Neurology Flashcards
Regarding drugs and its effects on the Central Nervous System, which of the following is
INCORRECT?
a. Tight junctions of the blood brain barrier prevent many drugs from crossing into the CNS, so only medications that can cross the blood brain barrier exert an effect there.
b. Increased lipid solubility enhances the passage of drugs across the blood brain barrier.
c. In most people, Penicillins have poor penetration across the blood brain barrier.
d. In most people, Aminoglycosides have poor penetration across the blood brain barrier.
e. There are a variety of transport mechanisms such as active transport pumps and receptor-mediated transport that allows selected substances across the blood brain barrier.
Answer: A
Drugs do not always have to cross the blood brain barrier in order to work on the central nervous system. Domperidone is an example of a drug that does not cross the blood brain
barrier, but can still have negative Dopamine effects at the antiemetic chemoreceptor trigger zone
Penicillins do not usually cross the blood brain barrier, but are used in the treatment of meningitis as the inflammation of meninges decreases the permeability of the blood brain
barrier, allowing penicillin to access the CNS.
When to use different MRI sequences - SWI, T2, FLAIR, DWI
SWI – have a google of SWI in CAA and hypertensive haemorrhages so you are familiar with the distribution. This sequence was previously called gradient echo (GRE)
T2 – good for brain pathology, CSF appears white, eg demyelination
FLAIR – subtype of T2, make CSF black and allows better differentiation of brain/CSF, particularly those close to cortex
DWI – used with ADC in assessment of acute infarction eg stroke, also used in other disease eg abscess
A 35 year old gentleman presents to hospital with sudden onset of right hand numbness associated with loss of cool sensation. Over the next 24 hours he develops diplopia, as well as vertigo. He begins to lose balance on mobilisation and is now unable to take a few steps before falling. His past medical history is unremarkable except for a heavy alcohol history drinking 1-2 bottles of wine a night. On examination he has right lateral rectus palsy, sustained nystagmus on lateral gaze, broad base gait. His motor examination is normal. Reflexes are all intact. A MRI is ordered. Where is the most specific abnormality seen in this gentleman’s condition?
A. Third ventricle
B. Mamillary bodies
C. Cerebellum
D. Red nucleus
B
Atrophy of the mamillary bodies is the most specific abnormality seen in Wernicke’s
A professor of marine biology who lectures at the university presents with deteriorating
cognition over 6 months to the point that his tenure has been ceased over issues of
disinhibited behaviour. Your examination reveals a MOCA of 12, myoclonus in all 4 limbs. An
EEG shows periodic sharp waves.
Which of the following findings on MRI would be most in keeping with his presumed
diagnosis?
A. Frontal lobe atrophy
B. Unilateral temporal lobe enhancement on T2/FLAIR
C. Midbrain atrophy producing a “Humming bird sign” on sagittal view
D. Caudate and putamen T2 hyperintensity, and diffusion restriction on DWI/ADC
Answer = D
The presentation is consistent with Creutzfeldt-Jakob disease, with rapid onset dementia, behavioural changes, and myoclonus. EEG shows a generalized periodic sharp wave pattern. MRI findings include diffusion restriction in the cortex and basal ganglia, with “cortical ribboning” a characteristic sign, and on T2 hyperintensity in the basal ganglia and the cortex
(less common).
A: frontotemporal dementia,
B: Herpes simplex encephalitis or limbic encephalitis, C: Progressive supranuclear palsy.
