General Flashcards
48) Which of the following represents an appropriate window width and level for viewing the bony structures on a CT scan of the brain?
a. width 80, level 35
b. width 400, level 40
c. width 250, level 70
d. width 2000, level 500
e. width 1500, level –500
d. width 2000, level 500
CT images are displayed with different window levels and widths to highlight differences in CT attenuation between the structures of interest. Narrow window widths (80–400 HU) and lower levels (20–80 HU) are used to emphasize differences between soft tissues, whereas wide widths (2000–3000 HU) and higher levels (300–600 HU) are used for optimal visualization of bony structures. Images are usually also reconstructed using specific bone algorithms to accentuate the bone–soft tissue interface.
@#e 61) On an axial section of the brain at the level of the third ventricle, which structure lies immediately lateral to the putamen?
a. internal capsule
b. globus pallidus
c. external capsule
d. thalamus
e. insular cortex
c. external capsule
The lentiform nucleus is composed of a larger lateral component (the putamen) and a smaller medial component (the globus pallidus), separated by a sheet of white matter. The lentiform nucleus is bounded medially by the internal capsule. Lateral to the lentiform nucleus lies the white matter of the external capsule, and then the claustrum, a thin sheet of grey matter. The extreme capsule lies lateral to the claustrum, and separates it from the insular cortex.
64) A 56-year-old male presents with a mass in the anterior triangle of the neck and is referred for ultrasound scan and biopsy. Ultrasound scan shows a vascular mass splaying the internal and external carotid arteries at their origin. How should cell sampling of the mass be undertaken?
a. perform FNA rather than core biopsy
b. use multiple passes
c. use a single pass
d. ensure that needle midway between internal and external carotid arteries
e. both FNA and core biopsy contraindicated
e. both FNA and core biopsy contraindicated
The imaging appearances are highly suggestive of a carotid body tumour (paraganglioma), and biopsy should not be performed, as haemorrhage would be certain due to the high vascularity of the lesion (in addition to the proximity of the carotid system). They present as painless, pulsatile masses in the neck of adults, below the angle of the jaw, and are laterally mobile but vertically fixed. There is splaying of the carotid bifurcation but preservation of calibre of the two arteries. Contrast imaging shows avid enhancement.
67) Which paired vein forms in the sylvian fissure and travels in the ambient cistern around the midbrain to enter the vein of Galen along with the internal cerebral vein?
a. superficial middle cerebral or sylvian vein
b. basal vein of Rosenthal
c. vein of Labbe
d. vein of Trolard
e. thalamostriate vein
b. basal vein of Rosenthal
These veins are all part of the supratentorial venous system.
The superficial middle cerebral vein forms an arc along the surface of the sylvian fissure and is continuous with the sphenoparietal sinus.
The veins of Trolard and Labbe are anastomotic veins that connect the superficial middle cerebral vein to the superior sagittal and transverse sinuses respectively.
The thalamostriate vein is a subependymal vein that passes across the floor of the lateral ventricle, over the thalamus and into the internal cerebral vein behind the foramen of Monro.
The paired internal cerebral veins run along the roof of the third ventricle and enter the vein of Galen with the paired basal veins of Rosenthal.
The vein of Galen joins the inferior sagittal sinus and the straight sinus at the ‘venous confluence’ within the quadrigeminal plate cistern.
The straight sinus lies along the junction of the falx and tentorium. The straight sinus, transverse sinus and superior sagittal sinus meet as the torcular herophili.
70) A 30-year-old man with a history of metastatic malignant melanoma presents with sudden onset of visual loss of the upper right quadrant in both eyes (right superior homonymous quadrantanopia). Emergency CT of the brain demonstrates a haemorrhagic cerebral metastasis with surrounding oedema. Which of the following is the most likely location of the lesion?
a. optic chiasm
b. right temporal lobe
c. left temporal lobe
d. left thalamus
e. right thalamus
c. left temporal lobe
The optic radiation runs from the optic chiasm posteriorly to the occipital visual cortex. Each radiation carries with it optical fibres carrying information from the contralateral half of the visual field of each eye. This means a lesion in the left optic radiation will result in loss of vision of the right half of the visual field in both eyes (right homonymous hemianopia). However, as the radiation passes posteriorly from the lateral geniculate nucleus of the thalamus, it divides into two, with one division taking a relatively direct course posteriorly and the other a longer course through the temporal lobe. This is known as Meyer’s loop, and the lengthier course means that these fibres are more prone to disruption. The fibres in Meyer’s loop carry information from the upper visual field only, so a left temporal lobe lesion that affected Meyer’s loop would result in loss of vision only of the upper right quadrants of each eye (right superior homonymous quadrantanopia). A lesion at the optic chasm, such as a pituitary macroadenoma, will affect only the fibres that decussate at the chiasm, causing bitemporal loss of vision (bitemporal hemianopia).
