neurology Flashcards

Question

describe the anatomy of dorsal columns medial leminiscus pathway

Answer 1

carries info on fine touch, proprioception and vibration sense 1st order = Abeta - into dorsal horn and ascend ipsilaterally to the medulla where they synapse with 2nd order 2nd order = from medulla cross to contralateral side and synapse to thalamus 3rd order = thal to cortex via internal capsule Fasciculus gracilis: Carries information from the lower body (below T6). Fasciculus cuneatus: Carries information from the upper body (above T6).

Answer 2

the descending pathways carry motor information from brain and brainstem to peripheries. The major one is the corticospinal tract which is responsible for conscious movement 1. starts in pre-central gyrus of motor cortex 2. UMN leave motor cortex and travel to medulla via the internal capsule 3. at medulla some fibres cross over and 10% remains ipsilateral. The 90% that crossed are called the lateral corticospinal tract and responsible for limb movement, the other 10% are the anterior corticospinal tract, responsible for posture. 4. at the ventral horn the UMN synapse with LMN 5. the lLMN leave ventral root and join spinal nerves to innervate muscles. other descending tracts includ corticobulbar e.g. responsible for head and neck. Also rubrospinal and others.

Answer 3

primary motor cortex = pre central gyrus basal ganglia = fine tuning amplitude cerebellum = coordination pre-motor areas = planning

Answer 4

the motor supply for the face is by the corticobulbar tract. this originates in cortex where UMN emerge and synapse with LMN at CN nuclei. Most of these have b/l innervation i.e. right and left cortex both synapse with R and L CN nuclei except for hypoglossal nerve and the top part of facial nerve. therefore the facial nerve - upper branches will show weakness if one side of brain is gone. the rest of the face will have innervation by other side. draw a pic to help

Answer 5

In the acute phase spinal shock is seen. which includes * hypotension * flaccid paralysis * hyporeflexia * pripism * urinary retention depending on place of injury .. if above C3 - diaphragm innervation effected - respiratory paralysis if above T8 - loss of intercostals, poor cough, reduced FRC at any level - loss of sensation/ motor control below that point. later spastic paralysis, and hyperreflexia - UMN signs.

Answer 6

this is the syndrome presenation seen when there is a hemisection of the spinal cord. i.e. one half is injured. it results in loss of contralateral spinothalamic pathways below the lesion. and loss of ipsilateral corticospinal and dorsal columns below the region.

Answer 7

stroke in the anterior spinal artery results in ischaemia to 2/3 anterior cord. hence - pain, temp, motor sparing of dorsal columns - proprioception and fine touch + vibration

Answer 8

this is where there is injury to the cente of the cord extending outwards e.g. syringomyelia (cyst in central canal) this will effect spinothalamic tracts crossin the cord at that level **it will also affect motor nerves upper >lower ** = hallmark sign it will also affect some dorsal columns

Answer 9

the cauda equina is a collection of spinal nerves that continues on after the spinal cord has ended (L2/3). Compression of these nerves results in a syndrome of back pain, saddle paraesthesia, loss of anal tone, b/l leg weakness and loss bladder / bowel control can be caused most commonly by L5/S1 disc prolapse but also tumours, abscess, trauma.

Answer 10

subacute degeneration of the cord lack of B12 means it cant act as a co-factor for methionine synthase which is required to replenish myelin hence dordal columns and lateral columns are most effected - loss of prop, vibration, fine touch - plus loss of lateral corticospinal - spasticity

Answer 11

The BBB is a physical barrier created between the blood and brain to protect the brain for chemical injury. It consists of endothelial cells with tight junctions, basement membrane and astrocytes. This results in a physical barrier making it hard for free flow of molecules between blood and brain hence * maintains extracellular environment of brain * protects from harmful chemicals * maintain local high conc of NT and prevents spread to systemic

Answer 12

simple diffusion - CO2, O2, inhalation agents (lipid soluble stuff) active transport - small ions - allows regulation of CSF composition fasciliated diffusion - GLUT1 and aquaporin pinocytosis - vesicle transport e.g. insulin

Answer 13

pituitary pineal choroid plexus median eminence of hypothalamus - osmoreceptors area postrema

