to medulla VA, spinal A, 12 th nerve Pontine cistern : b/w pons & clivus vertibrobasilar A, AICA & SCA origin, 6 th nerve Cisterna magna : b/w medulla & postroinfr . cerebellum PICA, 9 th 10 th 11 th cranial nerves (Triangular in saggital section)

49. 4 . Supr. cerebellar cistern : b/w tentorium & cerebellar H SCA, supr. vermian veins. CP angle cisterns : bounded by cerebellum, pons and tentorium . AICA, 5 th 7 th 8 th cranial nerves

50. SUPRASELLAR / BASAL CISTERNS 1 . Interpeduncular cistern : b/w Cerebral peduncles Basilar A, thalamoperf . A . Chiasmatic / Suprasellar cistern : above sella ICA, MCA & ACA origin, P comm. A, antr . Choroidal A; prox. basal V of Rosenthal; optic chiasma & tract; hypothalamus, infundibulum . (extends from infundibulum to postr . surface of frontal lobe and lies b/w uncus on either side. Contains circle of willis and so SAH seen)

51. MESENCEPHALIC CISTERNS Ambient cistern : surrounds mid brain. Connects Suprasellar , pontine & quadrigeminal cisterns. PCA, BA, SCA, 6 th cranial nerve . Quadrigeminal cistern : behind pineal & Q plate Connects ambient and supr. cerebellar cisterns. Pineal gland, postr 3 rd ventricle, V of Galen, V of Rosenthal. Velum interpositum : above 3 rd ventricle; below fornix & C.callosum ( antr . continuation of Quadrigeminal cistern) Internal cerebral V, Choroidal arteries .

52. LATERAL SUPERIOR CISTERNS Sylvian fissure : b/w insula & opercula. connects medially with suprasellar cistern MCA, supr. middle cerebral V. Convexity subarachnoid space contains cortical arteries and veins.

53. Line diagramn