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Neurology > Muscle and nerve disease > Flashcards

Muscle and nerve disease Flashcards

1
Q

Describe excitation-contraction coupling.

A

It is a link between the AP generated in the sarcolemma and the start of a muscle contraction.

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2
Q

What is muscle?

A

An intricate machine designed to convert chemical energy to mechanical energy.

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3
Q

What are the common symptoms of muscle disease?

A
  • weakness of skeletal muscle
  • SOB (respiratory muscles)
  • cardiomyopathy (Beckers MD starts with heart signs)
  • poor feeding, failure to thrive and floppy (for children)
  • cramp/pain
  • myoglobulinuria (urine is black)
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4
Q

What are common signs of muscle disease?

A
  • wasting/ hypertrophy/ pseudohypertrophy (muscle is replaced by fibrous tissue)
  • normal/ reduced tone and reflexes
  • motor weakness (NOT SENSORY)
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5
Q

What are the common investigations of muscle disease?

A
  • history and examination
  • CK (creatinine kinase - levels will be higher if muscle is being broken down)
  • EMG (electromyogram - records the electrical impulses in muscle)
  • muscle biopsy
  • genetic testing
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6
Q

What are the classifications of muscle diseases?

A
  • muscular dystrophies
  • channelopathies
  • metabolic muscle disease
  • inflammatory muscle disease
  • congenital myopathies

(all except inflammatory muscle disease are single gene defects)

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7
Q

What is abnormal in the muscular dystrophies?

A

Functional dystrophin and actin are needed for the contractile mechanism within the cell. Lots of different proteins work in sync to make this happen. In MD, dystrophin doesn’t work properly.

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8
Q

Give examples of muscular dystrophies.

A
  • Duchenne’s MD (dystrophin is completely abnormal)
  • Beckers MD (dystrophin is mildly abnormal)
  • Myotonic dystrophy (most common form)
  • Facioscapulohumeral MD
  • Limb-girdle MD
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9
Q

Which genetic phenomenon is seen with myotonic dystrophy?

A

Anticipation - caused by triplet repeats and so symptoms become more and more apparent as more repeats are added on in each generation, so gets more severe.

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10
Q

What are the channelopathies?

A

Disorders of Na, Ca and Cl channels.

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11
Q

Give some examples of channelopathies.

A
  • familial hypokalemic periodic paralysis: problem with contraction
  • hyperkalaemia periodic paralysis: problem with contraction
  • paramyotonia congenita: problem with relaxation
  • myotonia congenita: problem with relaxation
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12
Q

What is metabolic muscle disease?

A

Disorders of carbohydrate or lipid metabolism. Also mitochondrial myopathies/cytopathies.

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13
Q

Give examples of metabolic muscle diseases.

A

Disorders of carbohydrate metabolism:

  • McArdle’s: person finds it hard to exercise for the first min and so needs to consume sugar, then lipid metabolism takes over
  • hard to get going

Disorders of lipid metabolism:

  • during exercise they are fine for the 1st 10 mins as they are using carbohydrate metabolism, then they need to stop
  • can only exercise in short bursts
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14
Q

Give 2 examples of inflammatory muscle diseases.

A
  • polymyositis

- dermomyositis

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15
Q

What are the symptoms of inflammatory muscle disease?

A
  • painful, weak muscles
  • dermomyositis has a characteristic rash (heliptropic - eyes, fingers and elbows)
  • any age
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16
Q

How are inflammatory muscle diseases investigated and treated?

A

Investigation:

  • CK
  • EMG
  • biopsy (PM CD8 cells and DM Bcl/CD4 as humoral)

Treat with immunosuppression.

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17
Q

What is the normal process occurring at the NMJ?

A
  • nerve releases ACh
  • ACh binds to the AChR
  • muscle contracts
  • ACh broken down by acetylcholinesterase
18
Q

Name 1 disorder of the NMJ.

A

Myesthenia Gravis.

19
Q

What is the clinical presentation of MG?

A

FATIGUABLE WEAKNESS:

  • limbs
  • eyelids (ptosis)
  • talking
  • SOB
  • diplopia
20
Q

What causes MG?

A

Auto-antibodies block the AChR. When ACh comes along there’s not as many receptors for it to bind to as auto-antibodies are taking them all up.

21
Q

What are the investigations for MG?

A
  • AChR Ab (70% positive)
  • Anti-MuSK Ab (30% positive)
  • Neurophysiology (repetitive stimulation of the nerve will cause decrement)
  • CT chest (as differential is malignant thymoma)

Diagnostic:

  • Tensilon test: inject tensilon which blocks the anti-ACh Ab’s
22
Q

How is MG treated?

A

Symptomatic:

  • acetylcholinesterase inhibitor: prevents ACh breakdown so gives ACh time to find an AChR that hasn’t been taken upby autoantibodies

Immunosuppression:

  • prednisolone and a steroid-saving agent like azathioprine so that less steroid can be used

–> use both

23
Q

Why may MG present in the old and young?

A

Young: thymic hyperplasia

Old: malignant thymoma

–> thymectomy in females < 40 with malignant thymoma

24
Q

What do peripheral nerves consist of?

A
  • sensory axons: small fibres for pain and temp, large fibres for vibration sense and proprioception
  • motor axons
  • ANS
25
Q

What are the 3 causes of nerve root disease?

A
  • degenerative spine disease eg arthritis
  • inflammation eg Lyme/shingles
  • infiltration
26
Q

What are the 2 types of lesions of peripheral nerves?

A
  • compressive/entrapment neuropathy like carpal tunnel (medial nerve)
  • vasculitic like mononeuritis multiplex
27
Q

What are the features of generalised peripheral neuropathy?

A

Motor and/or sensory features with/without autonomic features. Start distally and move proximally.

28
Q

Name some causes of generalised peripheral neuropathy.

A
  • metabolic: DM
  • toxic: drugs
  • hereditary
  • infectious: Lyme
  • inflammatory demyelinating: acute or chronic
29
Q

Give an example of an acute inflammatory demyelinating cause of generalised peripheral neuropathy.

A

Guillain-Barre syndrome.

30
Q

What is the most common demyelinating disease?

A

MS

31
Q

What are some individual nerve signs of nerve disease?

A
  • wasting and weakness of the innervated muscle

- specific sensory changes

32
Q

What are some nerve root signs of nerve disease?

A
  • myotomal wasting and weakness
  • reflex changes
  • dermatomal sensory changes
33
Q

Which investigations can be performed to investigate nerve disease?

A
  • bloods: DM
  • genetic analysis
  • nerve conduction study
  • LP
  • nerve biopsy
34
Q

Name the 2 pyramidal tracts.

A
  • corticospinal

- corticobulbar

35
Q

Describe MND.

A

Usually limb onset, later bulbar and respiratory involvement. Combination of UMN and LMN signs with no sensory involvement.

36
Q

What is the prognosis of MND?

A

3-5 years from symptom onset or 2-3 years from diagnosis.

37
Q

What is the classic tongue sign seen in MND?

A

Wasted with fasciculations.

38
Q

How is MND diagnosed?

A

Only condition to present with UMN and LMN signs.

39
Q

Which treatments are available for MND?

A
  • riluzole (only approved treatment)

- rest supportive - PEG, NIV etc

40
Q

Define myelopathy.

A

Disease of the spinal cord.

41
Q

Define radiculopathy.

A

A condition in which one or more nerves are affected and do not work properly ie disease of the nerve roots.

Neurology (23 decks)

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