Answer 14

bile and ammonia drugs - L dopa, mannitol

Answer 15

CSF is fluid found between pia and arachnoid layers i.e. within the subarachnoid space. In total around 150ml of fluid at any one time and 500ml is produced per day by choroid plexus cells. it has a number of roles including 1. acting as a shock absorber by increasing boyancy 2. regulates ICP - can act as a buffer for pressure changes 3. helps maintain a constant chemical environment inc removal of waste 4. part of the mechanisms for respiratory control based on PaCO2 by producing H+

Answer 16

produced in lateral ventricles by choroid plexus travels via foramen monro into 3rd ventricle then via aqueduct of sylvius into 4th ventricle and then via 2 further foramen into the subarachnoid space whereby it is absorbed by archnoid granulations. foramen mag-en-die (medial foramen) foramen lushk - lateral (also produced by 3rd and 4th ventricles choroid plexus)

Answer 17

slightly more acidic - 7.32 more chloride less protein, less glucose, less bicarbonate same K, same Na , same osmolality

Answer 18

10-15mmHg lying down 20-30mmHg sitting up

Answer 19

if too much/ too little CSF is produced it can result in problems in intracranial pressure production - too much e.g. choroid tumour. too little e.g. choroid plexus are under perfused flow / obstruction - tumours, bleeding - pressure can build up removal - infection/ damage to arachnoid granulations - pressure builds up if pressure builds up it can result in hydrocephalus

Answer 20

increased volume of CSF can be as a result of increased production, obstruction to flow or decreased resorption pressure can build up and increase size of ventricles and compress the brain. can be classified by onset e.g. congential vs acquired. aquired causes include tumours, SAH, meningitis with adhesions. managed by ventricular drains / shunts

Answer 21

sampling of CSF is useful in diagnostics. The biochemistry, cellular counts and gram stain can be analysed for example a low glucose may suggest bacterial infection, high white cells could suggest autoimmunity or infection, bleeding/ xanthachromia could suggest SAH.

Answer 22

the circle of wilis describes the organisation of blod supply to the brain. there is a posterior and anterior circulation which anastomose anteriro = internal carotid posterior = vertebral arteries feeding basilar artery. basilar artery central one come down - not labelled on diagram.

Answer 23

anterior cerebral artery = frontal and parietal middle cerebral artery = lateral surfaces - temporal lobe posterior cerebral artery = temporal and occipital vertebral artery = brain stem and cerebellum

Answer 24

brain parenchyema is drain via cerebral veins which drain into sagital sinuses. eventually all meet into transverse sinus then sigmoid sinus then into IJV. superior and inferior saggital sinus drain cerebral and cerebellar cortices the superior sagital sinus drains into the transverse sinus the inferior sagital sinus drains into the straight sinus and then the transverse sinus

Answer 25

50ml/100g of brain tissue / min (around 750ml/min) - 15% of CO 50ml/min = 20% of total body consumption

Answer 26

CPP is the pressure that drives blood to perfuse the brain usually 60-80mmHg defined by .. CPP = MAP - ICP (or CVP if bigger) ICP normally less than 20. therefore MAP usually 80 -100. A CPP less than 60 -results in reduced venous saturations from IJV less than 30 results in critical ischaemia

Answer 27

cerebral blood flow = cerebral perfusion pressure / cerebral vascular resistance. hence anything affecting these will alter CBF CPP in turn is affected by MAP and ICP hence overall - MAP, ICP, radius vasculature, viscosity of blood all will effect blood flow cerebral blood flow is autoregulated and under influence of a nother of physiological variables to ensure blood flow meets demand. 1. autoregulation. CBF is autoregulated between a MAP of 50-150mmHg. therefore is MAP drops, there will be vasodilation to maintain blood flow (myogenic response) 2. PaCO2 - linear relationship until CO2 is high e.g. more than 10kpa or very low less than 3kpa. this is because CO2 causes vasodilation 3. PaO2 - minimal effect until less than 8kpa and then exponential rise with drop in PaO2. again due to vasodilation effect of hypoxia. 4. temperature also affects CBF - reduced temp, reduces O2 consumption and thus CBF due to coupling.

