The cerebellopontine angle is a triangular area located between the cerebellum, pons, and petrous ridge. It contains several cranial nerves including the 5th, 7th, and 8th nerves. Lesions in this area often damage the 7th and 8th nerves, causing symptoms like hearing loss, tinnitus, and facial weakness. A clinical exam assessing the function of these nerves can help localize pathologies in the cerebellopontine angle.

1. The Cerebello Pontine Angle
dr himanshu soni

2. the cerebellopontine angle
• it is a shallow triangle lying
between the cerebellum, the
lateral pone and the inner third
of the petrous ridge.
• the vertical extent of the angle is
from
– fifth nerve - above, on its course
from pons to the petrous apex
– ninth nerve - below, passing from
the lateral medulla to the jugular
foramen
– the abducent nerve - runs
upwards and forwards on the
medial edge of the area
– and the seventh & eighth nerves -
traversing the angle to enter the
internal auditory canal

3. • the hallmark of a lesion in this area
– clinical evidence of damage to the seventh and
eighth nerves
• wide range of vestibular, auditory and motor
abnormalities occur.
• clinical history and examination
– gives most clues to the diverse pathologies in the
region
• important to know the anatomy of the nerves
for the presentation
• should be able to test the nerves bedside

4. the trigeminal nerve
• it is the largest cranial nerve
• conveys sensation from the
face
• motor supply to the
muscles of mastication
• arises from the middle of
the pons, passes forwards
in the subarachnoid space
to its large ganglion
• lying on the tip of petrous
bone in Meckel's cave.
• three divisions

5. the ophthalmic nerve (V1)
• lies below the sixth nerve in
the lateral wall of the
cavernous sinus
• liable to damage by similar
pathology
• sensory to - forehead, nose,
scalp upto the vertex
• divides into three branches
as it enters the superior
orbital fissure
– lacrimal nerve
– frontal nerve
– nasociliary nerve

7. • LACRIMAL NERVE
– runs along the lateral
rectus to the lacrimal gland
– supplies the skin over the
lateral eyelid and the brow
– picks secretomotor fibres
from the
zyomaticotemporal nerve
and conveys to the lacrimal
gland
– receives proprioceptive
filaments from the facial
nerve

8. • FRONTAL NERVE
– divides into two branches
soon upon entering the
orbit
– supratrochlear &
supraorbital nerves -
supply the skin of the
forehead and scalp to the
vertex
– liable to damage by
minor injuries over the
brow

9. • NASOCILIARY NERVE
– main trunk traverses the orbit, enters
the anterior ethmoidal foramen into
the cranium, exits through the
cribirorm plate, enters the nose -
supplies the mucosa of the nasal
cavity and emerges at the lower end
of the nasal bone to supply the skin
over the nose tip, ala and vestibule
– in the orbit - gives branches to the
ciliary ganglion and two or three
LONG CILIARY NERVES , which carry
symphathetic pupillodilator fibres
and convey sensations from the
cornea
– infratrothlear branch - just behind
the anterior ethmoid foramen, lies
on the medial orbit wall - supplies
the skin over upper medial eyelid
and upper side of the nose

10. the maxillary nerve (V2)
• lies in the extreme lower lateral wall of the
cavernous sinus, exits through the foramen
rotundum
• it traverses the PTERYGOPALATINE GANGLION and
enters the floor of the orbit through the inferior
orbital fissure.
• first lies in the groove in the orbital floor, then
enters a short canal, then onto the face through the
infraorbital foramen.
• supplies - skin of the cheek, mid lateral nose, lateral
ala, lower eyelid, mucus membranes of the cheek
and upper lip

11. • MENINGEAL BRANCHES to the
floor of the middle cranial fossa
• two branches to the
SPHENOPALATINE GANGLION -
conveying secretomotor fibres
for the lacrimal gland
• ZYGOMATIC NERVE - floor of the
orbit, divides into
ZYGOMATICOTEMPORAL
(secretomotor of the lacrimal
gland & cutaneous to the
temporal area) &
ZYGOMATICOFACIAL (cutaneous
to the cheek, after piercing the
zygoma) nerves

12. the mandibular nerve (V3)
• largest branch of the fifth nerve,
includes motor component of the
nerve
• leaves through foramen ovale, the
main sensory trunk is joined by the
motor trunk just outside the skull
• MENINGEAL BRANCH reenters the
skull with middle meningeal artery
through the foramen spinosum and
supplies the lateral, middle and
anterior cranial fossa
• NERVE TO THE MEDIAL PTERYGOID,
supplies the medial pterygoid, tensor
tympani and tensor veli palatini
• then the main trunk divides into
anterior and posterior trunks

13. • the anterior trunk
– motor supply to the masseter,
temporalis and the lateral pterygoid
– BUCCAL nerve - merges with the facial
nerve branches to supply the skin over
the buccinator, mucosa of the cheek
and posterior part of the gum
• the posterior trunk gives
– AURICULOTEMPORAL NERVE - passes
behind the TM joint, joins facial nerve,
conveys the secretomotor branches to
parotid gland and fibres derived form
the tympanic branch of the
glossopharyngeal nerve from the otic
ganglion

14. – the LINGUAL nerve - sensation to
the presulcal tongue, floor of the
mouth and lower gums.
– it conveys taste fibres of the
chorda tympani to the mucosa of
the tongue.
– conveys secretomotor fibres from
the submandibular ganglion to the
sublingual and anterior lingual
glands.
– it communicates with the
hypoglossal nerve.
– INFERIOR ALVEOLAR NERVE -
enters the mandibular canal,
emerges through mental foramen,
gives off incisive and mental
branches

15. • motor component leaves the inferior alveolar
nerve, just before it enters the mandible as the
mylohyoid nerve supplying the mylohyoid and
anterio belly of digastric.

