Nerve and Muscle Disease Flashcards
Describe the basic route for the movement of a muscle
Upper Motor Neuron Anterior Horn Cell Lower Motor Neuron NMJ ACh release ACh receptor Muscle stimulated
What are these disorders, disorders of?
Muscle
Neuromuscular junction
Peripheral nerve
Anterior horn cell
What is muscle?
An intricate machine designed to convert chemical energy to mechanical energy
What are the components of the process for chemical energy -> mechanical energy
Excitation-contraction coupling
The contractile mechanism
Structural components
The energy system
What is the presentation of muscle disease?
- Weakness of skeletal muscle
- Short of breath (respiratory muscle)
- Cardiomyopathy
- Poor suck/ feeding/ Failure To Thrive/ Floppy
- Cramp, pain
- Myoglobinuria
- Wasting/ hypertrophy
- Motor weakness… NOT sensory
Explain why myoglobinuria occurs and what the results of it are
Muscles break down
Myglobin in blood
Filtered by kidneys
Makes urine look like coca cola
Large molecule so can clog kidneys up in large amounts -> renal failure
How are muscle diseases classified?
- Muscular dystrophies
- Channelopathies
- Metabolic muscle disease
- Inflammatory Muscle disease
- Congenital myopathies
What parts can fail in muscle disease
Dystrophin Actin Sarcoglycan complex Systroglycan complex Laminin
Name the muscular dystrophies
Duchenne's MD Becker's MD Facioscapulohumeral MD Myotonic Dystrophy Limb-Girdle MD
What is Duchenne’s MD?
X linked
No functional muscular dystrophin produced
Poor motor milestones
(arent walking when young, wheelchair by teens)
Investigations:
CK, Genetics, Muscle biopsy
What is Becker’s MD?
Allelic with DMD
Cardiomyopathy
Some dystrophin produced so less severe than DMD
What is Facioscapulohumeral MD?
Autosomal dominant
Affects the skeletal muscles of the face, scapula and upper arms initially
Usually present in teens
What is myotonic dystrophy?
Autosomal dominant trinucleotide repeat disorder
Multisystem disorder characterised by weakness and myotonia
myotonia = hard to relax muscles once contracted
What is limb-girdle MD?
Large family of autosomal dominant and recessive disorders affecting primaryily the limb girdles
What are channelopathies?
Disorders of Ca, Na and Cl channels
How are channelopathies divided?
Periodic paralysis:
- Familial hypokalemic periodic paralysis
- Hyperkalemic periodic paralysis
Partial Paralysis:
- Paramyotonia congenita
- Myotonia congenita
What is the difference between paramyotonia congenita and myotonia congenita?
Myotonia = the more you move the easier it gets
Paramyotonia = the more you move the harder it gets
What is metabolic muscle disease?
Muscle isnt supplied very well with what it needs to function.
Muscle breakdown during exercise is therefore excessive
Myogobinuria can cause renal failure
How can someone with metabolic muscle disease present?
Muscle pain (particularly after exercise) which is unusually excessive
Coca Cola urine
Renal failure
How is metabolic muscle disease divided?
Disorders of carbohydrate metabolism
DIsorders of lipid metabolism
Mitochondrial myopathies/ cytopathies
How can a patient get around disorders of carbohydrate metabolism?
Push through during exercise.
After 10-15 mins start to break down fat stores so will get “second wind”
What will mitochondrial myopathies/ cytopathies effect?
Many different systems, not just skeletal
What is Myositis?
Inflammation of the muscles
What is Polymyositis?
Inflammation of all the muscles
What is dermatomyositis?
Inflammation of muscles and skin
Gives a characteristic rash
Describe inflammatory muscle disease
Acute or subacute Painful weak muscles Characteristic rash of DM Any age Other symptoms may be involved
What is the characteristic rash of dermatomyositis?
Gottron’s sign = erythematous, scaly eruption occurring in symmetric fashion over the Metacarpal and interphalangeal joints (can mimic psoriasis).
The heliotrope or “lilac” rash = eruption on the upper eyelids and in rare cases on the lower eyelids as well, often with itching and swelling
What are the investigations for inflammatory muscle disease?
