Clinical Neurology Flashcards
What appears darker on CT scan, white matter or grey matter?
White matter is darker, as it is less dense due to the fatty myelin
What is used as artificial contrast in CT? And what can it be used to show?
Iodine, as it is dense in electrons. It can show an angiogram, then a venogram, then any disruption to BBB as it doesnt normally cross
What determines the contrast in CT and MRI?
CT = electron density; MRI = proton density
What are the advantages of CT over MRI and vice versa with neuroimaging?
CT shows better bone detail, fast, can be used with ICU/emergency equipment, better with stroke and head injury; however MRI shows better pathology contrast, multiples and no ionisation
Which areas of the brain are head injuries and contusions most commonly found?
At the junctions between lobes and hemispheres
What are T1 hyper intense MRIs (bright) best for?
Fat and the 4Ms (minerals, methemoglobin -subacute haematoma, melanin, mush)
What is Schizencephaly?
A large cleft forms in the cortex
What is Polymicrogyria?
Cortex in some areas is underdeveloped, with a smaller surface area so doesn’t have any gyri
What is the risk with any cortical abnormalities?
Seizures
What kind of inheritance is Duchenne’s Muscular Dystrophy?
X-linked recessive
What kind of inheritance is Huntington’s?
Autosomal dominant
How does curare cause paralysis?
It is a competitive antagonist of ACh. It therefore doesnt open the ion channel, preventing contraction and eventually stops respiration
How does Clostridium botulinum cause muscle paralysis?
Toxin cleaves presynaptic proteins involved in vesicle formation and block vesicle docking with the presynaptic membrane.
How does Lambert Eaton Myasthenic Syndrome cause muscle paralysis?
Antibodies to presynaptic calcium channels leads to less vesicle release
Where is the location of disorder in Myasthenia Gravis?
Post synaptic membrane of neuromuscular junction
What are fasciculations? What are their causes?
Visible, fast, fine, spontaneous twitches (e.g. eye twitch). May occur in healthy muscle – precitated by stress, caffeine, fatigue, or can occur in denervated muscle which become hyperexcitable.
What is myotonia?
Failure of muscle relaxation after use
*What are the 6 main types of muscle disorders?
*
What are some infective causes of muscle disorders?
Borrelia occurring as a result of Lyme disese in ticks; myalgic from viral infections
What are important aspects of examination of muscle?
Inspection (thin, wasting, fasciculations); palpation; Strength testing (power across joints); neck strength (flexion and extension - should never be able to over come these); core strength; fatiguability (ask them to repeat tasks several times then test again e.g. holding arms up or blinking)
Which system is used to grade muscle power?
MRC Muscle Power Grading (0 = no movement at all, 5 = full strength)
What is a normal adult ICP?
9-11 mmHg
What is the formula for Cerebral Perfusion Pressure (CPP)?
CPP = MAP - ICP (basically pressure coming up from the heart minus the pressure coming from the head pushing it back)
What CCP are you aiming for after head injury?
> 60mmHg (enough to perfect, but not too high an ICP to prevent perfusion)
What is global cerebral autoregulation?
Brain autoregulates the blood pressure to maintain constant CPP regardless of MAP
What is focal cerebral autoregulation?
Blood flow coupling to areas of high level of function
What constitutes a coma?
Do not open eyes, follow commands, speak. Equates to a GSC sum of 8 or less
What kills patients in coma with head injury?
Hypoxia, hypotension, raised ICP