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Random introduction stuff

  • Mnemonics
    • Cranial nerves - see wikipedia
    • Standing room only = where CNVII leaves skull
    • The zoo bought monkey clothes = for branches of facial nerve
    • Some say money matters, but my brother says big boobs matter most
      • Cranial nerve functions - for sensory/motor or both.
  • Functional neuroanatomy
    • Frontal lobe
      • Problem solving, higher toughtout, abstract thinking, motor controll, smell (prefrontal multimodal association cortex)
    • Precentral gyrus = primary motor cortex
  • Parietal lobe = sensory awareness esp postcentral gyrus, abstract reasoning, language interpretation, spatial orientation (neglect on right side, Wernicke's aphasia, loss of left and right, stop appreciating what their body looks like)
    • Primary sensory Cx = postcentral gyrus
  • Occipital = visual
  • Temporal = emotions, memory
  • Important areas (know which gyrus, so you can state it in exam!)
    • Auditory cortex - superior temporal gyrus
    • Wernicke's area
    • Angular gyrus
    • Broca's area
    • Motor strip
    • Sensory strip
  • Somatotopy - know the motor and sensory homunculus
    • Median fissure provides boundary of foot/leg
    • Note the slight differences between the

Spinal tracts

  • More medial = trunk/axial muscles
    • Further outwards = more appendicular/limbs, voluntary control
  • Posterior = flexors, anterior = extensors
  • Ventral horn = motor, dorsal = sensory
  • Remember all the tracts (see the diagram off wikpedia below); memorise this diagram below

Spinal cord tracts - English.svg

Corticospinal tract

  • Origin: 40% primary motor cortex (performing tasks), 30% secondary motor cortex (coordinated movement), 30% somatosensory cortex (anticipates touch - tone down sensory fibres, so you don't get surprised when you feel it)
    • Note the difference between premotor and supplementary motor
  • 90% lateral corticospinal for limb muscle control i.e. voluntary movement
  • 10% anterior corticospinal for axial muscle control i.e. posture
  • lateral decussates at medulla oblongata - pyramidal decussation, to go to lateral corticospinal tract
  • medial doesn't decussate at medulla - stays at anterior corticospinal tract (for posture), instead decussates
    • anterior white commissure = site of decussation of medial corticospinal
  • Physical exam of corticospinal = tone, power, reflex

Dorsal column - medial lemniscus

  • Fine touch
  • proprioception
  • vibration
  • discriminative touch (2 point discrimination)
  • decussate at medulla oblongata through the internal arcuate fibre (not fasciculus)
  • formed from the gracile and cuneate fasciculi
  • stimulate left foot: sensory neuron from foot --> synapse at dorsal column (GF neurons), ascends on ipsilateral side, then decussates at the medulla (internal arcuate fibres)
    • remember that at the end of the g and c fasciculi, there are synapses with the g and c nuclei
    • decussation: things that are more medial (gracile fasc) move to the front, and things more lateral (cuneate fasc.) move to back
    • then goes to the thalamus
    • then goes to the postcentral gyrus
  • Note also the trigeminal for the face (see diagram)
  • Note that there are normally 4 neurons in series for the spinothalamic pathway, and 3 in series for the lemniscal pathway

Spinothalamic

  • Pain (lateral)
  • Temperature (lateral)
  • Crude touch (anterior)
  • Decussate within the spinal cord within 2 segments through the anterior white commissure
  • Usually ascends 2 segments before synapsing (sometimes synapses and crosses over at same level)

Sample question

  • Hemi-transect of spinal cord at T4 (just below T3 nerve root level)
  • Compare and contrast upper and lower motor neuron disease
    • Definition
      • UMN = motor strip, stops at the ventral horn
      • LMN = below ventral horn
    • Table
      • Mechanism
      • Wasting
      • Fasciculations; due to random depolarisations
      • Fibrillations on EMB
      • Power
      • Tone
      • Reflex
      • Babinski reflex
      • Clonus - upward deflecting in UMN
  • Discuss what clinical features would be elicited on exam and explain the underlying mechanism
    • Colour in important areas on spinal cord
    • Mention that anterior and lateral corticospinal tract have different functions

Neuroplasticity

  • Grey matter can get redistributed according to need
  • After stroke, recovery and compensation occurs via axonal sprouting and neurogenesis
  1. Axonal sprouting = growth factors - GAP43 and downregulate inhibitory e.g. NogoA
  2. Neurogenesis due to EOP, that signals neuroblasts to move from subventricular zone to infarcted site

3 phases of brain reorganisation during language recovery:

  1. strongly reduced activation of language areas in left hemisphere in acute stage
  2. upregulation of recruitment homologue language zones to help with language improvement
  3. normalised activation of left language areas, showing consolidation of language
    • won't be as good as before lesion, but it will have improved

