Myopathies series -Part 5

Hello! :)

8. APPEARNACE OF MUSCLE :-

- Hypertrophy of Calf muscles = Dytrophinopathies or Limb girdle muscular dystrophy.

-Pseudohypertrophy= Duchene's muscular dystrophy, infiltration by sarcoid granulomas,amyloid deposit, bacterial and parasitic infections.

-Atrophy of gastrocnemius muscles in medial aspect = Dysferlinooathies 

- Atrophy of humeral muscles= FSHD

9. REFLEXES PRESERVED

10. LAB INVESTIGATIONS:-

1. ENZYMES: - I have already discussed its role in metabolic myopathies.

- ALT, AST, LDH,aldolase :- Found in both skeletal muscle and liver.Elevated GGT help to establish its liver origin.

-CK (MM) help to evaluate myopathies.

2. ELECTRODIAGNOSTIC STUDIES: 

-EMG: - diagnose myopathy and help to choose right muscle for biopsy.

-NCS (nerve conduction studies):-Help to differentiate myopathies from neuropathy and NMJ disorders.

       

Diagnostic test for specific type of myopathies:-

1. FOREARM EXERCISE TEST:-

- Place an indwelling catheter in to an antecubital vein and obtain baseline blood sample for lactic acid and ammonia.

-The forearm muscles are exercised. Vigorously squeeze the sphygmomanometer bulb for 1 min.

-Blood is then obtained at the intervals of 1,2,4,6 and 10 min for comparison with baseline.

Normally, Both glucose and ammonia increases with exercise.

Interpretation:-

-Glycolytic defects: - Lactic acid rise is absent or below normal while rise in ammonia will reach the control values.

-Myoadenylate deaminase deficiency: - there occur a selective failure to increase ammonia.

2. DNA ANALYSIS: - Some muscle disorder are associated with gene defects like deletions and mutations. (In Duchene muscular dystrophy, we will see it.)

3. MUSCLE BIOPSY:-

-Safe diagnostic procedure in establishing the final diagnosis of suspected myopathy.

-Different techniques of microscopic evaluation: - Histology, immunohistochemistry with antibodies, electron microscopy.

-SITE: - muscle selected may have mild to moderate muscle weakness.

-NOT PERFORMED ON: - Muscle injured by previous trauma,injections and EMG needles 

-COMMON MUSCLES USED FOR BIOPSY:-

PROXIMAL: biceps, triceps, quadriceps

DISTAL: - Extensor carpi radialis, Anterior tibialis.

*Claps* 

We are done with the basic for myopathy.

Now I will go through individual myopathy. :D

I remember age and progression of myopathy part. :) I will discuss it in next part. 

Take care.

-Upasana Y.