Dystrophin provides mechanical strength to muscle cell membranes. Its absence causes degeneration of muscle fibers, resulting in muscle weakness. Myopathies are muscle disorders involving primary impairment of skeletal muscle. Symptoms include proximal muscle weakness, cramps, myalgia, myotonia, and fatigue. Inflammatory myopathies like polymyositis and dermatomyositis can be acquired through infection or drugs and involve symmetrical weakness. Muscular dystrophies are hereditary and involve absence or reduction of dystrophin, leading to fiber degeneration. Duchenne muscular dystrophy occurs in boys under 10 and involves pseudohypertrophy of calf muscles. Becker's dystrophy has a later onset and may involve

1. Muzammil hameed
Neurophysiology
MUSCLE PHYSIOLOGY
Dystrophin (protein) provides mechanical strength to the sarcolemma (cell
membrane of muscle cells) and stabilizes the glycoprotein complex, its absence
causes digestion of the glycoprotein complex. This initiates degeneration of the
muscle fiber resulting in muscle weakness .
MYOPATHY
Myo means --- Muscle
Pathy means --- suffering
* A disorder in which there is a primary functional or structural impairment of
skeletal muscle.
SYMPTOMS
1) Proximal muscle weakness or atrophy
2) Muscle cramps (Involuntary contractions of muscle for seconds to minutes).
3) Myalgia (Muscle pain)
4) Myotonia (muscle relaxation impaired)
5) Fatigue ( tiredness and weakness)

2. LAB INVESTIGATIONS

4. INFLAMMATORY MYOPATHIES
(Acquired)
Polymyositis (PM) & Dermatomyositis (DM)
 Due to infection or drug reactions
 Polymyositis affects mainly adults.
 Dermatomyositis affects children and adults
 DM or PM is associated with another well-defined
connective tissue disorder such as scleroderma (disease that involves
tightening and hardening of skin)
POLYMYOSITIS (Autoimmune)
 Presents in adults (> 20 years), women > men
 Symmetrical weakness.
 Proximal >distal muscles.
 Mild pain and muscle tenderness.
 Dysphagia (swallowing problem)
DERMATOMYOSITIS
 Any age (adults,child)
 Female > Male.
 Weakness Proximal >distal, legs>arms.
 Difficulties swallowing, chewing, and speaking
 Skin rashes (both skin and muscles involve)

5. Diagnosis of PM & DM
 Symmetrical limbs girdle weakness
 CK level elevated in Polymyositis
 CK level normal in Dermatomyositis
 EMG shows myopathic pattern
NOTE: Any case with proximal weakness and normal CK is probably DM

6. MUSCULAR DYSTROPHIES(Hereditary)
 Duchenne (early age) and becker (late age)
 Dystrophin protein absent in Duchenne and reduced in beckers and its absence
causes digestion of the glycoprotein complex. This initiates degeneration of the
muscle fiber resulting in muscle weakness .
Duchenne Muscular Dystrophy (DMD)
 Boys (early age) Age: <10 years.
 Absence of dystrophin
 Positive Gowers sign (standing up with the help of hands)
 Weakness Distribution: Proximal > Distal, Symmetric, Legs & Arms.
 Muscle (Pseudo) hypertrophy: Especially calf. May be generalized.
 Complications: contractures, kypho-scoliosis, exaggerated lumbar lordosis
 Respiratory muscle weaken
Calf muscle psuedohypertropy

7. Becker’s Muscular Dystrophy
 Usually > 10 yrs (Older age at onset)
 Weakness: Proximal > Distal; Symmetric; Legs & Arms May be especially
prominent in quadriceps or hamstrings.
 Calf pain on exercise Muscle hypertrophy: Especially calves.
Myotonic Dystrophy
 Age of onset average is 29 years
 Prolonged muscle contractions (myotonia) and are not able to relax certain
muscles after use
 (eg, Difficulty releasing hand grip on a doorknob or handle)
 Ptosis and weakness of other facial muscles
 Weakness of the forearms and peroneal muscles

8. 
Myotonic dystropy >
LIMBS GIRDLE MUSCULAR DYSTROPY
 It is characterised by progressive muscle wasting which affects predominantly
hip and shoulder muscles.
 Limb-girdle pattern of weakness, LGMD2 is more common than LGMD1.
 MUSCLE INVOLVE IN LIMBS GIRDLE
MUSCULLAR DYSTROPY

9. Facioscapulohumeral dystrophy
 3rd most common dystrophy in adult
 Face: Initial manifestation: Frequency: 95% at age 30 with examination
 Bulbar dysfunction
 Facioscapulohumeral muscular dystrophy (FSHD) is a genetic muscle disorder in
which the muscles of the face, shoulder blades, and upper arms are among the
most affected.
 progresses very slowly and rarely affects the heart or respiratory system.

10. Muscular dystropy distribution
Dystropy types