16. CLINICAL EVALUATION
• symptoms
– spontaneous pain in the face
– area of painless numbness over
the face
– extremely ominous sign
indicating malignant infiltration
of the nerve
– weakness of the muscles of
mastication - if unilateral, rarely
produces significant disabillity
• testing
– sensations over the face
– jaw closure & wasting of the
masseter and temporalis
muscle

17. • jaw opening - much weaker movement. if the
muscle on the right is weak, the jaw will be
pushed to the right side

18. THE CORNEAL REFLEX
• most sensitive component of
the fifth nerve
• earliest sign of the fifth nerve
damage
• if numbness of the entire face is
found with intact corneal reflex,
organicity of the lesion is
doubtful.
• a wisp of cotton wool, twisted
to a point, should be tested.
• test the cornea, do not cross
the pupil, donor stroke the
bulbar conjunctiva.
• both eyes will blink.
• if the eyes dont blink, ask if the
patient felt the stimulus.

19. corneal response in presence of
paralysis of lid closure
• in LMN facial lesion, lid closure is affected
• tested in following ways
– patient is asked to compare sensation on both the sides
– observe whether eyeball rolls upward and away from
stimulus ( Bell's phenomena)
– the other eye shuts simultaneously
• if the reflex is impaired, suitable protection should be
arranged immediately either by
– eye patch as a short term measure
– tarsorrhaphy as a longer term measure
– deliberate paralysis of lid by botulinum in presence of
corneal ulceration

20. FACIAL NERVE
• motor for facial
muscles
• taste fibres from the
anterior two thirds of
the tongue in the
chorda tympani and
from the palate in the
nerve of the pterygoid
canal
• cutaneous supply to
the external ear via
vagus

21. • NERVUS INTERMEDIUS -
carries the above sensation,
runs with the eighth nerve in
the subrachnoid space,
• cell bodies lie in the geniculate
ganglion,
• also carries parasympathetic
secretomotor fibres to the
submandibular and sublingual
salivary glands.
• they originate in the superior
salivatory nucleus

22. branches of seventh nerve
• GREATER PETROSAL NERVE -
arises from the geniculate
ganglion
• carries taste fibres from palate
• conveys preganglionic
parasympathetic fibres to the
pterygopalatine ganglion and
via the zygomaticotemporal
and lacrimal nerves to the
lacrimal gland
• joined by the deep petrosal
nerve to form the nerve of the
pterygoid canal

23. • a branch joins the LESSER PETROSAL NERVE and
carried to the otic ganglion
• it conveys secretomotor fibres int eh
auriculotemporal nerve to the parotid gland
• also carries sympatetic fibres derived from the
carotid artery to the blood vessels of the gland

24. • nerve to STAPEDIUS arises 6
mm above the stylomastoid
foramen.
• CHORDA TYMPANI arises at
the same level and runs
forward across the middle
ear to enter the canal in the
petrotympanic fissure, joins
the lingual branch of fifth
nerve, distributed to the
presulcal tongue
• at the stylomastoid
foramen, twigs join the
VAGUS and the
GLOSSOPHARYNGEAL
nerves

25. • POSTERIOR AURICULAR NERVE supplies the muscles
of the ear and occipital belly of occipitofrontalis
• branches to the MUSCLE OF FACIAL EXPRESSION,
through the parotid and divides as temporal,
zygomatic, buccal, marginal, mandibular and
cervical branches
• cutaneous fibres distributed with the AURICULAR
BRANCH OF THE VAGUS, supplying the skin on both
sides of the auricle and part of the external auditory
canal and the tympanic membrane.

26. clinically important features
• almost purely motor, apart from the EAM and the
TM.
• chorda tympani, carrying the taste fibres, joins the
seventh nerve in the middle ear, theoretically,
absence of impaired taste sensation ought to be a
great localizing value, but not practically, as taste
fibres are often spared.
• it also supplies stapedius, which with tensor
tympani, damps down the oscillations of the TM,
hence with complete seventh lesion, alteration of
auditory acuity is seen

27. • it does not contribute to normal eye opening,
but contributes to forced eye opening.
• ptosis is not a feature of seventh palsy, but there
is weakness in eye closure
• in some individuals, posterior auricular branch
weakness, leads to inability to “wiggle the ears”.
• it supplies platysma, which is often forgotten to
be tested.

28. UMN vs LMN
• the cerebral hemisphere is most concerned with facial expression,
hence exerts control over the opposite lower facial muscles
• the forehead and eye closure are mainly concerned with reflex eye
closure and hence have a dual consensual innervation.
• hence, an upper motor neuron lesion affects only the lower face,
while a lower motor neuron lesion affects upper face also.

29. testing the facial nerve
• ability to wrinkle the head
• ability to shut the eyes - Bells phenomena
• ability to flare the nostrils, smile and show the
teeth
• evert the lowerlip
• taste sensations
– unimpaired taste sensation is not a reliable indicator
that the nerve is intact, but if the taste is affected, it
is certain that the lesion is proximal to or in the
petrous bone itself.

30. CP ANGLE LESIONS
• acoustic nerve tumors
• menigiomas
• cholesteatomas
• hemangioblastomas
• ectasia of the basilar artery
• metastatic deposits
• lymphoma
• pontine glioma
• medulloblastoma/astrocytoma
• carcinoma of the nasopharynx
• metastatic Hodgkin's disease
• meningeal involvement in Syphillis
• tuberculosis