CSGD Quiz 2 2010

1

A patient is being investigated for increasing headaches. The radiologist's report states that there is a 2.5 cm lesion in the right temporal lobe that shows abnormal contrast enhancement. In regard to CT or MRI brain imaging, which one of the following best explains the term contrast enhancing? (MRI = Magnetic Resonance Imaging; CT = Computed Tomography.)


  Brain lesions that show contrast enhancement are nearly always malignant tumours.

  Contrast enhancing means that the lesion appears brighter in an image after contrast injection than in the corresponding image before injection.

  A contrast-enhancing lesion is one that is more clearly seen with T2-weighted MRI than with T1- weighted MRI.

  A contrast-enhancing lesion is one that is more clearly seen with MRI compared to CT.

  Contrast enhancing means that lesion is surrounded by a distinct band of oedema or bleeding commonly associated with some tumours or vascular malformations.


In diagnostic imaging a contrast agent may be injected intravenously (or sometimes intra-arterially). An enhancing region is one which is brighter in the after-contrast image than it is in the before-contrast image. The use of contrast of increases sensitivity, and may provide clues as to the type of abnormality.

2

With respect to the anterior cerebral artery:


  It supplies blood to the upper limb region of the primary motor and somatosensory cortices.

  A cerebrovascular accident involving this artery can lead to medial medullary syndrome.

  It is a main branch of the vertebrobasilar system.

  Occlusion may result in spastic paralysis of the contralateral lower limb.

  It gives off the lenticulostriate arteries that supply the basal ganglia.

3

Which one of the following statements about hearing is correct?


  Hair cell transduction relies on a high potassium ion concentration in the perilymph.

  Sound results in a wave on the basilar membrane travelling from the apex to the base.

  The cochlea has a high acoustic impedance because of the incompressible nature of the perilymph and endolymph.

  Difference in the intensity of sound at the two ears is a reliable cue for the position of the sound source at low frequencies (less than 1500 Hz).

  Low frequency sounds will result in displacements of the basilar membrane that are greater at the base end than at the apical end.

4

Which one of the following statements is correct?


  Oligodendrogliomas typically show 3p and 20q deletions.

  Patients with glioblastoma multiforme have good prognosis.

  Acoustic neuromas involve the eighth cranial nerve.

  Meningiomas originate from astrocytes.

  Tumour cells from myelomas produce equal amounts of kappa and lambda light chains.


A is incorrect: Oligodendrogliomas typically show 1p and 19q deletions. B is incorrect: Patients with glioblastoma multiforme have worst prognosis. D is incorrect: Meningiomas originate from meningothelial cells. E is incorrect: Tumour cells from myelomas produce either kappa or lambda light chains but not both.

5

Which one of the following statements about cerebral infarction is most correct?


  It is commonly due to venous obstruction.

  It is always symptomatic.

  It always causes clinical effects that are proportional to the size of the infarct.

  It is histologically characterised by heavy infiltration by neutrophil polymorphs.

  It can be a complication of saccular aneurysm rupture.

6

Which one of the following statements about triplet repeat neurodegenerative conditions is correct?


  The gene responsible for spinocerebellar ataxia 1 codes for alpha1A calcium channel subunit.

  In Huntington disease anticipation is usually seen through the maternal line of transmission.

  A person with a CAG repeat of 42 in the gene for huntingtin will develop Huntington disease.

  Spinocerebellar ataxia 6 is most likely due to a novel gain-of function effect.

  In Friedreich ataxia point mutations account for about half of the cases.


The gene coding for alpha1A calcium channel subunit is found in SCA 6. In HD anticipation is usually seen through the paternal line. Mechanism in SCA 6 is thought to be through a dominant-negative effect. In FA point mutations account for about 4% of cases.

7

Which one of the following statements about phototransduction is correct?


  Light causes the membrane potential of photoreceptors to depolarize.

  Light causes cGMP-gated sodium channels in the membrane of photoreceptors to open.

  Light causes an increase in cGMP formation within photoreceptors.

  Light causes closure of cGMP-gated sodium channels in the membrane of photoreceptors.

  Light causes glutamate to be released from photoreceptor synaptic terminals.


Light stimulates the phototransduction cascade that ultimately leads to the breakdown of cGMP and closure of sodium channels in the membrane of photoreceptors.

8

Which one of the following statements about ON centre ganglion cells is correct?


  A spot of light shone in the peripheral part of the receptive field will cause this cell to depolarize.

  This cell depolarizes to light because it expresses mGluR6 receptors.

  This cell hyperpolarizes to light because it expresses AMPA/Kainate receptors.

  A spot of light shone on the centre part of the receptive field will cause this cell to depolarize.

  This cell will depolarize to light because it receives direct inhibitory input from horizontal cells.

9

Which one of the following statements regarding cerebral arterial imaging is correct?


  Duplex Doppler ultrasound is a completely non-invasive technique, which is able to show detailed images of the arterial circulation in the adult head and neck.

  Computed Tomographic Angiography (CTA) is an x-ray transmission technique involving the injection of iodinated contrast media directly into a selectively catheterised cerebral artery in order to outline it.

  Positron Emission Tomography (PET) and Single Photon Emission Computed Tomography (SPECT) are x-ray transmission techniques, which are able to image cerebral perfusion, but not the individual arteries.

  Magnetic Resonance Angiography (MRA) is a non-invasive technique utilising a strong magnetic field and radiofrequency pulses to demonstrate moving protons within cerebral arteries.

  Digital Subtraction Angiography (DSA) is a technique which uses intravenous injections of the rare earth metal gadolinium to outline cerebral arteries.


B is incorrect: The contrast is injected upstream of the cerebral artery.

10

Which one of the following statements about the mind is correct?


  Most humans older than 3, but only adult monkeys, show evidence of "Theory of Mind".

  The amygdala is required to generate mental states such as loneliness and resentment.

  Effective interpersonal communication is facilitated by removal of the ventral prefrontal cortex.

  "Acquired sociopathy" is a condition associated with damage to the hypothalamus.

  Thinking about the consequences of different social decisions typically generates autonomic responses.