Muscle and Nerve diseases Flashcards
What causes muscular dystrophy?
A faulty protein - one of the structural proteins that connect the muscle to something else isn’t working properly
Give five types of muscular dystrophies
Duchenne's MD Becker's MD Facioscapulohumeral MD Myotonic dystrophy Limb-girdle MD
What is the most common type of muscular dystrophy? Describe the genotype that causes this disease
Myotonic dystrophy:
Triplet-repeat problem in the gene, causes the gene to dysfunction - the longer the repeat, the more unstable it is. This means that the disease gets worse with each generation
Which ion channels are involved in muscle contraction and relaxation?
Calcium ion
Sodium ion
Chloride ion
Give four types of channelopathy
Familial hypokalemic periodic paralysis
Hyperkalemic periodic paralysis
Paramyotonia congenita
Myotonia congenita
How do inflammatory muscle diseases usually present?
Patient presents being perfectly normal beforehand with relatively sudden onset weakness and sore muscles
Characteristic rash (dermatomyositis)
Can affect any age group
How are inflammatory muscle diseases tested for?
Test blood for raised creatine kinase (CK)
Biopsy
Name a disease that affects the neuromuscular junction
Myasthenia Gravis
Describe the pathophysiology of Myasthenia Gravis
Antibodies block acetylcholine receptors
This causes muscles to fatigue very quickly as they cannot sustain contraction
Which parts of the body can be affected by Myasthenia Gravis?
Limbs Eyelids (causes ptosis) Muscles of mastication - also affects talking Respiratory muscles (causes SOB) Eye muscles (causes diplopia)
How would Myasthenia Gravis be diagnosed? What investigations would be carried out?
Blood test to look for AchR antibody (present in 70%)
Test for anti-MuSK antibody
Investigate neurophysiology
- Repetitive stimulation (action potential gets smaller and smaller as it progresses along the nerve)
- EMG
Tensilon test
How is Myasthenia Gravis treated?
Symptomatic treatment - acetylcholinesterase inhibitor Immunosuppression - prednisolone - steroid-saving agent (azathioprine)
Give three causes of nerve root disease
Degenerative spine disease e.g. arthritis
Inflammation
Infiltration e.g. herpes
Give two classifications of individual peripheral nerve lesions
Compressive/entrapment neuropathy
Vasculitis
What is generalised peripheral neuropathy?
Dying of the peripheral nerves; begins distally, moves proximally
Can be motor, sensory or both
May have associated autonomic features
List some potential causes of generalised peripheral neuropathy
Metabolic: diabetes, alcohol, B12 Toxic: drugs Hereditary Infectious: lyme, HIV, leprosy Malignancy Inflammatory demyelinating disease (usually follows an acute illness such as a viral infection, e.g. guillain-barre syndrome)
Describe the presentation of nerve root disease
Myotomal wasting and weakness
Reflex changes
Dermatological sensory changes
Describe the presentation of disease which affects individual nerves
Wasting and weakness of innervated muscle
Specific sensory change
What type of motor neurone disease affects both upper and lower motor neurones?
Amyotropic Lateral Sclerosis (ALS)
Describe the presentation of Amyotropic Lateral Sclerosis
Usually limb onset, later includes bulbar and respiratory involvement
Combinations of UMN and LMN signs
Progressive bulbar palsy
No sensory involvement
Electromyography (EMG) results aid diagnosis
How is Amyotropic Lateral Sclerosis treated?
Supportive - PEG tube, NIV
Riluzole (slows disease progression)
What is the prognosis for ALS?
50% will die within 14 months of symptom onset.
Riluzole can increase a patient’s life expectancy by up to six months.
What is multiple sclerosis?
A disease of the white matter, predominantly demyelination due to inflammation of the myelin sheath
Relapsing-remitting course of disease
Most patients develop progressive disability
What is meant by a “relapse” in multiple sclerosis?
Focal disturbance of function
Describe the process of demyelination in MS
Auto-immune process
Activated T-cells cross the blood brain barrier, causeing demyelination
There is also acute inflammation of the myelin sheath
This causes a loss of function
What is meant by “Post-inflammatory gliosis” in MS?
Scarring left by inflammation causes a functional deficit
THis can be seen as lesions or plaques on an MRI scan
What causes disability in MS? How can this be tested for?
Axonal loss - areas of axonal loss can be seen on MRI as black holes
What environmental factors are thought to be linked to MS?
Temperate climate
Epstein-Barr virus
Vitamin D deficiency
How does MS present?
Usually presents with a relapse
Gradual onset over days, then stablises within a few days or a week
Gradual resolution to complete or partial recovery
What are the effects of brainstem relapses in MS?
Loss of cranial nerve function; vertigo, nustagmus, ataxia
Describe the signs/symptoms present in the progressive phase of MS?
Fatigue Temperature sensitivity Sensory loss Balance problems Slurred speech Swallowing problems Bladder and bowel problems Diplopia/oscillopsia/visual loss Cognitive dementia Emotional disturbance
What type of imaging is most useful in aiding diagnosis of MS?
MRI scanning
Which investigations can be used to aid diagnosis of MS?
MRI scan
Lumbar puncture (look for oligoclonal bands and other signs of inflammation present in CSF but not serum)
Visual/somatosensory evoked response
Bloods (to exclude other inflammatory conditions)
Chest x-ray
Describe the differential diagnosis of MS
Depends on the patient! Acute disseminated encephalomyelitis Other autoimmune conditions Sarcoidosis Vasculitis Infections e.g. lyme disease, HTLV-1 Adrenoleucodystrophy Others!
Give four types of MS (classified based on patterns of impairment)
Relapsing-remitting
Secondary progressive
Sensory MS
Primary progressive (faster progression, no relapses)
Which patients are suitable for disease-modifying treatment of MS?
Those with frequent relapses - drugs have lots of side effects so are avoided as much as possible
What are the potential side effects of disease-modifying MS drugs?
Flu-like symptoms
Injection-site reaction
Abnormalities of blood count
Abnormal liver function
Give five first line disease-modifying MS drugs
Less aggressive (daily or weekly injections): - beta-interferons - glatiramer acetate More aggressive: - oral treatments - teriflunomide - dimethyl fumarate
How are acute relapses of MS treated?
Oral prednisolone
Symptomatic treatment (depending on nature or relapse/site of inflammation etc)
Look for an underlying infection