73) Between which structures do the dural venous sinuses lie?
a. skull and dura mater
b. dura mater and dura mater
c. dura mater and arachnoid mater
d. arachnoid mater and pia mater
e. pia mater and brain
b. dura mater and dura mater
Dural venous sinuses are large venous channels located between the two layers of dura. They also contain arachnoid granulations that are responsible for CSF resorption.
78) The fourth branch of the external carotid artery crosses the inferior border of the mandible before traversing the cheek, and forms an important connection between the external and internal carotid arteries by anastomosing with branches of the ophthalmic artery. Which artery is described?
a. ascending pharyngeal
b. lingual
c. facial
d. maxillary
e. superficial temporal
c. facial
The external carotid artery is usually described as having 8 branches but may have 4–12.
The terminal branches are the superficial temporal and maxillary arteries.
The usual branches in the order in which they arise are superior thyroid, ascending pharyngeal, lingual, facial, occipital and posterior auricular.
There is a plethora of anastomotic connections between branches of the external carotid artery, between external and internal carotid artery branches, and between external and vertebral artery branches.
82) In normal anatomy of the nasal cavity, which structure opens into the inferior meatus below the inferior nasal turbinate?
a. anterior ethmoidal ostium
b. posterior ethmoidal ostium
c. frontal sinus ostium
d. maxillary sinus ostium
e. nasolacrimal duct
e. nasolacrimal duct
The lateral nasal wall is separated into superior, middle and inferior meatuses by three curled bony shelves called turbinates (or conchae).
The nasolacrimal duct opens into the anterior aspect of the inferior meatus and is usually the only opening seen there.
The other ostia all open into the middle meatus, with the exceptions of the posterior ethmoidal ostia (superior meatus) and sphenoidal ostia (posterior to the superior turbinate in the sphenoethmoidal recess).
The sphenopalatine foramen lies inferior to the sphenoethmoidal recess posterior to the middle turbinate.
83) Regional cerebral blood flow imaging is required to localize an epileptic focus. Of the following radiopharmaceuticals, which is the most appropriate for this purpose?
a. 99mTc-labelled MAA
b. 99mTc-labelled DTPA
c. 99mTc-labelled pertechnetate
d. 99mTc-labelled glucoheptonate
e. 99mTc-labelled ECD
e. 99mTc-labelled ECD
Conventional radionuclide brain scans are not indicated when CTor MRI can be used.
Brain accumulation of radiotracer occurs at sites of blood–brain barrier disruption and increased vascularity such as cerebral metastases, meningioma and high-grade glioma. Reagents used are 99mTc-labelled pertechnetate, 99mTc-labelled DTPA, and, when it was available, 99mTc-labelled glucoheptonate.
Radionuclide imaging is also able to provide regional blood flow mapping, which is used to localize epileptic foci, map cerebrovascular disease, investigate dementia, assess treatments and confirm brain death. 99mTc-labelled HMPAO is the most used radiopharmaceutical overall. It is lipophilic and therefore crosses the blood–brain barrier, and in doing so is distributed in proportion to cerebral blood flow. 99mTc-labelled ECD is another regional blood flow imaging tracer and can therefore also be used in the localization of epileptic foci. 18FDG PET tracers are distributed through the brain according to metabolic activity.
89) Which of the following structures lies in the parapharyngeal space?
a. internal carotid artery
b. hypoglossal nerve
c. maxillary artery
d. lingual tonsil
e. vagus nerve
c. maxillary artery
The parapharyngeal space is triangular shaped and extends from the skull base to the hyoid.
It contains fat, branches of the mandibular division of the trigeminal nerve, maxillary artery, ascending pharyngeal artery and pharyngeal venous plexus.
The internal carotid artery, vagus nerve and hypoglossal nerve lie in the carotid space.
The lingual tonsils lie in the pharyngeal mucosal space.
85) A young patient presents with double vision and is found on examination to have a ptosis and dilated left pupil. The gaze in the same eye is fixed inferiorly and laterally and, when the ipsilateral light reflex is tested, there is constriction of the contralateral pupil only. CT shows a small spontaneous brain-stem haemorrhage thought to be due to an arteriovenous malformation. Which of the following locations of the haemorrhage best explains the presenting symptoms?
a. superior pons
b. inferior pons
c. superior midbrain
d. inferior midbrain
e. superior medulla
c. superior midbrain
The signs describe oculomotor nerve palsy.
This will result in a characteristic down-and-out position of the affected eye due to the unantagonized action of the superior oblique and lateral rectus muscles, which are supplied by the trochlear and abducent nerves respectively.
The palsy will also cause ptosis and pupillary dilatation due to loss of the motor component of the light reflex.
The nuclei of the oculomotor nerves are found in the superior midbrain within the tegmentum, at the level of the superior colliculi.
