Posterior Cranial Fossa with Cranial Nerves Relation

POSTERIOR FOSSA
AND RELATED
CRANIAL NERVES
YousufTahir Ali
4th year MBBS
Dow University of Health Sciences

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.

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

Cranial nerve exit via Skull Base

Parts of brain in the post fossa

Cranial nerves of the Brainstem

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.

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

■ “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.
1. semi-autonomous head and neck muscles(branchial arch
derivatives).(EFFERENTS)
2. Sense of balance and hearing are special senses

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

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

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.

General visceral efferent (GVE)
■ It comprises:
1. Dorsal nucleus of the vagus(CN-X)
2. Inf. Salivatory nucleus(CN-IX)
3. Sup. Salivatory nucleus(CN-VII)
4. 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

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

Nucleus ofTS(Some general features)

Genereal visceral affarent
(GVA)(medial component ofTractus
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.

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).

General sensory affarent (GSA)
■ Comprises 2, receive
■ GSA of Trigeminal nerve comprises:
1. Mesencephalic nucleus: proprioception of the face
2. 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).
3. 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.

General sensory affarent (GSA)
■ Comprises 2, (i)Trigeminal and (ii)GSA from entire body
■ GSA ofTrigeminal nerve comprises:
1. Mesencephalic nucleus: proprioception of the face
2. 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).
3. 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.

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.

Special somatic affarent (SpSA)
■ This comprises:
1. Vestibular nuclei(sup., lat., med. and inf.)
2. Cochlear nuclei(dorsal and ventral)
■ The vestibular nuclei lie lateral toTS 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.

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

LATERAL VIEW OF BRAINSTEM AND NERVES
EXITING IT

Lat. diagramatic view showing exit of
CNs

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

LEVEL OF SUPERIOR
COLLICULUS(MIDBRAIN)

LEVEL OF INFERIOR COLLICULUS(MIDBRAIN)

CRANIAL NERVEV
1)SESNSORY NUCLEUS
i) mesencephalic
ii)main sensory
iii)spinal nucleus of trigeminal
2)MOTOR NUCLEUS

LEVEL OFTRIGEMINAL NUCLEUS (PONS)

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

SPINAL ROOT OF ACCESSORY NERVE

Posterior Cranial Fossa with Cranial Nerves Relation

Posterior Cranial Fossa with Cranial Nerves Relation

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