Cranial Nerves and Epilepsy Flashcards
Describe the basic principles of cranial nerves
- 12 paired nerves arising from the brain
- Connect brain to various parts of head, neck and trunk
- Sensory, motor and parasympathetic function
Where do the cranial nerves arise from specifically in the brain?
- CNI and CNII from the cerebrum
- CNIII to CNXII originate from brain stem
Where does CNI exit the skull?
Cribriform plate
Where does CNII exit the skull?
Optic canal
Where does CNIII exit the skull?
Superior orbital fissure
Where does CNIV exit the skull?
Superior orbital fissure
Where does CNV (1) exit the skull?
Superior orbital fissure
Where does CNV (2) exit the skull?
Foramen rotundum
Where does CNV (3) exit the skull?
Foramen ovale
Where does CNVI exit the skull?
Superior orbital fissure
Where does CNVII exit the skull?
Internal acoustic meatus
Where does CNVIII exit the skull?
Internal acoustic meatus
Where does CNIX exit the skull?
Jugular foramen
Where does CNX exit the skull?
Jugular foramen
Where does CNXI exit the skull?
Jugular foramen
Where does CNXII exit the skull?
Hypoglossal canal
Describe CNI
- Olfactory nerve
- Provides visceral afferent fibres for smell
- Connects to brain (not brainstem)
Describe disorders of CNI
- Altered / loss of sense of smell
Describe CNII
- Optic nerve
- Provides somatic afferent fibres for vision
- Connects to brain (not brainstem)
Describe disorders of CNII
Optic field defects (pattern of defect determines position of lesion)
Describe CNIII
- Oculomotor
- Innervates extrinsic eye muscles than enables movements of the eye, raise the eyelid and constrict pupil
- Connects to midbrain
Describe 3 ways in which deficits of CNIII appear clinically
- Ptosis (drooping of upper eyelid)
- Mydriasis (pupil dilated)
- Down and Out (position of the eye)
Describe CNIV
- Trochlear
- Provides general somatic efferent to extraocular superior oblique muscle
- Assists in depressing and abducting the eye
- Connects to midbrain
Describe the deficit of CNIV
- Inferior oblique taken over so eye sits higher and mesially
- Patient often tilts head to combat double vision
Describe CNV
- Trigeminal
- Emerges from the pons with 3 divisions
- Mixed nerve with sensory and motor function
Name 3 divisions of the trigeminal nerve
- Ophthalmic
- Maxillary
- Mandibular
Describe 5 sensory functions of the ophthalmic nerve
- Cornea
- Skin of forehead
- Scalp
- Eyelids
- Mucous membranes of paranasal sinuses and nasal cavity
Describe 3 sensory functions of the maxillary nerve
- Skin over maxilla
- Upper teeth
- Mucous membrane of nose, maxillary sinus and palate
Describe the pathway of the maxillary nerve with regards to LA
- Enters infraorbital canal and exits through infraorbital foramen
- Gives of palatine nerves which can be blocked with anaesthetic
- Posterior and anterior superior alveolar nerves supply upper teeth
Describe 5 motor functions of the mandibular nerve
- Muscles of mastication
- Mylohyoid
- Anterior belly of digastric
- Tensor veli palatine
- Tensor tympani
Describe 5 sensory functions of the mandibular nerve
- Skin of cheek
- Skin over mandible and side of head
- Teeth of lower jaw and TMJ
- Anterior 2/3 of the tongue
- Mucous membrane of lower jaw
Describe the important branches of the mandibular nerve
- Splits into posterior and anterior division
- Anterior gives of buccal nerve which provides sensation to buccal mucosa
- Posterior division gives off lingual and inferior alveolar nerve
- Inferior alveolar nerve terminates in mental and incisive nerves
Describe sensory trigeminal neuropathy
- Progressive, painless loss of trigeminal sensation
- Normally unilateral
- May affect one or all trigeminal division
- No motor weakness
Name a common syndrome associated with sensory trigeminal neuropathy
Numb chin syndrome
Describe numb chin syndrome
- Sensory neuropathy presenting in numbness of chin
- Important symptom of metastatic disease (multiple reasons)
Describe trigeminal neuralgia
- Vascular compression of CNV
- Episodic neuropathic pain
- F>M
- 45 to 59 years old
- Related to pathology of idiopathic damage
Describe CNV
- Abducens
- Provides somatic efferent fibres for eye abduction
- Innervated lateral rectus muscle
Describe CN VII
- Facial nerve
- Mixed nerve with motor and sensory function
Describe 4 motor functions of CN VII
- Muscles of facial expression
- Strapedius
- Posterior belly of digastric
- Stylohyoid
Name 5 branches of CN VII
- Temporal
- Zygomatic
- Buccal
- Mandibular
- Cervical
Name 4 common facial nerve palsys
- Bell’s palsy
- Tumour
- Ramsay Hunt Syndrome
- Frey Syndrome
Describe Bell’s syndrome
- Drooping of eye, mouth and nasolabial fold
- Suspected viral irritation of CN VII
- High dose steroid management
Describe a facial nerve palsy caused by tumours
- When a tumour is either compressing facial nerve or invading nerve it may cause weakness
- Acoustic or facial neruoma in region of parotid gland are common
- May be accompanied by other symptoms
What is the best way to differentiate an UMNL and a LMNL?