Answer 28

CPP = CBF x cerebral vasc resistance i.e. V=IR therefore in terms of autoregulation - if pressure drops, resistance also drops via vasodilation to maintain the CBF

Answer 29

shifts to the right auto reg occurs over higher range e.g. 70-170mmHg therefore need to maintain a MAP about 70 in anaesthesia in those with HTN

Answer 30

CBF and metabolism are coupled in health i.e. regional blood flow varies with metabolic demadn this is regulated by products of metabolism e.g. K, adenosine, NO, CO2 causing vasodilation and increasing blood flow to that local region the overall blood flow is fairly constant however may be regional differences due to flow metabolism coupling.

Answer 31

CO2 affects CBF if high - increases - increased blood volume and ICP if low - descreases - ischaemia hence normocapnia important in brain injury, anaesthesia

Answer 32

volatile - increase CBF and reduce O2 consumption - uncoupling of flow metabolism coupling N20 - increases both CBF and O2 consumption NMBA = no effect ketamine = rise in ICP, O2 consumption and CBP benzos and IV inductions agents = reduce CBF and reduce O2 consumption

Answer 33

the mechanism by which an organ maintains a constant blood flow despite changes in mean arterial pressure. 2 mechanisms = myogenic and metabolic. e.g. demonstrated by kidneys and brain and others.

Answer 34

1. impaired autoregulation 2. rise in ICP - monro keille doctrine - from haemorrhage, can lead to iscaemia in areas 3. disruption of BBB 4. vasospasm 5. axonal injury

Answer 35

brain is a closed box composed of different compartments - brain tissue, blood, CSF. for ICP to be maintained, these 3 compartments must be balanced, increase in one leads to compensation by decrease in another. Eventually other compartments cant compensat and there is a sharp rise in pressure for small changes in volume. once ICP increases CPP drops unless MAP is increased further. (CPP = MAP - ICP) compensation occurs via - venous drainage and CSF drainage initially.

Answer 36

intracranial pressure is the pressure exerted by brain and CSF within the cranium. In health it is below 20mmHg (usually 8-12mmHg) this can be raised due to increase in any one of the compartments in the monro kielle doctrine hypothesis e.g. increase CSF - blocked drainage/ absorption or increased production e.g. increased brain tissue - tumour, abscess, bruising e.g. increased blood volume - haemorrhage, venous obstruction (venous sinus thrombus) other causes that are not explained with above include intracranial HTN and raised thoracic pressue e.g. coughing, PEEP.

Answer 37

this occurs following reduction in ICP which results in a viscious cycle... reduced MAP leads to fall in CPP this causes vasodilation (via autoreg) increase in blood volume further fall in ICP and so on.

Answer 38

measured via an ICP transducer e.g. ventricular drain or subarchnoid bolt 3 components - 1. pulse wave (split into 3) - P1 = arterial pressure - P2 = tidal wave - reflection of pulse on brain tisue - P3 - dicrotic wave - venous pressure. baseline = respiratory wave = varies with respiration some wave patterns can suggest pathology = slow wave = type A , B and C

Answer 39

headache, N&V, papilloema, low GCS bulging fontanelle in babies worse in morning, bending over cushings - HTN, bradycardia, irregular respirations pre terminal signs = apnoea, hypotension, fixed dilated pupils = herniation

Answer 40

ABC approach if GCS - intubation neuroprotective measures - principle is to maintain CPP and prevent secondary brain injury maintain CPP: CPP = MAP - ICP/CVP * ensure good venous drainage - head up 30degrees, loose ET ties, minimal PEEP * MAP 90mmHg (since ICP >20mmHg and CPP needs to be 70-80mmHg). * ideally would monitor ICP to target MAP correctly * may need vasopressors reduce ICP: * PAO2 - above 10kpa (reduces risk of vasodilation and raised ICP) * normocapnia - to reduce vasodilatory effects and too low results in vasoconstiction and poor O2 delivery. * sedate and paralyse to avoid straining * furosemide / mannitol / hypertonic saline * decompressive crainectomy / burr holes reduce cerebral metabolic O2 demand * sedation - propofol/thio * barbiturate coma * treat pyrexia - normothermia (hypothermia not beneficial) * normoglycaemia

