MRCS Part A—500 SBAs and EMQs Pradip K Datta, Christopher JK Bulstrode, William FM Wallace
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1Applied anatomy2

Skull and brainChapter 1

  1. A 25-year-old man, a footballer, presents to the emergency department after having lost consciousness during a game. He is very drowsy, with a Glasgow Coma Score of 13. A CT scan shows an extradural haemorrhage.
    Which blood vessel is the patient bleeding from?
    1. Internal carotid artery
    2. Middle cerebral artery
    3. Middle meningeal artery
    4. Superficial temporal artery
    5. Superior sagittal sinus
  1. A 35-year-old woman with an untreated infected lesion on her face complains of severe ocular pain, fever and chemosis, and has a pulsating proptosis.
    Which one of the following structures is involved?
    1. Cavernous sinus
    2. Optic nerve
    3. Pituitary gland
    4. Superior sagittal sinus
    5. Trigeminal nerve
  1. A 70-year-old man, a smoker, presents with intermittent amaurosis fugax (temporary visual loss) in the form of a shutter dropping in front of his eye. He has a systolic carotid bruit on the same side.
    The main artery that is affected enters the orbit through which one of the following foramina?
    1. Foramen rotundum
    2. Foramen spinosum
    3. Inferior orbital fissure
    4. Optic canal
    5. Superior orbital fissure
  1. A 45-year-old woman is diagnosed with a space-occupying lesion at the cerebellopontine angle.
    The lesion is arising from which one of the following structures?
    1. Basilar artery aneurysm
    2. Cerebellum
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    3. Glossopharyngeal nerve
    4. Hypoglossal nerve
    5. Vestibulocochlear (8th cranial) nerve
  1. A 55-year-old man presents with sudden onset of severe headache, which he likens to a ‘hammer blow’ to the back of the head. A gadolinium-enhanced MRI shows a haemorrhagic lesion in the anterior cranial fossa.
    Which one of the following vessels is involved
    1. Anterior communicating artery
    2. Basilar artery
    3. Internal carotid artery
    4. Middle cerebral artery
    5. Posterior communicating artery
  1. A 30-year-old man presents with an extradural haemorrhage with a dilated pupil.
    Dilatation of the pupil is due to pressure on the occulomotor (3rd cranial) nerve by which one of the following structures?
    1. Cerebellar tonsil
    2. Crus of the cerebral peduncle
    3. Falx cerebri
    4. Mammillary body
    5. Uncus of the temporal lobe
  1. A 30-year-old man, a recent immigrant from Africa, presents with an advanced right-sided nasopharyngeal carcinoma. A CT scan shows widespread extension into the right posterior base of the skull. On protruding the tongue, it deviates towards the side of the lesion.
    Which one of the following nerves is affected by the growth?
    1. Glossopharyngeal nerve
    2. Hypoglossal nerve
    3. Spinal part of accessory nerve
    4. Superior cervical sympathetic nerve
    5. Vagus nerve
  1. A 30-year-old man presents with anosmia, after sustaining a fracture of his anterior cranial fossa in a road traffic accident 5 weeks ago. At that time he had cerebrospinal rhinorrhoea.
    Fracture of which one of the following bones is causing his anosmia?
    1. Cribriform plate of the ethmoid bone
    2. Frontal process of the zygomatic bone
    3. Nasal bones
    4. Orbital plate of the frontal bone
    5. Squamous part of the temporal bone
5Answers
  1. C Middle meningeal artery
    The middle meningeal artery is a branch of the maxillary artery which along with the superficial temporal artery is one of the terminal branches of the external carotid artery. It enters the middle cranial fossa through the foramen spinosum and divides into an anterior and posterior branch. It is the cause of bleeding in extradural haemorrhage because it lies deep to the squamous part of the temporal bone which is a very thin part of the cranium, and therefore easily fractured. A burr hole is usually made at the level of the pterion to access the middle meningeal artery to stop the bleeding, although the ideal surgical procedure is a craniotomy.