Cerebral blood supply

  • Internal carotid arteries (anterior circulation)
    • opthalmic artery
    • anterior choroidal artery (gives off branches to part of internal capsule)
    • anterior cerebral artery
    • anterior communicating artery
    • middle cerebral artery (terminal branch)
  • vertebral arteries
    • anterior spinal artery
    • posterior spinal artery
    • posterior inferior cerebellar artery
    • combine to form the basilar artery
  • basilar artery (see wikipedia:Locked-in syndrome
    • pontine arteries
    • internal acoustic artery
    • anterior inferior cerebellar artery
    • superior cerebellar artery
    • posterior cerebral artery (terminal branch)
  • functional understanding (compare with homunculus)
    • ACA = medial/midline of brain up to superior part of lateral aspect of brain
    • MCA = lateral part of brain
    • PCA = occipital lobe, thalamus, etc
  • Answering a sample question
    • which artery is affected
    • what are the branches of this artery?
    • including branches, which areas of the brain are supplied by this artery (and therefore affected)?
    • what are the functional consequences
  • MCA stroke
    • draw diagram
    • artery affected: MCA
    • areas supplied - lateral surfaces of brain (including the sensory and motor homunculi except for leg and foot)
    • broca's and wernicke's area (of dominant hemisphere)
      • on the non-language side - neglect
    • basal ganglia and internal capsule
    • have a list of regions of the brain and what supplies them
    • contralateral hemiparesis (weakening)/hemiplegia (paralysis), mostly in muscles of arm and face
      • note that cranial nerves do not decussate, but their cortical map is still on the contralateral side
    • loss of sensation on the contralateral side of the face and arm (anaesthesia/hyposthesia)
    • aphasia (expressive and/or receptive) if dominant hemisphere involved
    • sensory neglect syndrome (if non-dominant hemisphere involved)
    • contralateral hemiparesis in the legs as well if the internal capsule is inveolved
    • hyperreflexia and hypertonia (upper motor neuron lesion)
  • remember end of cuneate = T6

Stroke

  • an abnormality of the brain of acute onset caused by a pathological process affecting blood vessels
  • 85% due to infarction, 15% hemorrhage
  • infarction risk factors: atherosclerosis, hypertension, heart disease, diabetes
  • Causes: thrombosis, embolism, vasospasm, herniation, local vasculitis, poor perfusion without acute obstruction
  • TIAs: episodes of non-traumatic focal loss of cerebral function (e.g. vision) lasting no more than 24 hours

Thrombotic stroke

  • Pale infarcts
  • Superimposed on atheromatous plaques
  • Key locations: internal carotid artery (carotid bifurcation), middle cerebral artery bifurcation, vertebrobasilar system
    • Recall Virchow's triad

Embolic stroke

  • Haemorrhagic infarct - not the same as haemorrhagic stroke
  • Could be from thrombus in carotid arteries
  • But heart is the most common source of emboli - mural thrombus overlying MI, valvular vegetations, thrombus in left atrium (atrial fibrillation)
  • Often end up in MCA territory

Sample question

  • Stroke 3 months ago, presenting for rehab. Past history includes an MI 10 years ago
  • Risk factors
    • Modifiable
    • Would this be thrombotic or embolic? Contrast the different pathophysiologies of these two subcategories
      • Use a table

Parkinson's disease

  • Disorder of the basal ganglia (death of dopaminergic neurons in the substantia nigra pars compacta)
  • Characterised by: tremor, hypokinesia (bradykinesia, akinesia), rigidity, postural instability
    • It's a TRAP - tremor, rigidity, akinesia, postural instability
  • Often, eventually develop cognitive and behavioural problems
    • Not simply a movement disorder as the disease progresses
  • For each drug, learn name, class (tag phrase e.g. dopamine agonist, MAOB inhibitor, etc), mechanism of action, side effects/contraindications
  • Don't forget nonpharmacological methods of treating (stretching and strengthening, training in transfer techniques)

List of drugs

  • Synthetic L-dopa (levodopa)
  • Peripheral dopamine decarboxylase inhibitors (carbidopa)
  • Monoamine oxidase B (MOAB) inhibitors (selegiline)
  • Catechol-O-methyltransferase (COMT) inhibitors (entacapone, tolcapone)
  • dopamine agonists (bromocriptine, cabergoline, etc)

Mechanism of action

Side effects

  • All dopaminergic drugs: nausea, vomiting, hallucinations
  • dyskinesias (end of dose, peak dose, early morning)
  • dopamine agonists: hypersexuality, gambling, addiction, punding (repetition of meaningless but complex motor tasks)

Sample q

  • Someone of PD, L-dopa is causing significant morbidity due to dyskinesias
  • list two other drugs used to treat PD
  • for each, state its mechanism of action, and list two side effects of the drug


  • Class: dopamine agonist
  • Names: ropinirole, pramipexole
  • Mech: increases stimulation of dopaminergic neurons in the SN
  • ARx: punding, gambling addiction, hypersexuality, etc