Neurosurgery Flashcards
What foramen does the oculomotor nerve pass through?
Superior orbital fissure
What cranial nerves pass through the jugular foramen?
Glossopharyngeal (CN IX)
Vagus (CN X)
Accessory (CN XI)
What cranial nerves pass through the internal acoustic meatus?
Facial Nerve (CN VII)
Vestibulocochlear Nerve (CN VIII)
What foramen does the middle meningeal artery pass through?
Foramen Spinosum
Name the 7 foramina that the cranial nerves pass through?
Optic Canal (II)
Superior Orbital Fissure (III, IV, V1, VI)
Foramen Rotundum (V2)
Foramen Ovale (V3)
Internal acoustic meatus (VII, VIII)
Jugular Foramen (IX, X, XI)
Hypoglossal Canal (XII)
Name the 4 cranial nerves that pass through the superior orbital fissure?
Occulomotor
Trochlear
Trigeminal - ophthalmic branch
Abducens
What foramina are part of the sphenoid bone?
Optic canal
Superior Orbital Fissure
Foramen Rotundum
Foramen Ovale
Foramen Spinosum
What sinuses join together to form the internal jugular vein?
Inferior Petrosal Sinus and Sigmoid Sinus
What nerve supplies the stapedius muscle?
Facial Nerve (CN VII)
Which nerve can be damaged during carotid surgery?
Hypoglossal Nerve
What structures pass through the foramen ovale?
O - Otic ganglion
V - V3 (mandibular nerve)
A - Accessory meningeal artery
L - Lesser petrosal nerve
E - Emissary veins
What structures pass through the superior orbital fissure?
Oculomotor Nerve (CN III)
Trochlear Nerve (CN IV)
Ophthalmic Nerve (CN V1) - Lacrimal, frontal and nasociliary branches
Abducens Nerve (CN VI)
Recurrent Meningeal Artery
Superior Ophthalmic Vein
Which nerves are at risk of damage during a carotid endarterectomy?
Hypoglossal nerve
Greater auricular nerve
Superior laryngeal nerve
Which of the cranial venous sinusus is unpaired?
Superior sagittal sinus
What blood vessel is most commonly ruptured in an extradural haematoma and where does it originate?
Middle meningeal artery <- Maxillary artery <- External Carotid
Which branches of the external carotid artery are responsible for blood supply to the scalp?
Posterior auricular - superior and posterior to ear
Occipital - back of scalp
Superficial temporal arteries - frontal and temporal regions
Also supplied with blood by ophthalmic artery which is the first branch of the internal carotid
Trauma to which part of the scalp causes middle meningeal artery rupture?
Pterion
Where does the internal carotid artery enter the cranium?
Carotid canal in the petrous part of the temporal bone
A lesion of what structure causes a homonymous hemianopia?
Optic tract
What visual field defect does compression of the optic chiasm result in?
Bitemporal hemianopia
What visual field defect does a lesion in the parietal lobe result in?
Inferior homonymous quadrantaopia
What visual field defect does a lesion in the temporal lobe result in?
Superior homonymous quadrantaopia
Causes of optic chiasm compression
Pituitary tumour - compression of the inferior part of the optic chiasm and results in a more significant defect in the superior quadrant
Craniopharyngioma - compression of the superior part of the optic chiasm and results in a more significant defect in the inferior quadrant
What nerve runs very closely to the base of the middle meningeal artery?
Auriculotemporal nerve - branch of Mandibular nerve (CN V3)
Which nerve is most likely to be damaged due to raised ICP?
Abducens
Which layer is the danger area of the scalp and why?
Loose areolar connective tissue - it contains emissary veins. These are valveless veins that connect the extracranial veins with intracranial sinuses and are potential cause for spread of infection.
Which 3 branches of the external carotid artery supply the scalp with blood?
Superficial temporal
Posterior auricular
Occipital
What branch of the internal carotid artery supplies the scalp with arterial blood?
Supratrochlear and supraorbital branches of the ophthalmic artery
What is the venous drainage of the deep temporal skull?
Pterygoid venous plexus
Why do scalp lacerations bleed profusely?
- The pull of the occipitofrontalis muscle prevents the closure of the bleeding vessel and surrounding skin.
- The blood vessels to the scalp are adhered to dense connective tissue, preventing the vasoconstriction that normally occurs in response to damage.
- The blood supply to the scalp is made up of many anastomoses, which contribute to profuse bleeding.
Which cranial nerve provides innervation to the scalp?
Trigeminal CN V
What causes the pupil to become fixed and dilated following head injury?
Increased intracranial pressure - > transtentorial herniation
3rd CN compression
What is the surgical procedure to decrease intracranial pressure following head injury?
Parieto-temporal craniotomy
What type of drug is given in SAH when there is no increase in ICP? and why?
CCB - it reduced vasospasm
What is the cushings reflex?
Physiological response to increased ICP - Hypertension and bradycardia.
It is also associated with wide pulse pressure and irregular breathing.
Hypertension occurs as ICP is greater than MAP so in order to maintain cerebral perfusion, MAP has to increase.
What does CN IV do and how does a 4th nerve palsy present?