Answer 41

mannitol is an osmotic diuretic causes diuresis and effectively this has a knock on osmotic effect in brain - causing fluid shift and reduction in oedema. as long as BBB intact also can scavenge free radicals and reduces CSF production. 0.25–2 g/kg, repeated if necessary, to be administered over 30-60 minutes, dose may be repeated 1–2 times after 4–8 hours. (1ml/kg of 20%) 2-3 ml/kg of 5% NaCl

Answer 42

by measuring ICP and MAP we can infer CPP and hence avoid secondary brain injury as best possible 1. external ventricular drain * gold standard * transduces pressure and releases fluid * increased risk of infection compared to others 2. subarchnoid bolt via burr hole * most common * continous measurement , slightly less accurate but less risk of infection (still risk) * however local pressure, may not represent global ICP 3. subdural pressure transducer * easy to place, less accurate 4. extradural fibreoptic probe via burr hole. * sits between dura and skull * easy and less infection risk. but doesnt drain fluid

Answer 43

A number of ways * ficks principle using N20 - kety schmidt method. i.e. flow = amount of N2O removed by brain per unit time / Av difference in N20 radioactive techniques - xenon 133 - measure radioactiveness wil show regional differences in blood flow transcranial doppler USS is most common method. USS is placed on temple and doppler principle used to determine blood flow via velocity and area of artery. this uses middle meningeal artery due to easy access. can also use basilar artery and anterior cerebral but not as easy. jugular bulb catheterisation -CVC via seldinger. jugular bulb is a dilation of jugular vein - measure pO2, sats and pH to give indication of overall adequacy of flow. if sats fall, suggests poor flow or potentially increased demand. downfalls are it only looks globally. also confounded by O2 demand e.g. if both demand and flow fall, it would appear normal. fucntional MRI and PET - rely on flow metabolism coupling. PET uses radioactive glucose. fMRI looks at areas of low and high O2

Answer 44

consists of 3 layers = pia, arachnoid, dura. subarchnoid space lies between pia and aracnoid and constains CSF. functions to protect brain , support and involved in CSF circulation

Answer 45

ischaemia = transient - seconds to min neuropraxia - local demyelination. axon intact. 1-3 weeks axonetmesis - axon damage, nerve tube intact (perineureum etc) wallarian degen 1-3mm/day neurotmesis - axon and nerve tube sethered. incomplete recovery.

Answer 46

neuronal pathways that produce rapid, automatic and predictable responses to stimuli often only include spinal cord and have minimal neuronal connections basic spinal reflex arc consists og 1. sensory neuron - myelinated A , to dorsal horn 2. interneuron - integrate signals within spinal cord 3. motor neuron - Aa from ventral horn

Answer 47

monosynaptic reflex arc that results in rapid contraction of quadricept in response to stretch of quadricep muscle. at same time as monosynaptic reflex there is also inhibitory interneuron which inhibits biceps femoris = reciprical innervation. similar stretch reflexes exist in many muscle groups and help to maintain posture and tone and prevent injury.

Answer 48

for example the withdrawal reflex in response to pain Ad fibres carrying pain - synapse with motor neurons for withdawal and contralateral limb for stability. multiple motor neurons are involved to coordinate the whole withdrawal movement. other inputs can over ride this.

Answer 49

sensory receptor located in tendons of muscle attached to the ends of muscle recognise muscle tension innervated by Ab fibres when innervated lead to inhibition of motor neuron via interneuron and thus relaxation of muscle. prevents excessive contraction.

Answer 50

within a muscle are intrafusal and extrafusal cells - the extrafusal are normal myocytes making up the contractile unit and innervated by Aa motor neuron the intrafusal fibres are the muscle spindle fibres. muscle spindles are a stretch receptor containing both nuclear bag and nuclear chain fibres. nuclear bag fibres = dynamic responses nuclear chain fibres = static responses. Send impulses via Aa (chain) and B (bag) fibres. involved in knee jerk reflex, but also give info to brain on posture and position. these are innervated by Ag motor neurons which alter their tension to match that of the overall muscle to maintain their sensitivity at detecting stretch.

