MYOPATHY

[Guest]

68 yr old man is evaluated in ur office coz he has noticed progressive inability to lift his head for last two months.He also comments that it is difficult to reach objects over his head.He has some myalgia and difficulty swallowing.O/Eextraocular movements are intact and there is no ptosis.There is marked weakness of extensor muscles of neck and moderate weakness of proximal muscle of arms and legs.Vibration over great toe is reduced.deep tendon reflexes r hypoactive with flexor plantar responses.
In addition to scheduling a CK determination and EMG which of following studies u shud ordr to confirm he diagnosis:
1-MRI cervical spine
2-Sural Nerve Bx
3-Skeletal Muscle Bx
4-Ach receptor Ab assay
5-CSF analysis
my ans is muscle biopsy.
Which of the following statements concerning muscle disease is correct?
Options
A. Thyrotoxic myopathy is usually associated with raised creatinine kinase
B. Hypothyroidism is a feature of myotonic dystrophy
C. Inclusion body myositis responds to steroids
D. Oculopharyngeal muscular dystrophy is associated with trinucleotide repeat expansions
E. Duchenne muscular dystrophy is not associated with reduced IQ


Thyrotoxic myopathy occurs in about a third of thyrotoxic patients. It features predominantly shoulder girdle weakness with mild wasting and occasional fasciculations which are related to motor unit instability resulting from the thyrotoxic state rather than denervation. Typically the CK is normal. The condition remits on successful treatment of the endocrine disorder. Hypothyroidism also causes muscle weakness but it is much milder. A condition simulating hypokalaemic periodic paralysis may be seen in patients with thyrotoxicosis (especially Orientals), and when the thyrotoxicosis is of autoimmune origin, other organ-specific autoimmune diseases such as myasthenia gravis.

Myotonic dystrophy is the commonest inherited myopathy in adults with an incidence of 10 per 100,000. The genetic basis is expansion a CTG repeat and it therefore shows anticipation. The adult form presents in late adolescence or early adulthood. Skeletal muscle features include ptosis, facial wasting, and distal limb weakness with delayed muscle relaxation following contraction or percussion (myotonia). Respiratory muscle weakness occurs late. There are many manifestations of the illness which are unrelated to its effect on skeletal muscle:
Cataracts
Cardiac muscle: arrhythmias cardiomyopathy
Smooth muscle: dysphagia constipation incontinence
CNS: low IQ daytime somnolence
Endocrine: testicular atrophy reduced fertility male pattern baldness glucose intolerance
Inclusion body myositis is chronic myopathy most commonly affecting elderly males. It presents with proximal and distal weakness, and wasting characteristically affecting the finger flexors and quadriceps. Dysphagia occurs late. There are no extramuscular features. Creatinine kinase is elevated and electromyographic features resemble those seen in polymyositis. Biopsy shows characteristic 15nm intracellular inclusions. Treatment with immunosuppression is largely ineffective.

Oculopharyngeal muscular dystrophy has autosomal dominant inheritance and is associated with trinucleotide repeat expansions. It presents with ptosis and mild external ophthalmoplegia after the age of 50 followed by dysphagia months to years later and finally (predominantly upper) limb girdle weakness. Management is symptomatic.

Duchenne muscular dystrophy is caused by mutations in the dystrophin gene and has X-linked recessive inheritance. Girls with Turner’s syndrome may be affected. The incidence is 30 per 100,000 males of which a third a new mutations. Clinically, progressive lower then upper limb weakness develops in the first year of life. Hypertrophy is most obvious in calves, quadriceps and masseters. Scoliosis develops as a result of weakness of axial musculature and together with respiratory muscle weakness leads to hypoventilation which may progress to respiratory failure. Cardiac involvement is universal but not commonly symptomatic; a small proportion develop heart failure. Most patients are mildly cognitively impaired with an average IQ of 80. Diagnosis is based on clinical features, raised CK, absence or deficiency of dystrophin on biopsy, and demonstration of the gene defect. Treatment is physiotherapy, prevention of contractures, non-invasive ventilation for respiratory failure, genetic counselling and psychological support.

Myasthenia gravis is the commonest neuromuscular disorder with a prevalence of 5–10 per 100,000. Amongst younger patients it is commoner in women. In cases of generalised myasthenia antibodies to acetylcholine receptors are seen in 80%, this falls to 50% in cases of pure ophthalmoplegia. It is associated with rheumatoid arthritis, systemic lupus erythematosus, other organ-specific autoimmune disorders, and penicillamine treatment. Clinically, any muscle may be affected but ptosis, ophthalmoplegia and dysphagia are most common. Proximal weakness exceeds distal. Weakness tends to worsen during the day and increased fatiguability is characteristic. Emotion, infection and heat may exacerbate weakness.

Diagnosis is by antiacetylcholine receptor antibodies, tensilon test, and EMG which shows a decremental response of the compound muscle action potential to repetitive nerve stimulation. A thymoma is present in about 10% of cases and should be removed although this does not usually improve the myasthenia. Symptomatic benefit is produced by oral anticholinesterases such as pyridostigmine. Specific treatment is with oral steroids (which may transiently worsen symptoms); azathioprine frequently needs to be added as a steroid-sparing agent. Plasma exchange can be used in rapidly worsening symptoms or if the disease is refractory to immunosuppressant treatment. A third of young patients with generalised myasthenia in whom the thymus is hyperplastic will benefit from thymectomy. Severe weakness associated with respiratory failure is termed myasthenic crisis; this may be confused with cholinergic crisis and should be managed by intubation and ventilation, withdrawal of anticholinesterase treatment, and plasma exchange or intravenous immunoglobulin.

Myasthenia gravis is sometimes hard to distinguish from the Lambert-Eaton Myasthenic Syndrome (LEMS), a disorder of the neuromuscular junction caused by antibodies to presynaptic voltage-gated calcium channels. It is frequently associated with malignancy, particularly small cell lung cancer, in which case it may be accompanied by other paraneoplastic syndromes such as SIADH. The clinical features are similar to myasthenia but the weakness usually affects the limbs proximally, and involvement of the ocular and pharyngeal musculature is less common. In addition, autonomic features such as dry mouth and postural hypotension are present, and examination often shows an increase in strength (and augmentation of deep tendon reflexes) following exercise. Treatment with steroids and pyridostigmine can be helpful but events are usually overtaken by progression of the underlying malignancy.
Myopathy is typically associated with:
A) excessive alcohol ingestion
B) McArdle's disease (phosphorylase deficiency)
C) strychnine poisoning
D) Guillain-Barre syndrome
E) hypothyroidism
Mc ardles
excess alcohol ingestion ..... myopathy.
Mcrdles..... metabolic myopathy
Hypothyroid.....hoffmans myopathy.
- True...myopath..rhabdomyolysis..acute myositis.
2- True...especialy with excersize
3-true..rhabdomyolysis in overdose.
4-FALSE..it is demyelinating polyradiculopathy
5-true ...myopathy..and may cause demyelinating neuropathy

[pgudsoorkar]

for the first q why not a CSF analysis
what do u suspect
i think u suspect polymousitis
is it so but then why should it have hypoactive muscle reflexes

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