Session 8 - Group work Flashcards
Why might a fractured cribriform plate of the ethmoid bone lead to a
loss of smell and a runny nose? State which clinical term is used to
describe loss of smell and a runny nose
Damage to olfactory nerves in the cribriform plate as they enter the floor of the anterior cranial fossa
• Anosmia
• Can mention CSF
rhinorrhea here if need
be
A patient complains that he cannot turn his right
eye to the right. What nerve lesion is the likely cause?
This is the presenting sign of abducent nerve palsy. • It results in paralysis of lateral rectus, hence failure to abduct the eye. • This gives rise to diplopia in adults - It also gives rise to convergent strabismus (one or more eye turns towards the nose)
Why might pressing a boil on the cheek lead to
palsy of the abducens nerve?
• There would be an increased risk of introducing pathogens from the boil into the carvenous sinus through venous channels of the face that are devoid of valves.
• This could then lead to
carvenous sinus thrombosis
• Cranial nerves III, IV, V and VI are close relations of the carvenous sinus and could thus be damaged if there is thrombosis in their vicinity of proximity to the carvenous sinus
Why might a lesion of the ophthalmic division
of the trigeminal nerve be dangerous to the eye?
The ophthalmic division of the trigeminal nerve provides for sensation of the cornea. • If this nerve is lesioned, the cornea will be at increased risk of abrasion from foreign substances on the cornea • Blinking will also be abolished, leading to drying and pathogenic settlement on the cornea.
If the auriculotemporal nerve is cut some
distance beyond its origin, what will happen to the
parotid gland?
Proximal damage to the auricolotemporal nerve as it emerges from the brain can lead to parasympathectomy of the parotid gland as this gland receives its autonomic supply from the glossopharyngeal nerve via the auriculotemporal nerve
Why do babies who have a forceps delivery
more commonly present with temporary facial palsies
Compression damage to the motor branch of the facial nerve as it exists the cranium via the exposed stylomastoid foramen
Where does the dentist inject an anaesthetic if
he wishes to numb your lower teeth?
The inner face of the infratemporal fossa at the level of the mandibular foramen, aiming at the inferior alveolar nerve as it enters the alveolar canal
Why might a tumour of the middle ear
cause abnormal sensations of taste?
Compression of the facial nerve by a tumour in the middle ear may lead to damage extending to the chorda tympani branch that supplies general sensation the anterior 2/3 of the tongue hence the alteration to taste.
Why might a tumour of the middle ear
cause abnormal sensations of taste?
Compression of the facial nerve by a tumour in the middle ear may lead to damage extending to the chorda tympani branch that supplies general sensation the anterior 2/3 of the tongue hence the alteration to taste.
Following the removal of the submandibular
gland from a cancerous growth, why might the
patient have a ‘drooped’ lower lip?
• Excision of the submandibular galns may lead to paralysis of the facial nerve supplying the lower lip, which will then droop. • It may alsolead to numbness of the tongue due to bruising of the lingual nerve
: How might a patient present if she had
a right hypoglossal nerve (RXII) palsy?
When asked to protruding the tongue, this will be found to deviate towards the side of the lesion. In this case, the tongue will point to the right hand side.
• Chronically, the tongue will
atrophy on the affected side
• The tongue will show furrows
on the denervated side
What is the relationship of the XII
cranial nerve to the carotid artery?
The hypoglossal nerve is the twelfth cranial nerve (XII), On emerging from the hypoglossal canal, it gives off a small meningeal branch and picks up a branch from the anterior ramus of C1. It spirals behind the vagus nerve and passes between the internal carotid artery and internal jugular vein lying on the carotid sheath. After passing deep to the posterior belly of the digastric muscle, it passes to the submandibular region to enter the tongue. • It supplies motor fibres to all of the muscles of the tongue, except the palatoglossus muscle, which is innervated by the vagus nerve (cranial nerve X
Discuss the effects on breathing and
speech of an external laryngeal nerve palsy
The external laryngeal nerve is the smaller, external branch (ramus externus) of the superior laryngeal nerve. • It descends on the larynx, beneath the sternothyroid muscle, to supply the cricothyroid muscle.
• It tenses vocal cords by activating the
cricothyroid muscle, thus increasing
pitch.
• The cricothyroid muscle is one of a
number of intrinsic muscles of the
larynx that control expiration of air in
phonation
• Paralysis of the criothyroid muscle can
lead to problems with maintenance of
patent airways during breathing and
also swallowing.
Discuss the effects on breathing and
speech of an external laryngeal nerve palsy
The external laryngeal nerve is the smaller, external branch (ramus externus) of the superior laryngeal nerve. • It descends on the larynx, beneath the sternothyroid muscle, to supply the cricothyroid muscle.
• It tenses vocal cords by activating the
cricothyroid muscle, thus increasing
pitch.
• The cricothyroid muscle is one of a
number of intrinsic muscles of the
larynx that control expiration of air in
phonation
• Paralysis of the criothyroid muscle can
lead to problems with maintenance of
patent airways during breathing and
also swallowing
Discuss the effects on breathing and speech of
a bilateral paralysis of the recurrent laryngeal nerve.
The recurrent (inferior) laryngeal nerve is a branch of the vagus nerve.
• It supplies motor function and sensation to the larynx (voice box).
• If the damage is unilateral, the patient may present with voice changes
including hoarseness.
•
• Bilateral nerve damage can result in breathing difficulties and aphonia,
the inability to speak.
• The recurrent laryngeal nerves provide motor supply to most intrinsic
muscles of the larynx (apart from cricothyrodeius).
• Intrinsic muscle of the larynx maintain and control airways during
phonation and swallowing.
• Paralysis of the recurrent laryngeal nerves will lead to disturbances of
breathing and phonation
