PONS – CN V, VII

DR TATHEER ZAHRA

ASSISTANT PROFESSOR ANATOMY

GROSS APPEARANCE

ANTERIOR VIEW

POSTERIOR VIEW

INTERNAL STRUCTURE

SCHEMATIC DIAGRAM OF THE PONS SHOWING ITS MAJOR DIVISIONS INTO TEGMENTUM AND BASIS PONTIS, AND TYPES OF FIBER BUNDLES

TRAVERSING THE BASIS PONTIS.

SCHEMATIC DIAGRAM OF THE PONS SHOWING THE MAJOR TRACTS TRAVERSING THE TEGMENTUM

LEVELS OF STUDY

T.S. THROUGH THE CAUDAL PART (FACIAL COLLICULUS)

T.S. THROUGH THE CRANIAL PART (TRIGEMINAL NUCLEI)

NUCLEI OF CRANIAL NERVES IN PONS

TRIGEMINAL NERVE

COMPOSITE SCHEMATIC DIAGRAM OF THE AFFERENT AND EFFERENT ROOTS OF THE

TRIGEMINAL NERVE (CRANIAL NERVE V) AND THEIR NUCLEI

CORNEAL REFLEX

TRIGEMINAL NEURALGIA

FACIAL NERVE

DISTRIBUTION

SCHEMATIC DIAGRAM SHOWING THE NUCLEI OF ORIGIN, COURSE, AND AREAS OF SUPPLY OF THE FACIAL NERVE (CRANIAL NERVE VII)

SCHEMATIC DIAGRAM SHOWING LESIONS IN THE FACIAL NERVE AT DIFFERENT SITES AND THE RESULTING CLINICAL MANIFESTATIONS

OF EACH

UMN LESION LMN LESION

LMN LESION (BELL PALSY)

TUMORS OF THE PONS

ASTROCYTOMA

PONTINE HEMORRHAGE/ INFARCTION

Site of a lesion in the basal pons involving corticospinal and other descending motor fibers and

fibers of the abducent nerve. This lesion results in “RAYMOND'S SYNDROME”. This lesion spares the

abducent nucleus and the nucleus and axons of the facial nerve.

Site of a lesion in the caudal part of the pons involving descending motor fibers and the axons and

nucleus of the facial nerve but sparing the nucleus and axons of the abducent nerve. This lesion results

in the “MILLARD-GÜBLER SYNDROME”.

Site of a lesion causing “FOVILLE'S SYNDROME”. Involvement of the abducent nucleus causes paralysis of

the contralateral medial rectus in addition to the ipsilateral lateral rectus muscle. The motor nucleus and

axons of the facial nerve are also destroyed, and the lesion extends ventrally to cause partial damage to corticospinal

and other descending motor tracts.

1. The following statements concern the pons:

(a) It is related superiorly to the dorsum sellae of the sphenoid bone.

(b) It lies in the middle cranial fossa.

(c) Glial tumors of the pons are rare.

(d) The corticopontine fibers terminate in the pontine nuclei.

(e) The pons receives its blood supply from the internal carotid artery.

2. The following statements concern the pons:

(a) The trigeminal nerve emerges on the lateral aspect of the pons.

(b) The glossopharyngeal nerve emerges on the anterior aspect of the brainstem in the groove between the pons and the medulla oblongata.

(c) The basilar artery lies in a centrally placed groove on the anterior aspect of the pons.

(d) Many nerve fibers present on the posterior aspect of the pons converge laterally to form the middle cerebellar peduncle.

(e) The pons forms the lower half of the floor of the fourth ventricle.

3. The following statements concern the posterior surface of the pons:

(a) Lateral to the median sulcus is an elongated swelling called the lateral eminence.

(b) The facial colliculus is produced by the root of the facial nerve winding around the nucleus of the abducent nerve.

(c) The floor of the inferior part of the sulcus limitans is pigmented and is called the substantia ferruginea.

(d) The vestibular area lies medial to the sulcus limitans.

(e) The cerebellum lies anterior to the pons.

4. The following statements concern a transverse section through the caudal part of the pons:

(a) The pontine nuclei lie between the transverse pontine fibers.

(b) The vestibular nuclei lie medial to the abducent nucleus.

(c) The trapezoid body is made up of fibers derived from the facial nerve nuclei.

(d) The tegmentum is the part of the pons lying anterior to the trapezoid body.

(e) The medial longitudinal fasciculus lies above the floor of the fourth ventricle on either side of the midline.

5. The following statements concern a transverse section through the cranial part of the pons:

(a) The motor nucleus of the trigeminal nerve lies lateral to the main sensory nucleus in the tegmentum.

(b) The medial lemniscus has rotated so that its long axis lies vertically.

(c) Bundles of corticospinal fibers lie among the transverse pontine fibers.

(d) The medial longitudinal fasciculus joins the thalamus to the spinal nucleus of the trigeminal N.

(e) The motor root of the trigeminal nerve is much larger than the sensory root.