  1. A Cavernous sinus
    The cavernous sinus is vulnerable to thrombosis in any serious infections of the face in the ‘danger area’ – upper lip, nose and medial part of cheek. This is a very serious condition and may lead to proptosis and ophthalmoplegia. The structures of the cavernous sinus are: internal carotid artery, ophthalmic division (1st division) and maxillary divisions (2nd division) of the 5th cranial nerve, 3rd, 4th and 6th cranial nerves. The other surgical condition that can occur within the cavernous sinus is an aneurysm of the internal carotid artery, resulting in a caroticocavernous fistula presenting clinically as a pulsating proptosis.
  1. D Optic canal
    The central artery of the retina is affected. It is a branch of the ophthalmic artery which enters the orbit through the optic canal inferolateral to the optic nerve within a common dural sheath. It supplies the extraocular muscles, the lachrymal gland and the eye. The eye is supplied by the central artery, an end artery (which supplies the optic nerve and retina) and the anterior and posterior ciliary arteries. The venous drainage from the orbit is by the superior ophthalmic vein which passes through the superior orbital fissure and the inferior ophthalmic vein that passes through the inferior orbital fissure.
  1. E Vestibulocochlear (8th cranial) nerve
    The lesion is arising from the vestibulocochlear nerve at its entrance to the auditory meatus. The auditory meatus is situated in the posterior cranial fossa in the petrous part of the temporal bone. In that area a cerebellopontine angle tumour arises from the nerve sheath of the 8th nerve (schwannoma, acoustic neuroma); it may press on the adjacent 7th nerve, causing facial numbness or weakness.
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  1. A Anterior communicating artery
    This patient has a classical presentation of a ruptured berry aneurysm resulting in subarachnoid haemorrhage. The commonest site for a berry aneurysm is the anterior communicating artery. Congenital berry aneurysms (so-called because of their resemblance to the fruit) occur in the circle of Willis, particularly at the junction of the vessels where the tunica media is weakest. Patients present with features of subarachnoid haemorrhage: complaining of a severe and sudden headache, where they feel a hammer-blow on the back of the head. Patients fast become unconscious. Unless suspected by clinical awareness, promptly investigated by MRI and immediately treated as an emergency, it carries a poor prognosis.
  1. E Uncus of the temporal lobe
    The uncus of the temporal lobe compresses the occulomotor nerve. The extradural haematoma causes the cerebral hemisphere to move to the opposite side resulting in a midline shift. As the haematoma enlarges the cerebrum is shifted more to the opposite side causing the uncus on the temporal lobe to impinge upon the occulomotor nerve. This causes paralysis of the parasympathetic innervation of the eye resulting in pupillary dilatation. This is a serious clinical finding. The patient needs an urgent CT scan followed by intracranial decompression.
  1. B Hypoglossal nerve
    The hypoglossal nerve exits the posterior cranial fossa through the hypoglossal canal. This is a separate foramen seen at the edge of the foramen magnum. Direct extension of the growth into the base of the skull infiltrates the hypoglossal nerve which may also be invaded by secondary lymph nodes. The nerve supplies all the intrinsic and extrinsic muscles of the tongue except the palatoglossus because the latter is essentially a muscle of the palate and hence supplied by the pharyngeal plexus. Iatrogenic damage is known to occur and this would cause the tongue to deviate to the paralysed side with atrophy of the tongue.
  1. A Cribriform plate of ethmoid bone
    After recovery from a head injury, the patient suffers from anosmia. This means that the olfactory (1st cranial) nerve has been damaged as a result of fracture of the cribriform plate of the ethmoid bone. The olfactory bulb may be separated from the olfactory nerves or the nerves may be torn as a result of the fracture. Such an injury will cause cerebrospinal rhinorrhoea at the time of initial injury.