Posterior Cranial Fossa with Cranial Nerves Relation

Posterior Cranial Fossa with Cranial Nerves Relation
By: Yousuf Tahir Ali

1. POSTERIOR FOSSA AND RELATED CRANIAL NERVES Yousuf Tahir Ali 4 th year MBBS Dow University of Health Sciences

2. Posterior Crania Fossa The posterior cranial fossa  is part of the  cranial cavity, located between the  foramen magnum  and  tentorium cerebelli . It contains the  brainstem  and  cerebellum. This is the most inferior of the  fossae . It houses the cerebellum, medulla and pons . Anteriorly it extends to the apex of the petrous temporal. Posteriorly it is enclosed by the occipital bone. Laterally portions of the squamous temporal and mastoid part of the temporal bone form its walls.

3. The posterior fossa is unique in that it receives 11/12 CNs with the exclusion of CN 1.

4. Cranial nerve exit via Skull Base

5. Parts of brain in the post fossa

6. Cranial nerves of the Brainstem

7. Cranial Nerve Nuclei

8. Arrangement of Nuclei The cranial nerve nuclei are located such that the efferent nuclei are located medially and are separated from the sensory nuclei, by the sulcus limitans , that lie laterally as may be seen in cross sectional views.

9. (SE) (SVE) (GVE) (GVA and SVA) (GSA) (SSA)

10. GENERAL TERMINOLOGIES

11. “ Somatic” refers to all the body areas especially body under voluntary control. “ Visceral ” refers to all the internal organs in the main cavities of the body e.g the intestines. “Special” refers to anything that dosen’t fit in all to the above two categories. E.g. semi-autonomous head and neck muscles( branchial arch derivatives).(EFFERENTS) Sense of balance and hearing are special senses

12. As a general rule, we have from medial to lateral, the arrangement of nuclei in the brain at all levels as; General Somatic efferent (GSE) Special visceral efferent ( SpVE ) General visceral efferent (GVE) Genreal visceral affarent (GVA) Special visceral affarent ( SpVA ) General sensory affarent (GSA) Special somatic affarent ( SpSA )

13. General Somatic efferent(GSE) For muscles derived from somitomeres (cells derived from paraxial mesoderm)

14. Special visceral efferent ( SpVE )/Nucleus ambiguous CNs IX, X and XI. Named as “nucleus ambiguous” due to its particular ambiguous(not clear or decided) position. Responsible for branchiomotor outflow(supplies muscles of the branchial (pharyngeal) arches which are semi-autonomous)i.e. semiautonomous head and neck muscles. The cell bodies for the preganglionic parasympathetic vagal neurons that innervate the heart reside in the nucleus ambiguous. Also branchial efferent motor fibers of the vagus nerve (CN X) terminating in the laryngeal and pharyngeal muscles, and musculus uvulae arise from this nucleus.

15. General visceral efferent (GVE) It comprises: Dorsal nucleus of the vagus (CN-X) Inf. Salivatory nucleus(CN-IX) Sup. Salivatory nucleus(CN-VII) Lacrimatory nucleus(CN-VII) Dorsal nucleus of the vagus (CN-X) serves parasympathetic vagal functions in the GIT, lungs, and other thoracic and abdominal  vagal innervations

16. TRACTUS SOLITARIUS[General Visceral Affarrent (GVA) + Special Visceral Affarent (SVA) It receives sensory( affarent ) fibers from CN-VII,IX and X.

17. Nucleus of TS(Some general features)

18. Genereal visceral affarent (GVA)(medial component of Tractus Solitarius ) CNs IX and X. Sensory information from the ear (Auricular branch of the vagus nerve(CN-X). Chemoreceptors and mechanoreceptors of the general visceral afferent pathway (GVA) in the  carotid body via glossopharyngeal nerve(CN-IX) , and aortic bodies, and the  atrial pacemaker, via the vagus nerve(CN-X) Chemically and mechanically sensitive neurons of the general visceral afferent pathway (GVA) with endings located in the heart, lungs, airways, gastrointestinal system, pharynx, and liver via the glossopharyngeal (CN-IX) and vagus nerves(CN-X). NOTE: Bodies serve chemoreception and sinus serves baroreception , but the aortic body serves both chemo and baroreception .

19. Special visceral affarent ( SpVA )(lateral component of Tractus Solitarius ) Taste is a special sense. CNs-VII, IX and X. Taste information from the facial nerve(CN-VII) (anterior 2/3 of the tongue), glossopharyngeal nerve(CN-IX) (posterior 1/3) and vagus nerve(CN-X) (small area on the epiglottis).

20. General sensory affarent (GSA) Comprises 2, receive GSA of Trigeminal nerve comprises: Mesencephalic nucleus: proprioception of the face Principal/ pontine nucleus: fine touch of face+conscious   proprioception of the jaw ( Conscious proprioception  is described as the ability to locate the different joints of our body consciously). Spinal nucleus: pain and temp. The spinal trigeminal nucleus is further subdivided into three parts, from rostral to caudal: Pars Oralis (from the Pons to the Hypoglossal nucleus) Pars Interpolaris (from the Hypoglossal nucleus to the obex ) Pars Caudalis (from the obex [the point in the human brain at which the fourth ventricle narrows to become the central canal of the spinal cord) to C2]. Decussation of sensory fibers occours at obex . The other GSA receives pain, touch and temp. from the entire body.

