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