Answer 51

muscle tone is a continuous basal level of muscle contraction controlled by descending extrapyramidal supraspinal neurons which innervate Ag motor neurons - these regulate the stretch of a muscle spinal which in turn will effect the overall tone of the muscle via the reflex arc.

Answer 52

patient clenches teeth/ pulls interlocked hands apart knee jerk reflex is attenuated this is because of descending modulation - increases Ag inputs to tighten the spindle and hence will seem more stretched.

Answer 53

babinski = stroking outside of foot causes toes to point up in UMN damage biceps = hit biceps tendon and contract of biceps (C5,6) knee jerk = L3/4 ankle= S1,2 pupillary light reflex - optic nerve and occulomotor to contrict pupil. gag/ corneal

Answer 54

Sits in anterior cranial fossa Primary motor cortex – precentral gyrus Supplementary motor and pre-motor areas Broca’s area – production of speech (left hemi) Personality, behaviour, judgement Dopamine reward pathways – behaviour and motivation

Answer 55

Primary sensory cortex – post central gyrus Calculation and writing Parietal association cortex – spatial awareness – damage leads to neglect of one side of body/ world

Answer 56

Wernicke's – understanding language Auditory cortex Smell, taste, emotion Memory and visual recognition of faces

Answer 57

Coordination of movements Balance Receives afferents from proprioceptors, eyes, vestibular apparatus .

Answer 58

carries axons of sensory, motor and optical fibres in the posterior limb It has a relatively weak blood supply – middle cerebral artery Stroke results in contralateral hemiparesis (motor fibres decussate after internal capsule)

Answer 59

MIDBRAIN, PONS, MEDULLA Midbrain involved in innate responses to fear - sound and vision Sleep wake and consciousness Contains nuclei III and IV Contains medial longitudinal bundle – to coordinate gaze Pons Some nuclei of respiration Body equilibrium and posture CN V, VI, VII and VIII Medulla Cardiac and respiratory centre, swallowing, digestion, vomiting CN IX, X, XI and XII

Answer 60

The basal ganglia are a set of structures that sit below the cortex and include Putamen and caudate nucleus and globus pallidus The basal ganglia are involved in fine tuning voluntary movements and procedural learning Majority of GABA neurons Direct and indirect pathways to control movement - involves dopamine .

Answer 61

consists of thalamus, pituitary and hypothalamus Thalamus – collection of nuclei that process sensory info from body and relay to cerebral cortex and vice versa . Hypothalamus – The hypothalamus contains neural centres for hunger, thirst and body temperature and thus is important in the regulation of homoeostasis. Other functions include sleep, emotion, sexual arousal,. major neuroendocrine hormone system. Pituitary gland – anterior and posterior - neuroendocrine secretion - linked closely to hypothalamus

Answer 62

Limbic system: Functional system including frontal lobe, thalamus, temporal lobe and amygdala, hypothalamus, hippocampus, cingulate gyrus Involved in learning, emotion, behaviour and endocrine responses via hypothalamus Hippocampus Located in the inferior temporal lobe Involved in new memory formation – damage leads to anterograde amnesia. also long term memory Amygdala Located in temporal lobe Fear, anger, emotions.

Answer 63

Hemiparesis – contralateral Brocas dysphasia Personality/behavioural change Incontinence Reduced executive function e.g. planning Anosmia

Answer 64

Dominant: Sensory inattention , reduced 2 point discrimination Dyslexia, dyscalclia Contralateral inferior homonymous quadrantanopia Non-dominant = spatial neglect (one side of a clock, one half of face shaved)

Answer 65

**Occipital lobe:** Homonymous hemianopia with macular sparing **Temporal lobe:** Dominant: contralateral upper quadrantanopia , Wernickes dysphagia, Poor memory, auditory agnosia, difficulty identifying faces Non dominant – sounds, emotions with any SoL can mention as lesion gets bigger - raised ICP (monro kielle doctrine) and brainstem herniation + cushings triad.