21. Obex

22. General sensory affarent (GSA) Comprises 2, ( i )Trigeminal and (ii)GSA from entire body GSA of Trigeminal nerve comprises: Mesencephalic nucleus: proprioception of the face Principal/ pontine nucleus: fine touch of face+conscious   proprioception of the jaw ( Conscious proprioception  is described as the ability to locate the different joints of our body consciously). Spinal nucleus: pain and temp. The spinal trigeminal nucleus is further subdivided into three parts, from rostral to caudal: Pars Oralis (from the Pons to the Hypoglossal nucleus) Pars Interpolaris (from the Hypoglossal nucleus to the obex ) Pars Caudalis (from the obex [the point in the human brain at which the fourth ventricle narrows to become the central canal of the spinal cord) to C2]. Decussation of sensory fibers occours at obex . The other GSA receives pain, touch and temp. from the entire body.

23. The sensory  trigeminal nerve nuclei  are the largest of the cranial  nerve nuclei , and extend through the whole of the midbrain, pons and medulla, and into the high cervical spinal cord.

24. Special somatic affarent ( SpSA ) This comprises: Vestibular nuclei(sup., lat., med. and inf.) Cochlear nuclei(dorsal and ventral) The vestibular nuclei lie lateral to TS and are concerned with the sense of balance. The dorsal and ventral cochlear nuclei are located dorsal and ventral to the inf. Cerebellar peduncle and are concerned with the sense of hearing.

25. As a general rule, we have from medial to lateral, the arrangement of nuclei in the brain at all levels as; General Somatic efferent (SE) Somatic visceral efferent (SVE) General visceral efferent (GVE) Genreal visceral affarent (GVA) Special visceral affarent (SVA) General sensory affarent (GSA) Special somatic affarent (SSA)

26. Lateral view of Brainstem

27. LATERAL VIEW OF BRAINSTEM AND NERVES EXITING IT

28. Lat. diagramatic view showing exit of CNs

29. 10 9 11 11 th cranial part 11 th spinal part 12 3 RD VENTRICLE MIDBRAIN PONS MEDIULLA INFERIOR CEREBELLAR PEDUNCLE LATERAL VIEW OF BRAINSTEM

30. Anterior view of Brainstem

31. ANTERIOR VIEW OF BRAINSTEM

32. CRANIAL NERVE III

33. 10 9 11 11 th cranial part 11 th spinal part 12 3 RD VENTRICLE MIDBRAIN PONS MEDIULLA INFERIOR CEREBELLAR PEDUNCLE LATERAL VIEW OF BRAINSTEM

34. LEVEL OF SUPERIOR COLLICULUS(MIDBRAIN)

35. CRANIAL NERVE IV

36. 10 9 11 11 th cranial part 11 th spinal part 12 3 RD VENTRICLE MIDBRAIN PONS MEDIULLA INFERIOR CEREBELLAR PEDUNCLE LATERAL VIEW OF BRAINSTEM

37. LEVEL OF INFERIOR COLLICULUS(MIDBRAIN)

38. CRANIAL NERVE V 1)SESNSORY NUCLEUS i ) mesencephalic ii)main sensory iii)spinal nucleus of trigeminal 2)MOTOR NUCLEUS

39. 10 9 11 11 th cranial part 11 th spinal part 12 3 RD VENTRICLE MIDBRAIN PONS MEDIULLA INFERIOR CEREBELLAR PEDUNCLE LATERAL VIEW OF BRAINSTEM

40. LEVEL OF TRIGEMINAL NUCLEUS (PONS)

41. CRANIAL NERVES VI, VII AND VIII

42. 10 9 11 11 th cranial part 11 th spinal part 12 3 RD VENTRICLE MIDBRAIN PONS MEDIULLA INFERIOR CEREBELLAR PEDUNCLE LATERAL VIEW OF BRAINSTEM

43. CRANIAL NERVE IX

44. 10 9 11 11 th cranial part 11 th spinal part 12 3 RD VENTRICLE MIDBRAIN PONS MEDIULLA INFERIOR CEREBELLAR PEDUNCLE LATERAL VIEW OF BRAINSTEM

45. CRANIAL NERVE X, XII

46. 10 9 11 11 th cranial part 11 th spinal part 12 3 RD VENTRICLE MIDBRAIN PONS MEDIULLA INFERIOR CEREBELLAR PEDUNCLE LATERAL VIEW OF BRAINSTEM

47. CRANIAL NERVE XI Two parts: 1. Cranial 2. Cervical

48. 10 9 11 11 th cranial part 11 th spinal part 12 3 RD VENTRICLE MIDBRAIN PONS MEDIULLA INFERIOR CEREBELLAR PEDUNCLE LATERAL VIEW OF BRAINSTEM

49. SPINAL ROOT OF ACCESSORY NERVE

50. THANKS!