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Muscle weakness Flashcards

1
Q

What are the 2 types of descending tracts?

A

Pyramidal tracts

Extrapyramidal tracts

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2
Q

Where do the pyramidal tracts originate?

A

Cerebral cortex

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3
Q

What is the function of the pyramidal tracts?

A

Voluntary control of musculature of body and face

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4
Q

Where do the pyramidal tracts pass through?

A

Medulla oblongata

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5
Q

Name the 3 pyramidal tracts

A

Corticospinal tracts - lateral and anterior

Cortiobullar

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6
Q

Where do the extrapyramidal tracts originate from?

A

Brainstem

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7
Q

What is the function of the extrapyramidal tracts?

A

Involuntary and automatic control of all musculature such as muscle tone, balance, posture and locomotion

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8
Q

Name the 4 extrapyramidal tracts

A

Vestibulospinal and reticulospinal (these don’t decussate)

Rubrospinal and tectospinal (decessate)

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9
Q

Where does the corticospinal tract divide into the lateral and anterior?

A

Caudal part of medulla

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10
Q

What is the route of the lateral corticospinal tract?

A

Decussates at medulla and terminates in ventral horn at segmental levels

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11
Q

What is the route of the anterior corticospinal tract?

A

Remains ipsilateral decussates in cervical and upper thoracic segmental levels

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12
Q

Which cranial nerve is NOT part of the PNS?

A

CN II

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13
Q

Where does the spinal cord end?

A

L1

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14
Q

What information about muscle weakness is important to get in a history?

A

Onset - instant/gradual
Distribution - proximal/distal, symmetrical/asymmetrical, mono (local process)/poly (diffuse), cranial involvement (bulbar/ophthalmoplegia/facial)
Variability - fatigueability/relapse-remission
Additional features - sensory symptoms (paraesthesia/loss of sensation)
Contact - recent illness, PMH, FH, drugs, alcohol

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15
Q

What the the UMN signs?

A 
Bulk - normal
Tone - increased
Strength - decreased
No fasciculations
Increased reflexes
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16
Q

What are the LMN signs?

A 
Reduced (wasting) bulk
Normal/decreased tone
Decreased strength
Fasciculations
Decreased/absent reflexes
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17
Q

How is muscle power graded?

A

MRC grading

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18
Q

What does 0 mean on MRC grading?

A

Complete paralysis

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19
Q

What does 1 mean on MRC grading?

A

Flicker of contraction possible

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20
Q

What does 2 on MRC grading mean?

A

Movement possible if gravity eliminated - hold elbow up and see if can extend

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21
Q

What does 3 on MRC grading mean?

A

Movement against gravity but not resistance

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22
Q

What does 4 on MRC grading mean?

A

Movement possible against some resistance

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23
Q

What does 5 on MRC grading mean?

A

Power normal (not normally possible to overcome a normal adult’s power)