Supplies innervation to superior oblique muscle
Vertical diplopia
Head tilts away from affected side
Unable to look down and medially
Which type of intracranial bleed causes sudden loss of consciousness and collapse without traumatic event?
SAH
How soon after the traumatic event do symptoms need to start in order for the sub dural haemorrhage to be classified as acute?
<72 hours
Which patient group is most likely to have an intraventricular haemorrhage?
Neonates
A 28 year old man falls and hits his head against a wall. There is a brief loss of consciousness. When assessed in accident and emergency he is alert and orientated with a GCS of 15, imaging shows no fracture of the skull. What is his risk of having an intracranial haematoma requiring removal?
1 in 6000
What is a signature fracture?
Depressed skull fracture where the impression resembles the source of impact
Which nerve accompanies the labyrinthine artery?
Facial nerve (CN V) and vesticulocochlear nerve (CN VIII)
What artery does the posterior inferior cerebellar artery arise from?
Vertebral
What are the contents of the cavernous sinus?
Occulomotor nerve (III)
Trochlear nerve (IV)
Ophthalmic nerve (V1)
Maxillary nerve (V2)
Carotid artery (internal)
Abducens nerve (VI)
O TOM CAT
What are the non-terminal branches of the facial nerve?
Intracranial:
Greater petrosal nerve
Nerve to stapedius
Chordatympani
Extracranial:
Posterior auricular nerve
Nerve to digastric
Nerve to sylohyoid
What are the branches of the facial nerve that arise within the parotid and what muscles do they innervate?
Temporal - frontalis, orbicularis oculi and corrugator supercilii
Zygomatic - orbicularis oculi
Buccal - orbicularis oris,levator anguli oris, buccinator and zygomaticus
Mandibular - depressor labii inferioris, depressor anguli oris and mentalis
Cervical - platysma
ipsilateral hyperacusis (hypersensitive to sound), is due to damage to which nerve?
Nerve to stapedius, branch of the facial nerve
What are the features of a glioblastoma?
Traverses the midline
Central necrosis
Extensive oedema
Which cranial nerves are autonomic?
III
VII
IX
X
What is the most common brain tumour in children?
Astrocytoma
What is the choroid plexus?
a network of blood vessels in each ventricle of the brain, producing the cerebrospinal fluid
What is the total volume of CSF?
100-150ml
What is the normal pressure of CSF?
10-15mmHg
Where does the cerebral aqueduct lie
between 3rd and 4th ventricles
What are the 3 types of nerve injury?
Neuropraxia - Nerve intact but electrical conduction affected eg crush injury
Axonotmesis - Axon damaged, myelin sheath intact. Wallerian degeneration occurs.
Neurotmesis - Both axon and myelin sheath are damaged. Wallerian degeneration occurs.
What is wallerian degeneration?
Axonal degeneration distal to the site of injury.
Typically begins 24-36 hours following injury.
Axons are excitable prior to degeneration occurring.
Myelin sheath degenerates and is phagocytosed by tissue macrophages.
At what rate does nerve repair occur?
1mm/day
What type of cell type do gliomas derive from?
Neuroglial cells
What does CSF pass through to get from the 3rd ventricle to the 4th ventricle?
Aqueduct of sylvius
What structures do the foramen of munro, magendie and luschka lie between?
Munro - lateral ventricles to third ventricle
Magendie and Luschka - fourth ventricle to cisterna magna
What is the most common childhood brain tumour?
Astrocytoma
What structure suspends the spinal cord in the dural sheath?
Denticulate ligaments - continuation of the pia mater
What is an Ependymoma?
Arises from the 4th ventricle and grows through the foramen of Luschka and Magendie
Accounts for 1/3 tumours in children <3 years
What is Klumpke’s paralysis?
Caused when a baby is delivered with it’s arm extended
Damage to C8-T1
Features:
- Claw hand (MCP joints extended and IP joints flexed)
- Loss of sensation over medial aspect of forearm and hand
- Horner’s syndrome
- Loss of flexors of the wrist
What is orbital apex syndrome?
Damage to occulomotor (CN III), trochlear (CN IV), abducens (CN VI) and ophthlamic nerves (CN V1) secondary to trauma to the orbital apex and therefore the superior orbital fissure.
Optic nerve also involved.
Symptoms include:
- Complete ophthalmoplegia
- Ptosis
- Ipsilateral vision loss
- Altered cutaneous sensation from the forehead to the vertex
What lesion is most likely to occur at the cerebellar pontine angle and what nerve is most likely to be affected?
Acoustic neuroma
CN 5 Trigeminal
What constitutes lateral medullary syndrome?
Nystagmus, ataxia, dysphagia, facial numbness and cranial nerve palsy
WITH CONTRALATERAL HEMISENSORY LOSS
What is cushing’s triad?
Widening of the pulse pressure
Respiratory changes
Bradycardia
Which cranial nerves carry parasympathetic nerve fibres?
3
7
9
10
Which part of the brain do the cranial nerves originate from?
CN1-2 = Cerebrum
CN3-4 = midbrain
CN5-8 = pons
CN9-12 = medulla