- Frontalis muscle is spared in UMNL
- If patient can wrinkle their forehead, UMNL, and if they cannot, LMNL
What is Ramsay Hunt syndrome?
- Reactivation of latent herpes zoster virus within vesicles within auditory canal
- Otalgia and varying levels of hearing loss occur
- Management with course of antivirals
Describe Frey Syndrome
- Most often occurs as a result of surgery in area of parotid gland
- Undesirable sweating and flushing after eating certain food
- Damage to sympathetic and parasympathetic nerves
Describe CN VIII
- Vestibulocochlear
- Provides special somatic afferent fibres for hearing and balance
Describe CN IX
- Glossopharyngeal nerve
- Mixed nerve with motor, sensory and secretomotor functions
Describe the 5 sensory functions of CN IX
- Tonsils
- Soft palate
- Pharynx
- Middle ear
- Posterior 1/3 of tongue
Describe the motor function of CN IX
Innervated stylopharyngeal muscle
Describe the secretomotor functions of CN IX
Parasympathetic to parotid gland
Describe CN X
- Vagus nerve
- Parasympathetic innervation of viscera
Describe CN XI
- Accessory nerve
- Reference to spinal part of nerve
- Motor control to trapezius and sternocleidomastoid muscles
Describe CN XII
- Hypoglossal
- Innervates muscles of tongue except palatoglossal
Describe hypoglossal palsy
- Rare in isolation
- Deviation and fasciculation to affected side
- Can be idiopathic, medical, trauma or metastatic disease
What is epilepsy?
A chronic disorder which causes unprovoked and recurrent seizures
Describe what is necessary for an epilepsy diagnosis
a) Over 2 unprovoked seizures more than 24 hours apart
b) A single unprovoked seizure with 60% change of having another within 10 years
Describe seizure aetiology
- Idiopathic
- Trauma
- CNS disease (tumour, stroke, CVD)
- Infection (meningitis, malaria)
- Hyperthermia
Name 5 possible triggers for a seizure
- Lack of sleep
- Illness / Stress
- Bright lights
- Caffeine, alcohol or medicine
- Menstruation
What is the difference between focal and generalized seizures?
Focal seizures occur in one hemisphere of the brain and generalized occur in both simultaneously
Describe the main symptoms of a sensory focal stroke
Disturbances in vision, hearing, taste and smell
Describe the main symptoms of a motor focal seizure
Reduction in motion in one limb but can spread
Describe a febrile seizure
- Related to infection and higher temperature
- Occurs in children between 6 months and 3 years
- May occur in subsequent illness
- Slight increase in risk of developing epilepsy
Describe a tonic clonic seizure
- Prodromal aura
- Loss of consciousness
- Initial tonic (stiff) then clonic (relaxation / contraction)
- Seen in stratus epilepticus
What is stratus epilepticus?
Seizures with no gain of consciousness in between or a single seizure lasting over 30 minutes
Describe a generalized absence seizure
- Much harder to spot than tonic clonic
- Sudden stop in motion without falling
- Chewing movements
- Cognitive problems
- Stopping speech midway
Name 4 complications of epilepsy
- Injury
- Drug reactions
- Death (asphyxiation / aspiration)
- Social (driving / employment)
Describe 4 ways a dentist should assess the risk of an epileptic fit occurring in the practice
- Up to date medical history
- Up to date social history
- Pattern of fits
- Treat during low risk phase
Describe 4 complications of epilepsy related to dentistry
- Injury
- Gingival hyperplasia with phenytoin
- Bleeding tendency with valproate
- Drug interactions
Describe the management of a patient who suffers a seizure in a dental surgery
- Safe surrounding and shout for help
- ABC (airway, breathing and circulation)
- Time the seizure
- Buccal midazolam 10mg if status epilepticus
- Do not move or restrain patient
- Ring 999
Describe post-ictal management of a patient
- Place in recovery position
- Do not allow patient to leave until sure they have made a full recovery and contact family if they are alone
- Do brief examination for sustained injuries but do not carry out further treatment