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24
Q

Name 2 causes of weakness

A

Neuropathies

Myopathies

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25
Name 3 causes of neuropathies
Peripheral neuropathy GBS MG MND
26
How are neuropathies classified?
``` Polyneuropathy (peripheral neuropathy) Mononeuropathy multiplex (mononeuritis multiplex) - at least 2 nerves Mononeuropathy - one single nerve ```
27
What is a peripheral neuropathy?
Disease affecting peripheral nerves
28
What might be the S&S of a peripheral neuropathy?
Chronic and slowly progressive Starting in legs and longer nerves Sensory/motor/both
29
What conditions cause predominantly motor loss in peripheral neuropathy?
``` GBS CIDP HSMN Diphtheria Porphyria ```
30
What condition cause predominantly sensory loss in peripheral neuropathy?
``` Deficiency states eg B12/folate Diabetes Alcohol/toxins/drugs Metabolic abnormalities eg uraemia Leprosy Amyloidosis ```
31
What is mononeuritis multiplex?
Painful, asymmetrical sensory and motor neuropathy Subacute presentation Immune/inflammation mediated
32
What causes mononeuritis multiplex?
Vasculitis eg churg strauss | Connective tissue disorder eg sarcoid
33
What is a mononeuropathy?
Individual nerve deficits in isolation | Upper limb nerves mostly affected at compression points
34
What is the most common mononeuropathy?
Median nerve entrapment at wrist | Carpel tunnel
35
What other nerves can get trapped in the upper limb and what does it look like?
Ulnar nerve at elbow (claw hand) | Radial nerve at axilla (wrist drop)
36
Which nerve entrapment in the leg is most common?
Common peroneal nerve (foot drop)
37
What investigations might you do in a neuropathy investigation?
``` Neuropathy screen (looks at screen) Vasculitis screen EMG/NCS CSF study Imaging/nerve biopsy ```
38
What happens in a neuropathy screen?
Bloods - FBC, ESR - U&E, glucose, TFT, CRP, serum electrophoresis - B12/folate - Anti-gliadin - TPHA, HIV
39
What happens in a vasculitis screen?
FBC, ESR U&E, Cr, CRP ANA, ANCA, anti-dsDNA, RhF, complement, cryoglobulins
40
What is the treatment of neuropathy?
20% idiopathic with no treatment Neuropathic analgesic - gabapentin, pregabalin, amitryptiline Treat/remove underlying cause eg DM/B12 deficiency Inflammatory neuropathy - prednisolone with steroid sparing agents Vasculitis - prednisolone with immunosuppressant
41
What is GBS?
Autoimmune response causing demyelination
42
When might GBS occur?
Post infections - resp/GI eg campylobacter
43
How does GBS present?
Subacute (< 6 weeks) ascending paralysis/numbness/areflexia | Always ask about breathing and swallowing!!
44
What will NCS studies show in GBS?
Demyelination
45
What will LP show in GBS?
Raised CSF protein
46
How do you treat GBS?
IV Ig or plasmapheresis Support Monitor FVC ITU review
47
How long can recovery from GBS take?
Weeks - years
48
What is myasthenia gravis?
Autoimmune disorder - antibodies against nicotinic acetylcholine receptors in the NMJ characterised by weakness and fatigueability of proximal limb, bulbar and ocular muscles Potentially fatal but treatable condition
49
What is also common in MG?
Thymus dysfunction - hyperplasia/thymoma
50
What are the S&S of MG?
``` Generalised - fatigueable weakness - proximal limbs, neck and face (head drop, ptosis), extraocular (complex diplopia), bulbar (speech/swallow) particularly elderly Ocular At risk of other autoimmune diseases Facial expression - myasthenic snarl Ptosis, diplopia Tendon reflexes normal but fatigueable Symptoms worse towards end of day Respiratory difficulties May fluctuate in severity over time ```
51
What investigations should you do for MG?
Tensilon test (allow accumulation of Ach in NMJ) - give IV edrophonium (short-acting anti-cholinesterase) - muscle power increases within seconds AchR antibodies (raised in 90%) and MuSK antibodies (anti-muscle specific tyrosine kinase) EMG - looks at NMJ and NCS CT thorax/MRI - hyperplasia/atrophy/tumour
52
How do you treat MG?
Acetylcholinesterase inhibitors - symptomatic treatment Immunosuppressants - steroids (start slowly), azathioprine, methotrexate, mycophenolate Thymectomy if onset < 50 and disease poorly controlled with anti-cholinesterases
53
What is a myasthenic crisis?
Severe weakness including respiratory muscles High risk of death Always ask about breathing and swallowing!!
54
What can cause a myasthenic crisis?
Infection Natural disease cycle Underdosing and overdosing of medication
55
How do you treat a myasthenic crisis?
Take change in myasthenic condition seriously Urgent review by neurologists Think about breathing and monitor FVC Anaesthetist review Plasmapheresis and IV Ig to identify and treat trigger of relapse
56
What is MND?
Degeneration of motor neurons in the motor cortex and anterior horns of spinal cord Mainly clinical diagnosis
57
How does MND present?
UMN and LMN signs No sensory, visual or bladder/bowel involvement Asymmetrical weakness Bulbar/limb onset
58
What investigations should you do for MND?
LP NCS/EMG MRI
59
What is the most common type of MND?
ALS
60
What is the survival rate of MND?
2-5 years
61
What are the most common muscle disorders?
Steroid myopathy Statin myopathy Metabolic and endocrine myopathies Myotonic dystrophy
62
What are the uncommon muscle disorders?
Muscular dystrophies eg Duchenne, Becker, facioscapulohumeral musclar dystrophy Inflammatory muscle disease - polymyositis/dermatomyositis Mitochondrial disorders
63
What are the symptoms of muscle disorders?
``` Stairs, chairs, and hair Wasting common Facial weakness Neck weakness Contractures Scoliosis Eye movement disorders rare ```
64
What investigations should you do in muscle disorders?
``` CK EMG ESR/CRP Genetics DMD Biopsy ```
65
How do you treat muscle disorders?
Remove causal agent if is one Supportive - physio, OT, back, renal, diet Immunosuppress if inflammatory
66
How common is MG?
More common in women 2:1 Peak age of incidence 30 with another smaller peak of incidence in men over 60 Prevalence 4 in 100,000
67
What can cause MG?
Under 50 and in women - other autoimmune diseases eg pernicious anaemia, SLE, rheumatoid arthritis, thymic hyperplasia Over 50 and in men - thymic atrophy or thymic tumour, rheumatoid arthritis, SLE Transient MG - D-penicillamine treatment for Wilson's
68
What is the pathology of MG?
Autoimmune disease mediated by antibodies to nicotinic acetylcholine receptor - anti-AChR antibodies, interfering with NMJ via depletion of working post-synaptic receptor sites Achieved by immune complex deposition of anti-AChR IgG and complement at post-synaptic membranes causing interference with and destruction of receptors Both B and T cells implicated Blocks excitatory effect of Ach on the nicotinic receptors due to less receptors resulting in muscle weakness
69
How can you demonstrate fatigueability in MG?
Ask patient to count to 50 - as reach higher numbers, voice becomes less audible Hold finger up high and ask patient to look at it without lifting head - after a few seconds will be unable to keep eyes raised
70
What might worsen MG symptoms?
Pregnancy, hypokalaemia, infection, emotion, exercise, drugs
71
What drugs might worsen MG symptoms?
Opiates, beta-blockers, gentamicin, tetracycline
72
What could be differentials for MG?
MS Hyperthyroidism Acute GBS Lambert-Eaton myasthenic syndrome
73
What is Lambert-Eaton myasthenic syndrome?
Paraneoplastic condition most often seen with small cell lung cancer due to defective Ach release at NMJ Causes defective Ach release at NMJ resulting in proximal limb weakness with some absent reflexes Weakness tends to improve after exercise - unlike MG
74
What are the S/E of anti-cholinesterases?
Increased salivation, lacrimation, sweating Vomiting Miosis (excessive pupillary constriction) Diarrhoea

Neuro and geriatrics (21 decks)

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