Those of the trochlear nerve are situated at the level of the inferior colliculi.
The oculomotor nerve arises from the anterior surface of the midbrain on the medial side of the cerebral peduncle, passing between the posterior cerebral and superior cerebellar arteries to enter the cavernous sinus and pass into the orbit via the superior orbital fissure.
94) The Wada test is performed before surgical treatment for medically refractory epilepsy. It involves intra-arterial injections of sodium amobarbital with 99mTc-labelled HMPAO followed by SPECT imaging to map the distribution of the barbiturate. What is the main indication for this test?
a. chemical ablation of epileptic foci
b. localization of speech and memory centres
c. mapping symmetry of brain vascular distribution
d. identification of interhemispheric collateral circulation
e. evaluation of cerebrovascular reserve
b. localization of speech and memory centres
SPECTof the central nervous system allows assessment of the collateral circulation during balloon occlusion, mapping the extent and distribution of vasospasm associated with subarachnoid haemorrhage, evaluation of cerebrovascular reserve prior to carotid endarterectomy, identification of seizure foci and guiding of stereotactic brain biopsy in tumour recurrence.
TheWada test is used to predict the probability of memory and speech complications in patients before they undergo anterior temporal lobectomy with amygdalohippocampectomy, a surgical treatment for medically refractory epilepsy.
The test involves injection of radiopharmaceutical and short-acting barbiturate (usually sodium amobarbital) into each of the carotid arteries in turn. Loss of memory or speech following one of the injections indicates that these centres lie in the ipsilateral temporal lobe.
The results of theWada test can be negated by vessels crossing the midline, and the presence of such collateral circulation may not be readily apparent without SPECT.
95) A 64-year-old man with squamous cell carcinoma of the lung presents with difficulty in speaking. On examination, he is noted to have dysarthric speech and deviation of the tongue to the left. CT of the brain is unremarkable, but review on bone windows reveals a destructive lesion of the left side of the skull base consistent with a bony metastasis. Which of following skull base structures is most likely to be involved?
a. foramen ovale
b. foramen rotundum
c. foramen lacerum
d. jugular foramen
e. hypoglossal canal
e. hypoglossal canal
Hypoglossal nerve (cranial nerve XII) palsy is uncommon, characteristically producing unilateral atrophy of the tongue musculature, and resulting in deviation of the tongue towards the weak side and dysarthric speech.
Supranuclear lesions cause contralateral paralysis (tongue deviation away from the side of the lesion) whereas nuclear and infranuclear lesions cause ipsilateral paralysis (tongue deviation towards the side of the lesion).
The hypoglossal nerve exits the skull base via the hypoglossal canal, and this segment of the nerve may be affected by benign or malignant tumours and trauma of the skull base.
Metastatic tumours most commonly arise from the lung, breast or prostate primaries. Direct extension from nasopharyngeal squamous cell carcinoma may also produce skull base erosion involving the hypoglossal canal. Other pathological conditions that can affect the nerve at this site include skull base infections, Paget’s disease and FD.
9 A young boy presents with repeated seizures. MR Imaging is normal._ Surgery is being considered. What would be the most sensitive radionuclide examination to identify the source?
(a) 99mTc-HMPAO SPECT inter-ictal imaging
(b) 99mTc-HMPAO SPECT ictal imaging
(c) 99mTc-iomazenil SPECT inter-ictal imaging
(d) 99mTc-iomazenil SPECT ictal imaging
(e) 99mTc-flumazenil SPECT post-ictal imaging
(b) 99mTc-HMPAO SPECT ictal imaging
99mTc-HMPAO SPECT ictal imaging is the most sensitive examination.
24 How many of Dolan’s lines can be interrupted by a ‘tripod’facial fracture?
(a) 1
(b) 2
(c) 3
(d) 4
(e) 5
24 (c)
Dolan only defined three lines (orbital, zygomatic and maxillary) – all can be disrupted by a tripod fracture.
39 Plain skull radiographs are performed. A possible abnormality is identified, and a CT head is requested. Which of the following measurements is abnormal?
(a) The tip of the odontoid process is 7 mm above McGregor’s Line
(b) The basal angle is 130 degrees
(c) There are 3 Wormian bones
(d) The largest Wormian bone is 3 x 3 mm
(e) The basal angle is 125 degrees
(a) The tip of the odontoid process is 7 mm above McGregor’s Line
The tip of the odontoid process should lie less than 5 mm above McGregor’s Line.
The basal angle (the angulation between the floor of the anterior cranial fossa and the clivus) should be less than 140 degrees.
Wormian bones should be less than 10 in number and less than 6 x 4 mm in size.
Cranial sutures should be < 10 mm at birth, < 3 mm at 2 years old, and < 2 mm at 3 years old.