History and examination
Increased CK
EMG
Biopsy
- PM = CD8 cells
- DM = humeral-mediated, B cells and CD4 cells
Genetic testing (more common than biopsy nowadays)
What is the treatment for inflammatory muscle disease?
Immunosuppression
What is EMG?
Electromyography
Evaluates and records the electrical activity produced by skeletal muscles.
Can see if muscle is normal or abnormal
Can see if the problem is msucle or nerve
Describe the function of the NMJ in normal patients
Ca mediated exocytosis of ACh
Binds to ACh receptor
Anticholinesterase breaksdown ACh so that muscle can relax
What happens to the NMJ in Myasthenia Gravis?
Autoantibodies block ACh receptors.
Less receptors so ACh less effective
Patients are fatiguable
What is the clinical presentation of Myasthenia Gravis?
Fatiguable Weakness:
- Limbs
- Eyelids (ptosis)
- Muscles of mastication (chewing is tiring, may switch diet to easier foods)
- Talking
- SOB
- Diplopia
What is the investigations into myasthenia gravis?
AChR antibody
Anti MuSK antibody
EMG
Tensilon test
CT chest
What is the tensilon test?
Nerve conduction of which you then look at the action potential
In myasthenia gravis you do repetative stimulation and AP will get smaller and smaller
What is the treatment for Myasthenia gravis?
Symptomatic
-Acetylcholinesterase inhibitor
Immunosuppression:
- Prednisolone
- Steroid saving agent (azathioprine)
Explain myasthenia gravis and the thymus
Must check thymus in MG
- In young associated with thymic hyperplasia
- In old may be associated with a malignant thymoma
?Thymectomy
-Females
What does peripheral nerve disease involve?
Lower motor neuron
Sensory axons:
- Small fibres (pain + temperature)
- Large fibres (joint position sense + vibration)
Motor axons
How is peripheral nerve disease divided?
Root disease
Lesion of individual peripheral nerve
Generalised peripheral neuropathy
What is Root nerve disease?
Degenerative spine disease
Nerve root disorders are precipitated by acute or chronic pressure on a root in or adjacent to the spinal column. The most common cause is
A herniated intervertebral disk (C5, 6, 7 or L5, S1)
Bone changes due to RA or osteoarthritis, especially in the cervical and lumbar areas, may also compress isolated nerve roots. (outside of load bearing areas
What are the symptoms of root nerve disease?
Dermatomal sensory change
Myotomal wasting and weakness
Fasciculations
What is a lesion of an individual peripheral nerve?
Compressive/ entrapment neuropathy
Vasculitis (mononeuritis multiplex)
What are the symptoms of a lesion of an individual peripheral nerve?
Specific sensory change
Wasting and weakness of innervated muscle
Fasciculations
What may generalised peripheral neuropathy involve?
What is it?
Motor/ sensory/ both
+/- autonomic features
Nerves start to die back from periphery
What are the causes of Generalised peripheral neuropathy?
Metabolic: DIABETES, ALCOHOL, B12
Toxic: drugs
Infectious: HIV, leprosy, Lymes disease
Malignancy: paraneoplastic
Inflammatory demyelination
- Acute: Guillain Barre syndrome
- Chronic = CIDP
What does CIDP stand for?
Chronic inflammatory demyelinating polyneuropathy
What are the symptoms of general peripheral neuropathy?
sensory and motor symptoms starting distally and moving proximally
What are the investigations for nerve disease?
Blood tests Genetic analysis EMG Lumbar puncture (CSF analysis) Nerve biopsy
What does anterior horn disease affect?
Upper motor neurone in corticospinal or corticobulbar tracts
Anterior horn cell
Describe Motor Neuron Disease (Amyotrophic Lateral Sclerosis)
Usually limb onset, later bulbar (muscles of mouth and throat) and respiratory involvement
Combination of UMN and LMN signs
-The more mixed the worse the prognosis
M:F 3:2
Terrible prognosis
What lower motor neuron symptoms may you see in ALS?
Wasting
weakness
muscle fasciculations
What upper motor neuron symptoms may you see in ALS?
Pyramidal weakness
Stiff
Brisk reflexes
How do you diagnose Motor neuron disease?
Unique combination of UMN and LMN signs
EMG
What is the treatment of ALS?
Supportive
- counseling
- multi diciplinary clinic
riluzole