Answer 66

Cerebellum: dysdiadokinesis, ataxia, nystagmus, intention tremor, slurred speech, hypotonia Causes – tumour, stroke, toxins (alcohol), B12/thiamine deficiency

Answer 67

**upper:** Wide spread i.e. not 1 myotome Suppination is weaker than pronation: pronator drift (this is the first muscles to be affected Hypertonia / spasticity Hyperreflexia – positive Hoffman and Babinski sign Clonus **Lower** Weakness in myotome Hypotonia Hyporeflexia Muscle wasting and fasciculations

Answer 68

overall cerbral blood flow = 50ml/100g/min (around 750ml/min) (15% of CO) grey matter = 70ml/100g/min white matter = 30ml/100g/min

Answer 69

3ml/100g/min of O2 consumped (50ml/min for whole brain) about 20% of total O2 consumption

Answer 70

CPP is usually around 60-80mmHg below 30mmHg - ischaemia develops therefore if the MAP-ICP is less than 30mmHg this wil occur. CPP and CBF are inversely related. In terms of CBF normal is 50ml/100g/min acidosis will occur below this --> oedema below 20ml/100g/min - neuronal functions caese below 10ml/100g/min - cell death occurs

Answer 71

normally around 8-12mmHg slightly more when supine and less when standing directly related to intrathoracic pressure and shows normal respiratory swing. thus increases with straning, coughing and PEEP.

Answer 72

IV induction agents e.g. propofol and thio cause a dose dependant reduction in ICP, blood flow and metabolic rate. thus reduce risk of secondary brain injury. ketamine can increase ICP and metabolic rate - however its advantage in CVS instability is favoured over this. voltatiles cause vasodialtion and thus increase ICP - avoided in neurosurgery if possible. N20 increases ICP and metabolic rate - again best avoided. benzos reduce flow and metabolic consumption. but not ICP NMBA do not alter ICP directly but prevent straining and coughing sux may have transient rise in ICP

Answer 73

phenytoin membrane stabiliser reduces Na/Ca influx and hence depolarisation

Answer 74

rapid infusion to have effects

Answer 75

diabetes insipidus lack of ADH dilute urine, low urinary sodium concentrated blood - high plasma sodium

Answer 76

glucose metabolised and then effectively hypotonic solution will diffuse across BBB and increase swelling however if patient is hypoglycaemic, may need to be given.

Answer 77

>3L in 24 hours >125ml/hr but usually much higher than this even like 20L/day (800ml/hr)

Answer 78

GCS pupils nuerological exam MAP and ICP to work out CPP trend in BP, HR and RR - cushings urine output - diabetes insipidus

Answer 79

1. Vagus nerve. 2. Superior laryngeal nerve. 3. Internal laryngeal nerve. 4. External laryngeal nerve. 5. Recurrent laryngeal nerve.

Answer 80

CN X medulla oblongata

Answer 81

dorsal nucleus nucleus ambiguus nucleus tractus solitarus

Answer 82

jugular foramen

Answer 83

CN IX, X, XII internal jugular vein

Answer 84

down within the carotid sheath with the carotid artery and IJV lies more deep to these and inbetween them.

Answer 85

On the right side, * passes across anterior to subclavian artery * descends by the side of the trachea to root of lung to pulmonary plexus and oesophageal plexus on left * enters the thorax between the left carotid and subclavian arteries,. * runs along the anterior surface of the oesophagus, * it unites with the nerve of the right side in the oesophageal plexus recurrent laryngeal nerve on the left - hooks under the arch of the aorta, ascending to innervate the majority of the intrinsic muscles of the larynx. hence longer course. right - hooks under subclavian

Answer 86

superior laryngeal recurrent laryngeal (inferior) in thorax cardiac branches bronchial branches oesophageal branches gastric , coeliac and hepatic branches in abdomen

Answer 87

K = -90mV Na +60mV Cl = -70mV

Answer 88

5 -15mmHg body position, hydration , pathology (hydrocephalus can increase it or brain tumours can reduce it ) or infection.

Answer 89

within dural sinuses

Answer 90

ammonium - astrocytes metabolise this (unless levels rise) bile some amino acids e.g histamine - acts as NT